/* * Copyright (c) Meta Platforms, Inc. and affiliates. * All rights reserved. * * This source code is licensed under both the BSD-style license (found in the * LICENSE file in the root directory of this source tree) and the GPLv2 (found * in the COPYING file in the root directory of this source tree). * You may select, at your option, one of the above-listed licenses. */ /* zstd_decompress_block : * this module takes care of decompressing _compressed_ block */ /*-******************************************************* * Dependencies *********************************************************/ #include "../common/zstd_deps.h" /* ZSTD_memcpy, ZSTD_memmove, ZSTD_memset */ #include "../common/compiler.h" /* prefetch */ #include "../common/cpu.h" /* bmi2 */ #include "../common/mem.h" /* low level memory routines */ #define FSE_STATIC_LINKING_ONLY #include "../common/fse.h" #include "../common/huf.h" #include "../common/zstd_internal.h" #include "zstd_decompress_internal.h" /* ZSTD_DCtx */ #include "zstd_ddict.h" /* ZSTD_DDictDictContent */ #include "zstd_decompress_block.h" #include "../common/bits.h" /* ZSTD_highbit32 */ /*_******************************************************* * Macros **********************************************************/ /* These two optional macros force the use one way or another of the two * ZSTD_decompressSequences implementations. You can't force in both directions * at the same time. */ #if defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT) && \ defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG) #error "Cannot force the use of the short and the long ZSTD_decompressSequences variants!" #endif /*_******************************************************* * Memory operations **********************************************************/ static void ZSTD_copy4(void* dst, const void* src) { ZSTD_memcpy(dst, src, 4); } /*-************************************************************* * Block decoding ***************************************************************/ static size_t ZSTD_blockSizeMax(ZSTD_DCtx const* dctx) { size_t const blockSizeMax = dctx->isFrameDecompression ? dctx->fParams.blockSizeMax : ZSTD_BLOCKSIZE_MAX; assert(blockSizeMax <= ZSTD_BLOCKSIZE_MAX); return blockSizeMax; } /*! ZSTD_getcBlockSize() : * Provides the size of compressed block from block header `src` */ size_t ZSTD_getcBlockSize(const void* src, size_t srcSize, blockProperties_t* bpPtr) { RETURN_ERROR_IF(srcSize < ZSTD_blockHeaderSize, srcSize_wrong, ""); { U32 const cBlockHeader = MEM_readLE24(src); U32 const cSize = cBlockHeader >> 3; bpPtr->lastBlock = cBlockHeader & 1; bpPtr->blockType = (blockType_e)((cBlockHeader >> 1) & 3); bpPtr->origSize = cSize; /* only useful for RLE */ if (bpPtr->blockType == bt_rle) return 1; RETURN_ERROR_IF(bpPtr->blockType == bt_reserved, corruption_detected, ""); return cSize; } } /* Allocate buffer for literals, either overlapping current dst, or split between dst and litExtraBuffer, or stored entirely within litExtraBuffer */ static void ZSTD_allocateLiteralsBuffer(ZSTD_DCtx* dctx, void* const dst, const size_t dstCapacity, const size_t litSize, const streaming_operation streaming, const size_t expectedWriteSize, const unsigned splitImmediately) { size_t const blockSizeMax = ZSTD_blockSizeMax(dctx); assert(litSize <= blockSizeMax); assert(dctx->isFrameDecompression || streaming == not_streaming); assert(expectedWriteSize <= blockSizeMax); if (streaming == not_streaming && dstCapacity > blockSizeMax + WILDCOPY_OVERLENGTH + litSize + WILDCOPY_OVERLENGTH) { /* If we aren't streaming, we can just put the literals after the output * of the current block. We don't need to worry about overwriting the * extDict of our window, because it doesn't exist. * So if we have space after the end of the block, just put it there. */ dctx->litBuffer = (BYTE*)dst + blockSizeMax + WILDCOPY_OVERLENGTH; dctx->litBufferEnd = dctx->litBuffer + litSize; dctx->litBufferLocation = ZSTD_in_dst; } else if (litSize <= ZSTD_LITBUFFEREXTRASIZE) { /* Literals fit entirely within the extra buffer, put them there to avoid * having to split the literals. */ dctx->litBuffer = dctx->litExtraBuffer; dctx->litBufferEnd = dctx->litBuffer + litSize; dctx->litBufferLocation = ZSTD_not_in_dst; } else { assert(blockSizeMax > ZSTD_LITBUFFEREXTRASIZE); /* Literals must be split between the output block and the extra lit * buffer. We fill the extra lit buffer with the tail of the literals, * and put the rest of the literals at the end of the block, with * WILDCOPY_OVERLENGTH of buffer room to allow for overreads. * This MUST not write more than our maxBlockSize beyond dst, because in * streaming mode, that could overwrite part of our extDict window. */ if (splitImmediately) { /* won't fit in litExtraBuffer, so it will be split between end of dst and extra buffer */ dctx->litBuffer = (BYTE*)dst + expectedWriteSize - litSize + ZSTD_LITBUFFEREXTRASIZE - WILDCOPY_OVERLENGTH; dctx->litBufferEnd = dctx->litBuffer + litSize - ZSTD_LITBUFFEREXTRASIZE; } else { /* initially this will be stored entirely in dst during huffman decoding, it will partially be shifted to litExtraBuffer after */ dctx->litBuffer = (BYTE*)dst + expectedWriteSize - litSize; dctx->litBufferEnd = (BYTE*)dst + expectedWriteSize; } dctx->litBufferLocation = ZSTD_split; assert(dctx->litBufferEnd <= (BYTE*)dst + expectedWriteSize); } } /*! ZSTD_decodeLiteralsBlock() : * Where it is possible to do so without being stomped by the output during decompression, the literals block will be stored * in the dstBuffer. If there is room to do so, it will be stored in full in the excess dst space after where the current * block will be output. Otherwise it will be stored at the end of the current dst blockspace, with a small portion being * stored in dctx->litExtraBuffer to help keep it "ahead" of the current output write. * * @return : nb of bytes read from src (< srcSize ) * note : symbol not declared but exposed for fullbench */ static size_t ZSTD_decodeLiteralsBlock(ZSTD_DCtx* dctx, const void* src, size_t srcSize, /* note : srcSize < BLOCKSIZE */ void* dst, size_t dstCapacity, const streaming_operation streaming) { DEBUGLOG(5, "ZSTD_decodeLiteralsBlock"); RETURN_ERROR_IF(srcSize < MIN_CBLOCK_SIZE, corruption_detected, ""); { const BYTE* const istart = (const BYTE*) src; symbolEncodingType_e const litEncType = (symbolEncodingType_e)(istart[0] & 3); size_t const blockSizeMax = ZSTD_blockSizeMax(dctx); switch(litEncType) { case set_repeat: DEBUGLOG(5, "set_repeat flag : re-using stats from previous compressed literals block"); RETURN_ERROR_IF(dctx->litEntropy==0, dictionary_corrupted, ""); ZSTD_FALLTHROUGH; case set_compressed: RETURN_ERROR_IF(srcSize < 5, corruption_detected, "srcSize >= MIN_CBLOCK_SIZE == 2; here we need up to 5 for case 3"); { size_t lhSize, litSize, litCSize; U32 singleStream=0; U32 const lhlCode = (istart[0] >> 2) & 3; U32 const lhc = MEM_readLE32(istart); size_t hufSuccess; size_t expectedWriteSize = MIN(blockSizeMax, dstCapacity); int const flags = 0 | (ZSTD_DCtx_get_bmi2(dctx) ? HUF_flags_bmi2 : 0) | (dctx->disableHufAsm ? HUF_flags_disableAsm : 0); switch(lhlCode) { case 0: case 1: default: /* note : default is impossible, since lhlCode into [0..3] */ /* 2 - 2 - 10 - 10 */ singleStream = !lhlCode; lhSize = 3; litSize = (lhc >> 4) & 0x3FF; litCSize = (lhc >> 14) & 0x3FF; break; case 2: /* 2 - 2 - 14 - 14 */ lhSize = 4; litSize = (lhc >> 4) & 0x3FFF; litCSize = lhc >> 18; break; case 3: /* 2 - 2 - 18 - 18 */ lhSize = 5; litSize = (lhc >> 4) & 0x3FFFF; litCSize = (lhc >> 22) + ((size_t)istart[4] << 10); break; } RETURN_ERROR_IF(litSize > 0 && dst == NULL, dstSize_tooSmall, "NULL not handled"); RETURN_ERROR_IF(litSize > blockSizeMax, corruption_detected, ""); if (!singleStream) RETURN_ERROR_IF(litSize < MIN_LITERALS_FOR_4_STREAMS, literals_headerWrong, "Not enough literals (%zu) for the 4-streams mode (min %u)", litSize, MIN_LITERALS_FOR_4_STREAMS); RETURN_ERROR_IF(litCSize + lhSize > srcSize, corruption_detected, ""); RETURN_ERROR_IF(expectedWriteSize < litSize , dstSize_tooSmall, ""); ZSTD_allocateLiteralsBuffer(dctx, dst, dstCapacity, litSize, streaming, expectedWriteSize, 0); /* prefetch huffman table if cold */ if (dctx->ddictIsCold && (litSize > 768 /* heuristic */)) { PREFETCH_AREA(dctx->HUFptr, sizeof(dctx->entropy.hufTable)); } if (litEncType==set_repeat) { if (singleStream) { hufSuccess = HUF_decompress1X_usingDTable( dctx->litBuffer, litSize, istart+lhSize, litCSize, dctx->HUFptr, flags); } else { assert(litSize >= MIN_LITERALS_FOR_4_STREAMS); hufSuccess = HUF_decompress4X_usingDTable( dctx->litBuffer, litSize, istart+lhSize, litCSize, dctx->HUFptr, flags); } } else { if (singleStream) { #if defined(HUF_FORCE_DECOMPRESS_X2) hufSuccess = HUF_decompress1X_DCtx_wksp( dctx->entropy.hufTable, dctx->litBuffer, litSize, istart+lhSize, litCSize, dctx->workspace, sizeof(dctx->workspace), flags); #else hufSuccess = HUF_decompress1X1_DCtx_wksp( dctx->entropy.hufTable, dctx->litBuffer, litSize, istart+lhSize, litCSize, dctx->workspace, sizeof(dctx->workspace), flags); #endif } else { hufSuccess = HUF_decompress4X_hufOnly_wksp( dctx->entropy.hufTable, dctx->litBuffer, litSize, istart+lhSize, litCSize, dctx->workspace, sizeof(dctx->workspace), flags); } } if (dctx->litBufferLocation == ZSTD_split) { assert(litSize > ZSTD_LITBUFFEREXTRASIZE); ZSTD_memcpy(dctx->litExtraBuffer, dctx->litBufferEnd - ZSTD_LITBUFFEREXTRASIZE, ZSTD_LITBUFFEREXTRASIZE); ZSTD_memmove(dctx->litBuffer + ZSTD_LITBUFFEREXTRASIZE - WILDCOPY_OVERLENGTH, dctx->litBuffer, litSize - ZSTD_LITBUFFEREXTRASIZE); dctx->litBuffer += ZSTD_LITBUFFEREXTRASIZE - WILDCOPY_OVERLENGTH; dctx->litBufferEnd -= WILDCOPY_OVERLENGTH; assert(dctx->litBufferEnd <= (BYTE*)dst + blockSizeMax); } RETURN_ERROR_IF(HUF_isError(hufSuccess), corruption_detected, ""); dctx->litPtr = dctx->litBuffer; dctx->litSize = litSize; dctx->litEntropy = 1; if (litEncType==set_compressed) dctx->HUFptr = dctx->entropy.hufTable; return litCSize + lhSize; } case set_basic: { size_t litSize, lhSize; U32 const lhlCode = ((istart[0]) >> 2) & 3; size_t expectedWriteSize = MIN(blockSizeMax, dstCapacity); switch(lhlCode) { case 0: case 2: default: /* note : default is impossible, since lhlCode into [0..3] */ lhSize = 1; litSize = istart[0] >> 3; break; case 1: lhSize = 2; litSize = MEM_readLE16(istart) >> 4; break; case 3: lhSize = 3; RETURN_ERROR_IF(srcSize<3, corruption_detected, "srcSize >= MIN_CBLOCK_SIZE == 2; here we need lhSize = 3"); litSize = MEM_readLE24(istart) >> 4; break; } RETURN_ERROR_IF(litSize > 0 && dst == NULL, dstSize_tooSmall, "NULL not handled"); RETURN_ERROR_IF(litSize > blockSizeMax, corruption_detected, ""); RETURN_ERROR_IF(expectedWriteSize < litSize, dstSize_tooSmall, ""); ZSTD_allocateLiteralsBuffer(dctx, dst, dstCapacity, litSize, streaming, expectedWriteSize, 1); if (lhSize+litSize+WILDCOPY_OVERLENGTH > srcSize) { /* risk reading beyond src buffer with wildcopy */ RETURN_ERROR_IF(litSize+lhSize > srcSize, corruption_detected, ""); if (dctx->litBufferLocation == ZSTD_split) { ZSTD_memcpy(dctx->litBuffer, istart + lhSize, litSize - ZSTD_LITBUFFEREXTRASIZE); ZSTD_memcpy(dctx->litExtraBuffer, istart + lhSize + litSize - ZSTD_LITBUFFEREXTRASIZE, ZSTD_LITBUFFEREXTRASIZE); } else { ZSTD_memcpy(dctx->litBuffer, istart + lhSize, litSize); } dctx->litPtr = dctx->litBuffer; dctx->litSize = litSize; return lhSize+litSize; } /* direct reference into compressed stream */ dctx->litPtr = istart+lhSize; dctx->litSize = litSize; dctx->litBufferEnd = dctx->litPtr + litSize; dctx->litBufferLocation = ZSTD_not_in_dst; return lhSize+litSize; } case set_rle: { U32 const lhlCode = ((istart[0]) >> 2) & 3; size_t litSize, lhSize; size_t expectedWriteSize = MIN(blockSizeMax, dstCapacity); switch(lhlCode) { case 0: case 2: default: /* note : default is impossible, since lhlCode into [0..3] */ lhSize = 1; litSize = istart[0] >> 3; break; case 1: lhSize = 2; RETURN_ERROR_IF(srcSize<3, corruption_detected, "srcSize >= MIN_CBLOCK_SIZE == 2; here we need lhSize+1 = 3"); litSize = MEM_readLE16(istart) >> 4; break; case 3: lhSize = 3; RETURN_ERROR_IF(srcSize<4, corruption_detected, "srcSize >= MIN_CBLOCK_SIZE == 2; here we need lhSize+1 = 4"); litSize = MEM_readLE24(istart) >> 4; break; } RETURN_ERROR_IF(litSize > 0 && dst == NULL, dstSize_tooSmall, "NULL not handled"); RETURN_ERROR_IF(litSize > blockSizeMax, corruption_detected, ""); RETURN_ERROR_IF(expectedWriteSize < litSize, dstSize_tooSmall, ""); ZSTD_allocateLiteralsBuffer(dctx, dst, dstCapacity, litSize, streaming, expectedWriteSize, 1); if (dctx->litBufferLocation == ZSTD_split) { ZSTD_memset(dctx->litBuffer, istart[lhSize], litSize - ZSTD_LITBUFFEREXTRASIZE); ZSTD_memset(dctx->litExtraBuffer, istart[lhSize], ZSTD_LITBUFFEREXTRASIZE); } else { ZSTD_memset(dctx->litBuffer, istart[lhSize], litSize); } dctx->litPtr = dctx->litBuffer; dctx->litSize = litSize; return lhSize+1; } default: RETURN_ERROR(corruption_detected, "impossible"); } } } /* Hidden declaration for fullbench */ size_t ZSTD_decodeLiteralsBlock_wrapper(ZSTD_DCtx* dctx, const void* src, size_t srcSize, void* dst, size_t dstCapacity); size_t ZSTD_decodeLiteralsBlock_wrapper(ZSTD_DCtx* dctx, const void* src, size_t srcSize, void* dst, size_t dstCapacity) { dctx->isFrameDecompression = 0; return ZSTD_decodeLiteralsBlock(dctx, src, srcSize, dst, dstCapacity, not_streaming); } /* Default FSE distribution tables. * These are pre-calculated FSE decoding tables using default distributions as defined in specification : * https://github.com/facebook/zstd/blob/release/doc/zstd_compression_format.md#default-distributions * They were generated programmatically with following method : * - start from default distributions, present in /lib/common/zstd_internal.h * - generate tables normally, using ZSTD_buildFSETable() * - printout the content of tables * - pretify output, report below, test with fuzzer to ensure it's correct */ /* Default FSE distribution table for Literal Lengths */ static const ZSTD_seqSymbol LL_defaultDTable[(1<tableLog = 0; DTableH->fastMode = 0; cell->nbBits = 0; cell->nextState = 0; assert(nbAddBits < 255); cell->nbAdditionalBits = nbAddBits; cell->baseValue = baseValue; } /* ZSTD_buildFSETable() : * generate FSE decoding table for one symbol (ll, ml or off) * cannot fail if input is valid => * all inputs are presumed validated at this stage */ FORCE_INLINE_TEMPLATE void ZSTD_buildFSETable_body(ZSTD_seqSymbol* dt, const short* normalizedCounter, unsigned maxSymbolValue, const U32* baseValue, const U8* nbAdditionalBits, unsigned tableLog, void* wksp, size_t wkspSize) { ZSTD_seqSymbol* const tableDecode = dt+1; U32 const maxSV1 = maxSymbolValue + 1; U32 const tableSize = 1 << tableLog; U16* symbolNext = (U16*)wksp; BYTE* spread = (BYTE*)(symbolNext + MaxSeq + 1); U32 highThreshold = tableSize - 1; /* Sanity Checks */ assert(maxSymbolValue <= MaxSeq); assert(tableLog <= MaxFSELog); assert(wkspSize >= ZSTD_BUILD_FSE_TABLE_WKSP_SIZE); (void)wkspSize; /* Init, lay down lowprob symbols */ { ZSTD_seqSymbol_header DTableH; DTableH.tableLog = tableLog; DTableH.fastMode = 1; { S16 const largeLimit= (S16)(1 << (tableLog-1)); U32 s; for (s=0; s= largeLimit) DTableH.fastMode=0; assert(normalizedCounter[s]>=0); symbolNext[s] = (U16)normalizedCounter[s]; } } } ZSTD_memcpy(dt, &DTableH, sizeof(DTableH)); } /* Spread symbols */ assert(tableSize <= 512); /* Specialized symbol spreading for the case when there are * no low probability (-1 count) symbols. When compressing * small blocks we avoid low probability symbols to hit this * case, since header decoding speed matters more. */ if (highThreshold == tableSize - 1) { size_t const tableMask = tableSize-1; size_t const step = FSE_TABLESTEP(tableSize); /* First lay down the symbols in order. * We use a uint64_t to lay down 8 bytes at a time. This reduces branch * misses since small blocks generally have small table logs, so nearly * all symbols have counts <= 8. We ensure we have 8 bytes at the end of * our buffer to handle the over-write. */ { U64 const add = 0x0101010101010101ull; size_t pos = 0; U64 sv = 0; U32 s; for (s=0; s=0); pos += (size_t)n; } } /* Now we spread those positions across the table. * The benefit of doing it in two stages is that we avoid the * variable size inner loop, which caused lots of branch misses. * Now we can run through all the positions without any branch misses. * We unroll the loop twice, since that is what empirically worked best. */ { size_t position = 0; size_t s; size_t const unroll = 2; assert(tableSize % unroll == 0); /* FSE_MIN_TABLELOG is 5 */ for (s = 0; s < (size_t)tableSize; s += unroll) { size_t u; for (u = 0; u < unroll; ++u) { size_t const uPosition = (position + (u * step)) & tableMask; tableDecode[uPosition].baseValue = spread[s + u]; } position = (position + (unroll * step)) & tableMask; } assert(position == 0); } } else { U32 const tableMask = tableSize-1; U32 const step = FSE_TABLESTEP(tableSize); U32 s, position = 0; for (s=0; s highThreshold)) position = (position + step) & tableMask; /* lowprob area */ } } assert(position == 0); /* position must reach all cells once, otherwise normalizedCounter is incorrect */ } /* Build Decoding table */ { U32 u; for (u=0; u max, corruption_detected, ""); { U32 const symbol = *(const BYTE*)src; U32 const baseline = baseValue[symbol]; U8 const nbBits = nbAdditionalBits[symbol]; ZSTD_buildSeqTable_rle(DTableSpace, baseline, nbBits); } *DTablePtr = DTableSpace; return 1; case set_basic : *DTablePtr = defaultTable; return 0; case set_repeat: RETURN_ERROR_IF(!flagRepeatTable, corruption_detected, ""); /* prefetch FSE table if used */ if (ddictIsCold && (nbSeq > 24 /* heuristic */)) { const void* const pStart = *DTablePtr; size_t const pSize = sizeof(ZSTD_seqSymbol) * (SEQSYMBOL_TABLE_SIZE(maxLog)); PREFETCH_AREA(pStart, pSize); } return 0; case set_compressed : { unsigned tableLog; S16 norm[MaxSeq+1]; size_t const headerSize = FSE_readNCount(norm, &max, &tableLog, src, srcSize); RETURN_ERROR_IF(FSE_isError(headerSize), corruption_detected, ""); RETURN_ERROR_IF(tableLog > maxLog, corruption_detected, ""); ZSTD_buildFSETable(DTableSpace, norm, max, baseValue, nbAdditionalBits, tableLog, wksp, wkspSize, bmi2); *DTablePtr = DTableSpace; return headerSize; } default : assert(0); RETURN_ERROR(GENERIC, "impossible"); } } size_t ZSTD_decodeSeqHeaders(ZSTD_DCtx* dctx, int* nbSeqPtr, const void* src, size_t srcSize) { const BYTE* const istart = (const BYTE*)src; const BYTE* const iend = istart + srcSize; const BYTE* ip = istart; int nbSeq; DEBUGLOG(5, "ZSTD_decodeSeqHeaders"); /* check */ RETURN_ERROR_IF(srcSize < MIN_SEQUENCES_SIZE, srcSize_wrong, ""); /* SeqHead */ nbSeq = *ip++; if (!nbSeq) { *nbSeqPtr=0; RETURN_ERROR_IF(srcSize != 1, srcSize_wrong, ""); return 1; } if (nbSeq > 0x7F) { if (nbSeq == 0xFF) { RETURN_ERROR_IF(ip+2 > iend, srcSize_wrong, ""); nbSeq = MEM_readLE16(ip) + LONGNBSEQ; ip+=2; } else { RETURN_ERROR_IF(ip >= iend, srcSize_wrong, ""); nbSeq = ((nbSeq-0x80)<<8) + *ip++; } } *nbSeqPtr = nbSeq; /* FSE table descriptors */ RETURN_ERROR_IF(ip+1 > iend, srcSize_wrong, ""); /* minimum possible size: 1 byte for symbol encoding types */ { symbolEncodingType_e const LLtype = (symbolEncodingType_e)(*ip >> 6); symbolEncodingType_e const OFtype = (symbolEncodingType_e)((*ip >> 4) & 3); symbolEncodingType_e const MLtype = (symbolEncodingType_e)((*ip >> 2) & 3); ip++; /* Build DTables */ { size_t const llhSize = ZSTD_buildSeqTable(dctx->entropy.LLTable, &dctx->LLTptr, LLtype, MaxLL, LLFSELog, ip, iend-ip, LL_base, LL_bits, LL_defaultDTable, dctx->fseEntropy, dctx->ddictIsCold, nbSeq, dctx->workspace, sizeof(dctx->workspace), ZSTD_DCtx_get_bmi2(dctx)); RETURN_ERROR_IF(ZSTD_isError(llhSize), corruption_detected, "ZSTD_buildSeqTable failed"); ip += llhSize; } { size_t const ofhSize = ZSTD_buildSeqTable(dctx->entropy.OFTable, &dctx->OFTptr, OFtype, MaxOff, OffFSELog, ip, iend-ip, OF_base, OF_bits, OF_defaultDTable, dctx->fseEntropy, dctx->ddictIsCold, nbSeq, dctx->workspace, sizeof(dctx->workspace), ZSTD_DCtx_get_bmi2(dctx)); RETURN_ERROR_IF(ZSTD_isError(ofhSize), corruption_detected, "ZSTD_buildSeqTable failed"); ip += ofhSize; } { size_t const mlhSize = ZSTD_buildSeqTable(dctx->entropy.MLTable, &dctx->MLTptr, MLtype, MaxML, MLFSELog, ip, iend-ip, ML_base, ML_bits, ML_defaultDTable, dctx->fseEntropy, dctx->ddictIsCold, nbSeq, dctx->workspace, sizeof(dctx->workspace), ZSTD_DCtx_get_bmi2(dctx)); RETURN_ERROR_IF(ZSTD_isError(mlhSize), corruption_detected, "ZSTD_buildSeqTable failed"); ip += mlhSize; } } return ip-istart; } typedef struct { size_t litLength; size_t matchLength; size_t offset; } seq_t; typedef struct { size_t state; const ZSTD_seqSymbol* table; } ZSTD_fseState; typedef struct { BIT_DStream_t DStream; ZSTD_fseState stateLL; ZSTD_fseState stateOffb; ZSTD_fseState stateML; size_t prevOffset[ZSTD_REP_NUM]; } seqState_t; /*! ZSTD_overlapCopy8() : * Copies 8 bytes from ip to op and updates op and ip where ip <= op. * If the offset is < 8 then the offset is spread to at least 8 bytes. * * Precondition: *ip <= *op * Postcondition: *op - *op >= 8 */ HINT_INLINE void ZSTD_overlapCopy8(BYTE** op, BYTE const** ip, size_t offset) { assert(*ip <= *op); if (offset < 8) { /* close range match, overlap */ static const U32 dec32table[] = { 0, 1, 2, 1, 4, 4, 4, 4 }; /* added */ static const int dec64table[] = { 8, 8, 8, 7, 8, 9,10,11 }; /* subtracted */ int const sub2 = dec64table[offset]; (*op)[0] = (*ip)[0]; (*op)[1] = (*ip)[1]; (*op)[2] = (*ip)[2]; (*op)[3] = (*ip)[3]; *ip += dec32table[offset]; ZSTD_copy4(*op+4, *ip); *ip -= sub2; } else { ZSTD_copy8(*op, *ip); } *ip += 8; *op += 8; assert(*op - *ip >= 8); } /*! ZSTD_safecopy() : * Specialized version of memcpy() that is allowed to READ up to WILDCOPY_OVERLENGTH past the input buffer * and write up to 16 bytes past oend_w (op >= oend_w is allowed). * This function is only called in the uncommon case where the sequence is near the end of the block. It * should be fast for a single long sequence, but can be slow for several short sequences. * * @param ovtype controls the overlap detection * - ZSTD_no_overlap: The source and destination are guaranteed to be at least WILDCOPY_VECLEN bytes apart. * - ZSTD_overlap_src_before_dst: The src and dst may overlap and may be any distance apart. * The src buffer must be before the dst buffer. */ static void ZSTD_safecopy(BYTE* op, const BYTE* const oend_w, BYTE const* ip, ptrdiff_t length, ZSTD_overlap_e ovtype) { ptrdiff_t const diff = op - ip; BYTE* const oend = op + length; assert((ovtype == ZSTD_no_overlap && (diff <= -8 || diff >= 8 || op >= oend_w)) || (ovtype == ZSTD_overlap_src_before_dst && diff >= 0)); if (length < 8) { /* Handle short lengths. */ while (op < oend) *op++ = *ip++; return; } if (ovtype == ZSTD_overlap_src_before_dst) { /* Copy 8 bytes and ensure the offset >= 8 when there can be overlap. */ assert(length >= 8); ZSTD_overlapCopy8(&op, &ip, diff); length -= 8; assert(op - ip >= 8); assert(op <= oend); } if (oend <= oend_w) { /* No risk of overwrite. */ ZSTD_wildcopy(op, ip, length, ovtype); return; } if (op <= oend_w) { /* Wildcopy until we get close to the end. */ assert(oend > oend_w); ZSTD_wildcopy(op, ip, oend_w - op, ovtype); ip += oend_w - op; op += oend_w - op; } /* Handle the leftovers. */ while (op < oend) *op++ = *ip++; } /* ZSTD_safecopyDstBeforeSrc(): * This version allows overlap with dst before src, or handles the non-overlap case with dst after src * Kept separate from more common ZSTD_safecopy case to avoid performance impact to the safecopy common case */ static void ZSTD_safecopyDstBeforeSrc(BYTE* op, BYTE const* ip, ptrdiff_t length) { ptrdiff_t const diff = op - ip; BYTE* const oend = op + length; if (length < 8 || diff > -8) { /* Handle short lengths, close overlaps, and dst not before src. */ while (op < oend) *op++ = *ip++; return; } if (op <= oend - WILDCOPY_OVERLENGTH && diff < -WILDCOPY_VECLEN) { ZSTD_wildcopy(op, ip, oend - WILDCOPY_OVERLENGTH - op, ZSTD_no_overlap); ip += oend - WILDCOPY_OVERLENGTH - op; op += oend - WILDCOPY_OVERLENGTH - op; } /* Handle the leftovers. */ while (op < oend) *op++ = *ip++; } /* ZSTD_execSequenceEnd(): * This version handles cases that are near the end of the output buffer. It requires * more careful checks to make sure there is no overflow. By separating out these hard * and unlikely cases, we can speed up the common cases. * * NOTE: This function needs to be fast for a single long sequence, but doesn't need * to be optimized for many small sequences, since those fall into ZSTD_execSequence(). */ FORCE_NOINLINE size_t ZSTD_execSequenceEnd(BYTE* op, BYTE* const oend, seq_t sequence, const BYTE** litPtr, const BYTE* const litLimit, const BYTE* const prefixStart, const BYTE* const virtualStart, const BYTE* const dictEnd) { BYTE* const oLitEnd = op + sequence.litLength; size_t const sequenceLength = sequence.litLength + sequence.matchLength; const BYTE* const iLitEnd = *litPtr + sequence.litLength; const BYTE* match = oLitEnd - sequence.offset; BYTE* const oend_w = oend - WILDCOPY_OVERLENGTH; /* bounds checks : careful of address space overflow in 32-bit mode */ RETURN_ERROR_IF(sequenceLength > (size_t)(oend - op), dstSize_tooSmall, "last match must fit within dstBuffer"); RETURN_ERROR_IF(sequence.litLength > (size_t)(litLimit - *litPtr), corruption_detected, "try to read beyond literal buffer"); assert(op < op + sequenceLength); assert(oLitEnd < op + sequenceLength); /* copy literals */ ZSTD_safecopy(op, oend_w, *litPtr, sequence.litLength, ZSTD_no_overlap); op = oLitEnd; *litPtr = iLitEnd; /* copy Match */ if (sequence.offset > (size_t)(oLitEnd - prefixStart)) { /* offset beyond prefix */ RETURN_ERROR_IF(sequence.offset > (size_t)(oLitEnd - virtualStart), corruption_detected, ""); match = dictEnd - (prefixStart - match); if (match + sequence.matchLength <= dictEnd) { ZSTD_memmove(oLitEnd, match, sequence.matchLength); return sequenceLength; } /* span extDict & currentPrefixSegment */ { size_t const length1 = dictEnd - match; ZSTD_memmove(oLitEnd, match, length1); op = oLitEnd + length1; sequence.matchLength -= length1; match = prefixStart; } } ZSTD_safecopy(op, oend_w, match, sequence.matchLength, ZSTD_overlap_src_before_dst); return sequenceLength; } /* ZSTD_execSequenceEndSplitLitBuffer(): * This version is intended to be used during instances where the litBuffer is still split. It is kept separate to avoid performance impact for the good case. */ FORCE_NOINLINE size_t ZSTD_execSequenceEndSplitLitBuffer(BYTE* op, BYTE* const oend, const BYTE* const oend_w, seq_t sequence, const BYTE** litPtr, const BYTE* const litLimit, const BYTE* const prefixStart, const BYTE* const virtualStart, const BYTE* const dictEnd) { BYTE* const oLitEnd = op + sequence.litLength; size_t const sequenceLength = sequence.litLength + sequence.matchLength; const BYTE* const iLitEnd = *litPtr + sequence.litLength; const BYTE* match = oLitEnd - sequence.offset; /* bounds checks : careful of address space overflow in 32-bit mode */ RETURN_ERROR_IF(sequenceLength > (size_t)(oend - op), dstSize_tooSmall, "last match must fit within dstBuffer"); RETURN_ERROR_IF(sequence.litLength > (size_t)(litLimit - *litPtr), corruption_detected, "try to read beyond literal buffer"); assert(op < op + sequenceLength); assert(oLitEnd < op + sequenceLength); /* copy literals */ RETURN_ERROR_IF(op > *litPtr && op < *litPtr + sequence.litLength, dstSize_tooSmall, "output should not catch up to and overwrite literal buffer"); ZSTD_safecopyDstBeforeSrc(op, *litPtr, sequence.litLength); op = oLitEnd; *litPtr = iLitEnd; /* copy Match */ if (sequence.offset > (size_t)(oLitEnd - prefixStart)) { /* offset beyond prefix */ RETURN_ERROR_IF(sequence.offset > (size_t)(oLitEnd - virtualStart), corruption_detected, ""); match = dictEnd - (prefixStart - match); if (match + sequence.matchLength <= dictEnd) { ZSTD_memmove(oLitEnd, match, sequence.matchLength); return sequenceLength; } /* span extDict & currentPrefixSegment */ { size_t const length1 = dictEnd - match; ZSTD_memmove(oLitEnd, match, length1); op = oLitEnd + length1; sequence.matchLength -= length1; match = prefixStart; } } ZSTD_safecopy(op, oend_w, match, sequence.matchLength, ZSTD_overlap_src_before_dst); return sequenceLength; } HINT_INLINE size_t ZSTD_execSequence(BYTE* op, BYTE* const oend, seq_t sequence, const BYTE** litPtr, const BYTE* const litLimit, const BYTE* const prefixStart, const BYTE* const virtualStart, const BYTE* const dictEnd) { BYTE* const oLitEnd = op + sequence.litLength; size_t const sequenceLength = sequence.litLength + sequence.matchLength; BYTE* const oMatchEnd = op + sequenceLength; /* risk : address space overflow (32-bits) */ BYTE* const oend_w = oend - WILDCOPY_OVERLENGTH; /* risk : address space underflow on oend=NULL */ const BYTE* const iLitEnd = *litPtr + sequence.litLength; const BYTE* match = oLitEnd - sequence.offset; assert(op != NULL /* Precondition */); assert(oend_w < oend /* No underflow */); #if defined(__aarch64__) /* prefetch sequence starting from match that will be used for copy later */ PREFETCH_L1(match); #endif /* Handle edge cases in a slow path: * - Read beyond end of literals * - Match end is within WILDCOPY_OVERLIMIT of oend * - 32-bit mode and the match length overflows */ if (UNLIKELY( iLitEnd > litLimit || oMatchEnd > oend_w || (MEM_32bits() && (size_t)(oend - op) < sequenceLength + WILDCOPY_OVERLENGTH))) return ZSTD_execSequenceEnd(op, oend, sequence, litPtr, litLimit, prefixStart, virtualStart, dictEnd); /* Assumptions (everything else goes into ZSTD_execSequenceEnd()) */ assert(op <= oLitEnd /* No overflow */); assert(oLitEnd < oMatchEnd /* Non-zero match & no overflow */); assert(oMatchEnd <= oend /* No underflow */); assert(iLitEnd <= litLimit /* Literal length is in bounds */); assert(oLitEnd <= oend_w /* Can wildcopy literals */); assert(oMatchEnd <= oend_w /* Can wildcopy matches */); /* Copy Literals: * Split out litLength <= 16 since it is nearly always true. +1.6% on gcc-9. * We likely don't need the full 32-byte wildcopy. */ assert(WILDCOPY_OVERLENGTH >= 16); ZSTD_copy16(op, (*litPtr)); if (UNLIKELY(sequence.litLength > 16)) { ZSTD_wildcopy(op + 16, (*litPtr) + 16, sequence.litLength - 16, ZSTD_no_overlap); } op = oLitEnd; *litPtr = iLitEnd; /* update for next sequence */ /* Copy Match */ if (sequence.offset > (size_t)(oLitEnd - prefixStart)) { /* offset beyond prefix -> go into extDict */ RETURN_ERROR_IF(UNLIKELY(sequence.offset > (size_t)(oLitEnd - virtualStart)), corruption_detected, ""); match = dictEnd + (match - prefixStart); if (match + sequence.matchLength <= dictEnd) { ZSTD_memmove(oLitEnd, match, sequence.matchLength); return sequenceLength; } /* span extDict & currentPrefixSegment */ { size_t const length1 = dictEnd - match; ZSTD_memmove(oLitEnd, match, length1); op = oLitEnd + length1; sequence.matchLength -= length1; match = prefixStart; } } /* Match within prefix of 1 or more bytes */ assert(op <= oMatchEnd); assert(oMatchEnd <= oend_w); assert(match >= prefixStart); assert(sequence.matchLength >= 1); /* Nearly all offsets are >= WILDCOPY_VECLEN bytes, which means we can use wildcopy * without overlap checking. */ if (LIKELY(sequence.offset >= WILDCOPY_VECLEN)) { /* We bet on a full wildcopy for matches, since we expect matches to be * longer than literals (in general). In silesia, ~10% of matches are longer * than 16 bytes. */ ZSTD_wildcopy(op, match, (ptrdiff_t)sequence.matchLength, ZSTD_no_overlap); return sequenceLength; } assert(sequence.offset < WILDCOPY_VECLEN); /* Copy 8 bytes and spread the offset to be >= 8. */ ZSTD_overlapCopy8(&op, &match, sequence.offset); /* If the match length is > 8 bytes, then continue with the wildcopy. */ if (sequence.matchLength > 8) { assert(op < oMatchEnd); ZSTD_wildcopy(op, match, (ptrdiff_t)sequence.matchLength - 8, ZSTD_overlap_src_before_dst); } return sequenceLength; } HINT_INLINE size_t ZSTD_execSequenceSplitLitBuffer(BYTE* op, BYTE* const oend, const BYTE* const oend_w, seq_t sequence, const BYTE** litPtr, const BYTE* const litLimit, const BYTE* const prefixStart, const BYTE* const virtualStart, const BYTE* const dictEnd) { BYTE* const oLitEnd = op + sequence.litLength; size_t const sequenceLength = sequence.litLength + sequence.matchLength; BYTE* const oMatchEnd = op + sequenceLength; /* risk : address space overflow (32-bits) */ const BYTE* const iLitEnd = *litPtr + sequence.litLength; const BYTE* match = oLitEnd - sequence.offset; assert(op != NULL /* Precondition */); assert(oend_w < oend /* No underflow */); /* Handle edge cases in a slow path: * - Read beyond end of literals * - Match end is within WILDCOPY_OVERLIMIT of oend * - 32-bit mode and the match length overflows */ if (UNLIKELY( iLitEnd > litLimit || oMatchEnd > oend_w || (MEM_32bits() && (size_t)(oend - op) < sequenceLength + WILDCOPY_OVERLENGTH))) return ZSTD_execSequenceEndSplitLitBuffer(op, oend, oend_w, sequence, litPtr, litLimit, prefixStart, virtualStart, dictEnd); /* Assumptions (everything else goes into ZSTD_execSequenceEnd()) */ assert(op <= oLitEnd /* No overflow */); assert(oLitEnd < oMatchEnd /* Non-zero match & no overflow */); assert(oMatchEnd <= oend /* No underflow */); assert(iLitEnd <= litLimit /* Literal length is in bounds */); assert(oLitEnd <= oend_w /* Can wildcopy literals */); assert(oMatchEnd <= oend_w /* Can wildcopy matches */); /* Copy Literals: * Split out litLength <= 16 since it is nearly always true. +1.6% on gcc-9. * We likely don't need the full 32-byte wildcopy. */ assert(WILDCOPY_OVERLENGTH >= 16); ZSTD_copy16(op, (*litPtr)); if (UNLIKELY(sequence.litLength > 16)) { ZSTD_wildcopy(op+16, (*litPtr)+16, sequence.litLength-16, ZSTD_no_overlap); } op = oLitEnd; *litPtr = iLitEnd; /* update for next sequence */ /* Copy Match */ if (sequence.offset > (size_t)(oLitEnd - prefixStart)) { /* offset beyond prefix -> go into extDict */ RETURN_ERROR_IF(UNLIKELY(sequence.offset > (size_t)(oLitEnd - virtualStart)), corruption_detected, ""); match = dictEnd + (match - prefixStart); if (match + sequence.matchLength <= dictEnd) { ZSTD_memmove(oLitEnd, match, sequence.matchLength); return sequenceLength; } /* span extDict & currentPrefixSegment */ { size_t const length1 = dictEnd - match; ZSTD_memmove(oLitEnd, match, length1); op = oLitEnd + length1; sequence.matchLength -= length1; match = prefixStart; } } /* Match within prefix of 1 or more bytes */ assert(op <= oMatchEnd); assert(oMatchEnd <= oend_w); assert(match >= prefixStart); assert(sequence.matchLength >= 1); /* Nearly all offsets are >= WILDCOPY_VECLEN bytes, which means we can use wildcopy * without overlap checking. */ if (LIKELY(sequence.offset >= WILDCOPY_VECLEN)) { /* We bet on a full wildcopy for matches, since we expect matches to be * longer than literals (in general). In silesia, ~10% of matches are longer * than 16 bytes. */ ZSTD_wildcopy(op, match, (ptrdiff_t)sequence.matchLength, ZSTD_no_overlap); return sequenceLength; } assert(sequence.offset < WILDCOPY_VECLEN); /* Copy 8 bytes and spread the offset to be >= 8. */ ZSTD_overlapCopy8(&op, &match, sequence.offset); /* If the match length is > 8 bytes, then continue with the wildcopy. */ if (sequence.matchLength > 8) { assert(op < oMatchEnd); ZSTD_wildcopy(op, match, (ptrdiff_t)sequence.matchLength-8, ZSTD_overlap_src_before_dst); } return sequenceLength; } static void ZSTD_initFseState(ZSTD_fseState* DStatePtr, BIT_DStream_t* bitD, const ZSTD_seqSymbol* dt) { const void* ptr = dt; const ZSTD_seqSymbol_header* const DTableH = (const ZSTD_seqSymbol_header*)ptr; DStatePtr->state = BIT_readBits(bitD, DTableH->tableLog); DEBUGLOG(6, "ZSTD_initFseState : val=%u using %u bits", (U32)DStatePtr->state, DTableH->tableLog); BIT_reloadDStream(bitD); DStatePtr->table = dt + 1; } FORCE_INLINE_TEMPLATE void ZSTD_updateFseStateWithDInfo(ZSTD_fseState* DStatePtr, BIT_DStream_t* bitD, U16 nextState, U32 nbBits) { size_t const lowBits = BIT_readBits(bitD, nbBits); DStatePtr->state = nextState + lowBits; } /* We need to add at most (ZSTD_WINDOWLOG_MAX_32 - 1) bits to read the maximum * offset bits. But we can only read at most STREAM_ACCUMULATOR_MIN_32 * bits before reloading. This value is the maximum number of bytes we read * after reloading when we are decoding long offsets. */ #define LONG_OFFSETS_MAX_EXTRA_BITS_32 \ (ZSTD_WINDOWLOG_MAX_32 > STREAM_ACCUMULATOR_MIN_32 \ ? ZSTD_WINDOWLOG_MAX_32 - STREAM_ACCUMULATOR_MIN_32 \ : 0) typedef enum { ZSTD_lo_isRegularOffset, ZSTD_lo_isLongOffset=1 } ZSTD_longOffset_e; FORCE_INLINE_TEMPLATE seq_t ZSTD_decodeSequence(seqState_t* seqState, const ZSTD_longOffset_e longOffsets) { seq_t seq; /* * ZSTD_seqSymbol is a structure with a total of 64 bits wide. So it can be * loaded in one operation and extracted its fields by simply shifting or * bit-extracting on aarch64. * GCC doesn't recognize this and generates more unnecessary ldr/ldrb/ldrh * operations that cause performance drop. This can be avoided by using this * ZSTD_memcpy hack. */ #if defined(__aarch64__) && (defined(__GNUC__) && !defined(__clang__)) ZSTD_seqSymbol llDInfoS, mlDInfoS, ofDInfoS; ZSTD_seqSymbol* const llDInfo = &llDInfoS; ZSTD_seqSymbol* const mlDInfo = &mlDInfoS; ZSTD_seqSymbol* const ofDInfo = &ofDInfoS; ZSTD_memcpy(llDInfo, seqState->stateLL.table + seqState->stateLL.state, sizeof(ZSTD_seqSymbol)); ZSTD_memcpy(mlDInfo, seqState->stateML.table + seqState->stateML.state, sizeof(ZSTD_seqSymbol)); ZSTD_memcpy(ofDInfo, seqState->stateOffb.table + seqState->stateOffb.state, sizeof(ZSTD_seqSymbol)); #else const ZSTD_seqSymbol* const llDInfo = seqState->stateLL.table + seqState->stateLL.state; const ZSTD_seqSymbol* const mlDInfo = seqState->stateML.table + seqState->stateML.state; const ZSTD_seqSymbol* const ofDInfo = seqState->stateOffb.table + seqState->stateOffb.state; #endif seq.matchLength = mlDInfo->baseValue; seq.litLength = llDInfo->baseValue; { U32 const ofBase = ofDInfo->baseValue; BYTE const llBits = llDInfo->nbAdditionalBits; BYTE const mlBits = mlDInfo->nbAdditionalBits; BYTE const ofBits = ofDInfo->nbAdditionalBits; BYTE const totalBits = llBits+mlBits+ofBits; U16 const llNext = llDInfo->nextState; U16 const mlNext = mlDInfo->nextState; U16 const ofNext = ofDInfo->nextState; U32 const llnbBits = llDInfo->nbBits; U32 const mlnbBits = mlDInfo->nbBits; U32 const ofnbBits = ofDInfo->nbBits; assert(llBits <= MaxLLBits); assert(mlBits <= MaxMLBits); assert(ofBits <= MaxOff); /* * As gcc has better branch and block analyzers, sometimes it is only * valuable to mark likeliness for clang, it gives around 3-4% of * performance. */ /* sequence */ { size_t offset; if (ofBits > 1) { ZSTD_STATIC_ASSERT(ZSTD_lo_isLongOffset == 1); ZSTD_STATIC_ASSERT(LONG_OFFSETS_MAX_EXTRA_BITS_32 == 5); ZSTD_STATIC_ASSERT(STREAM_ACCUMULATOR_MIN_32 > LONG_OFFSETS_MAX_EXTRA_BITS_32); ZSTD_STATIC_ASSERT(STREAM_ACCUMULATOR_MIN_32 - LONG_OFFSETS_MAX_EXTRA_BITS_32 >= MaxMLBits); if (MEM_32bits() && longOffsets && (ofBits >= STREAM_ACCUMULATOR_MIN_32)) { /* Always read extra bits, this keeps the logic simple, * avoids branches, and avoids accidentally reading 0 bits. */ U32 const extraBits = LONG_OFFSETS_MAX_EXTRA_BITS_32; offset = ofBase + (BIT_readBitsFast(&seqState->DStream, ofBits - extraBits) << extraBits); BIT_reloadDStream(&seqState->DStream); offset += BIT_readBitsFast(&seqState->DStream, extraBits); } else { offset = ofBase + BIT_readBitsFast(&seqState->DStream, ofBits/*>0*/); /* <= (ZSTD_WINDOWLOG_MAX-1) bits */ if (MEM_32bits()) BIT_reloadDStream(&seqState->DStream); } seqState->prevOffset[2] = seqState->prevOffset[1]; seqState->prevOffset[1] = seqState->prevOffset[0]; seqState->prevOffset[0] = offset; } else { U32 const ll0 = (llDInfo->baseValue == 0); if (LIKELY((ofBits == 0))) { offset = seqState->prevOffset[ll0]; seqState->prevOffset[1] = seqState->prevOffset[!ll0]; seqState->prevOffset[0] = offset; } else { offset = ofBase + ll0 + BIT_readBitsFast(&seqState->DStream, 1); { size_t temp = (offset==3) ? seqState->prevOffset[0] - 1 : seqState->prevOffset[offset]; temp += !temp; /* 0 is not valid; input is corrupted; force offset to 1 */ if (offset != 1) seqState->prevOffset[2] = seqState->prevOffset[1]; seqState->prevOffset[1] = seqState->prevOffset[0]; seqState->prevOffset[0] = offset = temp; } } } seq.offset = offset; } if (mlBits > 0) seq.matchLength += BIT_readBitsFast(&seqState->DStream, mlBits/*>0*/); if (MEM_32bits() && (mlBits+llBits >= STREAM_ACCUMULATOR_MIN_32-LONG_OFFSETS_MAX_EXTRA_BITS_32)) BIT_reloadDStream(&seqState->DStream); if (MEM_64bits() && UNLIKELY(totalBits >= STREAM_ACCUMULATOR_MIN_64-(LLFSELog+MLFSELog+OffFSELog))) BIT_reloadDStream(&seqState->DStream); /* Ensure there are enough bits to read the rest of data in 64-bit mode. */ ZSTD_STATIC_ASSERT(16+LLFSELog+MLFSELog+OffFSELog < STREAM_ACCUMULATOR_MIN_64); if (llBits > 0) seq.litLength += BIT_readBitsFast(&seqState->DStream, llBits/*>0*/); if (MEM_32bits()) BIT_reloadDStream(&seqState->DStream); DEBUGLOG(6, "seq: litL=%u, matchL=%u, offset=%u", (U32)seq.litLength, (U32)seq.matchLength, (U32)seq.offset); ZSTD_updateFseStateWithDInfo(&seqState->stateLL, &seqState->DStream, llNext, llnbBits); /* <= 9 bits */ ZSTD_updateFseStateWithDInfo(&seqState->stateML, &seqState->DStream, mlNext, mlnbBits); /* <= 9 bits */ if (MEM_32bits()) BIT_reloadDStream(&seqState->DStream); /* <= 18 bits */ ZSTD_updateFseStateWithDInfo(&seqState->stateOffb, &seqState->DStream, ofNext, ofnbBits); /* <= 8 bits */ } return seq; } #ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION MEM_STATIC int ZSTD_dictionaryIsActive(ZSTD_DCtx const* dctx, BYTE const* prefixStart, BYTE const* oLitEnd) { size_t const windowSize = dctx->fParams.windowSize; /* No dictionary used. */ if (dctx->dictContentEndForFuzzing == NULL) return 0; /* Dictionary is our prefix. */ if (prefixStart == dctx->dictContentBeginForFuzzing) return 1; /* Dictionary is not our ext-dict. */ if (dctx->dictEnd != dctx->dictContentEndForFuzzing) return 0; /* Dictionary is not within our window size. */ if ((size_t)(oLitEnd - prefixStart) >= windowSize) return 0; /* Dictionary is active. */ return 1; } MEM_STATIC void ZSTD_assertValidSequence( ZSTD_DCtx const* dctx, BYTE const* op, BYTE const* oend, seq_t const seq, BYTE const* prefixStart, BYTE const* virtualStart) { #if DEBUGLEVEL >= 1 if (dctx->isFrameDecompression) { size_t const windowSize = dctx->fParams.windowSize; size_t const sequenceSize = seq.litLength + seq.matchLength; BYTE const* const oLitEnd = op + seq.litLength; DEBUGLOG(6, "Checking sequence: litL=%u matchL=%u offset=%u", (U32)seq.litLength, (U32)seq.matchLength, (U32)seq.offset); assert(op <= oend); assert((size_t)(oend - op) >= sequenceSize); assert(sequenceSize <= ZSTD_blockSizeMax(dctx)); if (ZSTD_dictionaryIsActive(dctx, prefixStart, oLitEnd)) { size_t const dictSize = (size_t)((char const*)dctx->dictContentEndForFuzzing - (char const*)dctx->dictContentBeginForFuzzing); /* Offset must be within the dictionary. */ assert(seq.offset <= (size_t)(oLitEnd - virtualStart)); assert(seq.offset <= windowSize + dictSize); } else { /* Offset must be within our window. */ assert(seq.offset <= windowSize); } } #else (void)dctx, (void)op, (void)oend, (void)seq, (void)prefixStart, (void)virtualStart; #endif } #endif #ifndef ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG FORCE_INLINE_TEMPLATE size_t DONT_VECTORIZE ZSTD_decompressSequences_bodySplitLitBuffer( ZSTD_DCtx* dctx, void* dst, size_t maxDstSize, const void* seqStart, size_t seqSize, int nbSeq, const ZSTD_longOffset_e isLongOffset) { const BYTE* ip = (const BYTE*)seqStart; const BYTE* const iend = ip + seqSize; BYTE* const ostart = (BYTE*)dst; BYTE* const oend = ostart + maxDstSize; BYTE* op = ostart; const BYTE* litPtr = dctx->litPtr; const BYTE* litBufferEnd = dctx->litBufferEnd; const BYTE* const prefixStart = (const BYTE*) (dctx->prefixStart); const BYTE* const vBase = (const BYTE*) (dctx->virtualStart); const BYTE* const dictEnd = (const BYTE*) (dctx->dictEnd); DEBUGLOG(5, "ZSTD_decompressSequences_bodySplitLitBuffer"); /* Regen sequences */ if (nbSeq) { seqState_t seqState; dctx->fseEntropy = 1; { U32 i; for (i=0; ientropy.rep[i]; } RETURN_ERROR_IF( ERR_isError(BIT_initDStream(&seqState.DStream, ip, iend-ip)), corruption_detected, ""); ZSTD_initFseState(&seqState.stateLL, &seqState.DStream, dctx->LLTptr); ZSTD_initFseState(&seqState.stateOffb, &seqState.DStream, dctx->OFTptr); ZSTD_initFseState(&seqState.stateML, &seqState.DStream, dctx->MLTptr); assert(dst != NULL); ZSTD_STATIC_ASSERT( BIT_DStream_unfinished < BIT_DStream_completed && BIT_DStream_endOfBuffer < BIT_DStream_completed && BIT_DStream_completed < BIT_DStream_overflow); /* decompress without overrunning litPtr begins */ { seq_t sequence = ZSTD_decodeSequence(&seqState, isLongOffset); /* Align the decompression loop to 32 + 16 bytes. * * zstd compiled with gcc-9 on an Intel i9-9900k shows 10% decompression * speed swings based on the alignment of the decompression loop. This * performance swing is caused by parts of the decompression loop falling * out of the DSB. The entire decompression loop should fit in the DSB, * when it can't we get much worse performance. You can measure if you've * hit the good case or the bad case with this perf command for some * compressed file test.zst: * * perf stat -e cycles -e instructions -e idq.all_dsb_cycles_any_uops \ * -e idq.all_mite_cycles_any_uops -- ./zstd -tq test.zst * * If you see most cycles served out of the MITE you've hit the bad case. * If you see most cycles served out of the DSB you've hit the good case. * If it is pretty even then you may be in an okay case. * * This issue has been reproduced on the following CPUs: * - Kabylake: Macbook Pro (15-inch, 2019) 2.4 GHz Intel Core i9 * Use Instruments->Counters to get DSB/MITE cycles. * I never got performance swings, but I was able to * go from the good case of mostly DSB to half of the * cycles served from MITE. * - Coffeelake: Intel i9-9900k * - Coffeelake: Intel i7-9700k * * I haven't been able to reproduce the instability or DSB misses on any * of the following CPUS: * - Haswell * - Broadwell: Intel(R) Xeon(R) CPU E5-2680 v4 @ 2.40GH * - Skylake * * Alignment is done for each of the three major decompression loops: * - ZSTD_decompressSequences_bodySplitLitBuffer - presplit section of the literal buffer * - ZSTD_decompressSequences_bodySplitLitBuffer - postsplit section of the literal buffer * - ZSTD_decompressSequences_body * Alignment choices are made to minimize large swings on bad cases and influence on performance * from changes external to this code, rather than to overoptimize on the current commit. * * If you are seeing performance stability this script can help test. * It tests on 4 commits in zstd where I saw performance change. * * https://gist.github.com/terrelln/9889fc06a423fd5ca6e99351564473f4 */ #if defined(__GNUC__) && defined(__x86_64__) __asm__(".p2align 6"); # if __GNUC__ >= 7 /* good for gcc-7, gcc-9, and gcc-11 */ __asm__("nop"); __asm__(".p2align 5"); __asm__("nop"); __asm__(".p2align 4"); # if __GNUC__ == 8 || __GNUC__ == 10 /* good for gcc-8 and gcc-10 */ __asm__("nop"); __asm__(".p2align 3"); # endif # endif #endif /* Handle the initial state where litBuffer is currently split between dst and litExtraBuffer */ for (; litPtr + sequence.litLength <= dctx->litBufferEnd; ) { size_t const oneSeqSize = ZSTD_execSequenceSplitLitBuffer(op, oend, litPtr + sequence.litLength - WILDCOPY_OVERLENGTH, sequence, &litPtr, litBufferEnd, prefixStart, vBase, dictEnd); #if defined(FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION) && defined(FUZZING_ASSERT_VALID_SEQUENCE) assert(!ZSTD_isError(oneSeqSize)); ZSTD_assertValidSequence(dctx, op, oend, sequence, prefixStart, vBase); #endif if (UNLIKELY(ZSTD_isError(oneSeqSize))) return oneSeqSize; DEBUGLOG(6, "regenerated sequence size : %u", (U32)oneSeqSize); op += oneSeqSize; if (UNLIKELY(!--nbSeq)) break; BIT_reloadDStream(&(seqState.DStream)); sequence = ZSTD_decodeSequence(&seqState, isLongOffset); } /* If there are more sequences, they will need to read literals from litExtraBuffer; copy over the remainder from dst and update litPtr and litEnd */ if (nbSeq > 0) { const size_t leftoverLit = dctx->litBufferEnd - litPtr; if (leftoverLit) { RETURN_ERROR_IF(leftoverLit > (size_t)(oend - op), dstSize_tooSmall, "remaining lit must fit within dstBuffer"); ZSTD_safecopyDstBeforeSrc(op, litPtr, leftoverLit); sequence.litLength -= leftoverLit; op += leftoverLit; } litPtr = dctx->litExtraBuffer; litBufferEnd = dctx->litExtraBuffer + ZSTD_LITBUFFEREXTRASIZE; dctx->litBufferLocation = ZSTD_not_in_dst; { size_t const oneSeqSize = ZSTD_execSequence(op, oend, sequence, &litPtr, litBufferEnd, prefixStart, vBase, dictEnd); #if defined(FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION) && defined(FUZZING_ASSERT_VALID_SEQUENCE) assert(!ZSTD_isError(oneSeqSize)); ZSTD_assertValidSequence(dctx, op, oend, sequence, prefixStart, vBase); #endif if (UNLIKELY(ZSTD_isError(oneSeqSize))) return oneSeqSize; DEBUGLOG(6, "regenerated sequence size : %u", (U32)oneSeqSize); op += oneSeqSize; if (--nbSeq) BIT_reloadDStream(&(seqState.DStream)); } } } if (nbSeq > 0) /* there is remaining lit from extra buffer */ { #if defined(__GNUC__) && defined(__x86_64__) __asm__(".p2align 6"); __asm__("nop"); # if __GNUC__ != 7 /* worse for gcc-7 better for gcc-8, gcc-9, and gcc-10 and clang */ __asm__(".p2align 4"); __asm__("nop"); __asm__(".p2align 3"); # elif __GNUC__ >= 11 __asm__(".p2align 3"); # else __asm__(".p2align 5"); __asm__("nop"); __asm__(".p2align 3"); # endif #endif for (; ; ) { seq_t const sequence = ZSTD_decodeSequence(&seqState, isLongOffset); size_t const oneSeqSize = ZSTD_execSequence(op, oend, sequence, &litPtr, litBufferEnd, prefixStart, vBase, dictEnd); #if defined(FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION) && defined(FUZZING_ASSERT_VALID_SEQUENCE) assert(!ZSTD_isError(oneSeqSize)); ZSTD_assertValidSequence(dctx, op, oend, sequence, prefixStart, vBase); #endif if (UNLIKELY(ZSTD_isError(oneSeqSize))) return oneSeqSize; DEBUGLOG(6, "regenerated sequence size : %u", (U32)oneSeqSize); op += oneSeqSize; if (UNLIKELY(!--nbSeq)) break; BIT_reloadDStream(&(seqState.DStream)); } } /* check if reached exact end */ DEBUGLOG(5, "ZSTD_decompressSequences_bodySplitLitBuffer: after decode loop, remaining nbSeq : %i", nbSeq); RETURN_ERROR_IF(nbSeq, corruption_detected, ""); RETURN_ERROR_IF(BIT_reloadDStream(&seqState.DStream) < BIT_DStream_completed, corruption_detected, ""); /* save reps for next block */ { U32 i; for (i=0; ientropy.rep[i] = (U32)(seqState.prevOffset[i]); } } /* last literal segment */ if (dctx->litBufferLocation == ZSTD_split) /* split hasn't been reached yet, first get dst then copy litExtraBuffer */ { size_t const lastLLSize = litBufferEnd - litPtr; RETURN_ERROR_IF(lastLLSize > (size_t)(oend - op), dstSize_tooSmall, ""); if (op != NULL) { ZSTD_memmove(op, litPtr, lastLLSize); op += lastLLSize; } litPtr = dctx->litExtraBuffer; litBufferEnd = dctx->litExtraBuffer + ZSTD_LITBUFFEREXTRASIZE; dctx->litBufferLocation = ZSTD_not_in_dst; } { size_t const lastLLSize = litBufferEnd - litPtr; RETURN_ERROR_IF(lastLLSize > (size_t)(oend-op), dstSize_tooSmall, ""); if (op != NULL) { ZSTD_memcpy(op, litPtr, lastLLSize); op += lastLLSize; } } return op-ostart; } FORCE_INLINE_TEMPLATE size_t DONT_VECTORIZE ZSTD_decompressSequences_body(ZSTD_DCtx* dctx, void* dst, size_t maxDstSize, const void* seqStart, size_t seqSize, int nbSeq, const ZSTD_longOffset_e isLongOffset) { const BYTE* ip = (const BYTE*)seqStart; const BYTE* const iend = ip + seqSize; BYTE* const ostart = (BYTE*)dst; BYTE* const oend = dctx->litBufferLocation == ZSTD_not_in_dst ? ostart + maxDstSize : dctx->litBuffer; BYTE* op = ostart; const BYTE* litPtr = dctx->litPtr; const BYTE* const litEnd = litPtr + dctx->litSize; const BYTE* const prefixStart = (const BYTE*)(dctx->prefixStart); const BYTE* const vBase = (const BYTE*)(dctx->virtualStart); const BYTE* const dictEnd = (const BYTE*)(dctx->dictEnd); DEBUGLOG(5, "ZSTD_decompressSequences_body: nbSeq = %d", nbSeq); /* Regen sequences */ if (nbSeq) { seqState_t seqState; dctx->fseEntropy = 1; { U32 i; for (i = 0; i < ZSTD_REP_NUM; i++) seqState.prevOffset[i] = dctx->entropy.rep[i]; } RETURN_ERROR_IF( ERR_isError(BIT_initDStream(&seqState.DStream, ip, iend - ip)), corruption_detected, ""); ZSTD_initFseState(&seqState.stateLL, &seqState.DStream, dctx->LLTptr); ZSTD_initFseState(&seqState.stateOffb, &seqState.DStream, dctx->OFTptr); ZSTD_initFseState(&seqState.stateML, &seqState.DStream, dctx->MLTptr); assert(dst != NULL); ZSTD_STATIC_ASSERT( BIT_DStream_unfinished < BIT_DStream_completed && BIT_DStream_endOfBuffer < BIT_DStream_completed && BIT_DStream_completed < BIT_DStream_overflow); #if defined(__GNUC__) && defined(__x86_64__) __asm__(".p2align 6"); __asm__("nop"); # if __GNUC__ >= 7 __asm__(".p2align 5"); __asm__("nop"); __asm__(".p2align 3"); # else __asm__(".p2align 4"); __asm__("nop"); __asm__(".p2align 3"); # endif #endif for ( ; ; ) { seq_t const sequence = ZSTD_decodeSequence(&seqState, isLongOffset); size_t const oneSeqSize = ZSTD_execSequence(op, oend, sequence, &litPtr, litEnd, prefixStart, vBase, dictEnd); #if defined(FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION) && defined(FUZZING_ASSERT_VALID_SEQUENCE) assert(!ZSTD_isError(oneSeqSize)); ZSTD_assertValidSequence(dctx, op, oend, sequence, prefixStart, vBase); #endif if (UNLIKELY(ZSTD_isError(oneSeqSize))) return oneSeqSize; DEBUGLOG(6, "regenerated sequence size : %u", (U32)oneSeqSize); op += oneSeqSize; if (UNLIKELY(!--nbSeq)) break; BIT_reloadDStream(&(seqState.DStream)); } /* check if reached exact end */ DEBUGLOG(5, "ZSTD_decompressSequences_body: after decode loop, remaining nbSeq : %i", nbSeq); RETURN_ERROR_IF(nbSeq, corruption_detected, ""); RETURN_ERROR_IF(BIT_reloadDStream(&seqState.DStream) < BIT_DStream_completed, corruption_detected, ""); /* save reps for next block */ { U32 i; for (i=0; ientropy.rep[i] = (U32)(seqState.prevOffset[i]); } } /* last literal segment */ { size_t const lastLLSize = litEnd - litPtr; RETURN_ERROR_IF(lastLLSize > (size_t)(oend-op), dstSize_tooSmall, ""); if (op != NULL) { ZSTD_memcpy(op, litPtr, lastLLSize); op += lastLLSize; } } return op-ostart; } static size_t ZSTD_decompressSequences_default(ZSTD_DCtx* dctx, void* dst, size_t maxDstSize, const void* seqStart, size_t seqSize, int nbSeq, const ZSTD_longOffset_e isLongOffset) { return ZSTD_decompressSequences_body(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset); } static size_t ZSTD_decompressSequencesSplitLitBuffer_default(ZSTD_DCtx* dctx, void* dst, size_t maxDstSize, const void* seqStart, size_t seqSize, int nbSeq, const ZSTD_longOffset_e isLongOffset) { return ZSTD_decompressSequences_bodySplitLitBuffer(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset); } #endif /* ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG */ #ifndef ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT FORCE_INLINE_TEMPLATE size_t ZSTD_prefetchMatch(size_t prefetchPos, seq_t const sequence, const BYTE* const prefixStart, const BYTE* const dictEnd) { prefetchPos += sequence.litLength; { const BYTE* const matchBase = (sequence.offset > prefetchPos) ? dictEnd : prefixStart; const BYTE* const match = matchBase + prefetchPos - sequence.offset; /* note : this operation can overflow when seq.offset is really too large, which can only happen when input is corrupted. * No consequence though : memory address is only used for prefetching, not for dereferencing */ PREFETCH_L1(match); PREFETCH_L1(match+CACHELINE_SIZE); /* note : it's safe to invoke PREFETCH() on any memory address, including invalid ones */ } return prefetchPos + sequence.matchLength; } /* This decoding function employs prefetching * to reduce latency impact of cache misses. * It's generally employed when block contains a significant portion of long-distance matches * or when coupled with a "cold" dictionary */ FORCE_INLINE_TEMPLATE size_t ZSTD_decompressSequencesLong_body( ZSTD_DCtx* dctx, void* dst, size_t maxDstSize, const void* seqStart, size_t seqSize, int nbSeq, const ZSTD_longOffset_e isLongOffset) { const BYTE* ip = (const BYTE*)seqStart; const BYTE* const iend = ip + seqSize; BYTE* const ostart = (BYTE*)dst; BYTE* const oend = dctx->litBufferLocation == ZSTD_in_dst ? dctx->litBuffer : ostart + maxDstSize; BYTE* op = ostart; const BYTE* litPtr = dctx->litPtr; const BYTE* litBufferEnd = dctx->litBufferEnd; const BYTE* const prefixStart = (const BYTE*) (dctx->prefixStart); const BYTE* const dictStart = (const BYTE*) (dctx->virtualStart); const BYTE* const dictEnd = (const BYTE*) (dctx->dictEnd); /* Regen sequences */ if (nbSeq) { #define STORED_SEQS 8 #define STORED_SEQS_MASK (STORED_SEQS-1) #define ADVANCED_SEQS STORED_SEQS seq_t sequences[STORED_SEQS]; int const seqAdvance = MIN(nbSeq, ADVANCED_SEQS); seqState_t seqState; int seqNb; size_t prefetchPos = (size_t)(op-prefixStart); /* track position relative to prefixStart */ dctx->fseEntropy = 1; { int i; for (i=0; ientropy.rep[i]; } assert(dst != NULL); assert(iend >= ip); RETURN_ERROR_IF( ERR_isError(BIT_initDStream(&seqState.DStream, ip, iend-ip)), corruption_detected, ""); ZSTD_initFseState(&seqState.stateLL, &seqState.DStream, dctx->LLTptr); ZSTD_initFseState(&seqState.stateOffb, &seqState.DStream, dctx->OFTptr); ZSTD_initFseState(&seqState.stateML, &seqState.DStream, dctx->MLTptr); /* prepare in advance */ for (seqNb=0; (BIT_reloadDStream(&seqState.DStream) <= BIT_DStream_completed) && (seqNblitBufferLocation == ZSTD_split && litPtr + sequences[(seqNb - ADVANCED_SEQS) & STORED_SEQS_MASK].litLength > dctx->litBufferEnd) { /* lit buffer is reaching split point, empty out the first buffer and transition to litExtraBuffer */ const size_t leftoverLit = dctx->litBufferEnd - litPtr; if (leftoverLit) { RETURN_ERROR_IF(leftoverLit > (size_t)(oend - op), dstSize_tooSmall, "remaining lit must fit within dstBuffer"); ZSTD_safecopyDstBeforeSrc(op, litPtr, leftoverLit); sequences[(seqNb - ADVANCED_SEQS) & STORED_SEQS_MASK].litLength -= leftoverLit; op += leftoverLit; } litPtr = dctx->litExtraBuffer; litBufferEnd = dctx->litExtraBuffer + ZSTD_LITBUFFEREXTRASIZE; dctx->litBufferLocation = ZSTD_not_in_dst; oneSeqSize = ZSTD_execSequence(op, oend, sequences[(seqNb - ADVANCED_SEQS) & STORED_SEQS_MASK], &litPtr, litBufferEnd, prefixStart, dictStart, dictEnd); #if defined(FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION) && defined(FUZZING_ASSERT_VALID_SEQUENCE) assert(!ZSTD_isError(oneSeqSize)); ZSTD_assertValidSequence(dctx, op, oend, sequences[(seqNb - ADVANCED_SEQS) & STORED_SEQS_MASK], prefixStart, dictStart); #endif if (ZSTD_isError(oneSeqSize)) return oneSeqSize; prefetchPos = ZSTD_prefetchMatch(prefetchPos, sequence, prefixStart, dictEnd); sequences[seqNb & STORED_SEQS_MASK] = sequence; op += oneSeqSize; } else { /* lit buffer is either wholly contained in first or second split, or not split at all*/ oneSeqSize = dctx->litBufferLocation == ZSTD_split ? ZSTD_execSequenceSplitLitBuffer(op, oend, litPtr + sequences[(seqNb - ADVANCED_SEQS) & STORED_SEQS_MASK].litLength - WILDCOPY_OVERLENGTH, sequences[(seqNb - ADVANCED_SEQS) & STORED_SEQS_MASK], &litPtr, litBufferEnd, prefixStart, dictStart, dictEnd) : ZSTD_execSequence(op, oend, sequences[(seqNb - ADVANCED_SEQS) & STORED_SEQS_MASK], &litPtr, litBufferEnd, prefixStart, dictStart, dictEnd); #if defined(FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION) && defined(FUZZING_ASSERT_VALID_SEQUENCE) assert(!ZSTD_isError(oneSeqSize)); ZSTD_assertValidSequence(dctx, op, oend, sequences[(seqNb - ADVANCED_SEQS) & STORED_SEQS_MASK], prefixStart, dictStart); #endif if (ZSTD_isError(oneSeqSize)) return oneSeqSize; prefetchPos = ZSTD_prefetchMatch(prefetchPos, sequence, prefixStart, dictEnd); sequences[seqNb & STORED_SEQS_MASK] = sequence; op += oneSeqSize; } } RETURN_ERROR_IF(seqNblitBufferLocation == ZSTD_split && litPtr + sequence->litLength > dctx->litBufferEnd) { const size_t leftoverLit = dctx->litBufferEnd - litPtr; if (leftoverLit) { RETURN_ERROR_IF(leftoverLit > (size_t)(oend - op), dstSize_tooSmall, "remaining lit must fit within dstBuffer"); ZSTD_safecopyDstBeforeSrc(op, litPtr, leftoverLit); sequence->litLength -= leftoverLit; op += leftoverLit; } litPtr = dctx->litExtraBuffer; litBufferEnd = dctx->litExtraBuffer + ZSTD_LITBUFFEREXTRASIZE; dctx->litBufferLocation = ZSTD_not_in_dst; { size_t const oneSeqSize = ZSTD_execSequence(op, oend, *sequence, &litPtr, litBufferEnd, prefixStart, dictStart, dictEnd); #if defined(FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION) && defined(FUZZING_ASSERT_VALID_SEQUENCE) assert(!ZSTD_isError(oneSeqSize)); ZSTD_assertValidSequence(dctx, op, oend, sequences[seqNb&STORED_SEQS_MASK], prefixStart, dictStart); #endif if (ZSTD_isError(oneSeqSize)) return oneSeqSize; op += oneSeqSize; } } else { size_t const oneSeqSize = dctx->litBufferLocation == ZSTD_split ? ZSTD_execSequenceSplitLitBuffer(op, oend, litPtr + sequence->litLength - WILDCOPY_OVERLENGTH, *sequence, &litPtr, litBufferEnd, prefixStart, dictStart, dictEnd) : ZSTD_execSequence(op, oend, *sequence, &litPtr, litBufferEnd, prefixStart, dictStart, dictEnd); #if defined(FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION) && defined(FUZZING_ASSERT_VALID_SEQUENCE) assert(!ZSTD_isError(oneSeqSize)); ZSTD_assertValidSequence(dctx, op, oend, sequences[seqNb&STORED_SEQS_MASK], prefixStart, dictStart); #endif if (ZSTD_isError(oneSeqSize)) return oneSeqSize; op += oneSeqSize; } } /* save reps for next block */ { U32 i; for (i=0; ientropy.rep[i] = (U32)(seqState.prevOffset[i]); } } /* last literal segment */ if (dctx->litBufferLocation == ZSTD_split) /* first deplete literal buffer in dst, then copy litExtraBuffer */ { size_t const lastLLSize = litBufferEnd - litPtr; RETURN_ERROR_IF(lastLLSize > (size_t)(oend - op), dstSize_tooSmall, ""); if (op != NULL) { ZSTD_memmove(op, litPtr, lastLLSize); op += lastLLSize; } litPtr = dctx->litExtraBuffer; litBufferEnd = dctx->litExtraBuffer + ZSTD_LITBUFFEREXTRASIZE; } { size_t const lastLLSize = litBufferEnd - litPtr; RETURN_ERROR_IF(lastLLSize > (size_t)(oend-op), dstSize_tooSmall, ""); if (op != NULL) { ZSTD_memmove(op, litPtr, lastLLSize); op += lastLLSize; } } return op-ostart; } static size_t ZSTD_decompressSequencesLong_default(ZSTD_DCtx* dctx, void* dst, size_t maxDstSize, const void* seqStart, size_t seqSize, int nbSeq, const ZSTD_longOffset_e isLongOffset) { return ZSTD_decompressSequencesLong_body(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset); } #endif /* ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT */ #if DYNAMIC_BMI2 #ifndef ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG static BMI2_TARGET_ATTRIBUTE size_t DONT_VECTORIZE ZSTD_decompressSequences_bmi2(ZSTD_DCtx* dctx, void* dst, size_t maxDstSize, const void* seqStart, size_t seqSize, int nbSeq, const ZSTD_longOffset_e isLongOffset) { return ZSTD_decompressSequences_body(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset); } static BMI2_TARGET_ATTRIBUTE size_t DONT_VECTORIZE ZSTD_decompressSequencesSplitLitBuffer_bmi2(ZSTD_DCtx* dctx, void* dst, size_t maxDstSize, const void* seqStart, size_t seqSize, int nbSeq, const ZSTD_longOffset_e isLongOffset) { return ZSTD_decompressSequences_bodySplitLitBuffer(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset); } #endif /* ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG */ #ifndef ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT static BMI2_TARGET_ATTRIBUTE size_t ZSTD_decompressSequencesLong_bmi2(ZSTD_DCtx* dctx, void* dst, size_t maxDstSize, const void* seqStart, size_t seqSize, int nbSeq, const ZSTD_longOffset_e isLongOffset) { return ZSTD_decompressSequencesLong_body(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset); } #endif /* ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT */ #endif /* DYNAMIC_BMI2 */ typedef size_t (*ZSTD_decompressSequences_t)( ZSTD_DCtx* dctx, void* dst, size_t maxDstSize, const void* seqStart, size_t seqSize, int nbSeq, const ZSTD_longOffset_e isLongOffset); #ifndef ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG static size_t ZSTD_decompressSequences(ZSTD_DCtx* dctx, void* dst, size_t maxDstSize, const void* seqStart, size_t seqSize, int nbSeq, const ZSTD_longOffset_e isLongOffset) { DEBUGLOG(5, "ZSTD_decompressSequences"); #if DYNAMIC_BMI2 if (ZSTD_DCtx_get_bmi2(dctx)) { return ZSTD_decompressSequences_bmi2(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset); } #endif return ZSTD_decompressSequences_default(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset); } static size_t ZSTD_decompressSequencesSplitLitBuffer(ZSTD_DCtx* dctx, void* dst, size_t maxDstSize, const void* seqStart, size_t seqSize, int nbSeq, const ZSTD_longOffset_e isLongOffset) { DEBUGLOG(5, "ZSTD_decompressSequencesSplitLitBuffer"); #if DYNAMIC_BMI2 if (ZSTD_DCtx_get_bmi2(dctx)) { return ZSTD_decompressSequencesSplitLitBuffer_bmi2(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset); } #endif return ZSTD_decompressSequencesSplitLitBuffer_default(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset); } #endif /* ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG */ #ifndef ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT /* ZSTD_decompressSequencesLong() : * decompression function triggered when a minimum share of offsets is considered "long", * aka out of cache. * note : "long" definition seems overloaded here, sometimes meaning "wider than bitstream register", and sometimes meaning "farther than memory cache distance". * This function will try to mitigate main memory latency through the use of prefetching */ static size_t ZSTD_decompressSequencesLong(ZSTD_DCtx* dctx, void* dst, size_t maxDstSize, const void* seqStart, size_t seqSize, int nbSeq, const ZSTD_longOffset_e isLongOffset) { DEBUGLOG(5, "ZSTD_decompressSequencesLong"); #if DYNAMIC_BMI2 if (ZSTD_DCtx_get_bmi2(dctx)) { return ZSTD_decompressSequencesLong_bmi2(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset); } #endif return ZSTD_decompressSequencesLong_default(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset); } #endif /* ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT */ /** * @returns The total size of the history referenceable by zstd, including * both the prefix and the extDict. At @p op any offset larger than this * is invalid. */ static size_t ZSTD_totalHistorySize(BYTE* op, BYTE const* virtualStart) { return (size_t)(op - virtualStart); } typedef struct { unsigned longOffsetShare; unsigned maxNbAdditionalBits; } ZSTD_OffsetInfo; /* ZSTD_getOffsetInfo() : * condition : offTable must be valid * @return : "share" of long offsets (arbitrarily defined as > (1<<23)) * compared to maximum possible of (1< 22) info.longOffsetShare += 1; } assert(tableLog <= OffFSELog); info.longOffsetShare <<= (OffFSELog - tableLog); /* scale to OffFSELog */ } return info; } /** * @returns The maximum offset we can decode in one read of our bitstream, without * reloading more bits in the middle of the offset bits read. Any offsets larger * than this must use the long offset decoder. */ static size_t ZSTD_maxShortOffset(void) { if (MEM_64bits()) { /* We can decode any offset without reloading bits. * This might change if the max window size grows. */ ZSTD_STATIC_ASSERT(ZSTD_WINDOWLOG_MAX <= 31); return (size_t)-1; } else { /* The maximum offBase is (1 << (STREAM_ACCUMULATOR_MIN + 1)) - 1. * This offBase would require STREAM_ACCUMULATOR_MIN extra bits. * Then we have to subtract ZSTD_REP_NUM to get the maximum possible offset. */ size_t const maxOffbase = ((size_t)1 << (STREAM_ACCUMULATOR_MIN + 1)) - 1; size_t const maxOffset = maxOffbase - ZSTD_REP_NUM; assert(ZSTD_highbit32((U32)maxOffbase) == STREAM_ACCUMULATOR_MIN); return maxOffset; } } size_t ZSTD_decompressBlock_internal(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize, const streaming_operation streaming) { /* blockType == blockCompressed */ const BYTE* ip = (const BYTE*)src; DEBUGLOG(5, "ZSTD_decompressBlock_internal (size : %u)", (U32)srcSize); /* Note : the wording of the specification * allows compressed block to be sized exactly ZSTD_blockSizeMax(dctx). * This generally does not happen, as it makes little sense, * since an uncompressed block would feature same size and have no decompression cost. * Also, note that decoder from reference libzstd before < v1.5.4 * would consider this edge case as an error. * As a consequence, avoid generating compressed blocks of size ZSTD_blockSizeMax(dctx) * for broader compatibility with the deployed ecosystem of zstd decoders */ RETURN_ERROR_IF(srcSize > ZSTD_blockSizeMax(dctx), srcSize_wrong, ""); /* Decode literals section */ { size_t const litCSize = ZSTD_decodeLiteralsBlock(dctx, src, srcSize, dst, dstCapacity, streaming); DEBUGLOG(5, "ZSTD_decodeLiteralsBlock : cSize=%u, nbLiterals=%zu", (U32)litCSize, dctx->litSize); if (ZSTD_isError(litCSize)) return litCSize; ip += litCSize; srcSize -= litCSize; } /* Build Decoding Tables */ { /* Compute the maximum block size, which must also work when !frame and fParams are unset. * Additionally, take the min with dstCapacity to ensure that the totalHistorySize fits in a size_t. */ size_t const blockSizeMax = MIN(dstCapacity, ZSTD_blockSizeMax(dctx)); size_t const totalHistorySize = ZSTD_totalHistorySize((BYTE*)dst + blockSizeMax, (BYTE const*)dctx->virtualStart); /* isLongOffset must be true if there are long offsets. * Offsets are long if they are larger than ZSTD_maxShortOffset(). * We don't expect that to be the case in 64-bit mode. * * We check here to see if our history is large enough to allow long offsets. * If it isn't, then we can't possible have (valid) long offsets. If the offset * is invalid, then it is okay to read it incorrectly. * * If isLongOffsets is true, then we will later check our decoding table to see * if it is even possible to generate long offsets. */ ZSTD_longOffset_e isLongOffset = (ZSTD_longOffset_e)(MEM_32bits() && (totalHistorySize > ZSTD_maxShortOffset())); /* These macros control at build-time which decompressor implementation * we use. If neither is defined, we do some inspection and dispatch at * runtime. */ #if !defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT) && \ !defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG) int usePrefetchDecoder = dctx->ddictIsCold; #else /* Set to 1 to avoid computing offset info if we don't need to. * Otherwise this value is ignored. */ int usePrefetchDecoder = 1; #endif int nbSeq; size_t const seqHSize = ZSTD_decodeSeqHeaders(dctx, &nbSeq, ip, srcSize); if (ZSTD_isError(seqHSize)) return seqHSize; ip += seqHSize; srcSize -= seqHSize; RETURN_ERROR_IF((dst == NULL || dstCapacity == 0) && nbSeq > 0, dstSize_tooSmall, "NULL not handled"); RETURN_ERROR_IF(MEM_64bits() && sizeof(size_t) == sizeof(void*) && (size_t)(-1) - (size_t)dst < (size_t)(1 << 20), dstSize_tooSmall, "invalid dst"); /* If we could potentially have long offsets, or we might want to use the prefetch decoder, * compute information about the share of long offsets, and the maximum nbAdditionalBits. * NOTE: could probably use a larger nbSeq limit */ if (isLongOffset || (!usePrefetchDecoder && (totalHistorySize > (1u << 24)) && (nbSeq > 8))) { ZSTD_OffsetInfo const info = ZSTD_getOffsetInfo(dctx->OFTptr, nbSeq); if (isLongOffset && info.maxNbAdditionalBits <= STREAM_ACCUMULATOR_MIN) { /* If isLongOffset, but the maximum number of additional bits that we see in our table is small * enough, then we know it is impossible to have too long an offset in this block, so we can * use the regular offset decoder. */ isLongOffset = ZSTD_lo_isRegularOffset; } if (!usePrefetchDecoder) { U32 const minShare = MEM_64bits() ? 7 : 20; /* heuristic values, correspond to 2.73% and 7.81% */ usePrefetchDecoder = (info.longOffsetShare >= minShare); } } dctx->ddictIsCold = 0; #if !defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT) && \ !defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG) if (usePrefetchDecoder) { #else (void)usePrefetchDecoder; { #endif #ifndef ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT return ZSTD_decompressSequencesLong(dctx, dst, dstCapacity, ip, srcSize, nbSeq, isLongOffset); #endif } #ifndef ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG /* else */ if (dctx->litBufferLocation == ZSTD_split) return ZSTD_decompressSequencesSplitLitBuffer(dctx, dst, dstCapacity, ip, srcSize, nbSeq, isLongOffset); else return ZSTD_decompressSequences(dctx, dst, dstCapacity, ip, srcSize, nbSeq, isLongOffset); #endif } } void ZSTD_checkContinuity(ZSTD_DCtx* dctx, const void* dst, size_t dstSize) { if (dst != dctx->previousDstEnd && dstSize > 0) { /* not contiguous */ dctx->dictEnd = dctx->previousDstEnd; dctx->virtualStart = (const char*)dst - ((const char*)(dctx->previousDstEnd) - (const char*)(dctx->prefixStart)); dctx->prefixStart = dst; dctx->previousDstEnd = dst; } } size_t ZSTD_decompressBlock_deprecated(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize) { size_t dSize; dctx->isFrameDecompression = 0; ZSTD_checkContinuity(dctx, dst, dstCapacity); dSize = ZSTD_decompressBlock_internal(dctx, dst, dstCapacity, src, srcSize, not_streaming); dctx->previousDstEnd = (char*)dst + dSize; return dSize; } /* NOTE: Must just wrap ZSTD_decompressBlock_deprecated() */ size_t ZSTD_decompressBlock(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize) { return ZSTD_decompressBlock_deprecated(dctx, dst, dstCapacity, src, srcSize); }