Compress-Zstd

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ext/zstd/lib/decompress/zstd_decompress.c  view on Meta::CPAN


static size_t ZSTD_copyRawBlock(void* dst, size_t dstCapacity,
                          const void* src, size_t srcSize)
{
    DEBUGLOG(5, "ZSTD_copyRawBlock");
    if (dst == NULL) {
        if (srcSize == 0) return 0;
        RETURN_ERROR(dstBuffer_null);
    }
    RETURN_ERROR_IF(srcSize > dstCapacity, dstSize_tooSmall);
    memcpy(dst, src, srcSize);
    return srcSize;
}

static size_t ZSTD_setRleBlock(void* dst, size_t dstCapacity,
                               BYTE b,
                               size_t regenSize)
{
    if (dst == NULL) {
        if (regenSize == 0) return 0;
        RETURN_ERROR(dstBuffer_null);
    }
    RETURN_ERROR_IF(regenSize > dstCapacity, dstSize_tooSmall);
    memset(dst, b, regenSize);
    return regenSize;
}


/*! ZSTD_decompressFrame() :
 * @dctx must be properly initialized
 *  will update *srcPtr and *srcSizePtr,
 *  to make *srcPtr progress by one frame. */
static size_t ZSTD_decompressFrame(ZSTD_DCtx* dctx,
                                   void* dst, size_t dstCapacity,
                             const void** srcPtr, size_t *srcSizePtr)
{
    const BYTE* ip = (const BYTE*)(*srcPtr);
    BYTE* const ostart = (BYTE* const)dst;
    BYTE* const oend = ostart + dstCapacity;
    BYTE* op = ostart;
    size_t remainingSrcSize = *srcSizePtr;

    DEBUGLOG(4, "ZSTD_decompressFrame (srcSize:%i)", (int)*srcSizePtr);

    /* check */
    RETURN_ERROR_IF(
        remainingSrcSize < ZSTD_FRAMEHEADERSIZE_MIN+ZSTD_blockHeaderSize,
        srcSize_wrong);

    /* Frame Header */
    {   size_t const frameHeaderSize = ZSTD_frameHeaderSize(ip, ZSTD_FRAMEHEADERSIZE_PREFIX);
        if (ZSTD_isError(frameHeaderSize)) return frameHeaderSize;
        RETURN_ERROR_IF(remainingSrcSize < frameHeaderSize+ZSTD_blockHeaderSize,
                        srcSize_wrong);
        FORWARD_IF_ERROR( ZSTD_decodeFrameHeader(dctx, ip, frameHeaderSize) );
        ip += frameHeaderSize; remainingSrcSize -= frameHeaderSize;
    }

    /* Loop on each block */
    while (1) {
        size_t decodedSize;
        blockProperties_t blockProperties;
        size_t const cBlockSize = ZSTD_getcBlockSize(ip, remainingSrcSize, &blockProperties);
        if (ZSTD_isError(cBlockSize)) return cBlockSize;

        ip += ZSTD_blockHeaderSize;
        remainingSrcSize -= ZSTD_blockHeaderSize;
        RETURN_ERROR_IF(cBlockSize > remainingSrcSize, srcSize_wrong);

        switch(blockProperties.blockType)
        {
        case bt_compressed:
            decodedSize = ZSTD_decompressBlock_internal(dctx, op, oend-op, ip, cBlockSize, /* frame */ 1);
            break;
        case bt_raw :
            decodedSize = ZSTD_copyRawBlock(op, oend-op, ip, cBlockSize);
            break;
        case bt_rle :
            decodedSize = ZSTD_setRleBlock(op, oend-op, *ip, blockProperties.origSize);
            break;
        case bt_reserved :
        default:
            RETURN_ERROR(corruption_detected);
        }

        if (ZSTD_isError(decodedSize)) return decodedSize;
        if (dctx->fParams.checksumFlag)
            XXH64_update(&dctx->xxhState, op, decodedSize);
        op += decodedSize;
        ip += cBlockSize;
        remainingSrcSize -= cBlockSize;
        if (blockProperties.lastBlock) break;
    }

    if (dctx->fParams.frameContentSize != ZSTD_CONTENTSIZE_UNKNOWN) {
        RETURN_ERROR_IF((U64)(op-ostart) != dctx->fParams.frameContentSize,
                        corruption_detected);
    }
    if (dctx->fParams.checksumFlag) { /* Frame content checksum verification */
        U32 const checkCalc = (U32)XXH64_digest(&dctx->xxhState);
        U32 checkRead;
        RETURN_ERROR_IF(remainingSrcSize<4, checksum_wrong);
        checkRead = MEM_readLE32(ip);
        RETURN_ERROR_IF(checkRead != checkCalc, checksum_wrong);
        ip += 4;
        remainingSrcSize -= 4;
    }

    /* Allow caller to get size read */
    *srcPtr = ip;
    *srcSizePtr = remainingSrcSize;
    return op-ostart;
}

static size_t ZSTD_decompressMultiFrame(ZSTD_DCtx* dctx,
                                        void* dst, size_t dstCapacity,
                                  const void* src, size_t srcSize,
                                  const void* dict, size_t dictSize,
                                  const ZSTD_DDict* ddict)
{
    void* const dststart = dst;
    int moreThan1Frame = 0;

    DEBUGLOG(5, "ZSTD_decompressMultiFrame");
    assert(dict==NULL || ddict==NULL);  /* either dict or ddict set, not both */

    if (ddict) {
        dict = ZSTD_DDict_dictContent(ddict);
        dictSize = ZSTD_DDict_dictSize(ddict);
    }

    while (srcSize >= ZSTD_FRAMEHEADERSIZE_PREFIX) {

#if defined(ZSTD_LEGACY_SUPPORT) && (ZSTD_LEGACY_SUPPORT >= 1)
        if (ZSTD_isLegacy(src, srcSize)) {
            size_t decodedSize;
            size_t const frameSize = ZSTD_findFrameCompressedSizeLegacy(src, srcSize);
            if (ZSTD_isError(frameSize)) return frameSize;
            RETURN_ERROR_IF(dctx->staticSize, memory_allocation,
                "legacy support is not compatible with static dctx");

            decodedSize = ZSTD_decompressLegacy(dst, dstCapacity, src, frameSize, dict, dictSize);
            if (ZSTD_isError(decodedSize)) return decodedSize;

            assert(decodedSize <=- dstCapacity);
            dst = (BYTE*)dst + decodedSize;
            dstCapacity -= decodedSize;

            src = (const BYTE*)src + frameSize;
            srcSize -= frameSize;

            continue;
        }
#endif

        {   U32 const magicNumber = MEM_readLE32(src);
            DEBUGLOG(4, "reading magic number %08X (expecting %08X)",
                        (unsigned)magicNumber, ZSTD_MAGICNUMBER);
            if ((magicNumber & ZSTD_MAGIC_SKIPPABLE_MASK) == ZSTD_MAGIC_SKIPPABLE_START) {
                size_t const skippableSize = readSkippableFrameSize(src, srcSize);
                FORWARD_IF_ERROR(skippableSize);
                assert(skippableSize <= srcSize);

                src = (const BYTE *)src + skippableSize;
                srcSize -= skippableSize;
                continue;
        }   }

        if (ddict) {
            /* we were called from ZSTD_decompress_usingDDict */
            FORWARD_IF_ERROR(ZSTD_decompressBegin_usingDDict(dctx, ddict));
        } else {
            /* this will initialize correctly with no dict if dict == NULL, so
             * use this in all cases but ddict */
            FORWARD_IF_ERROR(ZSTD_decompressBegin_usingDict(dctx, dict, dictSize));
        }
        ZSTD_checkContinuity(dctx, dst);

        {   const size_t res = ZSTD_decompressFrame(dctx, dst, dstCapacity,
                                                    &src, &srcSize);
            RETURN_ERROR_IF(
                (ZSTD_getErrorCode(res) == ZSTD_error_prefix_unknown)
             && (moreThan1Frame==1),
                srcSize_wrong,
                "at least one frame successfully completed, but following "
                "bytes are garbage: it's more likely to be a srcSize error, "
                "specifying more bytes than compressed size of frame(s). This "
                "error message replaces ERROR(prefix_unknown), which would be "
                "confusing, as the first header is actually correct. Note that "
                "one could be unlucky, it might be a corruption error instead, "
                "happening right at the place where we expect zstd magic "
                "bytes. But this is _much_ less likely than a srcSize field "
                "error.");
            if (ZSTD_isError(res)) return res;
            assert(res <= dstCapacity);
            dst = (BYTE*)dst + res;
            dstCapacity -= res;
        }
        moreThan1Frame = 1;
    }  /* while (srcSize >= ZSTD_frameHeaderSize_prefix) */

    RETURN_ERROR_IF(srcSize, srcSize_wrong, "input not entirely consumed");

    return (BYTE*)dst - (BYTE*)dststart;
}

size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx,

ext/zstd/lib/decompress/zstd_decompress.c  view on Meta::CPAN

        return 0;

    case ZSTDds_decodeFrameHeader:
        assert(src != NULL);
        memcpy(dctx->headerBuffer + (dctx->headerSize - srcSize), src, srcSize);
        FORWARD_IF_ERROR(ZSTD_decodeFrameHeader(dctx, dctx->headerBuffer, dctx->headerSize));
        dctx->expected = ZSTD_blockHeaderSize;
        dctx->stage = ZSTDds_decodeBlockHeader;
        return 0;

    case ZSTDds_decodeBlockHeader:
        {   blockProperties_t bp;
            size_t const cBlockSize = ZSTD_getcBlockSize(src, ZSTD_blockHeaderSize, &bp);
            if (ZSTD_isError(cBlockSize)) return cBlockSize;
            RETURN_ERROR_IF(cBlockSize > dctx->fParams.blockSizeMax, corruption_detected, "Block Size Exceeds Maximum");
            dctx->expected = cBlockSize;
            dctx->bType = bp.blockType;
            dctx->rleSize = bp.origSize;
            if (cBlockSize) {
                dctx->stage = bp.lastBlock ? ZSTDds_decompressLastBlock : ZSTDds_decompressBlock;
                return 0;
            }
            /* empty block */
            if (bp.lastBlock) {
                if (dctx->fParams.checksumFlag) {
                    dctx->expected = 4;
                    dctx->stage = ZSTDds_checkChecksum;
                } else {
                    dctx->expected = 0; /* end of frame */
                    dctx->stage = ZSTDds_getFrameHeaderSize;
                }
            } else {
                dctx->expected = ZSTD_blockHeaderSize;  /* jump to next header */
                dctx->stage = ZSTDds_decodeBlockHeader;
            }
            return 0;
        }

    case ZSTDds_decompressLastBlock:
    case ZSTDds_decompressBlock:
        DEBUGLOG(5, "ZSTD_decompressContinue: case ZSTDds_decompressBlock");
        {   size_t rSize;
            switch(dctx->bType)
            {
            case bt_compressed:
                DEBUGLOG(5, "ZSTD_decompressContinue: case bt_compressed");
                rSize = ZSTD_decompressBlock_internal(dctx, dst, dstCapacity, src, srcSize, /* frame */ 1);
                break;
            case bt_raw :
                rSize = ZSTD_copyRawBlock(dst, dstCapacity, src, srcSize);
                break;
            case bt_rle :
                rSize = ZSTD_setRleBlock(dst, dstCapacity, *(const BYTE*)src, dctx->rleSize);
                break;
            case bt_reserved :   /* should never happen */
            default:
                RETURN_ERROR(corruption_detected);
            }
            if (ZSTD_isError(rSize)) return rSize;
            RETURN_ERROR_IF(rSize > dctx->fParams.blockSizeMax, corruption_detected, "Decompressed Block Size Exceeds Maximum");
            DEBUGLOG(5, "ZSTD_decompressContinue: decoded size from block : %u", (unsigned)rSize);
            dctx->decodedSize += rSize;
            if (dctx->fParams.checksumFlag) XXH64_update(&dctx->xxhState, dst, rSize);

            if (dctx->stage == ZSTDds_decompressLastBlock) {   /* end of frame */
                DEBUGLOG(4, "ZSTD_decompressContinue: decoded size from frame : %u", (unsigned)dctx->decodedSize);
                RETURN_ERROR_IF(
                    dctx->fParams.frameContentSize != ZSTD_CONTENTSIZE_UNKNOWN
                 && dctx->decodedSize != dctx->fParams.frameContentSize,
                    corruption_detected);
                if (dctx->fParams.checksumFlag) {  /* another round for frame checksum */
                    dctx->expected = 4;
                    dctx->stage = ZSTDds_checkChecksum;
                } else {
                    dctx->expected = 0;   /* ends here */
                    dctx->stage = ZSTDds_getFrameHeaderSize;
                }
            } else {
                dctx->stage = ZSTDds_decodeBlockHeader;
                dctx->expected = ZSTD_blockHeaderSize;
                dctx->previousDstEnd = (char*)dst + rSize;
            }
            return rSize;
        }

    case ZSTDds_checkChecksum:
        assert(srcSize == 4);  /* guaranteed by dctx->expected */
        {   U32 const h32 = (U32)XXH64_digest(&dctx->xxhState);
            U32 const check32 = MEM_readLE32(src);
            DEBUGLOG(4, "ZSTD_decompressContinue: checksum : calculated %08X :: %08X read", (unsigned)h32, (unsigned)check32);
            RETURN_ERROR_IF(check32 != h32, checksum_wrong);
            dctx->expected = 0;
            dctx->stage = ZSTDds_getFrameHeaderSize;
            return 0;
        }

    case ZSTDds_decodeSkippableHeader:
        assert(src != NULL);
        assert(srcSize <= ZSTD_SKIPPABLEHEADERSIZE);
        memcpy(dctx->headerBuffer + (ZSTD_SKIPPABLEHEADERSIZE - srcSize), src, srcSize);   /* complete skippable header */
        dctx->expected = MEM_readLE32(dctx->headerBuffer + ZSTD_FRAMEIDSIZE);   /* note : dctx->expected can grow seriously large, beyond local buffer size */
        dctx->stage = ZSTDds_skipFrame;
        return 0;

    case ZSTDds_skipFrame:
        dctx->expected = 0;
        dctx->stage = ZSTDds_getFrameHeaderSize;
        return 0;

    default:
        assert(0);   /* impossible */
        RETURN_ERROR(GENERIC);   /* some compiler require default to do something */
    }
}


static size_t ZSTD_refDictContent(ZSTD_DCtx* dctx, const void* dict, size_t dictSize)
{
    dctx->dictEnd = dctx->previousDstEnd;
    dctx->virtualStart = (const char*)dict - ((const char*)(dctx->previousDstEnd) - (const char*)(dctx->prefixStart));
    dctx->prefixStart = dict;
    dctx->previousDstEnd = (const char*)dict + dictSize;
    return 0;
}

/*! ZSTD_loadDEntropy() :
 *  dict : must point at beginning of a valid zstd dictionary.
 * @return : size of entropy tables read */
size_t

ext/zstd/lib/decompress/zstd_decompress.c  view on Meta::CPAN

        RETURN_ERROR_IF(matchlengthLog > MLFSELog, dictionary_corrupted);
        ZSTD_buildFSETable( entropy->MLTable,
                            matchlengthNCount, matchlengthMaxValue,
                            ML_base, ML_bits,
                            matchlengthLog);
        dictPtr += matchlengthHeaderSize;
    }

    {   short litlengthNCount[MaxLL+1];
        unsigned litlengthMaxValue = MaxLL, litlengthLog;
        size_t const litlengthHeaderSize = FSE_readNCount(litlengthNCount, &litlengthMaxValue, &litlengthLog, dictPtr, dictEnd-dictPtr);
        RETURN_ERROR_IF(FSE_isError(litlengthHeaderSize), dictionary_corrupted);
        RETURN_ERROR_IF(litlengthMaxValue > MaxLL, dictionary_corrupted);
        RETURN_ERROR_IF(litlengthLog > LLFSELog, dictionary_corrupted);
        ZSTD_buildFSETable( entropy->LLTable,
                            litlengthNCount, litlengthMaxValue,
                            LL_base, LL_bits,
                            litlengthLog);
        dictPtr += litlengthHeaderSize;
    }

    RETURN_ERROR_IF(dictPtr+12 > dictEnd, dictionary_corrupted);
    {   int i;
        size_t const dictContentSize = (size_t)(dictEnd - (dictPtr+12));
        for (i=0; i<3; i++) {
            U32 const rep = MEM_readLE32(dictPtr); dictPtr += 4;
            RETURN_ERROR_IF(rep==0 || rep >= dictContentSize,
                            dictionary_corrupted);
            entropy->rep[i] = rep;
    }   }

    return dictPtr - (const BYTE*)dict;
}

static size_t ZSTD_decompress_insertDictionary(ZSTD_DCtx* dctx, const void* dict, size_t dictSize)
{
    if (dictSize < 8) return ZSTD_refDictContent(dctx, dict, dictSize);
    {   U32 const magic = MEM_readLE32(dict);
        if (magic != ZSTD_MAGIC_DICTIONARY) {
            return ZSTD_refDictContent(dctx, dict, dictSize);   /* pure content mode */
    }   }
    dctx->dictID = MEM_readLE32((const char*)dict + ZSTD_FRAMEIDSIZE);

    /* load entropy tables */
    {   size_t const eSize = ZSTD_loadDEntropy(&dctx->entropy, dict, dictSize);
        RETURN_ERROR_IF(ZSTD_isError(eSize), dictionary_corrupted);
        dict = (const char*)dict + eSize;
        dictSize -= eSize;
    }
    dctx->litEntropy = dctx->fseEntropy = 1;

    /* reference dictionary content */
    return ZSTD_refDictContent(dctx, dict, dictSize);
}

size_t ZSTD_decompressBegin(ZSTD_DCtx* dctx)
{
    assert(dctx != NULL);
    dctx->expected = ZSTD_startingInputLength(dctx->format);  /* dctx->format must be properly set */
    dctx->stage = ZSTDds_getFrameHeaderSize;
    dctx->decodedSize = 0;
    dctx->previousDstEnd = NULL;
    dctx->prefixStart = NULL;
    dctx->virtualStart = NULL;
    dctx->dictEnd = NULL;
    dctx->entropy.hufTable[0] = (HUF_DTable)((HufLog)*0x1000001);  /* cover both little and big endian */
    dctx->litEntropy = dctx->fseEntropy = 0;
    dctx->dictID = 0;
    ZSTD_STATIC_ASSERT(sizeof(dctx->entropy.rep) == sizeof(repStartValue));
    memcpy(dctx->entropy.rep, repStartValue, sizeof(repStartValue));  /* initial repcodes */
    dctx->LLTptr = dctx->entropy.LLTable;
    dctx->MLTptr = dctx->entropy.MLTable;
    dctx->OFTptr = dctx->entropy.OFTable;
    dctx->HUFptr = dctx->entropy.hufTable;
    return 0;
}

size_t ZSTD_decompressBegin_usingDict(ZSTD_DCtx* dctx, const void* dict, size_t dictSize)
{
    FORWARD_IF_ERROR( ZSTD_decompressBegin(dctx) );
    if (dict && dictSize)
        RETURN_ERROR_IF(
            ZSTD_isError(ZSTD_decompress_insertDictionary(dctx, dict, dictSize)),
            dictionary_corrupted);
    return 0;
}


/* ======   ZSTD_DDict   ====== */

size_t ZSTD_decompressBegin_usingDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict)
{
    DEBUGLOG(4, "ZSTD_decompressBegin_usingDDict");
    assert(dctx != NULL);
    if (ddict) {
        const char* const dictStart = (const char*)ZSTD_DDict_dictContent(ddict);
        size_t const dictSize = ZSTD_DDict_dictSize(ddict);
        const void* const dictEnd = dictStart + dictSize;
        dctx->ddictIsCold = (dctx->dictEnd != dictEnd);
        DEBUGLOG(4, "DDict is %s",
                    dctx->ddictIsCold ? "~cold~" : "hot!");
    }
    FORWARD_IF_ERROR( ZSTD_decompressBegin(dctx) );
    if (ddict) {   /* NULL ddict is equivalent to no dictionary */
        ZSTD_copyDDictParameters(dctx, ddict);
    }
    return 0;
}

/*! ZSTD_getDictID_fromDict() :
 *  Provides the dictID stored within dictionary.
 *  if @return == 0, the dictionary is not conformant with Zstandard specification.
 *  It can still be loaded, but as a content-only dictionary. */
unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize)
{
    if (dictSize < 8) return 0;
    if (MEM_readLE32(dict) != ZSTD_MAGIC_DICTIONARY) return 0;
    return MEM_readLE32((const char*)dict + ZSTD_FRAMEIDSIZE);
}

/*! ZSTD_getDictID_fromFrame() :
 *  Provides the dictID required to decompress frame stored within `src`.
 *  If @return == 0, the dictID could not be decoded.
 *  This could for one of the following reasons :
 *  - The frame does not require a dictionary (most common case).
 *  - The frame was built with dictID intentionally removed.
 *    Needed dictionary is a hidden information.
 *    Note : this use case also happens when using a non-conformant dictionary.
 *  - `srcSize` is too small, and as a result, frame header could not be decoded.
 *    Note : possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`.
 *  - This is not a Zstandard frame.
 *  When identifying the exact failure cause, it's possible to use
 *  ZSTD_getFrameHeader(), which will provide a more precise error code. */
unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize)
{
    ZSTD_frameHeader zfp = { 0, 0, 0, ZSTD_frame, 0, 0, 0 };
    size_t const hError = ZSTD_getFrameHeader(&zfp, src, srcSize);
    if (ZSTD_isError(hError)) return 0;
    return zfp.dictID;
}


/*! ZSTD_decompress_usingDDict() :
*   Decompression using a pre-digested Dictionary
*   Use dictionary without significant overhead. */
size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx,
                                  void* dst, size_t dstCapacity,
                            const void* src, size_t srcSize,
                            const ZSTD_DDict* ddict)
{
    /* pass content and size in case legacy frames are encountered */
    return ZSTD_decompressMultiFrame(dctx, dst, dstCapacity, src, srcSize,
                                     NULL, 0,
                                     ddict);
}


/*=====================================
*   Streaming decompression
*====================================*/

ZSTD_DStream* ZSTD_createDStream(void)
{
    DEBUGLOG(3, "ZSTD_createDStream");
    return ZSTD_createDStream_advanced(ZSTD_defaultCMem);
}

ZSTD_DStream* ZSTD_initStaticDStream(void *workspace, size_t workspaceSize)
{
    return ZSTD_initStaticDCtx(workspace, workspaceSize);
}

ZSTD_DStream* ZSTD_createDStream_advanced(ZSTD_customMem customMem)
{
    return ZSTD_createDCtx_advanced(customMem);
}

size_t ZSTD_freeDStream(ZSTD_DStream* zds)
{
    return ZSTD_freeDCtx(zds);
}


/* ***  Initialization  *** */

size_t ZSTD_DStreamInSize(void)  { return ZSTD_BLOCKSIZE_MAX + ZSTD_blockHeaderSize; }
size_t ZSTD_DStreamOutSize(void) { return ZSTD_BLOCKSIZE_MAX; }

size_t ZSTD_DCtx_loadDictionary_advanced(ZSTD_DCtx* dctx,

ext/zstd/lib/decompress/zstd_decompress.c  view on Meta::CPAN

            DEBUGLOG(4, "Consume header");
            FORWARD_IF_ERROR(ZSTD_decompressBegin_usingDDict(zds, ZSTD_getDDict(zds)));

            if ((MEM_readLE32(zds->headerBuffer) & ZSTD_MAGIC_SKIPPABLE_MASK) == ZSTD_MAGIC_SKIPPABLE_START) {  /* skippable frame */
                zds->expected = MEM_readLE32(zds->headerBuffer + ZSTD_FRAMEIDSIZE);
                zds->stage = ZSTDds_skipFrame;
            } else {
                FORWARD_IF_ERROR(ZSTD_decodeFrameHeader(zds, zds->headerBuffer, zds->lhSize));
                zds->expected = ZSTD_blockHeaderSize;
                zds->stage = ZSTDds_decodeBlockHeader;
            }

            /* control buffer memory usage */
            DEBUGLOG(4, "Control max memory usage (%u KB <= max %u KB)",
                        (U32)(zds->fParams.windowSize >>10),
                        (U32)(zds->maxWindowSize >> 10) );
            zds->fParams.windowSize = MAX(zds->fParams.windowSize, 1U << ZSTD_WINDOWLOG_ABSOLUTEMIN);
            RETURN_ERROR_IF(zds->fParams.windowSize > zds->maxWindowSize,
                            frameParameter_windowTooLarge);

            /* Adapt buffer sizes to frame header instructions */
            {   size_t const neededInBuffSize = MAX(zds->fParams.blockSizeMax, 4 /* frame checksum */);
                size_t const neededOutBuffSize = ZSTD_decodingBufferSize_min(zds->fParams.windowSize, zds->fParams.frameContentSize);
                if ((zds->inBuffSize < neededInBuffSize) || (zds->outBuffSize < neededOutBuffSize)) {
                    size_t const bufferSize = neededInBuffSize + neededOutBuffSize;
                    DEBUGLOG(4, "inBuff  : from %u to %u",
                                (U32)zds->inBuffSize, (U32)neededInBuffSize);
                    DEBUGLOG(4, "outBuff : from %u to %u",
                                (U32)zds->outBuffSize, (U32)neededOutBuffSize);
                    if (zds->staticSize) {  /* static DCtx */
                        DEBUGLOG(4, "staticSize : %u", (U32)zds->staticSize);
                        assert(zds->staticSize >= sizeof(ZSTD_DCtx));  /* controlled at init */
                        RETURN_ERROR_IF(
                            bufferSize > zds->staticSize - sizeof(ZSTD_DCtx),
                            memory_allocation);
                    } else {
                        ZSTD_free(zds->inBuff, zds->customMem);
                        zds->inBuffSize = 0;
                        zds->outBuffSize = 0;
                        zds->inBuff = (char*)ZSTD_malloc(bufferSize, zds->customMem);
                        RETURN_ERROR_IF(zds->inBuff == NULL, memory_allocation);
                    }
                    zds->inBuffSize = neededInBuffSize;
                    zds->outBuff = zds->inBuff + zds->inBuffSize;
                    zds->outBuffSize = neededOutBuffSize;
            }   }
            zds->streamStage = zdss_read;
            /* fall-through */

        case zdss_read:
            DEBUGLOG(5, "stage zdss_read");
            {   size_t const neededInSize = ZSTD_nextSrcSizeToDecompress(zds);
                DEBUGLOG(5, "neededInSize = %u", (U32)neededInSize);
                if (neededInSize==0) {  /* end of frame */
                    zds->streamStage = zdss_init;
                    someMoreWork = 0;
                    break;
                }
                if ((size_t)(iend-ip) >= neededInSize) {  /* decode directly from src */
                    int const isSkipFrame = ZSTD_isSkipFrame(zds);
                    size_t const decodedSize = ZSTD_decompressContinue(zds,
                        zds->outBuff + zds->outStart, (isSkipFrame ? 0 : zds->outBuffSize - zds->outStart),
                        ip, neededInSize);
                    if (ZSTD_isError(decodedSize)) return decodedSize;
                    ip += neededInSize;
                    if (!decodedSize && !isSkipFrame) break;   /* this was just a header */
                    zds->outEnd = zds->outStart + decodedSize;
                    zds->streamStage = zdss_flush;
                    break;
            }   }
            if (ip==iend) { someMoreWork = 0; break; }   /* no more input */
            zds->streamStage = zdss_load;
            /* fall-through */

        case zdss_load:
            {   size_t const neededInSize = ZSTD_nextSrcSizeToDecompress(zds);
                size_t const toLoad = neededInSize - zds->inPos;
                int const isSkipFrame = ZSTD_isSkipFrame(zds);
                size_t loadedSize;
                if (isSkipFrame) {
                    loadedSize = MIN(toLoad, (size_t)(iend-ip));
                } else {
                    RETURN_ERROR_IF(toLoad > zds->inBuffSize - zds->inPos,
                                    corruption_detected,
                                    "should never happen");
                    loadedSize = ZSTD_limitCopy(zds->inBuff + zds->inPos, toLoad, ip, iend-ip);
                }
                ip += loadedSize;
                zds->inPos += loadedSize;
                if (loadedSize < toLoad) { someMoreWork = 0; break; }   /* not enough input, wait for more */

                /* decode loaded input */
                {   size_t const decodedSize = ZSTD_decompressContinue(zds,
                        zds->outBuff + zds->outStart, zds->outBuffSize - zds->outStart,
                        zds->inBuff, neededInSize);
                    if (ZSTD_isError(decodedSize)) return decodedSize;
                    zds->inPos = 0;   /* input is consumed */
                    if (!decodedSize && !isSkipFrame) { zds->streamStage = zdss_read; break; }   /* this was just a header */
                    zds->outEnd = zds->outStart +  decodedSize;
            }   }
            zds->streamStage = zdss_flush;
            /* fall-through */

        case zdss_flush:
            {   size_t const toFlushSize = zds->outEnd - zds->outStart;
                size_t const flushedSize = ZSTD_limitCopy(op, oend-op, zds->outBuff + zds->outStart, toFlushSize);
                op += flushedSize;
                zds->outStart += flushedSize;
                if (flushedSize == toFlushSize) {  /* flush completed */
                    zds->streamStage = zdss_read;
                    if ( (zds->outBuffSize < zds->fParams.frameContentSize)
                      && (zds->outStart + zds->fParams.blockSizeMax > zds->outBuffSize) ) {
                        DEBUGLOG(5, "restart filling outBuff from beginning (left:%i, needed:%u)",
                                (int)(zds->outBuffSize - zds->outStart),
                                (U32)zds->fParams.blockSizeMax);
                        zds->outStart = zds->outEnd = 0;
                    }
                    break;
            }   }
            /* cannot complete flush */
            someMoreWork = 0;
            break;

        default:
            assert(0);    /* impossible */
            RETURN_ERROR(GENERIC);   /* some compiler require default to do something */
    }   }

    /* result */
    input->pos = (size_t)(ip - (const char*)(input->src));
    output->pos = (size_t)(op - (char*)(output->dst));
    if ((ip==istart) && (op==ostart)) {  /* no forward progress */
        zds->noForwardProgress ++;
        if (zds->noForwardProgress >= ZSTD_NO_FORWARD_PROGRESS_MAX) {
            RETURN_ERROR_IF(op==oend, dstSize_tooSmall);
            RETURN_ERROR_IF(ip==iend, srcSize_wrong);
            assert(0);
        }
    } else {
        zds->noForwardProgress = 0;
    }
    {   size_t nextSrcSizeHint = ZSTD_nextSrcSizeToDecompress(zds);
        if (!nextSrcSizeHint) {   /* frame fully decoded */
            if (zds->outEnd == zds->outStart) {  /* output fully flushed */
                if (zds->hostageByte) {
                    if (input->pos >= input->size) {
                        /* can't release hostage (not present) */
                        zds->streamStage = zdss_read;
                        return 1;
                    }
                    input->pos++;  /* release hostage */
                }   /* zds->hostageByte */
                return 0;
            }  /* zds->outEnd == zds->outStart */
            if (!zds->hostageByte) { /* output not fully flushed; keep last byte as hostage; will be released when all output is flushed */
                input->pos--;   /* note : pos > 0, otherwise, impossible to finish reading last block */
                zds->hostageByte=1;
            }
            return 1;
        }  /* nextSrcSizeHint==0 */
        nextSrcSizeHint += ZSTD_blockHeaderSize * (ZSTD_nextInputType(zds) == ZSTDnit_block);   /* preload header of next block */
        assert(zds->inPos <= nextSrcSizeHint);
        nextSrcSizeHint -= zds->inPos;   /* part already loaded*/
        return nextSrcSizeHint;
    }
}

size_t ZSTD_decompressStream_simpleArgs (
                            ZSTD_DCtx* dctx,
                            void* dst, size_t dstCapacity, size_t* dstPos,
                      const void* src, size_t srcSize, size_t* srcPos)
{
    ZSTD_outBuffer output = { dst, dstCapacity, *dstPos };
    ZSTD_inBuffer  input  = { src, srcSize, *srcPos };
    /* ZSTD_compress_generic() will check validity of dstPos and srcPos */
    size_t const cErr = ZSTD_decompressStream(dctx, &output, &input);
    *dstPos = output.pos;
    *srcPos = input.pos;
    return cErr;
}



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