41 lines
2.1 KiB
C
41 lines
2.1 KiB
C
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/* zran.h -- example of zlib/gzip stream indexing and random access
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* Copyright (C) 2005, 2012, 2018 Mark Adler
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* For conditions of distribution and use, see copyright notice in zlib.h
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* Version 1.2 14 Oct 2018 Mark Adler */
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#include <stdio.h>
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#include "zlib.h"
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/* Access point list. */
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struct deflate_index {
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int have; /* number of list entries */
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int gzip; /* 1 if the index is of a gzip file, 0 if it is of a
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zlib stream */
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off_t length; /* total length of uncompressed data */
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void *list; /* allocated list of entries */
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};
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/* Make one entire pass through a zlib or gzip compressed stream and build an
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index, with access points about every span bytes of uncompressed output.
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gzip files with multiple members are indexed in their entirety. span should
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be chosen to balance the speed of random access against the memory
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requirements of the list, about 32K bytes per access point. The return value
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is the number of access points on success (>= 1), Z_MEM_ERROR for out of
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memory, Z_DATA_ERROR for an error in the input file, or Z_ERRNO for a file
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read error. On success, *built points to the resulting index. */
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int deflate_index_build(FILE *in, off_t span, struct deflate_index **built);
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/* Deallocate an index built by deflate_index_build() */
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void deflate_index_free(struct deflate_index *index);
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/* Use the index to read len bytes from offset into buf. Return bytes read or
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negative for error (Z_DATA_ERROR or Z_MEM_ERROR). If data is requested past
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the end of the uncompressed data, then deflate_index_extract() will return a
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value less than len, indicating how much was actually read into buf. This
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function should not return a data error unless the file was modified since
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the index was generated, since deflate_index_build() validated all of the
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input. deflate_index_extract() will return Z_ERRNO if there is an error on
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reading or seeking the input file. */
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int deflate_index_extract(FILE *in, struct deflate_index *index, off_t offset,
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unsigned char *buf, int len);
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