| /* |
| * 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. |
| */ |
| |
| /*-************************************* |
| * Dependencies |
| ***************************************/ |
| #include "zstd_compress_literals.h" |
| |
| |
| /* ************************************************************** |
| * Debug Traces |
| ****************************************************************/ |
| #if DEBUGLEVEL >= 2 |
| |
| static size_t showHexa(const void* src, size_t srcSize) |
| { |
| const BYTE* const ip = (const BYTE*)src; |
| size_t u; |
| for (u=0; u<srcSize; u++) { |
| RAWLOG(5, " %02X", ip[u]); (void)ip; |
| } |
| RAWLOG(5, " \n"); |
| return srcSize; |
| } |
| |
| #endif |
| |
| |
| /* ************************************************************** |
| * Literals compression - special cases |
| ****************************************************************/ |
| size_t ZSTD_noCompressLiterals (void* dst, size_t dstCapacity, const void* src, size_t srcSize) |
| { |
| BYTE* const ostart = (BYTE*)dst; |
| U32 const flSize = 1 + (srcSize>31) + (srcSize>4095); |
| |
| DEBUGLOG(5, "ZSTD_noCompressLiterals: srcSize=%zu, dstCapacity=%zu", srcSize, dstCapacity); |
| |
| RETURN_ERROR_IF(srcSize + flSize > dstCapacity, dstSize_tooSmall, ""); |
| |
| switch(flSize) |
| { |
| case 1: /* 2 - 1 - 5 */ |
| ostart[0] = (BYTE)((U32)set_basic + (srcSize<<3)); |
| break; |
| case 2: /* 2 - 2 - 12 */ |
| MEM_writeLE16(ostart, (U16)((U32)set_basic + (1<<2) + (srcSize<<4))); |
| break; |
| case 3: /* 2 - 2 - 20 */ |
| MEM_writeLE32(ostart, (U32)((U32)set_basic + (3<<2) + (srcSize<<4))); |
| break; |
| default: /* not necessary : flSize is {1,2,3} */ |
| assert(0); |
| } |
| |
| ZSTD_memcpy(ostart + flSize, src, srcSize); |
| DEBUGLOG(5, "Raw (uncompressed) literals: %u -> %u", (U32)srcSize, (U32)(srcSize + flSize)); |
| return srcSize + flSize; |
| } |
| |
| static int allBytesIdentical(const void* src, size_t srcSize) |
| { |
| assert(srcSize >= 1); |
| assert(src != NULL); |
| { const BYTE b = ((const BYTE*)src)[0]; |
| size_t p; |
| for (p=1; p<srcSize; p++) { |
| if (((const BYTE*)src)[p] != b) return 0; |
| } |
| return 1; |
| } |
| } |
| |
| size_t ZSTD_compressRleLiteralsBlock (void* dst, size_t dstCapacity, const void* src, size_t srcSize) |
| { |
| BYTE* const ostart = (BYTE*)dst; |
| U32 const flSize = 1 + (srcSize>31) + (srcSize>4095); |
| |
| assert(dstCapacity >= 4); (void)dstCapacity; |
| assert(allBytesIdentical(src, srcSize)); |
| |
| switch(flSize) |
| { |
| case 1: /* 2 - 1 - 5 */ |
| ostart[0] = (BYTE)((U32)set_rle + (srcSize<<3)); |
| break; |
| case 2: /* 2 - 2 - 12 */ |
| MEM_writeLE16(ostart, (U16)((U32)set_rle + (1<<2) + (srcSize<<4))); |
| break; |
| case 3: /* 2 - 2 - 20 */ |
| MEM_writeLE32(ostart, (U32)((U32)set_rle + (3<<2) + (srcSize<<4))); |
| break; |
| default: /* not necessary : flSize is {1,2,3} */ |
| assert(0); |
| } |
| |
| ostart[flSize] = *(const BYTE*)src; |
| DEBUGLOG(5, "RLE : Repeated Literal (%02X: %u times) -> %u bytes encoded", ((const BYTE*)src)[0], (U32)srcSize, (U32)flSize + 1); |
| return flSize+1; |
| } |
| |
| /* ZSTD_minLiteralsToCompress() : |
| * returns minimal amount of literals |
| * for literal compression to even be attempted. |
| * Minimum is made tighter as compression strategy increases. |
| */ |
| static size_t |
| ZSTD_minLiteralsToCompress(ZSTD_strategy strategy, HUF_repeat huf_repeat) |
| { |
| assert((int)strategy >= 0); |
| assert((int)strategy <= 9); |
| /* btultra2 : min 8 bytes; |
| * then 2x larger for each successive compression strategy |
| * max threshold 64 bytes */ |
| { int const shift = MIN(9-(int)strategy, 3); |
| size_t const mintc = (huf_repeat == HUF_repeat_valid) ? 6 : (size_t)8 << shift; |
| DEBUGLOG(7, "minLiteralsToCompress = %zu", mintc); |
| return mintc; |
| } |
| } |
| |
| size_t ZSTD_compressLiterals ( |
| void* dst, size_t dstCapacity, |
| const void* src, size_t srcSize, |
| void* entropyWorkspace, size_t entropyWorkspaceSize, |
| const ZSTD_hufCTables_t* prevHuf, |
| ZSTD_hufCTables_t* nextHuf, |
| ZSTD_strategy strategy, |
| int disableLiteralCompression, |
| int suspectUncompressible, |
| int bmi2) |
| { |
| size_t const lhSize = 3 + (srcSize >= 1 KB) + (srcSize >= 16 KB); |
| BYTE* const ostart = (BYTE*)dst; |
| U32 singleStream = srcSize < 256; |
| symbolEncodingType_e hType = set_compressed; |
| size_t cLitSize; |
| |
| DEBUGLOG(5,"ZSTD_compressLiterals (disableLiteralCompression=%i, srcSize=%u, dstCapacity=%zu)", |
| disableLiteralCompression, (U32)srcSize, dstCapacity); |
| |
| DEBUGLOG(6, "Completed literals listing (%zu bytes)", showHexa(src, srcSize)); |
| |
| /* Prepare nextEntropy assuming reusing the existing table */ |
| ZSTD_memcpy(nextHuf, prevHuf, sizeof(*prevHuf)); |
| |
| if (disableLiteralCompression) |
| return ZSTD_noCompressLiterals(dst, dstCapacity, src, srcSize); |
| |
| /* if too small, don't even attempt compression (speed opt) */ |
| if (srcSize < ZSTD_minLiteralsToCompress(strategy, prevHuf->repeatMode)) |
| return ZSTD_noCompressLiterals(dst, dstCapacity, src, srcSize); |
| |
| RETURN_ERROR_IF(dstCapacity < lhSize+1, dstSize_tooSmall, "not enough space for compression"); |
| { HUF_repeat repeat = prevHuf->repeatMode; |
| int const flags = 0 |
| | (bmi2 ? HUF_flags_bmi2 : 0) |
| | (strategy < ZSTD_lazy && srcSize <= 1024 ? HUF_flags_preferRepeat : 0) |
| | (strategy >= HUF_OPTIMAL_DEPTH_THRESHOLD ? HUF_flags_optimalDepth : 0) |
| | (suspectUncompressible ? HUF_flags_suspectUncompressible : 0); |
| |
| typedef size_t (*huf_compress_f)(void*, size_t, const void*, size_t, unsigned, unsigned, void*, size_t, HUF_CElt*, HUF_repeat*, int); |
| huf_compress_f huf_compress; |
| if (repeat == HUF_repeat_valid && lhSize == 3) singleStream = 1; |
| huf_compress = singleStream ? HUF_compress1X_repeat : HUF_compress4X_repeat; |
| cLitSize = huf_compress(ostart+lhSize, dstCapacity-lhSize, |
| src, srcSize, |
| HUF_SYMBOLVALUE_MAX, LitHufLog, |
| entropyWorkspace, entropyWorkspaceSize, |
| (HUF_CElt*)nextHuf->CTable, |
| &repeat, flags); |
| DEBUGLOG(5, "%zu literals compressed into %zu bytes (before header)", srcSize, cLitSize); |
| if (repeat != HUF_repeat_none) { |
| /* reused the existing table */ |
| DEBUGLOG(5, "reusing statistics from previous huffman block"); |
| hType = set_repeat; |
| } |
| } |
| |
| { size_t const minGain = ZSTD_minGain(srcSize, strategy); |
| if ((cLitSize==0) || (cLitSize >= srcSize - minGain) || ERR_isError(cLitSize)) { |
| ZSTD_memcpy(nextHuf, prevHuf, sizeof(*prevHuf)); |
| return ZSTD_noCompressLiterals(dst, dstCapacity, src, srcSize); |
| } } |
| if (cLitSize==1) { |
| /* A return value of 1 signals that the alphabet consists of a single symbol. |
| * However, in some rare circumstances, it could be the compressed size (a single byte). |
| * For that outcome to have a chance to happen, it's necessary that `srcSize < 8`. |
| * (it's also necessary to not generate statistics). |
| * Therefore, in such a case, actively check that all bytes are identical. */ |
| if ((srcSize >= 8) || allBytesIdentical(src, srcSize)) { |
| ZSTD_memcpy(nextHuf, prevHuf, sizeof(*prevHuf)); |
| return ZSTD_compressRleLiteralsBlock(dst, dstCapacity, src, srcSize); |
| } } |
| |
| if (hType == set_compressed) { |
| /* using a newly constructed table */ |
| nextHuf->repeatMode = HUF_repeat_check; |
| } |
| |
| /* Build header */ |
| switch(lhSize) |
| { |
| case 3: /* 2 - 2 - 10 - 10 */ |
| if (!singleStream) assert(srcSize >= MIN_LITERALS_FOR_4_STREAMS); |
| { U32 const lhc = hType + ((U32)(!singleStream) << 2) + ((U32)srcSize<<4) + ((U32)cLitSize<<14); |
| MEM_writeLE24(ostart, lhc); |
| break; |
| } |
| case 4: /* 2 - 2 - 14 - 14 */ |
| assert(srcSize >= MIN_LITERALS_FOR_4_STREAMS); |
| { U32 const lhc = hType + (2 << 2) + ((U32)srcSize<<4) + ((U32)cLitSize<<18); |
| MEM_writeLE32(ostart, lhc); |
| break; |
| } |
| case 5: /* 2 - 2 - 18 - 18 */ |
| assert(srcSize >= MIN_LITERALS_FOR_4_STREAMS); |
| { U32 const lhc = hType + (3 << 2) + ((U32)srcSize<<4) + ((U32)cLitSize<<22); |
| MEM_writeLE32(ostart, lhc); |
| ostart[4] = (BYTE)(cLitSize >> 10); |
| break; |
| } |
| default: /* not possible : lhSize is {3,4,5} */ |
| assert(0); |
| } |
| DEBUGLOG(5, "Compressed literals: %u -> %u", (U32)srcSize, (U32)(lhSize+cLitSize)); |
| return lhSize+cLitSize; |
| } |