path: root/contrib/libs/zstd/lib/compress/zstd_compress_superblock.c

/* 
 * Copyright (c) Yann Collet, Facebook, Inc.
 * 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_superblock.h" 
 
#include "../common/zstd_internal.h"  /* ZSTD_getSequenceLength */ 
#include "hist.h"                     /* HIST_countFast_wksp */ 
#include "zstd_compress_internal.h"   /* ZSTD_[huf|fse|entropy]CTablesMetadata_t */
#include "zstd_compress_sequences.h" 
#include "zstd_compress_literals.h" 
 
/** ZSTD_compressSubBlock_literal() : 
 *  Compresses literals section for a sub-block. 
 *  When we have to write the Huffman table we will sometimes choose a header 
 *  size larger than necessary. This is because we have to pick the header size 
 *  before we know the table size + compressed size, so we have a bound on the 
 *  table size. If we guessed incorrectly, we fall back to uncompressed literals. 
 * 
 *  We write the header when writeEntropy=1 and set entropyWritten=1 when we succeeded
 *  in writing the header, otherwise it is set to 0. 
 * 
 *  hufMetadata->hType has literals block type info. 
 *      If it is set_basic, all sub-blocks literals section will be Raw_Literals_Block. 
 *      If it is set_rle, all sub-blocks literals section will be RLE_Literals_Block. 
 *      If it is set_compressed, first sub-block's literals section will be Compressed_Literals_Block 
 *      If it is set_compressed, first sub-block's literals section will be Treeless_Literals_Block 
 *      and the following sub-blocks' literals sections will be Treeless_Literals_Block. 
 *  @return : compressed size of literals section of a sub-block 
 *            Or 0 if it unable to compress. 
 *            Or error code */ 
static size_t ZSTD_compressSubBlock_literal(const HUF_CElt* hufTable, 
                                    const ZSTD_hufCTablesMetadata_t* hufMetadata, 
                                    const BYTE* literals, size_t litSize, 
                                    void* dst, size_t dstSize, 
                                    const int bmi2, int writeEntropy, int* entropyWritten) 
{ 
    size_t const header = writeEntropy ? 200 : 0; 
    size_t const lhSize = 3 + (litSize >= (1 KB - header)) + (litSize >= (16 KB - header)); 
    BYTE* const ostart = (BYTE*)dst; 
    BYTE* const oend = ostart + dstSize; 
    BYTE* op = ostart + lhSize; 
    U32 const singleStream = lhSize == 3; 
    symbolEncodingType_e hType = writeEntropy ? hufMetadata->hType : set_repeat; 
    size_t cLitSize = 0; 
 
    (void)bmi2; /* TODO bmi2... */ 
 
    DEBUGLOG(5, "ZSTD_compressSubBlock_literal (litSize=%zu, lhSize=%zu, writeEntropy=%d)", litSize, lhSize, writeEntropy); 
 
    *entropyWritten = 0; 
    if (litSize == 0 || hufMetadata->hType == set_basic) { 
      DEBUGLOG(5, "ZSTD_compressSubBlock_literal using raw literal"); 
      return ZSTD_noCompressLiterals(dst, dstSize, literals, litSize); 
    } else if (hufMetadata->hType == set_rle) { 
      DEBUGLOG(5, "ZSTD_compressSubBlock_literal using rle literal"); 
      return ZSTD_compressRleLiteralsBlock(dst, dstSize, literals, litSize); 
    } 
 
    assert(litSize > 0); 
    assert(hufMetadata->hType == set_compressed || hufMetadata->hType == set_repeat); 
 
    if (writeEntropy && hufMetadata->hType == set_compressed) { 
        ZSTD_memcpy(op, hufMetadata->hufDesBuffer, hufMetadata->hufDesSize);
        op += hufMetadata->hufDesSize; 
        cLitSize += hufMetadata->hufDesSize; 
        DEBUGLOG(5, "ZSTD_compressSubBlock_literal (hSize=%zu)", hufMetadata->hufDesSize); 
    } 
 
    /* TODO bmi2 */ 
    {   const size_t cSize = singleStream ? HUF_compress1X_usingCTable(op, oend-op, literals, litSize, hufTable) 
                                          : HUF_compress4X_usingCTable(op, oend-op, literals, litSize, hufTable); 
        op += cSize; 
        cLitSize += cSize; 
        if (cSize == 0 || ERR_isError(cSize)) { 
            DEBUGLOG(5, "Failed to write entropy tables %s", ZSTD_getErrorName(cSize)); 
            return 0; 
        } 
        /* If we expand and we aren't writing a header then emit uncompressed */ 
        if (!writeEntropy && cLitSize >= litSize) { 
            DEBUGLOG(5, "ZSTD_compressSubBlock_literal using raw literal because uncompressible"); 
            return ZSTD_noCompressLiterals(dst, dstSize, literals, litSize); 
        } 
        /* If we are writing headers then allow expansion that doesn't change our header size. */ 
        if (lhSize < (size_t)(3 + (cLitSize >= 1 KB) + (cLitSize >= 16 KB))) { 
            assert(cLitSize > litSize); 
            DEBUGLOG(5, "Literals expanded beyond allowed header size"); 
            return ZSTD_noCompressLiterals(dst, dstSize, literals, litSize); 
        } 
        DEBUGLOG(5, "ZSTD_compressSubBlock_literal (cSize=%zu)", cSize); 
    } 
 
    /* Build header */ 
    switch(lhSize) 
    { 
    case 3: /* 2 - 2 - 10 - 10 */ 
        {   U32 const lhc = hType + ((!singleStream) << 2) + ((U32)litSize<<4) + ((U32)cLitSize<<14); 
            MEM_writeLE24(ostart, lhc); 
            break; 
        } 
    case 4: /* 2 - 2 - 14 - 14 */ 
        {   U32 const lhc = hType + (2 << 2) + ((U32)litSize<<4) + ((U32)cLitSize<<18); 
            MEM_writeLE32(ostart, lhc); 
            break; 
        } 
    case 5: /* 2 - 2 - 18 - 18 */ 
        {   U32 const lhc = hType + (3 << 2) + ((U32)litSize<<4) + ((U32)cLitSize<<22); 
            MEM_writeLE32(ostart, lhc); 
            ostart[4] = (BYTE)(cLitSize >> 10); 
            break; 
        } 
    default:  /* not possible : lhSize is {3,4,5} */ 
        assert(0); 
    } 
    *entropyWritten = 1; 
    DEBUGLOG(5, "Compressed literals: %u -> %u", (U32)litSize, (U32)(op-ostart)); 
    return op-ostart; 
} 
 
static size_t ZSTD_seqDecompressedSize(seqStore_t const* seqStore, const seqDef* sequences, size_t nbSeq, size_t litSize, int lastSequence) { 
    const seqDef* const sstart = sequences; 
    const seqDef* const send = sequences + nbSeq; 
    const seqDef* sp = sstart; 
    size_t matchLengthSum = 0; 
    size_t litLengthSum = 0; 
    (void)(litLengthSum); /* suppress unused variable warning on some environments */
    while (send-sp > 0) { 
        ZSTD_sequenceLength const seqLen = ZSTD_getSequenceLength(seqStore, sp); 
        litLengthSum += seqLen.litLength; 
        matchLengthSum += seqLen.matchLength; 
        sp++; 
    } 
    assert(litLengthSum <= litSize); 
    if (!lastSequence) { 
        assert(litLengthSum == litSize); 
    } 
    return matchLengthSum + litSize; 
} 
 
/** ZSTD_compressSubBlock_sequences() : 
 *  Compresses sequences section for a sub-block. 
 *  fseMetadata->llType, fseMetadata->ofType, and fseMetadata->mlType have 
 *  symbol compression modes for the super-block. 
 *  The first successfully compressed block will have these in its header. 
 *  We set entropyWritten=1 when we succeed in compressing the sequences. 
 *  The following sub-blocks will always have repeat mode. 
 *  @return : compressed size of sequences section of a sub-block 
 *            Or 0 if it is unable to compress 
 *            Or error code. */ 
static size_t ZSTD_compressSubBlock_sequences(const ZSTD_fseCTables_t* fseTables, 
                                              const ZSTD_fseCTablesMetadata_t* fseMetadata, 
                                              const seqDef* sequences, size_t nbSeq, 
                                              const BYTE* llCode, const BYTE* mlCode, const BYTE* ofCode, 
                                              const ZSTD_CCtx_params* cctxParams, 
                                              void* dst, size_t dstCapacity, 
                                              const int bmi2, int writeEntropy, int* entropyWritten) 
{ 
    const int longOffsets = cctxParams->cParams.windowLog > STREAM_ACCUMULATOR_MIN; 
    BYTE* const ostart = (BYTE*)dst; 
    BYTE* const oend = ostart + dstCapacity; 
    BYTE* op = ostart; 
    BYTE* seqHead; 
 
    DEBUGLOG(5, "ZSTD_compressSubBlock_sequences (nbSeq=%zu, writeEntropy=%d, longOffsets=%d)", nbSeq, writeEntropy, longOffsets); 
 
    *entropyWritten = 0; 
    /* Sequences Header */ 
    RETURN_ERROR_IF((oend-op) < 3 /*max nbSeq Size*/ + 1 /*seqHead*/, 
                    dstSize_tooSmall, ""); 
    if (nbSeq < 0x7F) 
        *op++ = (BYTE)nbSeq; 
    else if (nbSeq < LONGNBSEQ) 
        op[0] = (BYTE)((nbSeq>>8) + 0x80), op[1] = (BYTE)nbSeq, op+=2; 
    else 
        op[0]=0xFF, MEM_writeLE16(op+1, (U16)(nbSeq - LONGNBSEQ)), op+=3; 
    if (nbSeq==0) { 
        return op - ostart; 
    } 
 
    /* seqHead : flags for FSE encoding type */ 
    seqHead = op++; 
 
    DEBUGLOG(5, "ZSTD_compressSubBlock_sequences (seqHeadSize=%u)", (unsigned)(op-ostart)); 
 
    if (writeEntropy) { 
        const U32 LLtype = fseMetadata->llType; 
        const U32 Offtype = fseMetadata->ofType; 
        const U32 MLtype = fseMetadata->mlType; 
        DEBUGLOG(5, "ZSTD_compressSubBlock_sequences (fseTablesSize=%zu)", fseMetadata->fseTablesSize); 
        *seqHead = (BYTE)((LLtype<<6) + (Offtype<<4) + (MLtype<<2)); 
        ZSTD_memcpy(op, fseMetadata->fseTablesBuffer, fseMetadata->fseTablesSize);
        op += fseMetadata->fseTablesSize; 
    } else { 
        const U32 repeat = set_repeat; 
        *seqHead = (BYTE)((repeat<<6) + (repeat<<4) + (repeat<<2)); 
    } 
 
    {   size_t const bitstreamSize = ZSTD_encodeSequences( 
                                        op, oend - op, 
                                        fseTables->matchlengthCTable, mlCode, 
                                        fseTables->offcodeCTable, ofCode, 
                                        fseTables->litlengthCTable, llCode, 
                                        sequences, nbSeq, 
                                        longOffsets, bmi2); 
        FORWARD_IF_ERROR(bitstreamSize, "ZSTD_encodeSequences failed"); 
        op += bitstreamSize; 
        /* zstd versions <= 1.3.4 mistakenly report corruption when 
         * FSE_readNCount() receives a buffer < 4 bytes. 
         * Fixed by https://github.com/facebook/zstd/pull/1146. 
         * This can happen when the last set_compressed table present is 2 
         * bytes and the bitstream is only one byte. 
         * In this exceedingly rare case, we will simply emit an uncompressed 
         * block, since it isn't worth optimizing. 
         */ 
#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION 
        if (writeEntropy && fseMetadata->lastCountSize && fseMetadata->lastCountSize + bitstreamSize < 4) { 
            /* NCountSize >= 2 && bitstreamSize > 0 ==> lastCountSize == 3 */ 
            assert(fseMetadata->lastCountSize + bitstreamSize == 3); 
            DEBUGLOG(5, "Avoiding bug in zstd decoder in versions <= 1.3.4 by " 
                        "emitting an uncompressed block."); 
            return 0; 
        } 
#endif 
        DEBUGLOG(5, "ZSTD_compressSubBlock_sequences (bitstreamSize=%zu)", bitstreamSize); 
    } 
 
    /* zstd versions <= 1.4.0 mistakenly report error when 
     * sequences section body size is less than 3 bytes. 
     * Fixed by https://github.com/facebook/zstd/pull/1664. 
     * This can happen when the previous sequences section block is compressed 
     * with rle mode and the current block's sequences section is compressed 
     * with repeat mode where sequences section body size can be 1 byte. 
     */ 
#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION 
    if (op-seqHead < 4) { 
        DEBUGLOG(5, "Avoiding bug in zstd decoder in versions <= 1.4.0 by emitting " 
                    "an uncompressed block when sequences are < 4 bytes"); 
        return 0; 
    } 
#endif 
 
    *entropyWritten = 1; 
    return op - ostart; 
} 
 
/** ZSTD_compressSubBlock() : 
 *  Compresses a single sub-block. 
 *  @return : compressed size of the sub-block 
 *            Or 0 if it failed to compress. */ 
static size_t ZSTD_compressSubBlock(const ZSTD_entropyCTables_t* entropy, 
                                    const ZSTD_entropyCTablesMetadata_t* entropyMetadata, 
                                    const seqDef* sequences, size_t nbSeq, 
                                    const BYTE* literals, size_t litSize, 
                                    const BYTE* llCode, const BYTE* mlCode, const BYTE* ofCode, 
                                    const ZSTD_CCtx_params* cctxParams, 
                                    void* dst, size_t dstCapacity, 
                                    const int bmi2, 
                                    int writeLitEntropy, int writeSeqEntropy, 
                                    int* litEntropyWritten, int* seqEntropyWritten, 
                                    U32 lastBlock) 
{ 
    BYTE* const ostart = (BYTE*)dst; 
    BYTE* const oend = ostart + dstCapacity; 
    BYTE* op = ostart + ZSTD_blockHeaderSize; 
    DEBUGLOG(5, "ZSTD_compressSubBlock (litSize=%zu, nbSeq=%zu, writeLitEntropy=%d, writeSeqEntropy=%d, lastBlock=%d)", 
                litSize, nbSeq, writeLitEntropy, writeSeqEntropy, lastBlock); 
    {   size_t cLitSize = ZSTD_compressSubBlock_literal((const HUF_CElt*)entropy->huf.CTable, 
                                                        &entropyMetadata->hufMetadata, literals, litSize, 
                                                        op, oend-op, bmi2, writeLitEntropy, litEntropyWritten); 
        FORWARD_IF_ERROR(cLitSize, "ZSTD_compressSubBlock_literal failed"); 
        if (cLitSize == 0) return 0; 
        op += cLitSize; 
    } 
    {   size_t cSeqSize = ZSTD_compressSubBlock_sequences(&entropy->fse, 
                                                  &entropyMetadata->fseMetadata, 
                                                  sequences, nbSeq, 
                                                  llCode, mlCode, ofCode, 
                                                  cctxParams, 
                                                  op, oend-op, 
                                                  bmi2, writeSeqEntropy, seqEntropyWritten); 
        FORWARD_IF_ERROR(cSeqSize, "ZSTD_compressSubBlock_sequences failed"); 
        if (cSeqSize == 0) return 0; 
        op += cSeqSize; 
    } 
    /* Write block header */ 
    {   size_t cSize = (op-ostart)-ZSTD_blockHeaderSize; 
        U32 const cBlockHeader24 = lastBlock + (((U32)bt_compressed)<<1) + (U32)(cSize << 3); 
        MEM_writeLE24(ostart, cBlockHeader24); 
    } 
    return op-ostart; 
} 
 
static size_t ZSTD_estimateSubBlockSize_literal(const BYTE* literals, size_t litSize, 
                                                const ZSTD_hufCTables_t* huf, 
                                                const ZSTD_hufCTablesMetadata_t* hufMetadata, 
                                                void* workspace, size_t wkspSize, 
                                                int writeEntropy) 
{ 
    unsigned* const countWksp = (unsigned*)workspace; 
    unsigned maxSymbolValue = 255; 
    size_t literalSectionHeaderSize = 3; /* Use hard coded size of 3 bytes */ 
 
    if (hufMetadata->hType == set_basic) return litSize; 
    else if (hufMetadata->hType == set_rle) return 1; 
    else if (hufMetadata->hType == set_compressed || hufMetadata->hType == set_repeat) { 
        size_t const largest = HIST_count_wksp (countWksp, &maxSymbolValue, (const BYTE*)literals, litSize, workspace, wkspSize); 
        if (ZSTD_isError(largest)) return litSize; 
        {   size_t cLitSizeEstimate = HUF_estimateCompressedSize((const HUF_CElt*)huf->CTable, countWksp, maxSymbolValue); 
            if (writeEntropy) cLitSizeEstimate += hufMetadata->hufDesSize; 
            return cLitSizeEstimate + literalSectionHeaderSize; 
    }   } 
    assert(0); /* impossible */ 
    return 0; 
} 
 
static size_t ZSTD_estimateSubBlockSize_symbolType(symbolEncodingType_e type, 
                        const BYTE* codeTable, unsigned maxCode, 
                        size_t nbSeq, const FSE_CTable* fseCTable, 
                        const U8* additionalBits,
                        short const* defaultNorm, U32 defaultNormLog, U32 defaultMax,
                        void* workspace, size_t wkspSize) 
{ 
    unsigned* const countWksp = (unsigned*)workspace; 
    const BYTE* ctp = codeTable; 
    const BYTE* const ctStart = ctp; 
    const BYTE* const ctEnd = ctStart + nbSeq; 
    size_t cSymbolTypeSizeEstimateInBits = 0; 
    unsigned max = maxCode; 
 
    HIST_countFast_wksp(countWksp, &max, codeTable, nbSeq, workspace, wkspSize);  /* can't fail */ 
    if (type == set_basic) { 
        /* We selected this encoding type, so it must be valid. */
        assert(max <= defaultMax);
        cSymbolTypeSizeEstimateInBits = max <= defaultMax
                ? ZSTD_crossEntropyCost(defaultNorm, defaultNormLog, countWksp, max)
                : ERROR(GENERIC);
    } else if (type == set_rle) { 
        cSymbolTypeSizeEstimateInBits = 0; 
    } else if (type == set_compressed || type == set_repeat) { 
        cSymbolTypeSizeEstimateInBits = ZSTD_fseBitCost(fseCTable, countWksp, max); 
    } 
    if (ZSTD_isError(cSymbolTypeSizeEstimateInBits)) return nbSeq * 10; 
    while (ctp < ctEnd) { 
        if (additionalBits) cSymbolTypeSizeEstimateInBits += additionalBits[*ctp]; 
        else cSymbolTypeSizeEstimateInBits += *ctp; /* for offset, offset code is also the number of additional bits */ 
        ctp++; 
    } 
    return cSymbolTypeSizeEstimateInBits / 8; 
} 
 
static size_t ZSTD_estimateSubBlockSize_sequences(const BYTE* ofCodeTable, 
                                                  const BYTE* llCodeTable, 
                                                  const BYTE* mlCodeTable, 
                                                  size_t nbSeq, 
                                                  const ZSTD_fseCTables_t* fseTables, 
                                                  const ZSTD_fseCTablesMetadata_t* fseMetadata, 
                                                  void* workspace, size_t wkspSize, 
                                                  int writeEntropy) 
{ 
    size_t const sequencesSectionHeaderSize = 3; /* Use hard coded size of 3 bytes */
    size_t cSeqSizeEstimate = 0; 
    if (nbSeq == 0) return sequencesSectionHeaderSize;
    cSeqSizeEstimate += ZSTD_estimateSubBlockSize_symbolType(fseMetadata->ofType, ofCodeTable, MaxOff, 
                                         nbSeq, fseTables->offcodeCTable, NULL, 
                                         OF_defaultNorm, OF_defaultNormLog, DefaultMaxOff,
                                         workspace, wkspSize); 
    cSeqSizeEstimate += ZSTD_estimateSubBlockSize_symbolType(fseMetadata->llType, llCodeTable, MaxLL, 
                                         nbSeq, fseTables->litlengthCTable, LL_bits, 
                                         LL_defaultNorm, LL_defaultNormLog, MaxLL,
                                         workspace, wkspSize); 
    cSeqSizeEstimate += ZSTD_estimateSubBlockSize_symbolType(fseMetadata->mlType, mlCodeTable, MaxML, 
                                         nbSeq, fseTables->matchlengthCTable, ML_bits, 
                                         ML_defaultNorm, ML_defaultNormLog, MaxML,
                                         workspace, wkspSize); 
    if (writeEntropy) cSeqSizeEstimate += fseMetadata->fseTablesSize; 
    return cSeqSizeEstimate + sequencesSectionHeaderSize; 
} 
 
static size_t ZSTD_estimateSubBlockSize(const BYTE* literals, size_t litSize, 
                                        const BYTE* ofCodeTable, 
                                        const BYTE* llCodeTable, 
                                        const BYTE* mlCodeTable, 
                                        size_t nbSeq, 
                                        const ZSTD_entropyCTables_t* entropy, 
                                        const ZSTD_entropyCTablesMetadata_t* entropyMetadata, 
                                        void* workspace, size_t wkspSize, 
                                        int writeLitEntropy, int writeSeqEntropy) { 
    size_t cSizeEstimate = 0; 
    cSizeEstimate += ZSTD_estimateSubBlockSize_literal(literals, litSize, 
                                                         &entropy->huf, &entropyMetadata->hufMetadata, 
                                                         workspace, wkspSize, writeLitEntropy); 
    cSizeEstimate += ZSTD_estimateSubBlockSize_sequences(ofCodeTable, llCodeTable, mlCodeTable, 
                                                         nbSeq, &entropy->fse, &entropyMetadata->fseMetadata, 
                                                         workspace, wkspSize, writeSeqEntropy); 
    return cSizeEstimate + ZSTD_blockHeaderSize; 
} 
 
static int ZSTD_needSequenceEntropyTables(ZSTD_fseCTablesMetadata_t const* fseMetadata) 
{ 
    if (fseMetadata->llType == set_compressed || fseMetadata->llType == set_rle) 
        return 1; 
    if (fseMetadata->mlType == set_compressed || fseMetadata->mlType == set_rle) 
        return 1; 
    if (fseMetadata->ofType == set_compressed || fseMetadata->ofType == set_rle) 
        return 1; 
    return 0; 
} 
 
/** ZSTD_compressSubBlock_multi() : 
 *  Breaks super-block into multiple sub-blocks and compresses them. 
 *  Entropy will be written to the first block. 
 *  The following blocks will use repeat mode to compress. 
 *  All sub-blocks are compressed blocks (no raw or rle blocks). 
 *  @return : compressed size of the super block (which is multiple ZSTD blocks) 
 *            Or 0 if it failed to compress. */ 
static size_t ZSTD_compressSubBlock_multi(const seqStore_t* seqStorePtr, 
                            const ZSTD_compressedBlockState_t* prevCBlock, 
                            ZSTD_compressedBlockState_t* nextCBlock, 
                            const ZSTD_entropyCTablesMetadata_t* entropyMetadata, 
                            const ZSTD_CCtx_params* cctxParams, 
                                  void* dst, size_t dstCapacity, 
                            const void* src, size_t srcSize, 
                            const int bmi2, U32 lastBlock, 
                            void* workspace, size_t wkspSize) 
{ 
    const seqDef* const sstart = seqStorePtr->sequencesStart; 
    const seqDef* const send = seqStorePtr->sequences; 
    const seqDef* sp = sstart; 
    const BYTE* const lstart = seqStorePtr->litStart; 
    const BYTE* const lend = seqStorePtr->lit; 
    const BYTE* lp = lstart; 
    BYTE const* ip = (BYTE const*)src; 
    BYTE const* const iend = ip + srcSize; 
    BYTE* const ostart = (BYTE*)dst; 
    BYTE* const oend = ostart + dstCapacity; 
    BYTE* op = ostart; 
    const BYTE* llCodePtr = seqStorePtr->llCode; 
    const BYTE* mlCodePtr = seqStorePtr->mlCode; 
    const BYTE* ofCodePtr = seqStorePtr->ofCode; 
    size_t targetCBlockSize = cctxParams->targetCBlockSize; 
    size_t litSize, seqCount; 
    int writeLitEntropy = entropyMetadata->hufMetadata.hType == set_compressed; 
    int writeSeqEntropy = 1; 
    int lastSequence = 0; 
 
    DEBUGLOG(5, "ZSTD_compressSubBlock_multi (litSize=%u, nbSeq=%u)", 
                (unsigned)(lend-lp), (unsigned)(send-sstart)); 
 
    litSize = 0; 
    seqCount = 0; 
    do { 
        size_t cBlockSizeEstimate = 0; 
        if (sstart == send) { 
            lastSequence = 1; 
        } else { 
            const seqDef* const sequence = sp + seqCount; 
            lastSequence = sequence == send - 1; 
            litSize += ZSTD_getSequenceLength(seqStorePtr, sequence).litLength; 
            seqCount++; 
        } 
        if (lastSequence) { 
            assert(lp <= lend); 
            assert(litSize <= (size_t)(lend - lp)); 
            litSize = (size_t)(lend - lp); 
        } 
        /* I think there is an optimization opportunity here. 
         * Calling ZSTD_estimateSubBlockSize for every sequence can be wasteful 
         * since it recalculates estimate from scratch. 
         * For example, it would recount literal distribution and symbol codes every time.
         */ 
        cBlockSizeEstimate = ZSTD_estimateSubBlockSize(lp, litSize, ofCodePtr, llCodePtr, mlCodePtr, seqCount, 
                                                       &nextCBlock->entropy, entropyMetadata, 
                                                       workspace, wkspSize, writeLitEntropy, writeSeqEntropy); 
        if (cBlockSizeEstimate > targetCBlockSize || lastSequence) { 
            int litEntropyWritten = 0; 
            int seqEntropyWritten = 0; 
            const size_t decompressedSize = ZSTD_seqDecompressedSize(seqStorePtr, sp, seqCount, litSize, lastSequence); 
            const size_t cSize = ZSTD_compressSubBlock(&nextCBlock->entropy, entropyMetadata, 
                                                       sp, seqCount, 
                                                       lp, litSize, 
                                                       llCodePtr, mlCodePtr, ofCodePtr, 
                                                       cctxParams, 
                                                       op, oend-op, 
                                                       bmi2, writeLitEntropy, writeSeqEntropy, 
                                                       &litEntropyWritten, &seqEntropyWritten, 
                                                       lastBlock && lastSequence); 
            FORWARD_IF_ERROR(cSize, "ZSTD_compressSubBlock failed"); 
            if (cSize > 0 && cSize < decompressedSize) { 
                DEBUGLOG(5, "Committed the sub-block"); 
                assert(ip + decompressedSize <= iend); 
                ip += decompressedSize; 
                sp += seqCount; 
                lp += litSize; 
                op += cSize; 
                llCodePtr += seqCount; 
                mlCodePtr += seqCount; 
                ofCodePtr += seqCount; 
                litSize = 0; 
                seqCount = 0; 
                /* Entropy only needs to be written once */ 
                if (litEntropyWritten) { 
                    writeLitEntropy = 0; 
                } 
                if (seqEntropyWritten) { 
                    writeSeqEntropy = 0; 
                } 
            } 
        } 
    } while (!lastSequence); 
    if (writeLitEntropy) { 
        DEBUGLOG(5, "ZSTD_compressSubBlock_multi has literal entropy tables unwritten"); 
        ZSTD_memcpy(&nextCBlock->entropy.huf, &prevCBlock->entropy.huf, sizeof(prevCBlock->entropy.huf));
    } 
    if (writeSeqEntropy && ZSTD_needSequenceEntropyTables(&entropyMetadata->fseMetadata)) { 
        /* If we haven't written our entropy tables, then we've violated our contract and 
         * must emit an uncompressed block. 
         */ 
        DEBUGLOG(5, "ZSTD_compressSubBlock_multi has sequence entropy tables unwritten"); 
        return 0; 
    } 
    if (ip < iend) { 
        size_t const cSize = ZSTD_noCompressBlock(op, oend - op, ip, iend - ip, lastBlock); 
        DEBUGLOG(5, "ZSTD_compressSubBlock_multi last sub-block uncompressed, %zu bytes", (size_t)(iend - ip)); 
        FORWARD_IF_ERROR(cSize, "ZSTD_noCompressBlock failed"); 
        assert(cSize != 0); 
        op += cSize; 
        /* We have to regenerate the repcodes because we've skipped some sequences */ 
        if (sp < send) { 
            seqDef const* seq; 
            repcodes_t rep; 
            ZSTD_memcpy(&rep, prevCBlock->rep, sizeof(rep));
            for (seq = sstart; seq < sp; ++seq) { 
                ZSTD_updateRep(rep.rep, seq->offBase - 1, ZSTD_getSequenceLength(seqStorePtr, seq).litLength == 0);
            } 
            ZSTD_memcpy(nextCBlock->rep, &rep, sizeof(rep));
        } 
    } 
    DEBUGLOG(5, "ZSTD_compressSubBlock_multi compressed"); 
    return op-ostart; 
} 
 
size_t ZSTD_compressSuperBlock(ZSTD_CCtx* zc, 
                               void* dst, size_t dstCapacity, 
                               void const* src, size_t srcSize, 
                               unsigned lastBlock) { 
    ZSTD_entropyCTablesMetadata_t entropyMetadata; 
 
    FORWARD_IF_ERROR(ZSTD_buildBlockEntropyStats(&zc->seqStore,
          &zc->blockState.prevCBlock->entropy, 
          &zc->blockState.nextCBlock->entropy, 
          &zc->appliedParams, 
          &entropyMetadata, 
          zc->entropyWorkspace, ENTROPY_WORKSPACE_SIZE /* statically allocated in resetCCtx */), "");
 
    return ZSTD_compressSubBlock_multi(&zc->seqStore, 
            zc->blockState.prevCBlock, 
            zc->blockState.nextCBlock, 
            &entropyMetadata, 
            &zc->appliedParams, 
            dst, dstCapacity, 
            src, srcSize, 
            zc->bmi2, lastBlock, 
            zc->entropyWorkspace, ENTROPY_WORKSPACE_SIZE /* statically allocated in resetCCtx */);
}