2147 lines
125 KiB
HTML
2147 lines
125 KiB
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
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<title>zstd 1.5.5 Manual</title>
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</head>
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<body>
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<h1>zstd 1.5.5 Manual</h1>
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<hr>
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<a name="Contents"></a><h2>Contents</h2>
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<ol>
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<li><a href="#Chapter1">Introduction</a></li>
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<li><a href="#Chapter2">Version</a></li>
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<li><a href="#Chapter3">Simple API</a></li>
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<li><a href="#Chapter4">Explicit context</a></li>
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<li><a href="#Chapter5">Advanced compression API (Requires v1.4.0+)</a></li>
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<li><a href="#Chapter6">Advanced decompression API (Requires v1.4.0+)</a></li>
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<li><a href="#Chapter7">Streaming</a></li>
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<li><a href="#Chapter8">Streaming compression - HowTo</a></li>
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<li><a href="#Chapter9">Streaming decompression - HowTo</a></li>
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<li><a href="#Chapter10">Simple dictionary API</a></li>
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<li><a href="#Chapter11">Bulk processing dictionary API</a></li>
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<li><a href="#Chapter12">Dictionary helper functions</a></li>
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<li><a href="#Chapter13">Advanced dictionary and prefix API (Requires v1.4.0+)</a></li>
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<li><a href="#Chapter14">experimental API (static linking only)</a></li>
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<li><a href="#Chapter15">Frame header and size functions</a></li>
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<li><a href="#Chapter16">Memory management</a></li>
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<li><a href="#Chapter17">Advanced compression functions</a></li>
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<li><a href="#Chapter18">Advanced decompression functions</a></li>
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<li><a href="#Chapter19">Advanced streaming functions</a></li>
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<li><a href="#Chapter20">Buffer-less and synchronous inner streaming functions (DEPRECATED)</a></li>
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<li><a href="#Chapter21">Buffer-less streaming compression (synchronous mode)</a></li>
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<li><a href="#Chapter22">Buffer-less streaming decompression (synchronous mode)</a></li>
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<li><a href="#Chapter23">Block level API (DEPRECATED)</a></li>
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</ol>
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<hr>
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<a name="Chapter1"></a><h2>Introduction</h2><pre>
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zstd, short for Zstandard, is a fast lossless compression algorithm, targeting
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real-time compression scenarios at zlib-level and better compression ratios.
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The zstd compression library provides in-memory compression and decompression
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functions.
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The library supports regular compression levels from 1 up to ZSTD_maxCLevel(),
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which is currently 22. Levels >= 20, labeled `--ultra`, should be used with
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caution, as they require more memory. The library also offers negative
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compression levels, which extend the range of speed vs. ratio preferences.
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The lower the level, the faster the speed (at the cost of compression).
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Compression can be done in:
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- a single step (described as Simple API)
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- a single step, reusing a context (described as Explicit context)
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- unbounded multiple steps (described as Streaming compression)
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The compression ratio achievable on small data can be highly improved using
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a dictionary. Dictionary compression can be performed in:
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- a single step (described as Simple dictionary API)
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- a single step, reusing a dictionary (described as Bulk-processing
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dictionary API)
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Advanced experimental functions can be accessed using
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`#define ZSTD_STATIC_LINKING_ONLY` before including zstd.h.
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Advanced experimental APIs should never be used with a dynamically-linked
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library. They are not "stable"; their definitions or signatures may change in
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the future. Only static linking is allowed.
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<BR></pre>
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<a name="Chapter2"></a><h2>Version</h2><pre></pre>
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<pre><b>unsigned ZSTD_versionNumber(void);
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</b><p> Return runtime library version, the value is (MAJOR*100*100 + MINOR*100 + RELEASE).
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</p></pre><BR>
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<pre><b>const char* ZSTD_versionString(void);
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</b><p> Return runtime library version, like "1.4.5". Requires v1.3.0+.
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</p></pre><BR>
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<a name="Chapter3"></a><h2>Simple API</h2><pre></pre>
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<pre><b>size_t ZSTD_compress( void* dst, size_t dstCapacity,
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const void* src, size_t srcSize,
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int compressionLevel);
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</b><p> Compresses `src` content as a single zstd compressed frame into already allocated `dst`.
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NOTE: Providing `dstCapacity >= ZSTD_compressBound(srcSize)` guarantees that zstd will have
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enough space to successfully compress the data.
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@return : compressed size written into `dst` (<= `dstCapacity),
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or an error code if it fails (which can be tested using ZSTD_isError()).
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</p></pre><BR>
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<pre><b>size_t ZSTD_decompress( void* dst, size_t dstCapacity,
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const void* src, size_t compressedSize);
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</b><p> `compressedSize` : must be the _exact_ size of some number of compressed and/or skippable frames.
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`dstCapacity` is an upper bound of originalSize to regenerate.
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If user cannot imply a maximum upper bound, it's better to use streaming mode to decompress data.
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@return : the number of bytes decompressed into `dst` (<= `dstCapacity`),
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or an errorCode if it fails (which can be tested using ZSTD_isError()).
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</p></pre><BR>
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<pre><b>#define ZSTD_CONTENTSIZE_UNKNOWN (0ULL - 1)
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#define ZSTD_CONTENTSIZE_ERROR (0ULL - 2)
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unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize);
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</b><p> `src` should point to the start of a ZSTD encoded frame.
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`srcSize` must be at least as large as the frame header.
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hint : any size >= `ZSTD_frameHeaderSize_max` is large enough.
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@return : - decompressed size of `src` frame content, if known
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- ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined
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- ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small)
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note 1 : a 0 return value means the frame is valid but "empty".
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note 2 : decompressed size is an optional field, it may not be present, typically in streaming mode.
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When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
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In which case, it's necessary to use streaming mode to decompress data.
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Optionally, application can rely on some implicit limit,
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as ZSTD_decompress() only needs an upper bound of decompressed size.
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(For example, data could be necessarily cut into blocks <= 16 KB).
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note 3 : decompressed size is always present when compression is completed using single-pass functions,
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such as ZSTD_compress(), ZSTD_compressCCtx() ZSTD_compress_usingDict() or ZSTD_compress_usingCDict().
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note 4 : decompressed size can be very large (64-bits value),
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potentially larger than what local system can handle as a single memory segment.
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In which case, it's necessary to use streaming mode to decompress data.
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note 5 : If source is untrusted, decompressed size could be wrong or intentionally modified.
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Always ensure return value fits within application's authorized limits.
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Each application can set its own limits.
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note 6 : This function replaces ZSTD_getDecompressedSize()
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</p></pre><BR>
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<pre><b>ZSTD_DEPRECATED("Replaced by ZSTD_getFrameContentSize")
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ZSTDLIB_API
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unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize);
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</b><p> NOTE: This function is now obsolete, in favor of ZSTD_getFrameContentSize().
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Both functions work the same way, but ZSTD_getDecompressedSize() blends
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"empty", "unknown" and "error" results to the same return value (0),
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while ZSTD_getFrameContentSize() gives them separate return values.
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@return : decompressed size of `src` frame content _if known and not empty_, 0 otherwise.
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</p></pre><BR>
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<pre><b>size_t ZSTD_findFrameCompressedSize(const void* src, size_t srcSize);
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</b><p> `src` should point to the start of a ZSTD frame or skippable frame.
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`srcSize` must be >= first frame size
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@return : the compressed size of the first frame starting at `src`,
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suitable to pass as `srcSize` to `ZSTD_decompress` or similar,
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or an error code if input is invalid
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</p></pre><BR>
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<h3>Helper functions</h3><pre></pre><b><pre></b>/* ZSTD_compressBound() :<b>
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* maximum compressed size in worst case single-pass scenario.
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* When invoking `ZSTD_compress()` or any other one-pass compression function,
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* it's recommended to provide @dstCapacity >= ZSTD_compressBound(srcSize)
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* as it eliminates one potential failure scenario,
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* aka not enough room in dst buffer to write the compressed frame.
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* Note : ZSTD_compressBound() itself can fail, if @srcSize > ZSTD_MAX_INPUT_SIZE .
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* In which case, ZSTD_compressBound() will return an error code
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* which can be tested using ZSTD_isError().
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*
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* ZSTD_COMPRESSBOUND() :
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* same as ZSTD_compressBound(), but as a macro.
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* It can be used to produce constants, which can be useful for static allocation,
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* for example to size a static array on stack.
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* Will produce constant value 0 if srcSize too large.
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*/
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#define ZSTD_MAX_INPUT_SIZE ((sizeof(size_t)==8) ? 0xFF00FF00FF00FF00ULL : 0xFF00FF00U)
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#define ZSTD_COMPRESSBOUND(srcSize) (((size_t)(srcSize) >= ZSTD_MAX_INPUT_SIZE) ? 0 : (srcSize) + ((srcSize)>>8) + (((srcSize) < (128<<10)) ? (((128<<10) - (srcSize)) >> 11) </b>/* margin, from 64 to 0 */ : 0)) /* this formula ensures that bound(A) + bound(B) <= bound(A+B) as long as A and B >= 128 KB */<b>
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size_t ZSTD_compressBound(size_t srcSize); </b>/*!< maximum compressed size in worst case single-pass scenario */<b>
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</b>/* ZSTD_isError() :<b>
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* Most ZSTD_* functions returning a size_t value can be tested for error,
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* using ZSTD_isError().
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* @return 1 if error, 0 otherwise
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*/
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unsigned ZSTD_isError(size_t code); </b>/*!< tells if a `size_t` function result is an error code */<b>
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const char* ZSTD_getErrorName(size_t code); </b>/*!< provides readable string from an error code */<b>
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int ZSTD_minCLevel(void); </b>/*!< minimum negative compression level allowed, requires v1.4.0+ */<b>
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int ZSTD_maxCLevel(void); </b>/*!< maximum compression level available */<b>
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int ZSTD_defaultCLevel(void); </b>/*!< default compression level, specified by ZSTD_CLEVEL_DEFAULT, requires v1.5.0+ */<b>
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</pre></b><BR>
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<a name="Chapter4"></a><h2>Explicit context</h2><pre></pre>
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<h3>Compression context</h3><pre> When compressing many times,
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it is recommended to allocate a context just once,
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and reuse it for each successive compression operation.
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This will make workload friendlier for system's memory.
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Note : re-using context is just a speed / resource optimization.
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It doesn't change the compression ratio, which remains identical.
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Note 2 : In multi-threaded environments,
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use one different context per thread for parallel execution.
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</pre><b><pre>typedef struct ZSTD_CCtx_s ZSTD_CCtx;
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ZSTD_CCtx* ZSTD_createCCtx(void);
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size_t ZSTD_freeCCtx(ZSTD_CCtx* cctx); </b>/* accept NULL pointer */<b>
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</pre></b><BR>
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<pre><b>size_t ZSTD_compressCCtx(ZSTD_CCtx* cctx,
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void* dst, size_t dstCapacity,
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const void* src, size_t srcSize,
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int compressionLevel);
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</b><p> Same as ZSTD_compress(), using an explicit ZSTD_CCtx.
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Important : in order to behave similarly to `ZSTD_compress()`,
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this function compresses at requested compression level,
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__ignoring any other parameter__ .
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If any advanced parameter was set using the advanced API,
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they will all be reset. Only `compressionLevel` remains.
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</p></pre><BR>
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<h3>Decompression context</h3><pre> When decompressing many times,
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it is recommended to allocate a context only once,
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and reuse it for each successive compression operation.
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This will make workload friendlier for system's memory.
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Use one context per thread for parallel execution.
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</pre><b><pre>typedef struct ZSTD_DCtx_s ZSTD_DCtx;
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ZSTD_DCtx* ZSTD_createDCtx(void);
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size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx); </b>/* accept NULL pointer */<b>
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</pre></b><BR>
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<pre><b>size_t ZSTD_decompressDCtx(ZSTD_DCtx* dctx,
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void* dst, size_t dstCapacity,
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const void* src, size_t srcSize);
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</b><p> Same as ZSTD_decompress(),
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requires an allocated ZSTD_DCtx.
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Compatible with sticky parameters.
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</p></pre><BR>
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<a name="Chapter5"></a><h2>Advanced compression API (Requires v1.4.0+)</h2><pre></pre>
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<pre><b>typedef enum { ZSTD_fast=1,
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ZSTD_dfast=2,
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ZSTD_greedy=3,
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ZSTD_lazy=4,
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ZSTD_lazy2=5,
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ZSTD_btlazy2=6,
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ZSTD_btopt=7,
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ZSTD_btultra=8,
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ZSTD_btultra2=9
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</b>/* note : new strategies _might_ be added in the future.<b>
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Only the order (from fast to strong) is guaranteed */
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} ZSTD_strategy;
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</b></pre><BR>
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<pre><b>typedef enum {
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</b>/* compression parameters<b>
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* Note: When compressing with a ZSTD_CDict these parameters are superseded
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* by the parameters used to construct the ZSTD_CDict.
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* See ZSTD_CCtx_refCDict() for more info (superseded-by-cdict). */
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ZSTD_c_compressionLevel=100, </b>/* Set compression parameters according to pre-defined cLevel table.<b>
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* Note that exact compression parameters are dynamically determined,
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* depending on both compression level and srcSize (when known).
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* Default level is ZSTD_CLEVEL_DEFAULT==3.
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* Special: value 0 means default, which is controlled by ZSTD_CLEVEL_DEFAULT.
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* Note 1 : it's possible to pass a negative compression level.
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* Note 2 : setting a level does not automatically set all other compression parameters
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* to default. Setting this will however eventually dynamically impact the compression
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* parameters which have not been manually set. The manually set
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* ones will 'stick'. */
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</b>/* Advanced compression parameters :<b>
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* It's possible to pin down compression parameters to some specific values.
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* In which case, these values are no longer dynamically selected by the compressor */
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ZSTD_c_windowLog=101, </b>/* Maximum allowed back-reference distance, expressed as power of 2.<b>
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* This will set a memory budget for streaming decompression,
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* with larger values requiring more memory
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* and typically compressing more.
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* Must be clamped between ZSTD_WINDOWLOG_MIN and ZSTD_WINDOWLOG_MAX.
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* Special: value 0 means "use default windowLog".
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* Note: Using a windowLog greater than ZSTD_WINDOWLOG_LIMIT_DEFAULT
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* requires explicitly allowing such size at streaming decompression stage. */
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ZSTD_c_hashLog=102, </b>/* Size of the initial probe table, as a power of 2.<b>
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* Resulting memory usage is (1 << (hashLog+2)).
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* Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX.
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* Larger tables improve compression ratio of strategies <= dFast,
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* and improve speed of strategies > dFast.
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* Special: value 0 means "use default hashLog". */
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ZSTD_c_chainLog=103, </b>/* Size of the multi-probe search table, as a power of 2.<b>
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* Resulting memory usage is (1 << (chainLog+2)).
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* Must be clamped between ZSTD_CHAINLOG_MIN and ZSTD_CHAINLOG_MAX.
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* Larger tables result in better and slower compression.
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* This parameter is useless for "fast" strategy.
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* It's still useful when using "dfast" strategy,
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* in which case it defines a secondary probe table.
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* Special: value 0 means "use default chainLog". */
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ZSTD_c_searchLog=104, </b>/* Number of search attempts, as a power of 2.<b>
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* More attempts result in better and slower compression.
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* This parameter is useless for "fast" and "dFast" strategies.
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* Special: value 0 means "use default searchLog". */
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ZSTD_c_minMatch=105, </b>/* Minimum size of searched matches.<b>
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* Note that Zstandard can still find matches of smaller size,
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* it just tweaks its search algorithm to look for this size and larger.
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* Larger values increase compression and decompression speed, but decrease ratio.
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* Must be clamped between ZSTD_MINMATCH_MIN and ZSTD_MINMATCH_MAX.
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* Note that currently, for all strategies < btopt, effective minimum is 4.
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* , for all strategies > fast, effective maximum is 6.
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* Special: value 0 means "use default minMatchLength". */
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|
|
ZSTD_c_targetLength=106, </b>/* Impact of this field depends on strategy.<b>
|
||
|
|
* For strategies btopt, btultra & btultra2:
|
||
|
|
* Length of Match considered "good enough" to stop search.
|
||
|
|
* Larger values make compression stronger, and slower.
|
||
|
|
* For strategy fast:
|
||
|
|
* Distance between match sampling.
|
||
|
|
* Larger values make compression faster, and weaker.
|
||
|
|
* Special: value 0 means "use default targetLength". */
|
||
|
|
ZSTD_c_strategy=107, </b>/* See ZSTD_strategy enum definition.<b>
|
||
|
|
* The higher the value of selected strategy, the more complex it is,
|
||
|
|
* resulting in stronger and slower compression.
|
||
|
|
* Special: value 0 means "use default strategy". */
|
||
|
|
</b>/* LDM mode parameters */<b>
|
||
|
|
ZSTD_c_enableLongDistanceMatching=160, </b>/* Enable long distance matching.<b>
|
||
|
|
* This parameter is designed to improve compression ratio
|
||
|
|
* for large inputs, by finding large matches at long distance.
|
||
|
|
* It increases memory usage and window size.
|
||
|
|
* Note: enabling this parameter increases default ZSTD_c_windowLog to 128 MB
|
||
|
|
* except when expressly set to a different value.
|
||
|
|
* Note: will be enabled by default if ZSTD_c_windowLog >= 128 MB and
|
||
|
|
* compression strategy >= ZSTD_btopt (== compression level 16+) */
|
||
|
|
ZSTD_c_ldmHashLog=161, </b>/* Size of the table for long distance matching, as a power of 2.<b>
|
||
|
|
* Larger values increase memory usage and compression ratio,
|
||
|
|
* but decrease compression speed.
|
||
|
|
* Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX
|
||
|
|
* default: windowlog - 7.
|
||
|
|
* Special: value 0 means "automatically determine hashlog". */
|
||
|
|
ZSTD_c_ldmMinMatch=162, </b>/* Minimum match size for long distance matcher.<b>
|
||
|
|
* Larger/too small values usually decrease compression ratio.
|
||
|
|
* Must be clamped between ZSTD_LDM_MINMATCH_MIN and ZSTD_LDM_MINMATCH_MAX.
|
||
|
|
* Special: value 0 means "use default value" (default: 64). */
|
||
|
|
ZSTD_c_ldmBucketSizeLog=163, </b>/* Log size of each bucket in the LDM hash table for collision resolution.<b>
|
||
|
|
* Larger values improve collision resolution but decrease compression speed.
|
||
|
|
* The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX.
|
||
|
|
* Special: value 0 means "use default value" (default: 3). */
|
||
|
|
ZSTD_c_ldmHashRateLog=164, </b>/* Frequency of inserting/looking up entries into the LDM hash table.<b>
|
||
|
|
* Must be clamped between 0 and (ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN).
|
||
|
|
* Default is MAX(0, (windowLog - ldmHashLog)), optimizing hash table usage.
|
||
|
|
* Larger values improve compression speed.
|
||
|
|
* Deviating far from default value will likely result in a compression ratio decrease.
|
||
|
|
* Special: value 0 means "automatically determine hashRateLog". */
|
||
|
|
|
||
|
|
</b>/* frame parameters */<b>
|
||
|
|
ZSTD_c_contentSizeFlag=200, </b>/* Content size will be written into frame header _whenever known_ (default:1)<b>
|
||
|
|
* Content size must be known at the beginning of compression.
|
||
|
|
* This is automatically the case when using ZSTD_compress2(),
|
||
|
|
* For streaming scenarios, content size must be provided with ZSTD_CCtx_setPledgedSrcSize() */
|
||
|
|
ZSTD_c_checksumFlag=201, </b>/* A 32-bits checksum of content is written at end of frame (default:0) */<b>
|
||
|
|
ZSTD_c_dictIDFlag=202, </b>/* When applicable, dictionary's ID is written into frame header (default:1) */<b>
|
||
|
|
|
||
|
|
</b>/* multi-threading parameters */<b>
|
||
|
|
</b>/* These parameters are only active if multi-threading is enabled (compiled with build macro ZSTD_MULTITHREAD).<b>
|
||
|
|
* Otherwise, trying to set any other value than default (0) will be a no-op and return an error.
|
||
|
|
* In a situation where it's unknown if the linked library supports multi-threading or not,
|
||
|
|
* setting ZSTD_c_nbWorkers to any value >= 1 and consulting the return value provides a quick way to check this property.
|
||
|
|
*/
|
||
|
|
ZSTD_c_nbWorkers=400, </b>/* Select how many threads will be spawned to compress in parallel.<b>
|
||
|
|
* When nbWorkers >= 1, triggers asynchronous mode when invoking ZSTD_compressStream*() :
|
||
|
|
* ZSTD_compressStream*() consumes input and flush output if possible, but immediately gives back control to caller,
|
||
|
|
* while compression is performed in parallel, within worker thread(s).
|
||
|
|
* (note : a strong exception to this rule is when first invocation of ZSTD_compressStream2() sets ZSTD_e_end :
|
||
|
|
* in which case, ZSTD_compressStream2() delegates to ZSTD_compress2(), which is always a blocking call).
|
||
|
|
* More workers improve speed, but also increase memory usage.
|
||
|
|
* Default value is `0`, aka "single-threaded mode" : no worker is spawned,
|
||
|
|
* compression is performed inside Caller's thread, and all invocations are blocking */
|
||
|
|
ZSTD_c_jobSize=401, </b>/* Size of a compression job. This value is enforced only when nbWorkers >= 1.<b>
|
||
|
|
* Each compression job is completed in parallel, so this value can indirectly impact the nb of active threads.
|
||
|
|
* 0 means default, which is dynamically determined based on compression parameters.
|
||
|
|
* Job size must be a minimum of overlap size, or ZSTDMT_JOBSIZE_MIN (= 512 KB), whichever is largest.
|
||
|
|
* The minimum size is automatically and transparently enforced. */
|
||
|
|
ZSTD_c_overlapLog=402, </b>/* Control the overlap size, as a fraction of window size.<b>
|
||
|
|
* The overlap size is an amount of data reloaded from previous job at the beginning of a new job.
|
||
|
|
* It helps preserve compression ratio, while each job is compressed in parallel.
|
||
|
|
* This value is enforced only when nbWorkers >= 1.
|
||
|
|
* Larger values increase compression ratio, but decrease speed.
|
||
|
|
* Possible values range from 0 to 9 :
|
||
|
|
* - 0 means "default" : value will be determined by the library, depending on strategy
|
||
|
|
* - 1 means "no overlap"
|
||
|
|
* - 9 means "full overlap", using a full window size.
|
||
|
|
* Each intermediate rank increases/decreases load size by a factor 2 :
|
||
|
|
* 9: full window; 8: w/2; 7: w/4; 6: w/8; 5:w/16; 4: w/32; 3:w/64; 2:w/128; 1:no overlap; 0:default
|
||
|
|
* default value varies between 6 and 9, depending on strategy */
|
||
|
|
|
||
|
|
</b>/* note : additional experimental parameters are also available<b>
|
||
|
|
* within the experimental section of the API.
|
||
|
|
* At the time of this writing, they include :
|
||
|
|
* ZSTD_c_rsyncable
|
||
|
|
* ZSTD_c_format
|
||
|
|
* ZSTD_c_forceMaxWindow
|
||
|
|
* ZSTD_c_forceAttachDict
|
||
|
|
* ZSTD_c_literalCompressionMode
|
||
|
|
* ZSTD_c_targetCBlockSize
|
||
|
|
* ZSTD_c_srcSizeHint
|
||
|
|
* ZSTD_c_enableDedicatedDictSearch
|
||
|
|
* ZSTD_c_stableInBuffer
|
||
|
|
* ZSTD_c_stableOutBuffer
|
||
|
|
* ZSTD_c_blockDelimiters
|
||
|
|
* ZSTD_c_validateSequences
|
||
|
|
* ZSTD_c_useBlockSplitter
|
||
|
|
* ZSTD_c_useRowMatchFinder
|
||
|
|
* ZSTD_c_prefetchCDictTables
|
||
|
|
* ZSTD_c_enableSeqProducerFallback
|
||
|
|
* ZSTD_c_maxBlockSize
|
||
|
|
* Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them.
|
||
|
|
* note : never ever use experimentalParam? names directly;
|
||
|
|
* also, the enums values themselves are unstable and can still change.
|
||
|
|
*/
|
||
|
|
ZSTD_c_experimentalParam1=500,
|
||
|
|
ZSTD_c_experimentalParam2=10,
|
||
|
|
ZSTD_c_experimentalParam3=1000,
|
||
|
|
ZSTD_c_experimentalParam4=1001,
|
||
|
|
ZSTD_c_experimentalParam5=1002,
|
||
|
|
ZSTD_c_experimentalParam6=1003,
|
||
|
|
ZSTD_c_experimentalParam7=1004,
|
||
|
|
ZSTD_c_experimentalParam8=1005,
|
||
|
|
ZSTD_c_experimentalParam9=1006,
|
||
|
|
ZSTD_c_experimentalParam10=1007,
|
||
|
|
ZSTD_c_experimentalParam11=1008,
|
||
|
|
ZSTD_c_experimentalParam12=1009,
|
||
|
|
ZSTD_c_experimentalParam13=1010,
|
||
|
|
ZSTD_c_experimentalParam14=1011,
|
||
|
|
ZSTD_c_experimentalParam15=1012,
|
||
|
|
ZSTD_c_experimentalParam16=1013,
|
||
|
|
ZSTD_c_experimentalParam17=1014,
|
||
|
|
ZSTD_c_experimentalParam18=1015,
|
||
|
|
ZSTD_c_experimentalParam19=1016
|
||
|
|
} ZSTD_cParameter;
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>typedef struct {
|
||
|
|
size_t error;
|
||
|
|
int lowerBound;
|
||
|
|
int upperBound;
|
||
|
|
} ZSTD_bounds;
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>ZSTD_bounds ZSTD_cParam_getBounds(ZSTD_cParameter cParam);
|
||
|
|
</b><p> All parameters must belong to an interval with lower and upper bounds,
|
||
|
|
otherwise they will either trigger an error or be automatically clamped.
|
||
|
|
@return : a structure, ZSTD_bounds, which contains
|
||
|
|
- an error status field, which must be tested using ZSTD_isError()
|
||
|
|
- lower and upper bounds, both inclusive
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int value);
|
||
|
|
</b><p> Set one compression parameter, selected by enum ZSTD_cParameter.
|
||
|
|
All parameters have valid bounds. Bounds can be queried using ZSTD_cParam_getBounds().
|
||
|
|
Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter).
|
||
|
|
Setting a parameter is generally only possible during frame initialization (before starting compression).
|
||
|
|
Exception : when using multi-threading mode (nbWorkers >= 1),
|
||
|
|
the following parameters can be updated _during_ compression (within same frame):
|
||
|
|
=> compressionLevel, hashLog, chainLog, searchLog, minMatch, targetLength and strategy.
|
||
|
|
new parameters will be active for next job only (after a flush()).
|
||
|
|
@return : an error code (which can be tested using ZSTD_isError()).
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>size_t ZSTD_CCtx_setPledgedSrcSize(ZSTD_CCtx* cctx, unsigned long long pledgedSrcSize);
|
||
|
|
</b><p> Total input data size to be compressed as a single frame.
|
||
|
|
Value will be written in frame header, unless if explicitly forbidden using ZSTD_c_contentSizeFlag.
|
||
|
|
This value will also be controlled at end of frame, and trigger an error if not respected.
|
||
|
|
@result : 0, or an error code (which can be tested with ZSTD_isError()).
|
||
|
|
Note 1 : pledgedSrcSize==0 actually means zero, aka an empty frame.
|
||
|
|
In order to mean "unknown content size", pass constant ZSTD_CONTENTSIZE_UNKNOWN.
|
||
|
|
ZSTD_CONTENTSIZE_UNKNOWN is default value for any new frame.
|
||
|
|
Note 2 : pledgedSrcSize is only valid once, for the next frame.
|
||
|
|
It's discarded at the end of the frame, and replaced by ZSTD_CONTENTSIZE_UNKNOWN.
|
||
|
|
Note 3 : Whenever all input data is provided and consumed in a single round,
|
||
|
|
for example with ZSTD_compress2(),
|
||
|
|
or invoking immediately ZSTD_compressStream2(,,,ZSTD_e_end),
|
||
|
|
this value is automatically overridden by srcSize instead.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>typedef enum {
|
||
|
|
ZSTD_reset_session_only = 1,
|
||
|
|
ZSTD_reset_parameters = 2,
|
||
|
|
ZSTD_reset_session_and_parameters = 3
|
||
|
|
} ZSTD_ResetDirective;
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>size_t ZSTD_CCtx_reset(ZSTD_CCtx* cctx, ZSTD_ResetDirective reset);
|
||
|
|
</b><p> There are 2 different things that can be reset, independently or jointly :
|
||
|
|
- The session : will stop compressing current frame, and make CCtx ready to start a new one.
|
||
|
|
Useful after an error, or to interrupt any ongoing compression.
|
||
|
|
Any internal data not yet flushed is cancelled.
|
||
|
|
Compression parameters and dictionary remain unchanged.
|
||
|
|
They will be used to compress next frame.
|
||
|
|
Resetting session never fails.
|
||
|
|
- The parameters : changes all parameters back to "default".
|
||
|
|
This also removes any reference to any dictionary or external sequence producer.
|
||
|
|
Parameters can only be changed between 2 sessions (i.e. no compression is currently ongoing)
|
||
|
|
otherwise the reset fails, and function returns an error value (which can be tested using ZSTD_isError())
|
||
|
|
- Both : similar to resetting the session, followed by resetting parameters.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>size_t ZSTD_compress2( ZSTD_CCtx* cctx,
|
||
|
|
void* dst, size_t dstCapacity,
|
||
|
|
const void* src, size_t srcSize);
|
||
|
|
</b><p> Behave the same as ZSTD_compressCCtx(), but compression parameters are set using the advanced API.
|
||
|
|
ZSTD_compress2() always starts a new frame.
|
||
|
|
Should cctx hold data from a previously unfinished frame, everything about it is forgotten.
|
||
|
|
- Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*()
|
||
|
|
- The function is always blocking, returns when compression is completed.
|
||
|
|
NOTE: Providing `dstCapacity >= ZSTD_compressBound(srcSize)` guarantees that zstd will have
|
||
|
|
enough space to successfully compress the data, though it is possible it fails for other reasons.
|
||
|
|
@return : compressed size written into `dst` (<= `dstCapacity),
|
||
|
|
or an error code if it fails (which can be tested using ZSTD_isError()).
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<a name="Chapter6"></a><h2>Advanced decompression API (Requires v1.4.0+)</h2><pre></pre>
|
||
|
|
|
||
|
|
<pre><b>typedef enum {
|
||
|
|
|
||
|
|
ZSTD_d_windowLogMax=100, </b>/* Select a size limit (in power of 2) beyond which<b>
|
||
|
|
* the streaming API will refuse to allocate memory buffer
|
||
|
|
* in order to protect the host from unreasonable memory requirements.
|
||
|
|
* This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode.
|
||
|
|
* By default, a decompression context accepts window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT).
|
||
|
|
* Special: value 0 means "use default maximum windowLog". */
|
||
|
|
|
||
|
|
</b>/* note : additional experimental parameters are also available<b>
|
||
|
|
* within the experimental section of the API.
|
||
|
|
* At the time of this writing, they include :
|
||
|
|
* ZSTD_d_format
|
||
|
|
* ZSTD_d_stableOutBuffer
|
||
|
|
* ZSTD_d_forceIgnoreChecksum
|
||
|
|
* ZSTD_d_refMultipleDDicts
|
||
|
|
* ZSTD_d_disableHuffmanAssembly
|
||
|
|
* ZSTD_d_maxBlockSize
|
||
|
|
* Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them.
|
||
|
|
* note : never ever use experimentalParam? names directly
|
||
|
|
*/
|
||
|
|
ZSTD_d_experimentalParam1=1000,
|
||
|
|
ZSTD_d_experimentalParam2=1001,
|
||
|
|
ZSTD_d_experimentalParam3=1002,
|
||
|
|
ZSTD_d_experimentalParam4=1003,
|
||
|
|
ZSTD_d_experimentalParam5=1004,
|
||
|
|
ZSTD_d_experimentalParam6=1005
|
||
|
|
|
||
|
|
} ZSTD_dParameter;
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>ZSTD_bounds ZSTD_dParam_getBounds(ZSTD_dParameter dParam);
|
||
|
|
</b><p> All parameters must belong to an interval with lower and upper bounds,
|
||
|
|
otherwise they will either trigger an error or be automatically clamped.
|
||
|
|
@return : a structure, ZSTD_bounds, which contains
|
||
|
|
- an error status field, which must be tested using ZSTD_isError()
|
||
|
|
- both lower and upper bounds, inclusive
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>size_t ZSTD_DCtx_setParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int value);
|
||
|
|
</b><p> Set one compression parameter, selected by enum ZSTD_dParameter.
|
||
|
|
All parameters have valid bounds. Bounds can be queried using ZSTD_dParam_getBounds().
|
||
|
|
Providing a value beyond bound will either clamp it, or trigger an error (depending on parameter).
|
||
|
|
Setting a parameter is only possible during frame initialization (before starting decompression).
|
||
|
|
@return : 0, or an error code (which can be tested using ZSTD_isError()).
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>size_t ZSTD_DCtx_reset(ZSTD_DCtx* dctx, ZSTD_ResetDirective reset);
|
||
|
|
</b><p> Return a DCtx to clean state.
|
||
|
|
Session and parameters can be reset jointly or separately.
|
||
|
|
Parameters can only be reset when no active frame is being decompressed.
|
||
|
|
@return : 0, or an error code, which can be tested with ZSTD_isError()
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<a name="Chapter7"></a><h2>Streaming</h2><pre></pre>
|
||
|
|
|
||
|
|
<pre><b>typedef struct ZSTD_inBuffer_s {
|
||
|
|
const void* src; </b>/**< start of input buffer */<b>
|
||
|
|
size_t size; </b>/**< size of input buffer */<b>
|
||
|
|
size_t pos; </b>/**< position where reading stopped. Will be updated. Necessarily 0 <= pos <= size */<b>
|
||
|
|
} ZSTD_inBuffer;
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>typedef struct ZSTD_outBuffer_s {
|
||
|
|
void* dst; </b>/**< start of output buffer */<b>
|
||
|
|
size_t size; </b>/**< size of output buffer */<b>
|
||
|
|
size_t pos; </b>/**< position where writing stopped. Will be updated. Necessarily 0 <= pos <= size */<b>
|
||
|
|
} ZSTD_outBuffer;
|
||
|
|
</b></pre><BR>
|
||
|
|
<a name="Chapter8"></a><h2>Streaming compression - HowTo</h2><pre>
|
||
|
|
A ZSTD_CStream object is required to track streaming operation.
|
||
|
|
Use ZSTD_createCStream() and ZSTD_freeCStream() to create/release resources.
|
||
|
|
ZSTD_CStream objects can be reused multiple times on consecutive compression operations.
|
||
|
|
It is recommended to reuse ZSTD_CStream since it will play nicer with system's memory, by re-using already allocated memory.
|
||
|
|
|
||
|
|
For parallel execution, use one separate ZSTD_CStream per thread.
|
||
|
|
|
||
|
|
note : since v1.3.0, ZSTD_CStream and ZSTD_CCtx are the same thing.
|
||
|
|
|
||
|
|
Parameters are sticky : when starting a new compression on the same context,
|
||
|
|
it will reuse the same sticky parameters as previous compression session.
|
||
|
|
When in doubt, it's recommended to fully initialize the context before usage.
|
||
|
|
Use ZSTD_CCtx_reset() to reset the context and ZSTD_CCtx_setParameter(),
|
||
|
|
ZSTD_CCtx_setPledgedSrcSize(), or ZSTD_CCtx_loadDictionary() and friends to
|
||
|
|
set more specific parameters, the pledged source size, or load a dictionary.
|
||
|
|
|
||
|
|
Use ZSTD_compressStream2() with ZSTD_e_continue as many times as necessary to
|
||
|
|
consume input stream. The function will automatically update both `pos`
|
||
|
|
fields within `input` and `output`.
|
||
|
|
Note that the function may not consume the entire input, for example, because
|
||
|
|
the output buffer is already full, in which case `input.pos < input.size`.
|
||
|
|
The caller must check if input has been entirely consumed.
|
||
|
|
If not, the caller must make some room to receive more compressed data,
|
||
|
|
and then present again remaining input data.
|
||
|
|
note: ZSTD_e_continue is guaranteed to make some forward progress when called,
|
||
|
|
but doesn't guarantee maximal forward progress. This is especially relevant
|
||
|
|
when compressing with multiple threads. The call won't block if it can
|
||
|
|
consume some input, but if it can't it will wait for some, but not all,
|
||
|
|
output to be flushed.
|
||
|
|
@return : provides a minimum amount of data remaining to be flushed from internal buffers
|
||
|
|
or an error code, which can be tested using ZSTD_isError().
|
||
|
|
|
||
|
|
At any moment, it's possible to flush whatever data might remain stuck within internal buffer,
|
||
|
|
using ZSTD_compressStream2() with ZSTD_e_flush. `output->pos` will be updated.
|
||
|
|
Note that, if `output->size` is too small, a single invocation with ZSTD_e_flush might not be enough (return code > 0).
|
||
|
|
In which case, make some room to receive more compressed data, and call again ZSTD_compressStream2() with ZSTD_e_flush.
|
||
|
|
You must continue calling ZSTD_compressStream2() with ZSTD_e_flush until it returns 0, at which point you can change the
|
||
|
|
operation.
|
||
|
|
note: ZSTD_e_flush will flush as much output as possible, meaning when compressing with multiple threads, it will
|
||
|
|
block until the flush is complete or the output buffer is full.
|
||
|
|
@return : 0 if internal buffers are entirely flushed,
|
||
|
|
>0 if some data still present within internal buffer (the value is minimal estimation of remaining size),
|
||
|
|
or an error code, which can be tested using ZSTD_isError().
|
||
|
|
|
||
|
|
Calling ZSTD_compressStream2() with ZSTD_e_end instructs to finish a frame.
|
||
|
|
It will perform a flush and write frame epilogue.
|
||
|
|
The epilogue is required for decoders to consider a frame completed.
|
||
|
|
flush operation is the same, and follows same rules as calling ZSTD_compressStream2() with ZSTD_e_flush.
|
||
|
|
You must continue calling ZSTD_compressStream2() with ZSTD_e_end until it returns 0, at which point you are free to
|
||
|
|
start a new frame.
|
||
|
|
note: ZSTD_e_end will flush as much output as possible, meaning when compressing with multiple threads, it will
|
||
|
|
block until the flush is complete or the output buffer is full.
|
||
|
|
@return : 0 if frame fully completed and fully flushed,
|
||
|
|
>0 if some data still present within internal buffer (the value is minimal estimation of remaining size),
|
||
|
|
or an error code, which can be tested using ZSTD_isError().
|
||
|
|
|
||
|
|
|
||
|
|
<BR></pre>
|
||
|
|
|
||
|
|
<pre><b>typedef ZSTD_CCtx ZSTD_CStream; </b>/**< CCtx and CStream are now effectively same object (>= v1.3.0) */<b>
|
||
|
|
</b></pre><BR>
|
||
|
|
<h3>ZSTD_CStream management functions</h3><pre></pre><b><pre>ZSTD_CStream* ZSTD_createCStream(void);
|
||
|
|
size_t ZSTD_freeCStream(ZSTD_CStream* zcs); </b>/* accept NULL pointer */<b>
|
||
|
|
</pre></b><BR>
|
||
|
|
<h3>Streaming compression functions</h3><pre></pre><b><pre>typedef enum {
|
||
|
|
ZSTD_e_continue=0, </b>/* collect more data, encoder decides when to output compressed result, for optimal compression ratio */<b>
|
||
|
|
ZSTD_e_flush=1, </b>/* flush any data provided so far,<b>
|
||
|
|
* it creates (at least) one new block, that can be decoded immediately on reception;
|
||
|
|
* frame will continue: any future data can still reference previously compressed data, improving compression.
|
||
|
|
* note : multithreaded compression will block to flush as much output as possible. */
|
||
|
|
ZSTD_e_end=2 </b>/* flush any remaining data _and_ close current frame.<b>
|
||
|
|
* note that frame is only closed after compressed data is fully flushed (return value == 0).
|
||
|
|
* After that point, any additional data starts a new frame.
|
||
|
|
* note : each frame is independent (does not reference any content from previous frame).
|
||
|
|
: note : multithreaded compression will block to flush as much output as possible. */
|
||
|
|
} ZSTD_EndDirective;
|
||
|
|
</pre></b><BR>
|
||
|
|
<pre><b>size_t ZSTD_compressStream2( ZSTD_CCtx* cctx,
|
||
|
|
ZSTD_outBuffer* output,
|
||
|
|
ZSTD_inBuffer* input,
|
||
|
|
ZSTD_EndDirective endOp);
|
||
|
|
</b><p> Behaves about the same as ZSTD_compressStream, with additional control on end directive.
|
||
|
|
- Compression parameters are pushed into CCtx before starting compression, using ZSTD_CCtx_set*()
|
||
|
|
- Compression parameters cannot be changed once compression is started (save a list of exceptions in multi-threading mode)
|
||
|
|
- output->pos must be <= dstCapacity, input->pos must be <= srcSize
|
||
|
|
- output->pos and input->pos will be updated. They are guaranteed to remain below their respective limit.
|
||
|
|
- endOp must be a valid directive
|
||
|
|
- When nbWorkers==0 (default), function is blocking : it completes its job before returning to caller.
|
||
|
|
- When nbWorkers>=1, function is non-blocking : it copies a portion of input, distributes jobs to internal worker threads, flush to output whatever is available,
|
||
|
|
and then immediately returns, just indicating that there is some data remaining to be flushed.
|
||
|
|
The function nonetheless guarantees forward progress : it will return only after it reads or write at least 1+ byte.
|
||
|
|
- Exception : if the first call requests a ZSTD_e_end directive and provides enough dstCapacity, the function delegates to ZSTD_compress2() which is always blocking.
|
||
|
|
- @return provides a minimum amount of data remaining to be flushed from internal buffers
|
||
|
|
or an error code, which can be tested using ZSTD_isError().
|
||
|
|
if @return != 0, flush is not fully completed, there is still some data left within internal buffers.
|
||
|
|
This is useful for ZSTD_e_flush, since in this case more flushes are necessary to empty all buffers.
|
||
|
|
For ZSTD_e_end, @return == 0 when internal buffers are fully flushed and frame is completed.
|
||
|
|
- after a ZSTD_e_end directive, if internal buffer is not fully flushed (@return != 0),
|
||
|
|
only ZSTD_e_end or ZSTD_e_flush operations are allowed.
|
||
|
|
Before starting a new compression job, or changing compression parameters,
|
||
|
|
it is required to fully flush internal buffers.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>size_t ZSTD_CStreamInSize(void); </b>/**< recommended size for input buffer */<b>
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>size_t ZSTD_CStreamOutSize(void); </b>/**< recommended size for output buffer. Guarantee to successfully flush at least one complete compressed block. */<b>
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>size_t ZSTD_initCStream(ZSTD_CStream* zcs, int compressionLevel);
|
||
|
|
</b>/*!<b>
|
||
|
|
* Alternative for ZSTD_compressStream2(zcs, output, input, ZSTD_e_continue).
|
||
|
|
* NOTE: The return value is different. ZSTD_compressStream() returns a hint for
|
||
|
|
* the next read size (if non-zero and not an error). ZSTD_compressStream2()
|
||
|
|
* returns the minimum nb of bytes left to flush (if non-zero and not an error).
|
||
|
|
*/
|
||
|
|
size_t ZSTD_compressStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
|
||
|
|
</b>/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_flush). */<b>
|
||
|
|
size_t ZSTD_flushStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
|
||
|
|
</b>/*! Equivalent to ZSTD_compressStream2(zcs, output, &emptyInput, ZSTD_e_end). */<b>
|
||
|
|
size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output);
|
||
|
|
</b><p>
|
||
|
|
ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
|
||
|
|
ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any)
|
||
|
|
ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
|
||
|
|
|
||
|
|
Note that ZSTD_initCStream() clears any previously set dictionary. Use the new API
|
||
|
|
to compress with a dictionary.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<a name="Chapter9"></a><h2>Streaming decompression - HowTo</h2><pre>
|
||
|
|
A ZSTD_DStream object is required to track streaming operations.
|
||
|
|
Use ZSTD_createDStream() and ZSTD_freeDStream() to create/release resources.
|
||
|
|
ZSTD_DStream objects can be reused multiple times.
|
||
|
|
|
||
|
|
Use ZSTD_initDStream() to start a new decompression operation.
|
||
|
|
@return : recommended first input size
|
||
|
|
Alternatively, use advanced API to set specific properties.
|
||
|
|
|
||
|
|
Use ZSTD_decompressStream() repetitively to consume your input.
|
||
|
|
The function will update both `pos` fields.
|
||
|
|
If `input.pos < input.size`, some input has not been consumed.
|
||
|
|
It's up to the caller to present again remaining data.
|
||
|
|
The function tries to flush all data decoded immediately, respecting output buffer size.
|
||
|
|
If `output.pos < output.size`, decoder has flushed everything it could.
|
||
|
|
But if `output.pos == output.size`, there might be some data left within internal buffers.,
|
||
|
|
In which case, call ZSTD_decompressStream() again to flush whatever remains in the buffer.
|
||
|
|
Note : with no additional input provided, amount of data flushed is necessarily <= ZSTD_BLOCKSIZE_MAX.
|
||
|
|
@return : 0 when a frame is completely decoded and fully flushed,
|
||
|
|
or an error code, which can be tested using ZSTD_isError(),
|
||
|
|
or any other value > 0, which means there is still some decoding or flushing to do to complete current frame :
|
||
|
|
the return value is a suggested next input size (just a hint for better latency)
|
||
|
|
that will never request more than the remaining frame size.
|
||
|
|
|
||
|
|
<BR></pre>
|
||
|
|
|
||
|
|
<pre><b>typedef ZSTD_DCtx ZSTD_DStream; </b>/**< DCtx and DStream are now effectively same object (>= v1.3.0) */<b>
|
||
|
|
</b></pre><BR>
|
||
|
|
<h3>ZSTD_DStream management functions</h3><pre></pre><b><pre>ZSTD_DStream* ZSTD_createDStream(void);
|
||
|
|
size_t ZSTD_freeDStream(ZSTD_DStream* zds); </b>/* accept NULL pointer */<b>
|
||
|
|
</pre></b><BR>
|
||
|
|
<h3>Streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR>
|
||
|
|
<pre><b>size_t ZSTD_initDStream(ZSTD_DStream* zds);
|
||
|
|
</b><p> Initialize/reset DStream state for new decompression operation.
|
||
|
|
Call before new decompression operation using same DStream.
|
||
|
|
|
||
|
|
Note : This function is redundant with the advanced API and equivalent to:
|
||
|
|
ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
|
||
|
|
ZSTD_DCtx_refDDict(zds, NULL);
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input);
|
||
|
|
</b><p> Streaming decompression function.
|
||
|
|
Call repetitively to consume full input updating it as necessary.
|
||
|
|
Function will update both input and output `pos` fields exposing current state via these fields:
|
||
|
|
- `input.pos < input.size`, some input remaining and caller should provide remaining input
|
||
|
|
on the next call.
|
||
|
|
- `output.pos < output.size`, decoder finished and flushed all remaining buffers.
|
||
|
|
- `output.pos == output.size`, potentially uncflushed data present in the internal buffers,
|
||
|
|
call ZSTD_decompressStream() again to flush remaining data to output.
|
||
|
|
Note : with no additional input, amount of data flushed <= ZSTD_BLOCKSIZE_MAX.
|
||
|
|
|
||
|
|
@return : 0 when a frame is completely decoded and fully flushed,
|
||
|
|
or an error code, which can be tested using ZSTD_isError(),
|
||
|
|
or any other value > 0, which means there is some decoding or flushing to do to complete current frame.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>size_t ZSTD_DStreamInSize(void); </b>/*!< recommended size for input buffer */<b>
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>size_t ZSTD_DStreamOutSize(void); </b>/*!< recommended size for output buffer. Guarantee to successfully flush at least one complete block in all circumstances. */<b>
|
||
|
|
</b></pre><BR>
|
||
|
|
<a name="Chapter10"></a><h2>Simple dictionary API</h2><pre></pre>
|
||
|
|
|
||
|
|
<pre><b>size_t ZSTD_compress_usingDict(ZSTD_CCtx* ctx,
|
||
|
|
void* dst, size_t dstCapacity,
|
||
|
|
const void* src, size_t srcSize,
|
||
|
|
const void* dict,size_t dictSize,
|
||
|
|
int compressionLevel);
|
||
|
|
</b><p> Compression at an explicit compression level using a Dictionary.
|
||
|
|
A dictionary can be any arbitrary data segment (also called a prefix),
|
||
|
|
or a buffer with specified information (see zdict.h).
|
||
|
|
Note : This function loads the dictionary, resulting in significant startup delay.
|
||
|
|
It's intended for a dictionary used only once.
|
||
|
|
Note 2 : When `dict == NULL || dictSize < 8` no dictionary is used.
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx,
|
||
|
|
void* dst, size_t dstCapacity,
|
||
|
|
const void* src, size_t srcSize,
|
||
|
|
const void* dict,size_t dictSize);
|
||
|
|
</b><p> Decompression using a known Dictionary.
|
||
|
|
Dictionary must be identical to the one used during compression.
|
||
|
|
Note : This function loads the dictionary, resulting in significant startup delay.
|
||
|
|
It's intended for a dictionary used only once.
|
||
|
|
Note : When `dict == NULL || dictSize < 8` no dictionary is used.
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<a name="Chapter11"></a><h2>Bulk processing dictionary API</h2><pre></pre>
|
||
|
|
|
||
|
|
<pre><b>ZSTD_CDict* ZSTD_createCDict(const void* dictBuffer, size_t dictSize,
|
||
|
|
int compressionLevel);
|
||
|
|
</b><p> When compressing multiple messages or blocks using the same dictionary,
|
||
|
|
it's recommended to digest the dictionary only once, since it's a costly operation.
|
||
|
|
ZSTD_createCDict() will create a state from digesting a dictionary.
|
||
|
|
The resulting state can be used for future compression operations with very limited startup cost.
|
||
|
|
ZSTD_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only.
|
||
|
|
@dictBuffer can be released after ZSTD_CDict creation, because its content is copied within CDict.
|
||
|
|
Note 1 : Consider experimental function `ZSTD_createCDict_byReference()` if you prefer to not duplicate @dictBuffer content.
|
||
|
|
Note 2 : A ZSTD_CDict can be created from an empty @dictBuffer,
|
||
|
|
in which case the only thing that it transports is the @compressionLevel.
|
||
|
|
This can be useful in a pipeline featuring ZSTD_compress_usingCDict() exclusively,
|
||
|
|
expecting a ZSTD_CDict parameter with any data, including those without a known dictionary.
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>size_t ZSTD_freeCDict(ZSTD_CDict* CDict);
|
||
|
|
</b><p> Function frees memory allocated by ZSTD_createCDict().
|
||
|
|
If a NULL pointer is passed, no operation is performed.
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>size_t ZSTD_compress_usingCDict(ZSTD_CCtx* cctx,
|
||
|
|
void* dst, size_t dstCapacity,
|
||
|
|
const void* src, size_t srcSize,
|
||
|
|
const ZSTD_CDict* cdict);
|
||
|
|
</b><p> Compression using a digested Dictionary.
|
||
|
|
Recommended when same dictionary is used multiple times.
|
||
|
|
Note : compression level is _decided at dictionary creation time_,
|
||
|
|
and frame parameters are hardcoded (dictID=yes, contentSize=yes, checksum=no)
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTD_DDict* ZSTD_createDDict(const void* dictBuffer, size_t dictSize);
|
||
|
|
</b><p> Create a digested dictionary, ready to start decompression operation without startup delay.
|
||
|
|
dictBuffer can be released after DDict creation, as its content is copied inside DDict.
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>size_t ZSTD_freeDDict(ZSTD_DDict* ddict);
|
||
|
|
</b><p> Function frees memory allocated with ZSTD_createDDict()
|
||
|
|
If a NULL pointer is passed, no operation is performed.
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx,
|
||
|
|
void* dst, size_t dstCapacity,
|
||
|
|
const void* src, size_t srcSize,
|
||
|
|
const ZSTD_DDict* ddict);
|
||
|
|
</b><p> Decompression using a digested Dictionary.
|
||
|
|
Recommended when same dictionary is used multiple times.
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<a name="Chapter12"></a><h2>Dictionary helper functions</h2><pre></pre>
|
||
|
|
|
||
|
|
<pre><b>unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize);
|
||
|
|
</b><p> Provides the dictID stored within dictionary.
|
||
|
|
if @return == 0, the dictionary is not conformant with Zstandard specification.
|
||
|
|
It can still be loaded, but as a content-only dictionary.
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>unsigned ZSTD_getDictID_fromCDict(const ZSTD_CDict* cdict);
|
||
|
|
</b><p> Provides the dictID of the dictionary loaded into `cdict`.
|
||
|
|
If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
|
||
|
|
Non-conformant dictionaries can still be loaded, but as content-only dictionaries.
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>unsigned ZSTD_getDictID_fromDDict(const ZSTD_DDict* ddict);
|
||
|
|
</b><p> Provides the dictID of the dictionary loaded into `ddict`.
|
||
|
|
If @return == 0, the dictionary is not conformant to Zstandard specification, or empty.
|
||
|
|
Non-conformant dictionaries can still be loaded, but as content-only dictionaries.
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize);
|
||
|
|
</b><p> Provides the dictID required to decompressed the frame stored within `src`.
|
||
|
|
If @return == 0, the dictID could not be decoded.
|
||
|
|
This could for one of the following reasons :
|
||
|
|
- The frame does not require a dictionary to be decoded (most common case).
|
||
|
|
- The frame was built with dictID intentionally removed. Whatever dictionary is necessary is a hidden piece of information.
|
||
|
|
Note : this use case also happens when using a non-conformant dictionary.
|
||
|
|
- `srcSize` is too small, and as a result, the frame header could not be decoded (only possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`).
|
||
|
|
- This is not a Zstandard frame.
|
||
|
|
When identifying the exact failure cause, it's possible to use ZSTD_getFrameHeader(), which will provide a more precise error code.
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<a name="Chapter13"></a><h2>Advanced dictionary and prefix API (Requires v1.4.0+)</h2><pre>
|
||
|
|
This API allows dictionaries to be used with ZSTD_compress2(),
|
||
|
|
ZSTD_compressStream2(), and ZSTD_decompressDCtx().
|
||
|
|
Dictionaries are sticky, they remain valid when same context is reused,
|
||
|
|
they only reset when the context is reset
|
||
|
|
with ZSTD_reset_parameters or ZSTD_reset_session_and_parameters.
|
||
|
|
In contrast, Prefixes are single-use.
|
||
|
|
<BR></pre>
|
||
|
|
|
||
|
|
<pre><b>size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
|
||
|
|
</b><p> Create an internal CDict from `dict` buffer.
|
||
|
|
Decompression will have to use same dictionary.
|
||
|
|
@result : 0, or an error code (which can be tested with ZSTD_isError()).
|
||
|
|
Special: Loading a NULL (or 0-size) dictionary invalidates previous dictionary,
|
||
|
|
meaning "return to no-dictionary mode".
|
||
|
|
Note 1 : Dictionary is sticky, it will be used for all future compressed frames,
|
||
|
|
until parameters are reset, a new dictionary is loaded, or the dictionary
|
||
|
|
is explicitly invalidated by loading a NULL dictionary.
|
||
|
|
Note 2 : Loading a dictionary involves building tables.
|
||
|
|
It's also a CPU consuming operation, with non-negligible impact on latency.
|
||
|
|
Tables are dependent on compression parameters, and for this reason,
|
||
|
|
compression parameters can no longer be changed after loading a dictionary.
|
||
|
|
Note 3 :`dict` content will be copied internally.
|
||
|
|
Use experimental ZSTD_CCtx_loadDictionary_byReference() to reference content instead.
|
||
|
|
In such a case, dictionary buffer must outlive its users.
|
||
|
|
Note 4 : Use ZSTD_CCtx_loadDictionary_advanced()
|
||
|
|
to precisely select how dictionary content must be interpreted.
|
||
|
|
Note 5 : This method does not benefit from LDM (long distance mode).
|
||
|
|
If you want to employ LDM on some large dictionary content,
|
||
|
|
prefer employing ZSTD_CCtx_refPrefix() described below.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>size_t ZSTD_CCtx_refCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict);
|
||
|
|
</b><p> Reference a prepared dictionary, to be used for all future compressed frames.
|
||
|
|
Note that compression parameters are enforced from within CDict,
|
||
|
|
and supersede any compression parameter previously set within CCtx.
|
||
|
|
The parameters ignored are labelled as "superseded-by-cdict" in the ZSTD_cParameter enum docs.
|
||
|
|
The ignored parameters will be used again if the CCtx is returned to no-dictionary mode.
|
||
|
|
The dictionary will remain valid for future compressed frames using same CCtx.
|
||
|
|
@result : 0, or an error code (which can be tested with ZSTD_isError()).
|
||
|
|
Special : Referencing a NULL CDict means "return to no-dictionary mode".
|
||
|
|
Note 1 : Currently, only one dictionary can be managed.
|
||
|
|
Referencing a new dictionary effectively "discards" any previous one.
|
||
|
|
Note 2 : CDict is just referenced, its lifetime must outlive its usage within CCtx.
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>size_t ZSTD_CCtx_refPrefix(ZSTD_CCtx* cctx,
|
||
|
|
const void* prefix, size_t prefixSize);
|
||
|
|
</b><p> Reference a prefix (single-usage dictionary) for next compressed frame.
|
||
|
|
A prefix is **only used once**. Tables are discarded at end of frame (ZSTD_e_end).
|
||
|
|
Decompression will need same prefix to properly regenerate data.
|
||
|
|
Compressing with a prefix is similar in outcome as performing a diff and compressing it,
|
||
|
|
but performs much faster, especially during decompression (compression speed is tunable with compression level).
|
||
|
|
This method is compatible with LDM (long distance mode).
|
||
|
|
@result : 0, or an error code (which can be tested with ZSTD_isError()).
|
||
|
|
Special: Adding any prefix (including NULL) invalidates any previous prefix or dictionary
|
||
|
|
Note 1 : Prefix buffer is referenced. It **must** outlive compression.
|
||
|
|
Its content must remain unmodified during compression.
|
||
|
|
Note 2 : If the intention is to diff some large src data blob with some prior version of itself,
|
||
|
|
ensure that the window size is large enough to contain the entire source.
|
||
|
|
See ZSTD_c_windowLog.
|
||
|
|
Note 3 : Referencing a prefix involves building tables, which are dependent on compression parameters.
|
||
|
|
It's a CPU consuming operation, with non-negligible impact on latency.
|
||
|
|
If there is a need to use the same prefix multiple times, consider loadDictionary instead.
|
||
|
|
Note 4 : By default, the prefix is interpreted as raw content (ZSTD_dct_rawContent).
|
||
|
|
Use experimental ZSTD_CCtx_refPrefix_advanced() to alter dictionary interpretation.
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>size_t ZSTD_DCtx_loadDictionary(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
|
||
|
|
</b><p> Create an internal DDict from dict buffer, to be used to decompress all future frames.
|
||
|
|
The dictionary remains valid for all future frames, until explicitly invalidated, or
|
||
|
|
a new dictionary is loaded.
|
||
|
|
@result : 0, or an error code (which can be tested with ZSTD_isError()).
|
||
|
|
Special : Adding a NULL (or 0-size) dictionary invalidates any previous dictionary,
|
||
|
|
meaning "return to no-dictionary mode".
|
||
|
|
Note 1 : Loading a dictionary involves building tables,
|
||
|
|
which has a non-negligible impact on CPU usage and latency.
|
||
|
|
It's recommended to "load once, use many times", to amortize the cost
|
||
|
|
Note 2 :`dict` content will be copied internally, so `dict` can be released after loading.
|
||
|
|
Use ZSTD_DCtx_loadDictionary_byReference() to reference dictionary content instead.
|
||
|
|
Note 3 : Use ZSTD_DCtx_loadDictionary_advanced() to take control of
|
||
|
|
how dictionary content is loaded and interpreted.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>size_t ZSTD_DCtx_refDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict);
|
||
|
|
</b><p> Reference a prepared dictionary, to be used to decompress next frames.
|
||
|
|
The dictionary remains active for decompression of future frames using same DCtx.
|
||
|
|
|
||
|
|
If called with ZSTD_d_refMultipleDDicts enabled, repeated calls of this function
|
||
|
|
will store the DDict references in a table, and the DDict used for decompression
|
||
|
|
will be determined at decompression time, as per the dict ID in the frame.
|
||
|
|
The memory for the table is allocated on the first call to refDDict, and can be
|
||
|
|
freed with ZSTD_freeDCtx().
|
||
|
|
|
||
|
|
If called with ZSTD_d_refMultipleDDicts disabled (the default), only one dictionary
|
||
|
|
will be managed, and referencing a dictionary effectively "discards" any previous one.
|
||
|
|
|
||
|
|
@result : 0, or an error code (which can be tested with ZSTD_isError()).
|
||
|
|
Special: referencing a NULL DDict means "return to no-dictionary mode".
|
||
|
|
Note 2 : DDict is just referenced, its lifetime must outlive its usage from DCtx.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>size_t ZSTD_DCtx_refPrefix(ZSTD_DCtx* dctx,
|
||
|
|
const void* prefix, size_t prefixSize);
|
||
|
|
</b><p> Reference a prefix (single-usage dictionary) to decompress next frame.
|
||
|
|
This is the reverse operation of ZSTD_CCtx_refPrefix(),
|
||
|
|
and must use the same prefix as the one used during compression.
|
||
|
|
Prefix is **only used once**. Reference is discarded at end of frame.
|
||
|
|
End of frame is reached when ZSTD_decompressStream() returns 0.
|
||
|
|
@result : 0, or an error code (which can be tested with ZSTD_isError()).
|
||
|
|
Note 1 : Adding any prefix (including NULL) invalidates any previously set prefix or dictionary
|
||
|
|
Note 2 : Prefix buffer is referenced. It **must** outlive decompression.
|
||
|
|
Prefix buffer must remain unmodified up to the end of frame,
|
||
|
|
reached when ZSTD_decompressStream() returns 0.
|
||
|
|
Note 3 : By default, the prefix is treated as raw content (ZSTD_dct_rawContent).
|
||
|
|
Use ZSTD_CCtx_refPrefix_advanced() to alter dictMode (Experimental section)
|
||
|
|
Note 4 : Referencing a raw content prefix has almost no cpu nor memory cost.
|
||
|
|
A full dictionary is more costly, as it requires building tables.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>size_t ZSTD_sizeof_CCtx(const ZSTD_CCtx* cctx);
|
||
|
|
size_t ZSTD_sizeof_DCtx(const ZSTD_DCtx* dctx);
|
||
|
|
size_t ZSTD_sizeof_CStream(const ZSTD_CStream* zcs);
|
||
|
|
size_t ZSTD_sizeof_DStream(const ZSTD_DStream* zds);
|
||
|
|
size_t ZSTD_sizeof_CDict(const ZSTD_CDict* cdict);
|
||
|
|
size_t ZSTD_sizeof_DDict(const ZSTD_DDict* ddict);
|
||
|
|
</b><p> These functions give the _current_ memory usage of selected object.
|
||
|
|
Note that object memory usage can evolve (increase or decrease) over time.
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<a name="Chapter14"></a><h2>experimental API (static linking only)</h2><pre>
|
||
|
|
The following symbols and constants
|
||
|
|
are not planned to join "stable API" status in the near future.
|
||
|
|
They can still change in future versions.
|
||
|
|
Some of them are planned to remain in the static_only section indefinitely.
|
||
|
|
Some of them might be removed in the future (especially when redundant with existing stable functions)
|
||
|
|
|
||
|
|
<BR></pre>
|
||
|
|
|
||
|
|
<pre><b>typedef struct {
|
||
|
|
unsigned int offset; </b>/* The offset of the match. (NOT the same as the offset code)<b>
|
||
|
|
* If offset == 0 and matchLength == 0, this sequence represents the last
|
||
|
|
* literals in the block of litLength size.
|
||
|
|
*/
|
||
|
|
|
||
|
|
unsigned int litLength; </b>/* Literal length of the sequence. */<b>
|
||
|
|
unsigned int matchLength; </b>/* Match length of the sequence. */<b>
|
||
|
|
|
||
|
|
</b>/* Note: Users of this API may provide a sequence with matchLength == litLength == offset == 0.<b>
|
||
|
|
* In this case, we will treat the sequence as a marker for a block boundary.
|
||
|
|
*/
|
||
|
|
|
||
|
|
unsigned int rep; </b>/* Represents which repeat offset is represented by the field 'offset'.<b>
|
||
|
|
* Ranges from [0, 3].
|
||
|
|
*
|
||
|
|
* Repeat offsets are essentially previous offsets from previous sequences sorted in
|
||
|
|
* recency order. For more detail, see doc/zstd_compression_format.md
|
||
|
|
*
|
||
|
|
* If rep == 0, then 'offset' does not contain a repeat offset.
|
||
|
|
* If rep > 0:
|
||
|
|
* If litLength != 0:
|
||
|
|
* rep == 1 --> offset == repeat_offset_1
|
||
|
|
* rep == 2 --> offset == repeat_offset_2
|
||
|
|
* rep == 3 --> offset == repeat_offset_3
|
||
|
|
* If litLength == 0:
|
||
|
|
* rep == 1 --> offset == repeat_offset_2
|
||
|
|
* rep == 2 --> offset == repeat_offset_3
|
||
|
|
* rep == 3 --> offset == repeat_offset_1 - 1
|
||
|
|
*
|
||
|
|
* Note: This field is optional. ZSTD_generateSequences() will calculate the value of
|
||
|
|
* 'rep', but repeat offsets do not necessarily need to be calculated from an external
|
||
|
|
* sequence provider's perspective. For example, ZSTD_compressSequences() does not
|
||
|
|
* use this 'rep' field at all (as of now).
|
||
|
|
*/
|
||
|
|
} ZSTD_Sequence;
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>typedef struct {
|
||
|
|
unsigned windowLog; </b>/**< largest match distance : larger == more compression, more memory needed during decompression */<b>
|
||
|
|
unsigned chainLog; </b>/**< fully searched segment : larger == more compression, slower, more memory (useless for fast) */<b>
|
||
|
|
unsigned hashLog; </b>/**< dispatch table : larger == faster, more memory */<b>
|
||
|
|
unsigned searchLog; </b>/**< nb of searches : larger == more compression, slower */<b>
|
||
|
|
unsigned minMatch; </b>/**< match length searched : larger == faster decompression, sometimes less compression */<b>
|
||
|
|
unsigned targetLength; </b>/**< acceptable match size for optimal parser (only) : larger == more compression, slower */<b>
|
||
|
|
ZSTD_strategy strategy; </b>/**< see ZSTD_strategy definition above */<b>
|
||
|
|
} ZSTD_compressionParameters;
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>typedef struct {
|
||
|
|
int contentSizeFlag; </b>/**< 1: content size will be in frame header (when known) */<b>
|
||
|
|
int checksumFlag; </b>/**< 1: generate a 32-bits checksum using XXH64 algorithm at end of frame, for error detection */<b>
|
||
|
|
int noDictIDFlag; </b>/**< 1: no dictID will be saved into frame header (dictID is only useful for dictionary compression) */<b>
|
||
|
|
} ZSTD_frameParameters;
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>typedef struct {
|
||
|
|
ZSTD_compressionParameters cParams;
|
||
|
|
ZSTD_frameParameters fParams;
|
||
|
|
} ZSTD_parameters;
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>typedef enum {
|
||
|
|
ZSTD_dct_auto = 0, </b>/* dictionary is "full" when starting with ZSTD_MAGIC_DICTIONARY, otherwise it is "rawContent" */<b>
|
||
|
|
ZSTD_dct_rawContent = 1, </b>/* ensures dictionary is always loaded as rawContent, even if it starts with ZSTD_MAGIC_DICTIONARY */<b>
|
||
|
|
ZSTD_dct_fullDict = 2 </b>/* refuses to load a dictionary if it does not respect Zstandard's specification, starting with ZSTD_MAGIC_DICTIONARY */<b>
|
||
|
|
} ZSTD_dictContentType_e;
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>typedef enum {
|
||
|
|
ZSTD_dlm_byCopy = 0, </b>/**< Copy dictionary content internally */<b>
|
||
|
|
ZSTD_dlm_byRef = 1 </b>/**< Reference dictionary content -- the dictionary buffer must outlive its users. */<b>
|
||
|
|
} ZSTD_dictLoadMethod_e;
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>typedef enum {
|
||
|
|
ZSTD_f_zstd1 = 0, </b>/* zstd frame format, specified in zstd_compression_format.md (default) */<b>
|
||
|
|
ZSTD_f_zstd1_magicless = 1 </b>/* Variant of zstd frame format, without initial 4-bytes magic number.<b>
|
||
|
|
* Useful to save 4 bytes per generated frame.
|
||
|
|
* Decoder cannot recognise automatically this format, requiring this instruction. */
|
||
|
|
} ZSTD_format_e;
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>typedef enum {
|
||
|
|
</b>/* Note: this enum controls ZSTD_d_forceIgnoreChecksum */<b>
|
||
|
|
ZSTD_d_validateChecksum = 0,
|
||
|
|
ZSTD_d_ignoreChecksum = 1
|
||
|
|
} ZSTD_forceIgnoreChecksum_e;
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>typedef enum {
|
||
|
|
</b>/* Note: this enum controls ZSTD_d_refMultipleDDicts */<b>
|
||
|
|
ZSTD_rmd_refSingleDDict = 0,
|
||
|
|
ZSTD_rmd_refMultipleDDicts = 1
|
||
|
|
} ZSTD_refMultipleDDicts_e;
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>typedef enum {
|
||
|
|
</b>/* Note: this enum and the behavior it controls are effectively internal<b>
|
||
|
|
* implementation details of the compressor. They are expected to continue
|
||
|
|
* to evolve and should be considered only in the context of extremely
|
||
|
|
* advanced performance tuning.
|
||
|
|
*
|
||
|
|
* Zstd currently supports the use of a CDict in three ways:
|
||
|
|
*
|
||
|
|
* - The contents of the CDict can be copied into the working context. This
|
||
|
|
* means that the compression can search both the dictionary and input
|
||
|
|
* while operating on a single set of internal tables. This makes
|
||
|
|
* the compression faster per-byte of input. However, the initial copy of
|
||
|
|
* the CDict's tables incurs a fixed cost at the beginning of the
|
||
|
|
* compression. For small compressions (< 8 KB), that copy can dominate
|
||
|
|
* the cost of the compression.
|
||
|
|
*
|
||
|
|
* - The CDict's tables can be used in-place. In this model, compression is
|
||
|
|
* slower per input byte, because the compressor has to search two sets of
|
||
|
|
* tables. However, this model incurs no start-up cost (as long as the
|
||
|
|
* working context's tables can be reused). For small inputs, this can be
|
||
|
|
* faster than copying the CDict's tables.
|
||
|
|
*
|
||
|
|
* - The CDict's tables are not used at all, and instead we use the working
|
||
|
|
* context alone to reload the dictionary and use params based on the source
|
||
|
|
* size. See ZSTD_compress_insertDictionary() and ZSTD_compress_usingDict().
|
||
|
|
* This method is effective when the dictionary sizes are very small relative
|
||
|
|
* to the input size, and the input size is fairly large to begin with.
|
||
|
|
*
|
||
|
|
* Zstd has a simple internal heuristic that selects which strategy to use
|
||
|
|
* at the beginning of a compression. However, if experimentation shows that
|
||
|
|
* Zstd is making poor choices, it is possible to override that choice with
|
||
|
|
* this enum.
|
||
|
|
*/
|
||
|
|
ZSTD_dictDefaultAttach = 0, </b>/* Use the default heuristic. */<b>
|
||
|
|
ZSTD_dictForceAttach = 1, </b>/* Never copy the dictionary. */<b>
|
||
|
|
ZSTD_dictForceCopy = 2, </b>/* Always copy the dictionary. */<b>
|
||
|
|
ZSTD_dictForceLoad = 3 </b>/* Always reload the dictionary */<b>
|
||
|
|
} ZSTD_dictAttachPref_e;
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>typedef enum {
|
||
|
|
ZSTD_lcm_auto = 0, </b>/**< Automatically determine the compression mode based on the compression level.<b>
|
||
|
|
* Negative compression levels will be uncompressed, and positive compression
|
||
|
|
* levels will be compressed. */
|
||
|
|
ZSTD_lcm_huffman = 1, </b>/**< Always attempt Huffman compression. Uncompressed literals will still be<b>
|
||
|
|
* emitted if Huffman compression is not profitable. */
|
||
|
|
ZSTD_lcm_uncompressed = 2 </b>/**< Always emit uncompressed literals. */<b>
|
||
|
|
} ZSTD_literalCompressionMode_e;
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>typedef enum {
|
||
|
|
</b>/* Note: This enum controls features which are conditionally beneficial. Zstd typically will make a final<b>
|
||
|
|
* decision on whether or not to enable the feature (ZSTD_ps_auto), but setting the switch to ZSTD_ps_enable
|
||
|
|
* or ZSTD_ps_disable allow for a force enable/disable the feature.
|
||
|
|
*/
|
||
|
|
ZSTD_ps_auto = 0, </b>/* Let the library automatically determine whether the feature shall be enabled */<b>
|
||
|
|
ZSTD_ps_enable = 1, </b>/* Force-enable the feature */<b>
|
||
|
|
ZSTD_ps_disable = 2 </b>/* Do not use the feature */<b>
|
||
|
|
} ZSTD_paramSwitch_e;
|
||
|
|
</b></pre><BR>
|
||
|
|
<a name="Chapter15"></a><h2>Frame header and size functions</h2><pre></pre>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize);
|
||
|
|
</b><p> `src` should point to the start of a series of ZSTD encoded and/or skippable frames
|
||
|
|
`srcSize` must be the _exact_ size of this series
|
||
|
|
(i.e. there should be a frame boundary at `src + srcSize`)
|
||
|
|
@return : - decompressed size of all data in all successive frames
|
||
|
|
- if the decompressed size cannot be determined: ZSTD_CONTENTSIZE_UNKNOWN
|
||
|
|
- if an error occurred: ZSTD_CONTENTSIZE_ERROR
|
||
|
|
|
||
|
|
note 1 : decompressed size is an optional field, that may not be present, especially in streaming mode.
|
||
|
|
When `return==ZSTD_CONTENTSIZE_UNKNOWN`, data to decompress could be any size.
|
||
|
|
In which case, it's necessary to use streaming mode to decompress data.
|
||
|
|
note 2 : decompressed size is always present when compression is done with ZSTD_compress()
|
||
|
|
note 3 : decompressed size can be very large (64-bits value),
|
||
|
|
potentially larger than what local system can handle as a single memory segment.
|
||
|
|
In which case, it's necessary to use streaming mode to decompress data.
|
||
|
|
note 4 : If source is untrusted, decompressed size could be wrong or intentionally modified.
|
||
|
|
Always ensure result fits within application's authorized limits.
|
||
|
|
Each application can set its own limits.
|
||
|
|
note 5 : ZSTD_findDecompressedSize handles multiple frames, and so it must traverse the input to
|
||
|
|
read each contained frame header. This is fast as most of the data is skipped,
|
||
|
|
however it does mean that all frame data must be present and valid.
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API unsigned long long ZSTD_decompressBound(const void* src, size_t srcSize);
|
||
|
|
</b><p> `src` should point to the start of a series of ZSTD encoded and/or skippable frames
|
||
|
|
`srcSize` must be the _exact_ size of this series
|
||
|
|
(i.e. there should be a frame boundary at `src + srcSize`)
|
||
|
|
@return : - upper-bound for the decompressed size of all data in all successive frames
|
||
|
|
- if an error occurred: ZSTD_CONTENTSIZE_ERROR
|
||
|
|
|
||
|
|
note 1 : an error can occur if `src` contains an invalid or incorrectly formatted frame.
|
||
|
|
note 2 : the upper-bound is exact when the decompressed size field is available in every ZSTD encoded frame of `src`.
|
||
|
|
in this case, `ZSTD_findDecompressedSize` and `ZSTD_decompressBound` return the same value.
|
||
|
|
note 3 : when the decompressed size field isn't available, the upper-bound for that frame is calculated by:
|
||
|
|
upper-bound = # blocks * min(128 KB, Window_Size)
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize);
|
||
|
|
</b><p> srcSize must be >= ZSTD_FRAMEHEADERSIZE_PREFIX.
|
||
|
|
@return : size of the Frame Header,
|
||
|
|
or an error code (if srcSize is too small)
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>typedef enum { ZSTD_frame, ZSTD_skippableFrame } ZSTD_frameType_e;
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>typedef struct {
|
||
|
|
unsigned long long frameContentSize; </b>/* if == ZSTD_CONTENTSIZE_UNKNOWN, it means this field is not available. 0 means "empty" */<b>
|
||
|
|
unsigned long long windowSize; </b>/* can be very large, up to <= frameContentSize */<b>
|
||
|
|
unsigned blockSizeMax;
|
||
|
|
ZSTD_frameType_e frameType; </b>/* if == ZSTD_skippableFrame, frameContentSize is the size of skippable content */<b>
|
||
|
|
unsigned headerSize;
|
||
|
|
unsigned dictID;
|
||
|
|
unsigned checksumFlag;
|
||
|
|
unsigned _reserved1;
|
||
|
|
unsigned _reserved2;
|
||
|
|
} ZSTD_frameHeader;
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize); </b>/**< doesn't consume input */<b>
|
||
|
|
</b>/*! ZSTD_getFrameHeader_advanced() :<b>
|
||
|
|
* same as ZSTD_getFrameHeader(),
|
||
|
|
* with added capability to select a format (like ZSTD_f_zstd1_magicless) */
|
||
|
|
ZSTDLIB_STATIC_API size_t ZSTD_getFrameHeader_advanced(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize, ZSTD_format_e format);
|
||
|
|
</b><p> decode Frame Header, or requires larger `srcSize`.
|
||
|
|
@return : 0, `zfhPtr` is correctly filled,
|
||
|
|
>0, `srcSize` is too small, value is wanted `srcSize` amount,
|
||
|
|
or an error code, which can be tested using ZSTD_isError()
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_decompressionMargin(const void* src, size_t srcSize);
|
||
|
|
</b><p> Zstd supports in-place decompression, where the input and output buffers overlap.
|
||
|
|
In this case, the output buffer must be at least (Margin + Output_Size) bytes large,
|
||
|
|
and the input buffer must be at the end of the output buffer.
|
||
|
|
|
||
|
|
_______________________ Output Buffer ________________________
|
||
|
|
| |
|
||
|
|
| ____ Input Buffer ____|
|
||
|
|
| | |
|
||
|
|
v v v
|
||
|
|
|---------------------------------------|-----------|----------|
|
||
|
|
^ ^ ^
|
||
|
|
|___________________ Output_Size ___________________|_ Margin _|
|
||
|
|
|
||
|
|
NOTE: See also ZSTD_DECOMPRESSION_MARGIN().
|
||
|
|
NOTE: This applies only to single-pass decompression through ZSTD_decompress() or
|
||
|
|
ZSTD_decompressDCtx().
|
||
|
|
NOTE: This function supports multi-frame input.
|
||
|
|
|
||
|
|
@param src The compressed frame(s)
|
||
|
|
@param srcSize The size of the compressed frame(s)
|
||
|
|
@returns The decompression margin or an error that can be checked with ZSTD_isError().
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>#define ZSTD_DECOMPRESSION_MARGIN(originalSize, blockSize) ((size_t)( \
|
||
|
|
ZSTD_FRAMEHEADERSIZE_MAX </b>/* Frame header */ + \<b>
|
||
|
|
4 </b>/* checksum */ + \<b>
|
||
|
|
((originalSize) == 0 ? 0 : 3 * (((originalSize) + (blockSize) - 1) / blockSize)) </b>/* 3 bytes per block */ + \<b>
|
||
|
|
(blockSize) </b>/* One block of margin */ \<b>
|
||
|
|
))
|
||
|
|
</b><p> Similar to ZSTD_decompressionMargin(), but instead of computing the margin from
|
||
|
|
the compressed frame, compute it from the original size and the blockSizeLog.
|
||
|
|
See ZSTD_decompressionMargin() for details.
|
||
|
|
|
||
|
|
WARNING: This macro does not support multi-frame input, the input must be a single
|
||
|
|
zstd frame. If you need that support use the function, or implement it yourself.
|
||
|
|
|
||
|
|
@param originalSize The original uncompressed size of the data.
|
||
|
|
@param blockSize The block size == MIN(windowSize, ZSTD_BLOCKSIZE_MAX).
|
||
|
|
Unless you explicitly set the windowLog smaller than
|
||
|
|
ZSTD_BLOCKSIZELOG_MAX you can just use ZSTD_BLOCKSIZE_MAX.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>typedef enum {
|
||
|
|
ZSTD_sf_noBlockDelimiters = 0, </b>/* Representation of ZSTD_Sequence has no block delimiters, sequences only */<b>
|
||
|
|
ZSTD_sf_explicitBlockDelimiters = 1 </b>/* Representation of ZSTD_Sequence contains explicit block delimiters */<b>
|
||
|
|
} ZSTD_sequenceFormat_e;
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_sequenceBound(size_t srcSize);
|
||
|
|
</b><p> `srcSize` : size of the input buffer
|
||
|
|
@return : upper-bound for the number of sequences that can be generated
|
||
|
|
from a buffer of srcSize bytes
|
||
|
|
|
||
|
|
note : returns number of sequences - to get bytes, multiply by sizeof(ZSTD_Sequence).
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b></b><p> Generate sequences using ZSTD_compress2(), given a source buffer.
|
||
|
|
|
||
|
|
Each block will end with a dummy sequence
|
||
|
|
with offset == 0, matchLength == 0, and litLength == length of last literals.
|
||
|
|
litLength may be == 0, and if so, then the sequence of (of: 0 ml: 0 ll: 0)
|
||
|
|
simply acts as a block delimiter.
|
||
|
|
|
||
|
|
@zc can be used to insert custom compression params.
|
||
|
|
This function invokes ZSTD_compress2().
|
||
|
|
|
||
|
|
The output of this function can be fed into ZSTD_compressSequences() with CCtx
|
||
|
|
setting of ZSTD_c_blockDelimiters as ZSTD_sf_explicitBlockDelimiters
|
||
|
|
@return : number of sequences generated
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_mergeBlockDelimiters(ZSTD_Sequence* sequences, size_t seqsSize);
|
||
|
|
</b><p> Given an array of ZSTD_Sequence, remove all sequences that represent block delimiters/last literals
|
||
|
|
by merging them into the literals of the next sequence.
|
||
|
|
|
||
|
|
As such, the final generated result has no explicit representation of block boundaries,
|
||
|
|
and the final last literals segment is not represented in the sequences.
|
||
|
|
|
||
|
|
The output of this function can be fed into ZSTD_compressSequences() with CCtx
|
||
|
|
setting of ZSTD_c_blockDelimiters as ZSTD_sf_noBlockDelimiters
|
||
|
|
@return : number of sequences left after merging
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t
|
||
|
|
ZSTD_compressSequences( ZSTD_CCtx* cctx, void* dst, size_t dstSize,
|
||
|
|
const ZSTD_Sequence* inSeqs, size_t inSeqsSize,
|
||
|
|
const void* src, size_t srcSize);
|
||
|
|
</b><p> Compress an array of ZSTD_Sequence, associated with @src buffer, into dst.
|
||
|
|
@src contains the entire input (not just the literals).
|
||
|
|
If @srcSize > sum(sequence.length), the remaining bytes are considered all literals
|
||
|
|
If a dictionary is included, then the cctx should reference the dict. (see: ZSTD_CCtx_refCDict(), ZSTD_CCtx_loadDictionary(), etc.)
|
||
|
|
The entire source is compressed into a single frame.
|
||
|
|
|
||
|
|
The compression behavior changes based on cctx params. In particular:
|
||
|
|
If ZSTD_c_blockDelimiters == ZSTD_sf_noBlockDelimiters, the array of ZSTD_Sequence is expected to contain
|
||
|
|
no block delimiters (defined in ZSTD_Sequence). Block boundaries are roughly determined based on
|
||
|
|
the block size derived from the cctx, and sequences may be split. This is the default setting.
|
||
|
|
|
||
|
|
If ZSTD_c_blockDelimiters == ZSTD_sf_explicitBlockDelimiters, the array of ZSTD_Sequence is expected to contain
|
||
|
|
block delimiters (defined in ZSTD_Sequence). Behavior is undefined if no block delimiters are provided.
|
||
|
|
|
||
|
|
If ZSTD_c_validateSequences == 0, this function will blindly accept the sequences provided. Invalid sequences cause undefined
|
||
|
|
behavior. If ZSTD_c_validateSequences == 1, then if sequence is invalid (see doc/zstd_compression_format.md for
|
||
|
|
specifics regarding offset/matchlength requirements) then the function will bail out and return an error.
|
||
|
|
|
||
|
|
In addition to the two adjustable experimental params, there are other important cctx params.
|
||
|
|
- ZSTD_c_minMatch MUST be set as less than or equal to the smallest match generated by the match finder. It has a minimum value of ZSTD_MINMATCH_MIN.
|
||
|
|
- ZSTD_c_compressionLevel accordingly adjusts the strength of the entropy coder, as it would in typical compression.
|
||
|
|
- ZSTD_c_windowLog affects offset validation: this function will return an error at higher debug levels if a provided offset
|
||
|
|
is larger than what the spec allows for a given window log and dictionary (if present). See: doc/zstd_compression_format.md
|
||
|
|
|
||
|
|
Note: Repcodes are, as of now, always re-calculated within this function, so ZSTD_Sequence::rep is unused.
|
||
|
|
Note 2: Once we integrate ability to ingest repcodes, the explicit block delims mode must respect those repcodes exactly,
|
||
|
|
and cannot emit an RLE block that disagrees with the repcode history
|
||
|
|
@return : final compressed size, or a ZSTD error code.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_writeSkippableFrame(void* dst, size_t dstCapacity,
|
||
|
|
const void* src, size_t srcSize, unsigned magicVariant);
|
||
|
|
</b><p> Generates a zstd skippable frame containing data given by src, and writes it to dst buffer.
|
||
|
|
|
||
|
|
Skippable frames begin with a 4-byte magic number. There are 16 possible choices of magic number,
|
||
|
|
ranging from ZSTD_MAGIC_SKIPPABLE_START to ZSTD_MAGIC_SKIPPABLE_START+15.
|
||
|
|
As such, the parameter magicVariant controls the exact skippable frame magic number variant used, so
|
||
|
|
the magic number used will be ZSTD_MAGIC_SKIPPABLE_START + magicVariant.
|
||
|
|
|
||
|
|
Returns an error if destination buffer is not large enough, if the source size is not representable
|
||
|
|
with a 4-byte unsigned int, or if the parameter magicVariant is greater than 15 (and therefore invalid).
|
||
|
|
|
||
|
|
@return : number of bytes written or a ZSTD error.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>size_t ZSTD_readSkippableFrame(void* dst, size_t dstCapacity, unsigned* magicVariant,
|
||
|
|
const void* src, size_t srcSize);
|
||
|
|
</b><p> Retrieves a zstd skippable frame containing data given by src, and writes it to dst buffer.
|
||
|
|
|
||
|
|
The parameter magicVariant will receive the magicVariant that was supplied when the frame was written,
|
||
|
|
i.e. magicNumber - ZSTD_MAGIC_SKIPPABLE_START. This can be NULL if the caller is not interested
|
||
|
|
in the magicVariant.
|
||
|
|
|
||
|
|
Returns an error if destination buffer is not large enough, or if the frame is not skippable.
|
||
|
|
|
||
|
|
@return : number of bytes written or a ZSTD error.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>unsigned ZSTD_isSkippableFrame(const void* buffer, size_t size);
|
||
|
|
</b><p> Tells if the content of `buffer` starts with a valid Frame Identifier for a skippable frame.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<a name="Chapter16"></a><h2>Memory management</h2><pre></pre>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize(int maxCompressionLevel);
|
||
|
|
ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize_usingCParams(ZSTD_compressionParameters cParams);
|
||
|
|
ZSTDLIB_STATIC_API size_t ZSTD_estimateCCtxSize_usingCCtxParams(const ZSTD_CCtx_params* params);
|
||
|
|
ZSTDLIB_STATIC_API size_t ZSTD_estimateDCtxSize(void);
|
||
|
|
</b><p> These functions make it possible to estimate memory usage
|
||
|
|
of a future {D,C}Ctx, before its creation.
|
||
|
|
This is useful in combination with ZSTD_initStatic(),
|
||
|
|
which makes it possible to employ a static buffer for ZSTD_CCtx* state.
|
||
|
|
|
||
|
|
ZSTD_estimateCCtxSize() will provide a memory budget large enough
|
||
|
|
to compress data of any size using one-shot compression ZSTD_compressCCtx() or ZSTD_compress2()
|
||
|
|
associated with any compression level up to max specified one.
|
||
|
|
The estimate will assume the input may be arbitrarily large,
|
||
|
|
which is the worst case.
|
||
|
|
|
||
|
|
Note that the size estimation is specific for one-shot compression,
|
||
|
|
it is not valid for streaming (see ZSTD_estimateCStreamSize*())
|
||
|
|
nor other potential ways of using a ZSTD_CCtx* state.
|
||
|
|
|
||
|
|
When srcSize can be bound by a known and rather "small" value,
|
||
|
|
this knowledge can be used to provide a tighter budget estimation
|
||
|
|
because the ZSTD_CCtx* state will need less memory for small inputs.
|
||
|
|
This tighter estimation can be provided by employing more advanced functions
|
||
|
|
ZSTD_estimateCCtxSize_usingCParams(), which can be used in tandem with ZSTD_getCParams(),
|
||
|
|
and ZSTD_estimateCCtxSize_usingCCtxParams(), which can be used in tandem with ZSTD_CCtxParams_setParameter().
|
||
|
|
Both can be used to estimate memory using custom compression parameters and arbitrary srcSize limits.
|
||
|
|
|
||
|
|
Note : only single-threaded compression is supported.
|
||
|
|
ZSTD_estimateCCtxSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize(int maxCompressionLevel);
|
||
|
|
ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize_usingCParams(ZSTD_compressionParameters cParams);
|
||
|
|
ZSTDLIB_STATIC_API size_t ZSTD_estimateCStreamSize_usingCCtxParams(const ZSTD_CCtx_params* params);
|
||
|
|
ZSTDLIB_STATIC_API size_t ZSTD_estimateDStreamSize(size_t maxWindowSize);
|
||
|
|
ZSTDLIB_STATIC_API size_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize);
|
||
|
|
</b><p> ZSTD_estimateCStreamSize() will provide a memory budget large enough for streaming compression
|
||
|
|
using any compression level up to the max specified one.
|
||
|
|
It will also consider src size to be arbitrarily "large", which is a worst case scenario.
|
||
|
|
If srcSize is known to always be small, ZSTD_estimateCStreamSize_usingCParams() can provide a tighter estimation.
|
||
|
|
ZSTD_estimateCStreamSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
|
||
|
|
ZSTD_estimateCStreamSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParams_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_c_nbWorkers is >= 1.
|
||
|
|
Note : CStream size estimation is only correct for single-threaded compression.
|
||
|
|
ZSTD_estimateCStreamSize_usingCCtxParams() will return an error code if ZSTD_c_nbWorkers is >= 1.
|
||
|
|
Note 2 : ZSTD_estimateCStreamSize* functions are not compatible with the Block-Level Sequence Producer API at this time.
|
||
|
|
Size estimates assume that no external sequence producer is registered.
|
||
|
|
|
||
|
|
ZSTD_DStream memory budget depends on frame's window Size.
|
||
|
|
This information can be passed manually, using ZSTD_estimateDStreamSize,
|
||
|
|
or deducted from a valid frame Header, using ZSTD_estimateDStreamSize_fromFrame();
|
||
|
|
Any frame requesting a window size larger than max specified one will be rejected.
|
||
|
|
Note : if streaming is init with function ZSTD_init?Stream_usingDict(),
|
||
|
|
an internal ?Dict will be created, which additional size is not estimated here.
|
||
|
|
In this case, get total size by adding ZSTD_estimate?DictSize
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_estimateCDictSize(size_t dictSize, int compressionLevel);
|
||
|
|
ZSTDLIB_STATIC_API size_t ZSTD_estimateCDictSize_advanced(size_t dictSize, ZSTD_compressionParameters cParams, ZSTD_dictLoadMethod_e dictLoadMethod);
|
||
|
|
ZSTDLIB_STATIC_API size_t ZSTD_estimateDDictSize(size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod);
|
||
|
|
</b><p> ZSTD_estimateCDictSize() will bet that src size is relatively "small", and content is copied, like ZSTD_createCDict().
|
||
|
|
ZSTD_estimateCDictSize_advanced() makes it possible to control compression parameters precisely, like ZSTD_createCDict_advanced().
|
||
|
|
Note : dictionaries created by reference (`ZSTD_dlm_byRef`) are logically smaller.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API ZSTD_CCtx* ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize);
|
||
|
|
ZSTDLIB_STATIC_API ZSTD_CStream* ZSTD_initStaticCStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticCCtx() */<b>
|
||
|
|
</b><p> Initialize an object using a pre-allocated fixed-size buffer.
|
||
|
|
workspace: The memory area to emplace the object into.
|
||
|
|
Provided pointer *must be 8-bytes aligned*.
|
||
|
|
Buffer must outlive object.
|
||
|
|
workspaceSize: Use ZSTD_estimate*Size() to determine
|
||
|
|
how large workspace must be to support target scenario.
|
||
|
|
@return : pointer to object (same address as workspace, just different type),
|
||
|
|
or NULL if error (size too small, incorrect alignment, etc.)
|
||
|
|
Note : zstd will never resize nor malloc() when using a static buffer.
|
||
|
|
If the object requires more memory than available,
|
||
|
|
zstd will just error out (typically ZSTD_error_memory_allocation).
|
||
|
|
Note 2 : there is no corresponding "free" function.
|
||
|
|
Since workspace is allocated externally, it must be freed externally too.
|
||
|
|
Note 3 : cParams : use ZSTD_getCParams() to convert a compression level
|
||
|
|
into its associated cParams.
|
||
|
|
Limitation 1 : currently not compatible with internal dictionary creation, triggered by
|
||
|
|
ZSTD_CCtx_loadDictionary(), ZSTD_initCStream_usingDict() or ZSTD_initDStream_usingDict().
|
||
|
|
Limitation 2 : static cctx currently not compatible with multi-threading.
|
||
|
|
Limitation 3 : static dctx is incompatible with legacy support.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API ZSTD_DStream* ZSTD_initStaticDStream(void* workspace, size_t workspaceSize); </b>/**< same as ZSTD_initStaticDCtx() */<b>
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>typedef void* (*ZSTD_allocFunction) (void* opaque, size_t size);
|
||
|
|
typedef void (*ZSTD_freeFunction) (void* opaque, void* address);
|
||
|
|
typedef struct { ZSTD_allocFunction customAlloc; ZSTD_freeFunction customFree; void* opaque; } ZSTD_customMem;
|
||
|
|
static
|
||
|
|
#ifdef __GNUC__
|
||
|
|
__attribute__((__unused__))
|
||
|
|
#endif
|
||
|
|
ZSTD_customMem const ZSTD_defaultCMem = { NULL, NULL, NULL }; </b>/**< this constant defers to stdlib's functions */<b>
|
||
|
|
</b><p> These prototypes make it possible to pass your own allocation/free functions.
|
||
|
|
ZSTD_customMem is provided at creation time, using ZSTD_create*_advanced() variants listed below.
|
||
|
|
All allocation/free operations will be completed using these custom variants instead of regular <stdlib.h> ones.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>typedef struct POOL_ctx_s ZSTD_threadPool;
|
||
|
|
ZSTDLIB_STATIC_API ZSTD_threadPool* ZSTD_createThreadPool(size_t numThreads);
|
||
|
|
ZSTDLIB_STATIC_API void ZSTD_freeThreadPool (ZSTD_threadPool* pool); </b>/* accept NULL pointer */<b>
|
||
|
|
ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refThreadPool(ZSTD_CCtx* cctx, ZSTD_threadPool* pool);
|
||
|
|
</b><p> These prototypes make it possible to share a thread pool among multiple compression contexts.
|
||
|
|
This can limit resources for applications with multiple threads where each one uses
|
||
|
|
a threaded compression mode (via ZSTD_c_nbWorkers parameter).
|
||
|
|
ZSTD_createThreadPool creates a new thread pool with a given number of threads.
|
||
|
|
Note that the lifetime of such pool must exist while being used.
|
||
|
|
ZSTD_CCtx_refThreadPool assigns a thread pool to a context (use NULL argument value
|
||
|
|
to use an internal thread pool).
|
||
|
|
ZSTD_freeThreadPool frees a thread pool, accepts NULL pointer.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<a name="Chapter17"></a><h2>Advanced compression functions</h2><pre></pre>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API ZSTD_CDict* ZSTD_createCDict_byReference(const void* dictBuffer, size_t dictSize, int compressionLevel);
|
||
|
|
</b><p> Create a digested dictionary for compression
|
||
|
|
Dictionary content is just referenced, not duplicated.
|
||
|
|
As a consequence, `dictBuffer` **must** outlive CDict,
|
||
|
|
and its content must remain unmodified throughout the lifetime of CDict.
|
||
|
|
note: equivalent to ZSTD_createCDict_advanced(), with dictLoadMethod==ZSTD_dlm_byRef
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API ZSTD_compressionParameters ZSTD_getCParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
|
||
|
|
</b><p> @return ZSTD_compressionParameters structure for a selected compression level and estimated srcSize.
|
||
|
|
`estimatedSrcSize` value is optional, select 0 if not known
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API ZSTD_parameters ZSTD_getParams(int compressionLevel, unsigned long long estimatedSrcSize, size_t dictSize);
|
||
|
|
</b><p> same as ZSTD_getCParams(), but @return a full `ZSTD_parameters` object instead of sub-component `ZSTD_compressionParameters`.
|
||
|
|
All fields of `ZSTD_frameParameters` are set to default : contentSize=1, checksum=0, noDictID=0
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_checkCParams(ZSTD_compressionParameters params);
|
||
|
|
</b><p> Ensure param values remain within authorized range.
|
||
|
|
@return 0 on success, or an error code (can be checked with ZSTD_isError())
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, unsigned long long srcSize, size_t dictSize);
|
||
|
|
</b><p> optimize params for a given `srcSize` and `dictSize`.
|
||
|
|
`srcSize` can be unknown, in which case use ZSTD_CONTENTSIZE_UNKNOWN.
|
||
|
|
`dictSize` must be `0` when there is no dictionary.
|
||
|
|
cPar can be invalid : all parameters will be clamped within valid range in the @return struct.
|
||
|
|
This function never fails (wide contract)
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setCParams(ZSTD_CCtx* cctx, ZSTD_compressionParameters cparams);
|
||
|
|
</b><p> Set all parameters provided within @p cparams into the working @p cctx.
|
||
|
|
Note : if modifying parameters during compression (MT mode only),
|
||
|
|
note that changes to the .windowLog parameter will be ignored.
|
||
|
|
@return 0 on success, or an error code (can be checked with ZSTD_isError()).
|
||
|
|
On failure, no parameters are updated.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setFParams(ZSTD_CCtx* cctx, ZSTD_frameParameters fparams);
|
||
|
|
</b><p> Set all parameters provided within @p fparams into the working @p cctx.
|
||
|
|
@return 0 on success, or an error code (can be checked with ZSTD_isError()).
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setParams(ZSTD_CCtx* cctx, ZSTD_parameters params);
|
||
|
|
</b><p> Set all parameters provided within @p params into the working @p cctx.
|
||
|
|
@return 0 on success, or an error code (can be checked with ZSTD_isError()).
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTD_DEPRECATED("use ZSTD_compress2")
|
||
|
|
ZSTDLIB_STATIC_API
|
||
|
|
size_t ZSTD_compress_advanced(ZSTD_CCtx* cctx,
|
||
|
|
void* dst, size_t dstCapacity,
|
||
|
|
const void* src, size_t srcSize,
|
||
|
|
const void* dict,size_t dictSize,
|
||
|
|
ZSTD_parameters params);
|
||
|
|
</b><p> Note : this function is now DEPRECATED.
|
||
|
|
It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_setParameter() and other parameter setters.
|
||
|
|
This prototype will generate compilation warnings.
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTD_DEPRECATED("use ZSTD_compress2 with ZSTD_CCtx_loadDictionary")
|
||
|
|
ZSTDLIB_STATIC_API
|
||
|
|
size_t ZSTD_compress_usingCDict_advanced(ZSTD_CCtx* cctx,
|
||
|
|
void* dst, size_t dstCapacity,
|
||
|
|
const void* src, size_t srcSize,
|
||
|
|
const ZSTD_CDict* cdict,
|
||
|
|
ZSTD_frameParameters fParams);
|
||
|
|
</b><p> Note : this function is now DEPRECATED.
|
||
|
|
It can be replaced by ZSTD_compress2(), in combination with ZSTD_CCtx_loadDictionary() and other parameter setters.
|
||
|
|
This prototype will generate compilation warnings.
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_loadDictionary_byReference(ZSTD_CCtx* cctx, const void* dict, size_t dictSize);
|
||
|
|
</b><p> Same as ZSTD_CCtx_loadDictionary(), but dictionary content is referenced, instead of being copied into CCtx.
|
||
|
|
It saves some memory, but also requires that `dict` outlives its usage within `cctx`
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_loadDictionary_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType);
|
||
|
|
</b><p> Same as ZSTD_CCtx_loadDictionary(), but gives finer control over
|
||
|
|
how to load the dictionary (by copy ? by reference ?)
|
||
|
|
and how to interpret it (automatic ? force raw mode ? full mode only ?)
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType);
|
||
|
|
</b><p> Same as ZSTD_CCtx_refPrefix(), but gives finer control over
|
||
|
|
how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?)
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_getParameter(const ZSTD_CCtx* cctx, ZSTD_cParameter param, int* value);
|
||
|
|
</b><p> Get the requested compression parameter value, selected by enum ZSTD_cParameter,
|
||
|
|
and store it into int* value.
|
||
|
|
@return : 0, or an error code (which can be tested with ZSTD_isError()).
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API ZSTD_CCtx_params* ZSTD_createCCtxParams(void);
|
||
|
|
ZSTDLIB_STATIC_API size_t ZSTD_freeCCtxParams(ZSTD_CCtx_params* params); </b>/* accept NULL pointer */<b>
|
||
|
|
</b><p> Quick howto :
|
||
|
|
- ZSTD_createCCtxParams() : Create a ZSTD_CCtx_params structure
|
||
|
|
- ZSTD_CCtxParams_setParameter() : Push parameters one by one into
|
||
|
|
an existing ZSTD_CCtx_params structure.
|
||
|
|
This is similar to
|
||
|
|
ZSTD_CCtx_setParameter().
|
||
|
|
- ZSTD_CCtx_setParametersUsingCCtxParams() : Apply parameters to
|
||
|
|
an existing CCtx.
|
||
|
|
These parameters will be applied to
|
||
|
|
all subsequent frames.
|
||
|
|
- ZSTD_compressStream2() : Do compression using the CCtx.
|
||
|
|
- ZSTD_freeCCtxParams() : Free the memory, accept NULL pointer.
|
||
|
|
|
||
|
|
This can be used with ZSTD_estimateCCtxSize_advanced_usingCCtxParams()
|
||
|
|
for static allocation of CCtx for single-threaded compression.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_reset(ZSTD_CCtx_params* params);
|
||
|
|
</b><p> Reset params to default values.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_init(ZSTD_CCtx_params* cctxParams, int compressionLevel);
|
||
|
|
</b><p> Initializes the compression parameters of cctxParams according to
|
||
|
|
compression level. All other parameters are reset to their default values.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_init_advanced(ZSTD_CCtx_params* cctxParams, ZSTD_parameters params);
|
||
|
|
</b><p> Initializes the compression and frame parameters of cctxParams according to
|
||
|
|
params. All other parameters are reset to their default values.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_setParameter(ZSTD_CCtx_params* params, ZSTD_cParameter param, int value);
|
||
|
|
</b><p> Similar to ZSTD_CCtx_setParameter.
|
||
|
|
Set one compression parameter, selected by enum ZSTD_cParameter.
|
||
|
|
Parameters must be applied to a ZSTD_CCtx using
|
||
|
|
ZSTD_CCtx_setParametersUsingCCtxParams().
|
||
|
|
@result : a code representing success or failure (which can be tested with
|
||
|
|
ZSTD_isError()).
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtxParams_getParameter(const ZSTD_CCtx_params* params, ZSTD_cParameter param, int* value);
|
||
|
|
</b><p> Similar to ZSTD_CCtx_getParameter.
|
||
|
|
Get the requested value of one compression parameter, selected by enum ZSTD_cParameter.
|
||
|
|
@result : 0, or an error code (which can be tested with ZSTD_isError()).
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_CCtx_setParametersUsingCCtxParams(
|
||
|
|
ZSTD_CCtx* cctx, const ZSTD_CCtx_params* params);
|
||
|
|
</b><p> Apply a set of ZSTD_CCtx_params to the compression context.
|
||
|
|
This can be done even after compression is started,
|
||
|
|
if nbWorkers==0, this will have no impact until a new compression is started.
|
||
|
|
if nbWorkers>=1, new parameters will be picked up at next job,
|
||
|
|
with a few restrictions (windowLog, pledgedSrcSize, nbWorkers, jobSize, and overlapLog are not updated).
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_compressStream2_simpleArgs (
|
||
|
|
ZSTD_CCtx* cctx,
|
||
|
|
void* dst, size_t dstCapacity, size_t* dstPos,
|
||
|
|
const void* src, size_t srcSize, size_t* srcPos,
|
||
|
|
ZSTD_EndDirective endOp);
|
||
|
|
</b><p> Same as ZSTD_compressStream2(),
|
||
|
|
but using only integral types as arguments.
|
||
|
|
This variant might be helpful for binders from dynamic languages
|
||
|
|
which have troubles handling structures containing memory pointers.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<a name="Chapter18"></a><h2>Advanced decompression functions</h2><pre></pre>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API unsigned ZSTD_isFrame(const void* buffer, size_t size);
|
||
|
|
</b><p> Tells if the content of `buffer` starts with a valid Frame Identifier.
|
||
|
|
Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0.
|
||
|
|
Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled.
|
||
|
|
Note 3 : Skippable Frame Identifiers are considered valid.
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API ZSTD_DDict* ZSTD_createDDict_byReference(const void* dictBuffer, size_t dictSize);
|
||
|
|
</b><p> Create a digested dictionary, ready to start decompression operation without startup delay.
|
||
|
|
Dictionary content is referenced, and therefore stays in dictBuffer.
|
||
|
|
It is important that dictBuffer outlives DDict,
|
||
|
|
it must remain read accessible throughout the lifetime of DDict
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_loadDictionary_byReference(ZSTD_DCtx* dctx, const void* dict, size_t dictSize);
|
||
|
|
</b><p> Same as ZSTD_DCtx_loadDictionary(),
|
||
|
|
but references `dict` content instead of copying it into `dctx`.
|
||
|
|
This saves memory if `dict` remains around.,
|
||
|
|
However, it's imperative that `dict` remains accessible (and unmodified) while being used, so it must outlive decompression.
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_loadDictionary_advanced(ZSTD_DCtx* dctx, const void* dict, size_t dictSize, ZSTD_dictLoadMethod_e dictLoadMethod, ZSTD_dictContentType_e dictContentType);
|
||
|
|
</b><p> Same as ZSTD_DCtx_loadDictionary(),
|
||
|
|
but gives direct control over
|
||
|
|
how to load the dictionary (by copy ? by reference ?)
|
||
|
|
and how to interpret it (automatic ? force raw mode ? full mode only ?).
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_refPrefix_advanced(ZSTD_DCtx* dctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType);
|
||
|
|
</b><p> Same as ZSTD_DCtx_refPrefix(), but gives finer control over
|
||
|
|
how to interpret prefix content (automatic ? force raw mode (default) ? full mode only ?)
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_setMaxWindowSize(ZSTD_DCtx* dctx, size_t maxWindowSize);
|
||
|
|
</b><p> Refuses allocating internal buffers for frames requiring a window size larger than provided limit.
|
||
|
|
This protects a decoder context from reserving too much memory for itself (potential attack scenario).
|
||
|
|
This parameter is only useful in streaming mode, since no internal buffer is allocated in single-pass mode.
|
||
|
|
By default, a decompression context accepts all window sizes <= (1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT)
|
||
|
|
@return : 0, or an error code (which can be tested using ZSTD_isError()).
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_DCtx_getParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int* value);
|
||
|
|
</b><p> Get the requested decompression parameter value, selected by enum ZSTD_dParameter,
|
||
|
|
and store it into int* value.
|
||
|
|
@return : 0, or an error code (which can be tested with ZSTD_isError()).
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_setParameter() instead")
|
||
|
|
ZSTDLIB_STATIC_API
|
||
|
|
size_t ZSTD_DCtx_setFormat(ZSTD_DCtx* dctx, ZSTD_format_e format);
|
||
|
|
</b><p> This function is REDUNDANT. Prefer ZSTD_DCtx_setParameter().
|
||
|
|
Instruct the decoder context about what kind of data to decode next.
|
||
|
|
This instruction is mandatory to decode data without a fully-formed header,
|
||
|
|
such ZSTD_f_zstd1_magicless for example.
|
||
|
|
@return : 0, or an error code (which can be tested using ZSTD_isError()).
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_decompressStream_simpleArgs (
|
||
|
|
ZSTD_DCtx* dctx,
|
||
|
|
void* dst, size_t dstCapacity, size_t* dstPos,
|
||
|
|
const void* src, size_t srcSize, size_t* srcPos);
|
||
|
|
</b><p> Same as ZSTD_decompressStream(),
|
||
|
|
but using only integral types as arguments.
|
||
|
|
This can be helpful for binders from dynamic languages
|
||
|
|
which have troubles handling structures containing memory pointers.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<a name="Chapter19"></a><h2>Advanced streaming functions</h2><pre> Warning : most of these functions are now redundant with the Advanced API.
|
||
|
|
Once Advanced API reaches "stable" status,
|
||
|
|
redundant functions will be deprecated, and then at some point removed.
|
||
|
|
<BR></pre>
|
||
|
|
|
||
|
|
<h3>Advanced Streaming compression functions</h3><pre></pre><b><pre></pre></b><BR>
|
||
|
|
<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
|
||
|
|
ZSTDLIB_STATIC_API
|
||
|
|
size_t ZSTD_initCStream_srcSize(ZSTD_CStream* zcs,
|
||
|
|
int compressionLevel,
|
||
|
|
unsigned long long pledgedSrcSize);
|
||
|
|
</b><p> This function is DEPRECATED, and equivalent to:
|
||
|
|
ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
|
||
|
|
ZSTD_CCtx_refCDict(zcs, NULL); // clear the dictionary (if any)
|
||
|
|
ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
|
||
|
|
ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
|
||
|
|
|
||
|
|
pledgedSrcSize must be correct. If it is not known at init time, use
|
||
|
|
ZSTD_CONTENTSIZE_UNKNOWN. Note that, for compatibility with older programs,
|
||
|
|
"0" also disables frame content size field. It may be enabled in the future.
|
||
|
|
This prototype will generate compilation warnings.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
|
||
|
|
ZSTDLIB_STATIC_API
|
||
|
|
size_t ZSTD_initCStream_usingDict(ZSTD_CStream* zcs,
|
||
|
|
const void* dict, size_t dictSize,
|
||
|
|
int compressionLevel);
|
||
|
|
</b><p> This function is DEPRECATED, and is equivalent to:
|
||
|
|
ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
|
||
|
|
ZSTD_CCtx_setParameter(zcs, ZSTD_c_compressionLevel, compressionLevel);
|
||
|
|
ZSTD_CCtx_loadDictionary(zcs, dict, dictSize);
|
||
|
|
|
||
|
|
Creates of an internal CDict (incompatible with static CCtx), except if
|
||
|
|
dict == NULL or dictSize < 8, in which case no dict is used.
|
||
|
|
Note: dict is loaded with ZSTD_dct_auto (treated as a full zstd dictionary if
|
||
|
|
it begins with ZSTD_MAGIC_DICTIONARY, else as raw content) and ZSTD_dlm_byCopy.
|
||
|
|
This prototype will generate compilation warnings.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
|
||
|
|
ZSTDLIB_STATIC_API
|
||
|
|
size_t ZSTD_initCStream_advanced(ZSTD_CStream* zcs,
|
||
|
|
const void* dict, size_t dictSize,
|
||
|
|
ZSTD_parameters params,
|
||
|
|
unsigned long long pledgedSrcSize);
|
||
|
|
</b><p> This function is DEPRECATED, and is equivalent to:
|
||
|
|
ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
|
||
|
|
ZSTD_CCtx_setParams(zcs, params);
|
||
|
|
ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
|
||
|
|
ZSTD_CCtx_loadDictionary(zcs, dict, dictSize);
|
||
|
|
|
||
|
|
dict is loaded with ZSTD_dct_auto and ZSTD_dlm_byCopy.
|
||
|
|
pledgedSrcSize must be correct.
|
||
|
|
If srcSize is not known at init time, use value ZSTD_CONTENTSIZE_UNKNOWN.
|
||
|
|
This prototype will generate compilation warnings.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset and ZSTD_CCtx_refCDict, see zstd.h for detailed instructions")
|
||
|
|
ZSTDLIB_STATIC_API
|
||
|
|
size_t ZSTD_initCStream_usingCDict(ZSTD_CStream* zcs, const ZSTD_CDict* cdict);
|
||
|
|
</b><p> This function is DEPRECATED, and equivalent to:
|
||
|
|
ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
|
||
|
|
ZSTD_CCtx_refCDict(zcs, cdict);
|
||
|
|
|
||
|
|
note : cdict will just be referenced, and must outlive compression session
|
||
|
|
This prototype will generate compilation warnings.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset and ZSTD_CCtx_refCDict, see zstd.h for detailed instructions")
|
||
|
|
ZSTDLIB_STATIC_API
|
||
|
|
size_t ZSTD_initCStream_usingCDict_advanced(ZSTD_CStream* zcs,
|
||
|
|
const ZSTD_CDict* cdict,
|
||
|
|
ZSTD_frameParameters fParams,
|
||
|
|
unsigned long long pledgedSrcSize);
|
||
|
|
</b><p> This function is DEPRECATED, and is equivalent to:
|
||
|
|
ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
|
||
|
|
ZSTD_CCtx_setFParams(zcs, fParams);
|
||
|
|
ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
|
||
|
|
ZSTD_CCtx_refCDict(zcs, cdict);
|
||
|
|
|
||
|
|
same as ZSTD_initCStream_usingCDict(), with control over frame parameters.
|
||
|
|
pledgedSrcSize must be correct. If srcSize is not known at init time, use
|
||
|
|
value ZSTD_CONTENTSIZE_UNKNOWN.
|
||
|
|
This prototype will generate compilation warnings.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTD_DEPRECATED("use ZSTD_CCtx_reset, see zstd.h for detailed instructions")
|
||
|
|
ZSTDLIB_STATIC_API
|
||
|
|
size_t ZSTD_resetCStream(ZSTD_CStream* zcs, unsigned long long pledgedSrcSize);
|
||
|
|
</b><p> This function is DEPRECATED, and is equivalent to:
|
||
|
|
ZSTD_CCtx_reset(zcs, ZSTD_reset_session_only);
|
||
|
|
ZSTD_CCtx_setPledgedSrcSize(zcs, pledgedSrcSize);
|
||
|
|
Note: ZSTD_resetCStream() interprets pledgedSrcSize == 0 as ZSTD_CONTENTSIZE_UNKNOWN, but
|
||
|
|
ZSTD_CCtx_setPledgedSrcSize() does not do the same, so ZSTD_CONTENTSIZE_UNKNOWN must be
|
||
|
|
explicitly specified.
|
||
|
|
|
||
|
|
start a new frame, using same parameters from previous frame.
|
||
|
|
This is typically useful to skip dictionary loading stage, since it will reuse it in-place.
|
||
|
|
Note that zcs must be init at least once before using ZSTD_resetCStream().
|
||
|
|
If pledgedSrcSize is not known at reset time, use macro ZSTD_CONTENTSIZE_UNKNOWN.
|
||
|
|
If pledgedSrcSize > 0, its value must be correct, as it will be written in header, and controlled at the end.
|
||
|
|
For the time being, pledgedSrcSize==0 is interpreted as "srcSize unknown" for compatibility with older programs,
|
||
|
|
but it will change to mean "empty" in future version, so use macro ZSTD_CONTENTSIZE_UNKNOWN instead.
|
||
|
|
@return : 0, or an error code (which can be tested using ZSTD_isError())
|
||
|
|
This prototype will generate compilation warnings.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>typedef struct {
|
||
|
|
unsigned long long ingested; </b>/* nb input bytes read and buffered */<b>
|
||
|
|
unsigned long long consumed; </b>/* nb input bytes actually compressed */<b>
|
||
|
|
unsigned long long produced; </b>/* nb of compressed bytes generated and buffered */<b>
|
||
|
|
unsigned long long flushed; </b>/* nb of compressed bytes flushed : not provided; can be tracked from caller side */<b>
|
||
|
|
unsigned currentJobID; </b>/* MT only : latest started job nb */<b>
|
||
|
|
unsigned nbActiveWorkers; </b>/* MT only : nb of workers actively compressing at probe time */<b>
|
||
|
|
} ZSTD_frameProgression;
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_toFlushNow(ZSTD_CCtx* cctx);
|
||
|
|
</b><p> Tell how many bytes are ready to be flushed immediately.
|
||
|
|
Useful for multithreading scenarios (nbWorkers >= 1).
|
||
|
|
Probe the oldest active job, defined as oldest job not yet entirely flushed,
|
||
|
|
and check its output buffer.
|
||
|
|
@return : amount of data stored in oldest job and ready to be flushed immediately.
|
||
|
|
if @return == 0, it means either :
|
||
|
|
+ there is no active job (could be checked with ZSTD_frameProgression()), or
|
||
|
|
+ oldest job is still actively compressing data,
|
||
|
|
but everything it has produced has also been flushed so far,
|
||
|
|
therefore flush speed is limited by production speed of oldest job
|
||
|
|
irrespective of the speed of concurrent (and newer) jobs.
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<h3>Advanced Streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR>
|
||
|
|
<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset + ZSTD_DCtx_loadDictionary, see zstd.h for detailed instructions")
|
||
|
|
ZSTDLIB_STATIC_API size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize);
|
||
|
|
</b><p>
|
||
|
|
ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
|
||
|
|
ZSTD_DCtx_loadDictionary(zds, dict, dictSize);
|
||
|
|
|
||
|
|
note: no dictionary will be used if dict == NULL or dictSize < 8
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset + ZSTD_DCtx_refDDict, see zstd.h for detailed instructions")
|
||
|
|
ZSTDLIB_STATIC_API size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* zds, const ZSTD_DDict* ddict);
|
||
|
|
</b><p>
|
||
|
|
ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
|
||
|
|
ZSTD_DCtx_refDDict(zds, ddict);
|
||
|
|
|
||
|
|
note : ddict is referenced, it must outlive decompression session
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTD_DEPRECATED("use ZSTD_DCtx_reset, see zstd.h for detailed instructions")
|
||
|
|
ZSTDLIB_STATIC_API size_t ZSTD_resetDStream(ZSTD_DStream* zds);
|
||
|
|
</b><p>
|
||
|
|
ZSTD_DCtx_reset(zds, ZSTD_reset_session_only);
|
||
|
|
|
||
|
|
reuse decompression parameters from previous init; saves dictionary loading
|
||
|
|
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API void
|
||
|
|
ZSTD_registerSequenceProducer(
|
||
|
|
ZSTD_CCtx* cctx,
|
||
|
|
void* sequenceProducerState,
|
||
|
|
ZSTD_sequenceProducer_F sequenceProducer
|
||
|
|
);
|
||
|
|
</b><p> Instruct zstd to use a block-level external sequence producer function.
|
||
|
|
|
||
|
|
The sequenceProducerState must be initialized by the caller, and the caller is
|
||
|
|
responsible for managing its lifetime. This parameter is sticky across
|
||
|
|
compressions. It will remain set until the user explicitly resets compression
|
||
|
|
parameters.
|
||
|
|
|
||
|
|
Sequence producer registration is considered to be an "advanced parameter",
|
||
|
|
part of the "advanced API". This means it will only have an effect on compression
|
||
|
|
APIs which respect advanced parameters, such as compress2() and compressStream2().
|
||
|
|
Older compression APIs such as compressCCtx(), which predate the introduction of
|
||
|
|
"advanced parameters", will ignore any external sequence producer setting.
|
||
|
|
|
||
|
|
The sequence producer can be "cleared" by registering a NULL function pointer. This
|
||
|
|
removes all limitations described above in the "LIMITATIONS" section of the API docs.
|
||
|
|
|
||
|
|
The user is strongly encouraged to read the full API documentation (above) before
|
||
|
|
calling this function.
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API void
|
||
|
|
ZSTD_CCtxParams_registerSequenceProducer(
|
||
|
|
ZSTD_CCtx_params* params,
|
||
|
|
void* sequenceProducerState,
|
||
|
|
ZSTD_sequenceProducer_F sequenceProducer
|
||
|
|
);
|
||
|
|
</b><p> Same as ZSTD_registerSequenceProducer(), but operates on ZSTD_CCtx_params.
|
||
|
|
This is used for accurate size estimation with ZSTD_estimateCCtxSize_usingCCtxParams(),
|
||
|
|
which is needed when creating a ZSTD_CCtx with ZSTD_initStaticCCtx().
|
||
|
|
|
||
|
|
If you are using the external sequence producer API in a scenario where ZSTD_initStaticCCtx()
|
||
|
|
is required, then this function is for you. Otherwise, you probably don't need it.
|
||
|
|
|
||
|
|
See tests/zstreamtest.c for example usage.
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<a name="Chapter20"></a><h2>Buffer-less and synchronous inner streaming functions (DEPRECATED)</h2><pre>
|
||
|
|
This API is deprecated, and will be removed in a future version.
|
||
|
|
It allows streaming (de)compression with user allocated buffers.
|
||
|
|
However, it is hard to use, and not as well tested as the rest of
|
||
|
|
our API.
|
||
|
|
|
||
|
|
Please use the normal streaming API instead: ZSTD_compressStream2,
|
||
|
|
and ZSTD_decompressStream.
|
||
|
|
If there is functionality that you need, but it doesn't provide,
|
||
|
|
please open an issue on our GitHub.
|
||
|
|
|
||
|
|
<BR></pre>
|
||
|
|
|
||
|
|
<a name="Chapter21"></a><h2>Buffer-less streaming compression (synchronous mode)</h2><pre>
|
||
|
|
A ZSTD_CCtx object is required to track streaming operations.
|
||
|
|
Use ZSTD_createCCtx() / ZSTD_freeCCtx() to manage resource.
|
||
|
|
ZSTD_CCtx object can be reused multiple times within successive compression operations.
|
||
|
|
|
||
|
|
Start by initializing a context.
|
||
|
|
Use ZSTD_compressBegin(), or ZSTD_compressBegin_usingDict() for dictionary compression.
|
||
|
|
|
||
|
|
Then, consume your input using ZSTD_compressContinue().
|
||
|
|
There are some important considerations to keep in mind when using this advanced function :
|
||
|
|
- ZSTD_compressContinue() has no internal buffer. It uses externally provided buffers only.
|
||
|
|
- Interface is synchronous : input is consumed entirely and produces 1+ compressed blocks.
|
||
|
|
- Caller must ensure there is enough space in `dst` to store compressed data under worst case scenario.
|
||
|
|
Worst case evaluation is provided by ZSTD_compressBound().
|
||
|
|
ZSTD_compressContinue() doesn't guarantee recover after a failed compression.
|
||
|
|
- ZSTD_compressContinue() presumes prior input ***is still accessible and unmodified*** (up to maximum distance size, see WindowLog).
|
||
|
|
It remembers all previous contiguous blocks, plus one separated memory segment (which can itself consists of multiple contiguous blocks)
|
||
|
|
- ZSTD_compressContinue() detects that prior input has been overwritten when `src` buffer overlaps.
|
||
|
|
In which case, it will "discard" the relevant memory section from its history.
|
||
|
|
|
||
|
|
Finish a frame with ZSTD_compressEnd(), which will write the last block(s) and optional checksum.
|
||
|
|
It's possible to use srcSize==0, in which case, it will write a final empty block to end the frame.
|
||
|
|
Without last block mark, frames are considered unfinished (hence corrupted) by compliant decoders.
|
||
|
|
|
||
|
|
`ZSTD_CCtx` object can be reused (ZSTD_compressBegin()) to compress again.
|
||
|
|
<BR></pre>
|
||
|
|
|
||
|
|
<h3>Buffer-less streaming compression functions</h3><pre></pre><b><pre>ZSTD_DEPRECATED("The buffer-less API is deprecated in favor of the normal streaming API. See docs.")
|
||
|
|
ZSTDLIB_STATIC_API size_t ZSTD_compressBegin(ZSTD_CCtx* cctx, int compressionLevel);
|
||
|
|
ZSTD_DEPRECATED("The buffer-less API is deprecated in favor of the normal streaming API. See docs.")
|
||
|
|
ZSTDLIB_STATIC_API size_t ZSTD_compressBegin_usingDict(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, int compressionLevel);
|
||
|
|
ZSTD_DEPRECATED("The buffer-less API is deprecated in favor of the normal streaming API. See docs.")
|
||
|
|
ZSTDLIB_STATIC_API size_t ZSTD_compressBegin_usingCDict(ZSTD_CCtx* cctx, const ZSTD_CDict* cdict); </b>/**< note: fails if cdict==NULL */<b>
|
||
|
|
</pre></b><BR>
|
||
|
|
<pre><b>size_t ZSTD_copyCCtx(ZSTD_CCtx* cctx, const ZSTD_CCtx* preparedCCtx, unsigned long long pledgedSrcSize); </b>/**< note: if pledgedSrcSize is not known, use ZSTD_CONTENTSIZE_UNKNOWN */<b>
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>size_t ZSTD_compressBegin_advanced(ZSTD_CCtx* cctx, const void* dict, size_t dictSize, ZSTD_parameters params, unsigned long long pledgedSrcSize); </b>/**< pledgedSrcSize : If srcSize is not known at init time, use ZSTD_CONTENTSIZE_UNKNOWN */<b>
|
||
|
|
</b></pre><BR>
|
||
|
|
<a name="Chapter22"></a><h2>Buffer-less streaming decompression (synchronous mode)</h2><pre>
|
||
|
|
A ZSTD_DCtx object is required to track streaming operations.
|
||
|
|
Use ZSTD_createDCtx() / ZSTD_freeDCtx() to manage it.
|
||
|
|
A ZSTD_DCtx object can be reused multiple times.
|
||
|
|
|
||
|
|
First typical operation is to retrieve frame parameters, using ZSTD_getFrameHeader().
|
||
|
|
Frame header is extracted from the beginning of compressed frame, so providing only the frame's beginning is enough.
|
||
|
|
Data fragment must be large enough to ensure successful decoding.
|
||
|
|
`ZSTD_frameHeaderSize_max` bytes is guaranteed to always be large enough.
|
||
|
|
result : 0 : successful decoding, the `ZSTD_frameHeader` structure is correctly filled.
|
||
|
|
>0 : `srcSize` is too small, please provide at least result bytes on next attempt.
|
||
|
|
errorCode, which can be tested using ZSTD_isError().
|
||
|
|
|
||
|
|
It fills a ZSTD_frameHeader structure with important information to correctly decode the frame,
|
||
|
|
such as the dictionary ID, content size, or maximum back-reference distance (`windowSize`).
|
||
|
|
Note that these values could be wrong, either because of data corruption, or because a 3rd party deliberately spoofs false information.
|
||
|
|
As a consequence, check that values remain within valid application range.
|
||
|
|
For example, do not allocate memory blindly, check that `windowSize` is within expectation.
|
||
|
|
Each application can set its own limits, depending on local restrictions.
|
||
|
|
For extended interoperability, it is recommended to support `windowSize` of at least 8 MB.
|
||
|
|
|
||
|
|
ZSTD_decompressContinue() needs previous data blocks during decompression, up to `windowSize` bytes.
|
||
|
|
ZSTD_decompressContinue() is very sensitive to contiguity,
|
||
|
|
if 2 blocks don't follow each other, make sure that either the compressor breaks contiguity at the same place,
|
||
|
|
or that previous contiguous segment is large enough to properly handle maximum back-reference distance.
|
||
|
|
There are multiple ways to guarantee this condition.
|
||
|
|
|
||
|
|
The most memory efficient way is to use a round buffer of sufficient size.
|
||
|
|
Sufficient size is determined by invoking ZSTD_decodingBufferSize_min(),
|
||
|
|
which can return an error code if required value is too large for current system (in 32-bits mode).
|
||
|
|
In a round buffer methodology, ZSTD_decompressContinue() decompresses each block next to previous one,
|
||
|
|
up to the moment there is not enough room left in the buffer to guarantee decoding another full block,
|
||
|
|
which maximum size is provided in `ZSTD_frameHeader` structure, field `blockSizeMax`.
|
||
|
|
At which point, decoding can resume from the beginning of the buffer.
|
||
|
|
Note that already decoded data stored in the buffer should be flushed before being overwritten.
|
||
|
|
|
||
|
|
There are alternatives possible, for example using two or more buffers of size `windowSize` each, though they consume more memory.
|
||
|
|
|
||
|
|
Finally, if you control the compression process, you can also ignore all buffer size rules,
|
||
|
|
as long as the encoder and decoder progress in "lock-step",
|
||
|
|
aka use exactly the same buffer sizes, break contiguity at the same place, etc.
|
||
|
|
|
||
|
|
Once buffers are setup, start decompression, with ZSTD_decompressBegin().
|
||
|
|
If decompression requires a dictionary, use ZSTD_decompressBegin_usingDict() or ZSTD_decompressBegin_usingDDict().
|
||
|
|
|
||
|
|
Then use ZSTD_nextSrcSizeToDecompress() and ZSTD_decompressContinue() alternatively.
|
||
|
|
ZSTD_nextSrcSizeToDecompress() tells how many bytes to provide as 'srcSize' to ZSTD_decompressContinue().
|
||
|
|
ZSTD_decompressContinue() requires this _exact_ amount of bytes, or it will fail.
|
||
|
|
|
||
|
|
result of ZSTD_decompressContinue() is the number of bytes regenerated within 'dst' (necessarily <= dstCapacity).
|
||
|
|
It can be zero : it just means ZSTD_decompressContinue() has decoded some metadata item.
|
||
|
|
It can also be an error code, which can be tested with ZSTD_isError().
|
||
|
|
|
||
|
|
A frame is fully decoded when ZSTD_nextSrcSizeToDecompress() returns zero.
|
||
|
|
Context can then be reset to start a new decompression.
|
||
|
|
|
||
|
|
Note : it's possible to know if next input to present is a header or a block, using ZSTD_nextInputType().
|
||
|
|
This information is not required to properly decode a frame.
|
||
|
|
|
||
|
|
== Special case : skippable frames
|
||
|
|
|
||
|
|
Skippable frames allow integration of user-defined data into a flow of concatenated frames.
|
||
|
|
Skippable frames will be ignored (skipped) by decompressor.
|
||
|
|
The format of skippable frames is as follows :
|
||
|
|
a) Skippable frame ID - 4 Bytes, Little endian format, any value from 0x184D2A50 to 0x184D2A5F
|
||
|
|
b) Frame Size - 4 Bytes, Little endian format, unsigned 32-bits
|
||
|
|
c) Frame Content - any content (User Data) of length equal to Frame Size
|
||
|
|
For skippable frames ZSTD_getFrameHeader() returns zfhPtr->frameType==ZSTD_skippableFrame.
|
||
|
|
For skippable frames ZSTD_decompressContinue() always returns 0 : it only skips the content.
|
||
|
|
<BR></pre>
|
||
|
|
|
||
|
|
<h3>Buffer-less streaming decompression functions</h3><pre></pre><b><pre></pre></b><BR>
|
||
|
|
<pre><b>ZSTDLIB_STATIC_API size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long long frameContentSize); </b>/**< when frame content size is not known, pass in frameContentSize == ZSTD_CONTENTSIZE_UNKNOWN */<b>
|
||
|
|
</b></pre><BR>
|
||
|
|
<pre><b>typedef enum { ZSTDnit_frameHeader, ZSTDnit_blockHeader, ZSTDnit_block, ZSTDnit_lastBlock, ZSTDnit_checksum, ZSTDnit_skippableFrame } ZSTD_nextInputType_e;
|
||
|
|
</b></pre><BR>
|
||
|
|
<a name="Chapter23"></a><h2>Block level API (DEPRECATED)</h2><pre></pre>
|
||
|
|
|
||
|
|
<pre><b></b><p> You can get the frame header down to 2 bytes by setting:
|
||
|
|
- ZSTD_c_format = ZSTD_f_zstd1_magicless
|
||
|
|
- ZSTD_c_contentSizeFlag = 0
|
||
|
|
- ZSTD_c_checksumFlag = 0
|
||
|
|
- ZSTD_c_dictIDFlag = 0
|
||
|
|
|
||
|
|
This API is not as well tested as our normal API, so we recommend not using it.
|
||
|
|
We will be removing it in a future version. If the normal API doesn't provide
|
||
|
|
the functionality you need, please open a GitHub issue.
|
||
|
|
|
||
|
|
Block functions produce and decode raw zstd blocks, without frame metadata.
|
||
|
|
Frame metadata cost is typically ~12 bytes, which can be non-negligible for very small blocks (< 100 bytes).
|
||
|
|
But users will have to take in charge needed metadata to regenerate data, such as compressed and content sizes.
|
||
|
|
|
||
|
|
A few rules to respect :
|
||
|
|
- Compressing and decompressing require a context structure
|
||
|
|
+ Use ZSTD_createCCtx() and ZSTD_createDCtx()
|
||
|
|
- It is necessary to init context before starting
|
||
|
|
+ compression : any ZSTD_compressBegin*() variant, including with dictionary
|
||
|
|
+ decompression : any ZSTD_decompressBegin*() variant, including with dictionary
|
||
|
|
- Block size is limited, it must be <= ZSTD_getBlockSize() <= ZSTD_BLOCKSIZE_MAX == 128 KB
|
||
|
|
+ If input is larger than a block size, it's necessary to split input data into multiple blocks
|
||
|
|
+ For inputs larger than a single block, consider using regular ZSTD_compress() instead.
|
||
|
|
Frame metadata is not that costly, and quickly becomes negligible as source size grows larger than a block.
|
||
|
|
- When a block is considered not compressible enough, ZSTD_compressBlock() result will be 0 (zero) !
|
||
|
|
===> In which case, nothing is produced into `dst` !
|
||
|
|
+ User __must__ test for such outcome and deal directly with uncompressed data
|
||
|
|
+ A block cannot be declared incompressible if ZSTD_compressBlock() return value was != 0.
|
||
|
|
Doing so would mess up with statistics history, leading to potential data corruption.
|
||
|
|
+ ZSTD_decompressBlock() _doesn't accept uncompressed data as input_ !!
|
||
|
|
+ In case of multiple successive blocks, should some of them be uncompressed,
|
||
|
|
decoder must be informed of their existence in order to follow proper history.
|
||
|
|
Use ZSTD_insertBlock() for such a case.
|
||
|
|
</p></pre><BR>
|
||
|
|
|
||
|
|
<h3>Raw zstd block functions</h3><pre></pre><b><pre>ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.")
|
||
|
|
ZSTDLIB_STATIC_API size_t ZSTD_getBlockSize (const ZSTD_CCtx* cctx);
|
||
|
|
ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.")
|
||
|
|
ZSTDLIB_STATIC_API size_t ZSTD_compressBlock (ZSTD_CCtx* cctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
|
||
|
|
ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.")
|
||
|
|
ZSTDLIB_STATIC_API size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize);
|
||
|
|
ZSTD_DEPRECATED("The block API is deprecated in favor of the normal compression API. See docs.")
|
||
|
|
ZSTDLIB_STATIC_API size_t ZSTD_insertBlock (ZSTD_DCtx* dctx, const void* blockStart, size_t blockSize); </b>/**< insert uncompressed block into `dctx` history. Useful for multi-blocks decompression. */<b>
|
||
|
|
</pre></b><BR>
|
||
|
|
</html>
|
||
|
|
</body>
|