lib/lz4frame.c

/*
LZ4 auto-framing library
Copyright (C) 2011-2016, Yann Collet.

BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above
copyright notice, this list of conditions and the following disclaimer
in the documentation and/or other materials provided with the
distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

You can contact the author at :
- LZ4 homepage : http://www.lz4.org
- LZ4 source repository : https://github.com/lz4/lz4
*/

/* LZ4F is a stand-alone API to create LZ4-compressed Frames
*  in full conformance with specification v1.5.0
*  All related operations, including memory management, are handled by the library.
* */


/*-************************************
*  Compiler Options
**************************************/
#ifdef _MSC_VER    /* Visual Studio */
#  pragma warning(disable : 4127)        /* disable: C4127: conditional expression is constant */
#endif


/*-************************************
*  Memory routines
**************************************/
#include <stdlib.h>   /* malloc, calloc, free */
#define ALLOCATOR(s)   calloc(1,s)
#define FREEMEM        free
#include <string.h>   /* memset, memcpy, memmove */
#define MEM_INIT       memset


/*-************************************
*  Includes
**************************************/
#include "lz4frame_static.h"
#include "lz4.h"
#include "lz4hc.h"
#define XXH_STATIC_LINKING_ONLY
#include "xxhash.h"


/*-************************************
*  Common Utils
**************************************/
#define LZ4_STATIC_ASSERT(c)    { enum { LZ4_static_assert = 1/(int)(!!(c)) }; }   /* use only *after* variable declarations */


/*-************************************
*  Basic Types
**************************************/
#if !defined (__VMS) && (defined (__cplusplus) || (defined (__STDC_VERSION__) && (__STDC_VERSION__ >= 199901L) /* C99 */) )
# include <stdint.h>
  typedef  uint8_t BYTE;
  typedef uint16_t U16;
  typedef uint32_t U32;
  typedef  int32_t S32;
  typedef uint64_t U64;
#else
  typedef unsigned char       BYTE;
  typedef unsigned short      U16;
  typedef unsigned int        U32;
  typedef   signed int        S32;
  typedef unsigned long long  U64;
#endif


/* unoptimized version; solves endianess & alignment issues */
static U32 LZ4F_readLE32 (const void* src)
{
    const BYTE* const srcPtr = (const BYTE*)src;
    U32 value32 = srcPtr[0];
    value32 += (srcPtr[1]<<8);
    value32 += (srcPtr[2]<<16);
    value32 += ((U32)srcPtr[3])<<24;
    return value32;
}

static void LZ4F_writeLE32 (void* dst, U32 value32)
{
    BYTE* const dstPtr = (BYTE*)dst;
    dstPtr[0] = (BYTE)value32;
    dstPtr[1] = (BYTE)(value32 >> 8);
    dstPtr[2] = (BYTE)(value32 >> 16);
    dstPtr[3] = (BYTE)(value32 >> 24);
}

static U64 LZ4F_readLE64 (const void* src)
{
    const BYTE* const srcPtr = (const BYTE*)src;
    U64 value64 = srcPtr[0];
    value64 += ((U64)srcPtr[1]<<8);
    value64 += ((U64)srcPtr[2]<<16);
    value64 += ((U64)srcPtr[3]<<24);
    value64 += ((U64)srcPtr[4]<<32);
    value64 += ((U64)srcPtr[5]<<40);
    value64 += ((U64)srcPtr[6]<<48);
    value64 += ((U64)srcPtr[7]<<56);
    return value64;
}

static void LZ4F_writeLE64 (void* dst, U64 value64)
{
    BYTE* const dstPtr = (BYTE*)dst;
    dstPtr[0] = (BYTE)value64;
    dstPtr[1] = (BYTE)(value64 >> 8);
    dstPtr[2] = (BYTE)(value64 >> 16);
    dstPtr[3] = (BYTE)(value64 >> 24);
    dstPtr[4] = (BYTE)(value64 >> 32);
    dstPtr[5] = (BYTE)(value64 >> 40);
    dstPtr[6] = (BYTE)(value64 >> 48);
    dstPtr[7] = (BYTE)(value64 >> 56);
}


/*-************************************
*  Constants
**************************************/
#define KB *(1<<10)
#define MB *(1<<20)
#define GB *(1<<30)

#define _1BIT  0x01
#define _2BITS 0x03
#define _3BITS 0x07
#define _4BITS 0x0F
#define _8BITS 0xFF

#define LZ4F_MAGIC_SKIPPABLE_START 0x184D2A50U
#define LZ4F_MAGICNUMBER 0x184D2204U
#define LZ4F_BLOCKUNCOMPRESSED_FLAG 0x80000000U
#define LZ4F_BLOCKSIZEID_DEFAULT LZ4F_max64KB

static const size_t minFHSize = 7;
static const size_t maxFHSize = 15;
static const size_t BHSize = 4;


/*-************************************
*  Structures and local types
**************************************/
typedef struct LZ4F_cctx_s
{
    LZ4F_preferences_t prefs;
    U32    version;
    U32    cStage;
    size_t maxBlockSize;
    size_t maxBufferSize;
    BYTE*  tmpBuff;
    BYTE*  tmpIn;
    size_t tmpInSize;
    U64    totalInSize;
    XXH32_state_t xxh;
    void*  lz4CtxPtr;
    U32    lz4CtxLevel;     /* 0: unallocated;  1: LZ4_stream_t;  3: LZ4_streamHC_t */
} LZ4F_cctx_t;


/*-************************************
*  Error management
**************************************/
#define LZ4F_GENERATE_STRING(STRING) #STRING,
static const char* LZ4F_errorStrings[] = { LZ4F_LIST_ERRORS(LZ4F_GENERATE_STRING) };


unsigned LZ4F_isError(LZ4F_errorCode_t code)
{
    return (code > (LZ4F_errorCode_t)(-LZ4F_ERROR_maxCode));
}

const char* LZ4F_getErrorName(LZ4F_errorCode_t code)
{
    static const char* codeError = "Unspecified error code";
    if (LZ4F_isError(code)) return LZ4F_errorStrings[-(int)(code)];
    return codeError;
}

static LZ4F_errorCode_t err0r(LZ4F_errorCodes code)
{
    LZ4_STATIC_ASSERT(sizeof(ptrdiff_t) >= sizeof(size_t));    /* A compilation error here means sizeof(ptrdiff_t) is not large enough */
    return (LZ4F_errorCode_t)-(ptrdiff_t)code; 
}

unsigned LZ4F_getVersion(void) { return LZ4F_VERSION; }


/*-************************************
*  Private functions
**************************************/
static size_t LZ4F_getBlockSize(unsigned blockSizeID)
{
    static const size_t blockSizes[4] = { 64 KB, 256 KB, 1 MB, 4 MB };

    if (blockSizeID == 0) blockSizeID = LZ4F_BLOCKSIZEID_DEFAULT;
    blockSizeID -= 4;
    if (blockSizeID > 3) return err0r(LZ4F_ERROR_maxBlockSize_invalid);
    return blockSizes[blockSizeID];
}


static BYTE LZ4F_headerChecksum (const void* header, size_t length)
{
    U32 const xxh = XXH32(header, length, 0);
    return (BYTE)(xxh >> 8);
}


/*-************************************
*  Simple compression functions
**************************************/
static LZ4F_blockSizeID_t LZ4F_optimalBSID(const LZ4F_blockSizeID_t requestedBSID, const size_t srcSize)
{
    LZ4F_blockSizeID_t proposedBSID = LZ4F_max64KB;
    size_t maxBlockSize = 64 KB;
    while (requestedBSID > proposedBSID)
    {
        if (srcSize <= maxBlockSize)
            return proposedBSID;
        proposedBSID = (LZ4F_blockSizeID_t)((int)proposedBSID + 1);
        maxBlockSize <<= 2;
    }
    return requestedBSID;
}


size_t LZ4F_compressFrameBound(size_t srcSize, const LZ4F_preferences_t* preferencesPtr)
{
    LZ4F_preferences_t prefs;
    size_t headerSize;
    size_t streamSize;

    if (preferencesPtr!=NULL) prefs = *preferencesPtr;
    else memset(&prefs, 0, sizeof(prefs));

    prefs.frameInfo.blockSizeID = LZ4F_optimalBSID(prefs.frameInfo.blockSizeID, srcSize);
    prefs.autoFlush = 1;

    headerSize = maxFHSize;      /* header size, including magic number and frame content size*/
    streamSize = LZ4F_compressBound(srcSize, &prefs);

    return headerSize + streamSize;
}


/*! LZ4F_compressFrame() :
* Compress an entire srcBuffer into a valid LZ4 frame, as defined by specification v1.5.0, in a single step.
* The most important rule is that dstBuffer MUST be large enough (dstMaxSize) to ensure compression completion even in worst case.
* You can get the minimum value of dstMaxSize by using LZ4F_compressFrameBound()
* If this condition is not respected, LZ4F_compressFrame() will fail (result is an errorCode)
* The LZ4F_preferences_t structure is optional : you can provide NULL as argument. All preferences will then be set to default.
* The result of the function is the number of bytes written into dstBuffer.
* The function outputs an error code if it fails (can be tested using LZ4F_isError())
*/
size_t LZ4F_compressFrame(void* dstBuffer, size_t dstCapacity, const void* srcBuffer, size_t srcSize, const LZ4F_preferences_t* preferencesPtr)
{
    LZ4F_cctx_t cctxI;
    LZ4_stream_t lz4ctx;
    LZ4F_preferences_t prefs;
    LZ4F_compressOptions_t options;
    BYTE* const dstStart = (BYTE*) dstBuffer;
    BYTE* dstPtr = dstStart;
    BYTE* const dstEnd = dstStart + dstCapacity;

    memset(&cctxI, 0, sizeof(cctxI));   /* works because no allocation */
    memset(&options, 0, sizeof(options));

    cctxI.version = LZ4F_VERSION;
    cctxI.maxBufferSize = 5 MB;   /* mess with real buffer size to prevent allocation; works because autoflush==1 & stableSrc==1 */

    if (preferencesPtr!=NULL)
        prefs = *preferencesPtr;
    else
        memset(&prefs, 0, sizeof(prefs));
    if (prefs.frameInfo.contentSize != 0)
        prefs.frameInfo.contentSize = (U64)srcSize;   /* auto-correct content size if selected (!=0) */

    if (prefs.compressionLevel < LZ4HC_MIN_CLEVEL) {
        cctxI.lz4CtxPtr = &lz4ctx;
        cctxI.lz4CtxLevel = 1;
    }

    prefs.frameInfo.blockSizeID = LZ4F_optimalBSID(prefs.frameInfo.blockSizeID, srcSize);
    prefs.autoFlush = 1;
    if (srcSize <= LZ4F_getBlockSize(prefs.frameInfo.blockSizeID))
        prefs.frameInfo.blockMode = LZ4F_blockIndependent;   /* no need for linked blocks */

    options.stableSrc = 1;

    if (dstCapacity < LZ4F_compressFrameBound(srcSize, &prefs))
        return err0r(LZ4F_ERROR_dstMaxSize_tooSmall);

    { size_t const headerSize = LZ4F_compressBegin(&cctxI, dstBuffer, dstCapacity, &prefs);  /* write header */
      if (LZ4F_isError(headerSize)) return headerSize;
      dstPtr += headerSize;   /* header size */ }

    { size_t const cSize = LZ4F_compressUpdate(&cctxI, dstPtr, dstEnd-dstPtr, srcBuffer, srcSize, &options);
      if (LZ4F_isError(cSize)) return cSize;
      dstPtr += cSize; }

    { size_t const tailSize = LZ4F_compressEnd(&cctxI, dstPtr, dstEnd-dstPtr, &options);   /* flush last block, and generate suffix */
      if (LZ4F_isError(tailSize)) return tailSize;
      dstPtr += tailSize; }

    if (prefs.compressionLevel >= LZ4HC_MIN_CLEVEL)   /* no allocation done with lz4 fast */
        FREEMEM(cctxI.lz4CtxPtr);

    return (dstPtr - dstStart);
}


/*-*********************************
*  Advanced compression functions
***********************************/

/*! LZ4F_createCompressionContext() :
 * The first thing to do is to create a compressionContext object, which will be used in all compression operations.
 * This is achieved using LZ4F_createCompressionContext(), which takes as argument a version and an LZ4F_preferences_t structure.
 * The version provided MUST be LZ4F_VERSION. It is intended to track potential version differences between different binaries.
 * The function will provide a pointer to an allocated LZ4F_compressionContext_t object.
 * If the result LZ4F_errorCode_t is not OK_NoError, there was an error during context creation.
 * Object can release its memory using LZ4F_freeCompressionContext();
 */
LZ4F_errorCode_t LZ4F_createCompressionContext(LZ4F_compressionContext_t* LZ4F_compressionContextPtr, unsigned version)
{
    LZ4F_cctx_t* const cctxPtr = (LZ4F_cctx_t*)ALLOCATOR(sizeof(LZ4F_cctx_t));
    if (cctxPtr==NULL) return err0r(LZ4F_ERROR_allocation_failed);

    cctxPtr->version = version;
    cctxPtr->cStage = 0;   /* Next stage : write header */

    *LZ4F_compressionContextPtr = (LZ4F_compressionContext_t)cctxPtr;

    return LZ4F_OK_NoError;
}


LZ4F_errorCode_t LZ4F_freeCompressionContext(LZ4F_compressionContext_t LZ4F_compressionContext)
{
    LZ4F_cctx_t* const cctxPtr = (LZ4F_cctx_t*)LZ4F_compressionContext;

    if (cctxPtr != NULL) {  /* null pointers can be safely provided to this function, like free() */
       FREEMEM(cctxPtr->lz4CtxPtr);
       FREEMEM(cctxPtr->tmpBuff);
       FREEMEM(LZ4F_compressionContext);
    }

    return LZ4F_OK_NoError;
}


/*! LZ4F_compressBegin() :
 * will write the frame header into dstBuffer.
 * dstBuffer must be large enough to accommodate a header (dstMaxSize). Maximum header size is LZ4F_MAXHEADERFRAME_SIZE bytes.
 * @return : number of bytes written into dstBuffer for the header
 *           or an error code (can be tested using LZ4F_isError())
 */
size_t LZ4F_compressBegin(LZ4F_cctx* cctxPtr, void* dstBuffer, size_t dstMaxSize, const LZ4F_preferences_t* preferencesPtr)
{
    LZ4F_preferences_t prefNull;
    BYTE* const dstStart = (BYTE*)dstBuffer;
    BYTE* dstPtr = dstStart;
    BYTE* headerStart;
    size_t requiredBuffSize;

    if (dstMaxSize < maxFHSize) return err0r(LZ4F_ERROR_dstMaxSize_tooSmall);
    if (cctxPtr->cStage != 0) return err0r(LZ4F_ERROR_GENERIC);
    memset(&prefNull, 0, sizeof(prefNull));
    if (preferencesPtr == NULL) preferencesPtr = &prefNull;
    cctxPtr->prefs = *preferencesPtr;

    /* ctx Management */
    {   U32 const tableID = (cctxPtr->prefs.compressionLevel < LZ4HC_MIN_CLEVEL) ? 1 : 2;  /* 0:nothing ; 1:LZ4 table ; 2:HC tables */
        if (cctxPtr->lz4CtxLevel < tableID) {
            FREEMEM(cctxPtr->lz4CtxPtr);
            if (cctxPtr->prefs.compressionLevel < LZ4HC_MIN_CLEVEL)
                cctxPtr->lz4CtxPtr = (void*)LZ4_createStream();
            else
                cctxPtr->lz4CtxPtr = (void*)LZ4_createStreamHC();
            cctxPtr->lz4CtxLevel = tableID;
        }
    }

    /* Buffer Management */
    if (cctxPtr->prefs.frameInfo.blockSizeID == 0) cctxPtr->prefs.frameInfo.blockSizeID = LZ4F_BLOCKSIZEID_DEFAULT;
    cctxPtr->maxBlockSize = LZ4F_getBlockSize(cctxPtr->prefs.frameInfo.blockSizeID);

    requiredBuffSize = cctxPtr->maxBlockSize + ((cctxPtr->prefs.frameInfo.blockMode == LZ4F_blockLinked) * 128 KB);
    if (preferencesPtr->autoFlush)
        requiredBuffSize = (cctxPtr->prefs.frameInfo.blockMode == LZ4F_blockLinked) * 64 KB;   /* just needs dict */

    if (cctxPtr->maxBufferSize < requiredBuffSize) {
        cctxPtr->maxBufferSize = requiredBuffSize;
        FREEMEM(cctxPtr->tmpBuff);
        cctxPtr->tmpBuff = (BYTE*)ALLOCATOR(requiredBuffSize);
        if (cctxPtr->tmpBuff == NULL) return err0r(LZ4F_ERROR_allocation_failed);
    }
    cctxPtr->tmpIn = cctxPtr->tmpBuff;
    cctxPtr->tmpInSize = 0;
    XXH32_reset(&(cctxPtr->xxh), 0);
    if (cctxPtr->prefs.compressionLevel < LZ4HC_MIN_CLEVEL)
        LZ4_resetStream((LZ4_stream_t*)(cctxPtr->lz4CtxPtr));
    else
        LZ4_resetStreamHC((LZ4_streamHC_t*)(cctxPtr->lz4CtxPtr), cctxPtr->prefs.compressionLevel);

    /* Magic Number */
    LZ4F_writeLE32(dstPtr, LZ4F_MAGICNUMBER);
    dstPtr += 4;
    headerStart = dstPtr;

    /* FLG Byte */
    *dstPtr++ = (BYTE)(((1 & _2BITS) << 6)    /* Version('01') */
        + ((cctxPtr->prefs.frameInfo.blockMode & _1BIT ) << 5)    /* Block mode */
        + ((cctxPtr->prefs.frameInfo.contentChecksumFlag & _1BIT ) << 2)   /* Frame checksum */
        + ((cctxPtr->prefs.frameInfo.contentSize > 0) << 3));   /* Frame content size */
    /* BD Byte */
    *dstPtr++ = (BYTE)((cctxPtr->prefs.frameInfo.blockSizeID & _3BITS) << 4);
    /* Optional Frame content size field */
    if (cctxPtr->prefs.frameInfo.contentSize) {
        LZ4F_writeLE64(dstPtr, cctxPtr->prefs.frameInfo.contentSize);
        dstPtr += 8;
        cctxPtr->totalInSize = 0;
    }
    /* CRC Byte */
    *dstPtr = LZ4F_headerChecksum(headerStart, dstPtr - headerStart);
    dstPtr++;

    cctxPtr->cStage = 1;   /* header written, now request input data block */

    return (dstPtr - dstStart);
}


/* LZ4F_compressBound() : gives the size of Dst buffer given a srcSize to handle worst case situations.
*                        The LZ4F_frameInfo_t structure is optional :
*                        you can provide NULL as argument, preferences will then be set to cover worst case situations.
* */
size_t LZ4F_compressBound(size_t srcSize, const LZ4F_preferences_t* preferencesPtr)
{
    LZ4F_preferences_t prefsNull;
    memset(&prefsNull, 0, sizeof(prefsNull));
    prefsNull.frameInfo.contentChecksumFlag = LZ4F_contentChecksumEnabled;   /* worst case */
    {   const LZ4F_preferences_t* const prefsPtr = (preferencesPtr==NULL) ? &prefsNull : preferencesPtr;
        LZ4F_blockSizeID_t const bid = prefsPtr->frameInfo.blockSizeID;
        size_t const blockSize = LZ4F_getBlockSize(bid);
        unsigned const nbBlocks = (unsigned)(srcSize / blockSize) + 1;
        size_t const lastBlockSize = prefsPtr->autoFlush ? srcSize % blockSize : blockSize;
        size_t const blockInfo = 4;   /* default, without block CRC option */
        size_t const frameEnd = 4 + (prefsPtr->frameInfo.contentChecksumFlag*4);

        return (blockInfo * nbBlocks) + (blockSize * (nbBlocks-1)) + lastBlockSize + frameEnd;;
    }
}


typedef int (*compressFunc_t)(void* ctx, const char* src, char* dst, int srcSize, int dstSize, int level);

static size_t LZ4F_compressBlock(void* dst, const void* src, size_t srcSize, compressFunc_t compress, void* lz4ctx, int level)
{
    /* compress one block */
    BYTE* const cSizePtr = (BYTE*)dst;
    U32 cSize = (U32)compress(lz4ctx, (const char*)src, (char*)(cSizePtr+4), (int)(srcSize), (int)(srcSize-1), level);
    LZ4F_writeLE32(cSizePtr, cSize);
    if (cSize == 0) {  /* compression failed */
        cSize = (U32)srcSize;
        LZ4F_writeLE32(cSizePtr, cSize + LZ4F_BLOCKUNCOMPRESSED_FLAG);
        memcpy(cSizePtr+4, src, srcSize);
    }
    return cSize + 4;
}


static int LZ4F_localLZ4_compress_limitedOutput_withState(void* ctx, const char* src, char* dst, int srcSize, int dstSize, int level)
{
    (void) level;
    return LZ4_compress_limitedOutput_withState(ctx, src, dst, srcSize, dstSize);
}

static int LZ4F_localLZ4_compress_limitedOutput_continue(void* ctx, const char* src, char* dst, int srcSize, int dstSize, int level)
{
    (void) level;
    return LZ4_compress_limitedOutput_continue((LZ4_stream_t*)ctx, src, dst, srcSize, dstSize);
}

static int LZ4F_localLZ4_compressHC_limitedOutput_continue(void* ctx, const char* src, char* dst, int srcSize, int dstSize, int level)
{
    (void) level;
    return LZ4_compress_HC_continue((LZ4_streamHC_t*)ctx, src, dst, srcSize, dstSize);
}

static compressFunc_t LZ4F_selectCompression(LZ4F_blockMode_t blockMode, int level)
{
    if (level < LZ4HC_MIN_CLEVEL) {
        if (blockMode == LZ4F_blockIndependent) return LZ4F_localLZ4_compress_limitedOutput_withState;
        return LZ4F_localLZ4_compress_limitedOutput_continue;
    }
    if (blockMode == LZ4F_blockIndependent) return LZ4_compress_HC_extStateHC;
    return LZ4F_localLZ4_compressHC_limitedOutput_continue;
}

static int LZ4F_localSaveDict(LZ4F_cctx_t* cctxPtr)
{
    if (cctxPtr->prefs.compressionLevel < LZ4HC_MIN_CLEVEL)
        return LZ4_saveDict ((LZ4_stream_t*)(cctxPtr->lz4CtxPtr), (char*)(cctxPtr->tmpBuff), 64 KB);
    return LZ4_saveDictHC ((LZ4_streamHC_t*)(cctxPtr->lz4CtxPtr), (char*)(cctxPtr->tmpBuff), 64 KB);
}

typedef enum { notDone, fromTmpBuffer, fromSrcBuffer } LZ4F_lastBlockStatus;

/*! LZ4F_compressUpdate() :
* LZ4F_compressUpdate() can be called repetitively to compress as much data as necessary.
* The most important rule is that dstBuffer MUST be large enough (dstMaxSize) to ensure compression completion even in worst case.
* If this condition is not respected, LZ4F_compress() will fail (result is an errorCode)
* You can get the minimum value of dstMaxSize by using LZ4F_compressBound()
* The LZ4F_compressOptions_t structure is optional : you can provide NULL as argument.
* The result of the function is the number of bytes written into dstBuffer : it can be zero, meaning input data was just buffered.
* The function outputs an error code if it fails (can be tested using LZ4F_isError())
*/
size_t LZ4F_compressUpdate(LZ4F_cctx* cctxPtr, void* dstBuffer, size_t dstMaxSize, const void* srcBuffer, size_t srcSize, const LZ4F_compressOptions_t* compressOptionsPtr)
{
    LZ4F_compressOptions_t cOptionsNull;
    size_t const blockSize = cctxPtr->maxBlockSize;
    const BYTE* srcPtr = (const BYTE*)srcBuffer;
    const BYTE* const srcEnd = srcPtr + srcSize;
    BYTE* const dstStart = (BYTE*)dstBuffer;
    BYTE* dstPtr = dstStart;
    LZ4F_lastBlockStatus lastBlockCompressed = notDone;
    compressFunc_t compress;


    if (cctxPtr->cStage != 1) return err0r(LZ4F_ERROR_GENERIC);
    if (dstMaxSize < LZ4F_compressBound(srcSize, &(cctxPtr->prefs))) return err0r(LZ4F_ERROR_dstMaxSize_tooSmall);
    memset(&cOptionsNull, 0, sizeof(cOptionsNull));
    if (compressOptionsPtr == NULL) compressOptionsPtr = &cOptionsNull;

    /* select compression function */
    compress = LZ4F_selectCompression(cctxPtr->prefs.frameInfo.blockMode, cctxPtr->prefs.compressionLevel);

    /* complete tmp buffer */
    if (cctxPtr->tmpInSize > 0) {   /* some data already within tmp buffer */
        size_t const sizeToCopy = blockSize - cctxPtr->tmpInSize;
        if (sizeToCopy > srcSize) {
            /* add src to tmpIn buffer */
            memcpy(cctxPtr->tmpIn + cctxPtr->tmpInSize, srcBuffer, srcSize);
            srcPtr = srcEnd;
            cctxPtr->tmpInSize += srcSize;
            /* still needs some CRC */
        } else {
            /* complete tmpIn block and then compress it */
            lastBlockCompressed = fromTmpBuffer;
            memcpy(cctxPtr->tmpIn + cctxPtr->tmpInSize, srcBuffer, sizeToCopy);
            srcPtr += sizeToCopy;

            dstPtr += LZ4F_compressBlock(dstPtr, cctxPtr->tmpIn, blockSize, compress, cctxPtr->lz4CtxPtr, cctxPtr->prefs.compressionLevel);

            if (cctxPtr->prefs.frameInfo.blockMode==LZ4F_blockLinked) cctxPtr->tmpIn += blockSize;
            cctxPtr->tmpInSize = 0;
        }
    }

    while ((size_t)(srcEnd - srcPtr) >= blockSize) {
        /* compress full block */
        lastBlockCompressed = fromSrcBuffer;
        dstPtr += LZ4F_compressBlock(dstPtr, srcPtr, blockSize, compress, cctxPtr->lz4CtxPtr, cctxPtr->prefs.compressionLevel);
        srcPtr += blockSize;
    }

    if ((cctxPtr->prefs.autoFlush) && (srcPtr < srcEnd)) {
        /* compress remaining input < blockSize */
        lastBlockCompressed = fromSrcBuffer;
        dstPtr += LZ4F_compressBlock(dstPtr, srcPtr, srcEnd - srcPtr, compress, cctxPtr->lz4CtxPtr, cctxPtr->prefs.compressionLevel);
        srcPtr  = srcEnd;
    }

    /* preserve dictionary if necessary */
    if ((cctxPtr->prefs.frameInfo.blockMode==LZ4F_blockLinked) && (lastBlockCompressed==fromSrcBuffer)) {
        if (compressOptionsPtr->stableSrc) {
            cctxPtr->tmpIn = cctxPtr->tmpBuff;
        } else {
            int realDictSize = LZ4F_localSaveDict(cctxPtr);
            if (realDictSize==0) return err0r(LZ4F_ERROR_GENERIC);
            cctxPtr->tmpIn = cctxPtr->tmpBuff + realDictSize;
        }
    }

    /* keep tmpIn within limits */
    if ((cctxPtr->tmpIn + blockSize) > (cctxPtr->tmpBuff + cctxPtr->maxBufferSize)   /* necessarily LZ4F_blockLinked && lastBlockCompressed==fromTmpBuffer */
        && !(cctxPtr->prefs.autoFlush))
    {
        int realDictSize = LZ4F_localSaveDict(cctxPtr);
        cctxPtr->tmpIn = cctxPtr->tmpBuff + realDictSize;
    }

    /* some input data left, necessarily < blockSize */
    if (srcPtr < srcEnd) {
        /* fill tmp buffer */
        size_t const sizeToCopy = srcEnd - srcPtr;
        memcpy(cctxPtr->tmpIn, srcPtr, sizeToCopy);
        cctxPtr->tmpInSize = sizeToCopy;
    }

    if (cctxPtr->prefs.frameInfo.contentChecksumFlag == LZ4F_contentChecksumEnabled)
        XXH32_update(&(cctxPtr->xxh), srcBuffer, srcSize);

    cctxPtr->totalInSize += srcSize;
    return dstPtr - dstStart;
}


/*! LZ4F_flush() :
* Should you need to create compressed data immediately, without waiting for a block to be filled,
* you can call LZ4_flush(), which will immediately compress any remaining data stored within compressionContext.
* The result of the function is the number of bytes written into dstBuffer
* (it can be zero, this means there was no data left within compressionContext)
* The function outputs an error code if it fails (can be tested using LZ4F_isError())
* The LZ4F_compressOptions_t structure is optional : you can provide NULL as argument.
*/
size_t LZ4F_flush(LZ4F_cctx* cctxPtr, void* dstBuffer, size_t dstMaxSize, const LZ4F_compressOptions_t* compressOptionsPtr)
{
    BYTE* const dstStart = (BYTE*)dstBuffer;
    BYTE* dstPtr = dstStart;
    compressFunc_t compress;

    if (cctxPtr->tmpInSize == 0) return 0;   /* nothing to flush */
    if (cctxPtr->cStage != 1) return err0r(LZ4F_ERROR_GENERIC);
    if (dstMaxSize < (cctxPtr->tmpInSize + 8)) return err0r(LZ4F_ERROR_dstMaxSize_tooSmall);   /* +8 : block header(4) + block checksum(4) */
    (void)compressOptionsPtr;   /* not yet useful */

    /* select compression function */
    compress = LZ4F_selectCompression(cctxPtr->prefs.frameInfo.blockMode, cctxPtr->prefs.compressionLevel);

    /* compress tmp buffer */
    dstPtr += LZ4F_compressBlock(dstPtr, cctxPtr->tmpIn, cctxPtr->tmpInSize, compress, cctxPtr->lz4CtxPtr, cctxPtr->prefs.compressionLevel);
    if (cctxPtr->prefs.frameInfo.blockMode==LZ4F_blockLinked) cctxPtr->tmpIn += cctxPtr->tmpInSize;
    cctxPtr->tmpInSize = 0;

    /* keep tmpIn within limits */
    if ((cctxPtr->tmpIn + cctxPtr->maxBlockSize) > (cctxPtr->tmpBuff + cctxPtr->maxBufferSize)) {  /* necessarily LZ4F_blockLinked */
        int realDictSize = LZ4F_localSaveDict(cctxPtr);
        cctxPtr->tmpIn = cctxPtr->tmpBuff + realDictSize;
    }

    return dstPtr - dstStart;
}


/*! LZ4F_compressEnd() :
* When you want to properly finish the compressed frame, just call LZ4F_compressEnd().
* It will flush whatever data remained within compressionContext (like LZ4_flush())
* but also properly finalize the frame, with an endMark and a checksum.
* The result of the function is the number of bytes written into dstBuffer (necessarily >= 4 (endMark size))
* The function outputs an error code if it fails (can be tested using LZ4F_isError())
* The LZ4F_compressOptions_t structure is optional : you can provide NULL as argument.
* compressionContext can then be used again, starting with LZ4F_compressBegin(). The preferences will remain the same.
*/
size_t LZ4F_compressEnd(LZ4F_cctx* cctxPtr, void* dstBuffer, size_t dstMaxSize, const LZ4F_compressOptions_t* compressOptionsPtr)
{
    BYTE* const dstStart = (BYTE*)dstBuffer;
    BYTE* dstPtr = dstStart;

    size_t const flushSize = LZ4F_flush(cctxPtr, dstBuffer, dstMaxSize, compressOptionsPtr);
    if (LZ4F_isError(flushSize)) return flushSize;
    dstPtr += flushSize;

    LZ4F_writeLE32(dstPtr, 0);
    dstPtr+=4;   /* endMark */

    if (cctxPtr->prefs.frameInfo.contentChecksumFlag == LZ4F_contentChecksumEnabled) {
        U32 const xxh = XXH32_digest(&(cctxPtr->xxh));
        LZ4F_writeLE32(dstPtr, xxh);
        dstPtr+=4;   /* content Checksum */
    }

    cctxPtr->cStage = 0;   /* state is now re-usable (with identical preferences) */
    cctxPtr->maxBufferSize = 0;  /* reuse HC context */

    if (cctxPtr->prefs.frameInfo.contentSize) {
        if (cctxPtr->prefs.frameInfo.contentSize != cctxPtr->totalInSize)
            return err0r(LZ4F_ERROR_frameSize_wrong);
    }

    return dstPtr - dstStart;
}


/*-***************************************************
*   Frame Decompression
*****************************************************/

struct LZ4F_dctx_s {
    LZ4F_frameInfo_t frameInfo;
    U32    version;
    U32    dStage;
    U64    frameRemainingSize;
    size_t maxBlockSize;
    size_t maxBufferSize;
    BYTE*  tmpIn;
    size_t tmpInSize;
    size_t tmpInTarget;
    BYTE*  tmpOutBuffer;
    const BYTE*  dict;
    size_t dictSize;
    BYTE*  tmpOut;
    size_t tmpOutSize;
    size_t tmpOutStart;
    XXH32_state_t xxh;
    BYTE   header[16];
};  /* typedef'd to LZ4F_dctx in lz4frame.h */


/*! LZ4F_createDecompressionContext() :
*   Create a decompressionContext object, which will track all decompression operations.
*   Provides a pointer to a fully allocated and initialized LZ4F_decompressionContext object.
*   Object can later be released using LZ4F_freeDecompressionContext().
*   @return : if != 0, there was an error during context creation.
*/
LZ4F_errorCode_t LZ4F_createDecompressionContext(LZ4F_dctx** LZ4F_decompressionContextPtr, unsigned versionNumber)
{
    LZ4F_dctx* const dctxPtr = (LZ4F_dctx*)ALLOCATOR(sizeof(LZ4F_dctx));
    if (dctxPtr==NULL) return err0r(LZ4F_ERROR_GENERIC);

    dctxPtr->version = versionNumber;
    *LZ4F_decompressionContextPtr = dctxPtr;
    return LZ4F_OK_NoError;
}

LZ4F_errorCode_t LZ4F_freeDecompressionContext(LZ4F_dctx* const dctxPtr)
{
    LZ4F_errorCode_t result = LZ4F_OK_NoError;
    if (dctxPtr != NULL) {   /* can accept NULL input, like free() */
      result = (LZ4F_errorCode_t)dctxPtr->dStage;
      FREEMEM(dctxPtr->tmpIn);
      FREEMEM(dctxPtr->tmpOutBuffer);
      FREEMEM(dctxPtr);
    }
    return result;
}


/*==---   Streaming Decompression operations   ---==*/

typedef enum { dstage_getHeader=0, dstage_storeHeader,
    dstage_getCBlockSize, dstage_storeCBlockSize,
    dstage_copyDirect,
    dstage_getCBlock, dstage_storeCBlock,
    dstage_decodeCBlock, dstage_decodeCBlock_intoDst,
    dstage_decodeCBlock_intoTmp, dstage_flushOut,
    dstage_getSuffix, dstage_storeSuffix,
    dstage_getSFrameSize, dstage_storeSFrameSize,
    dstage_skipSkippable
} dStage_t;


/*! LZ4F_headerSize() :
*   @return : size of frame header
*             or an error code, which can be tested using LZ4F_isError()
*/
static size_t LZ4F_headerSize(const void* src, size_t srcSize)
{
    /* minimal srcSize to determine header size */
    if (srcSize < 5) return err0r(LZ4F_ERROR_frameHeader_incomplete);

    /* special case : skippable frames */
    if ((LZ4F_readLE32(src) & 0xFFFFFFF0U) == LZ4F_MAGIC_SKIPPABLE_START) return 8;

    /* control magic number */
    if (LZ4F_readLE32(src) != LZ4F_MAGICNUMBER) return err0r(LZ4F_ERROR_frameType_unknown);

    /* Frame Header Size */
    {   BYTE const FLG = ((const BYTE*)src)[4];
        U32 const contentSizeFlag = (FLG>>3) & _1BIT;
        return contentSizeFlag ? maxFHSize : minFHSize;
    }
}


/*! LZ4F_decodeHeader() :
   input   : `src` points at the **beginning of the frame**
   output  : set internal values of dctx, such as
             dctxPtr->frameInfo and dctxPtr->dStage.
             Also allocates internal buffers.
   @return : nb Bytes read from srcVoidPtr (necessarily <= srcSize)
             or an error code (testable with LZ4F_isError())
*/
static size_t LZ4F_decodeHeader(LZ4F_dctx* dctxPtr, const void* src, size_t srcSize)
{
    BYTE FLG, BD, HC;
    unsigned version, blockMode, blockChecksumFlag, contentSizeFlag, contentChecksumFlag, blockSizeID;
    size_t bufferNeeded;
    size_t frameHeaderSize;
    const BYTE* srcPtr = (const BYTE*)src;

    /* need to decode header to get frameInfo */
    if (srcSize < minFHSize) return err0r(LZ4F_ERROR_frameHeader_incomplete);   /* minimal frame header size */
    memset(&(dctxPtr->frameInfo), 0, sizeof(dctxPtr->frameInfo));

    /* special case : skippable frames */
    if ((LZ4F_readLE32(srcPtr) & 0xFFFFFFF0U) == LZ4F_MAGIC_SKIPPABLE_START) {
        dctxPtr->frameInfo.frameType = LZ4F_skippableFrame;
        if (src == (void*)(dctxPtr->header)) {
            dctxPtr->tmpInSize = srcSize;
            dctxPtr->tmpInTarget = 8;
            dctxPtr->dStage = dstage_storeSFrameSize;
            return srcSize;
        } else {
            dctxPtr->dStage = dstage_getSFrameSize;
            return 4;
        }
    }

    /* control magic number */
    if (LZ4F_readLE32(srcPtr) != LZ4F_MAGICNUMBER) return err0r(LZ4F_ERROR_frameType_unknown);
    dctxPtr->frameInfo.frameType = LZ4F_frame;

    /* Flags */
    FLG = srcPtr[4];
    version = (FLG>>6) & _2BITS;
    blockMode = (FLG>>5) & _1BIT;
    blockChecksumFlag = (FLG>>4) & _1BIT;
    contentSizeFlag = (FLG>>3) & _1BIT;
    contentChecksumFlag = (FLG>>2) & _1BIT;

    /* Frame Header Size */
    frameHeaderSize = contentSizeFlag ? maxFHSize : minFHSize;

    if (srcSize < frameHeaderSize) {
        /* not enough input to fully decode frame header */
        if (srcPtr != dctxPtr->header)
            memcpy(dctxPtr->header, srcPtr, srcSize);
        dctxPtr->tmpInSize = srcSize;
        dctxPtr->tmpInTarget = frameHeaderSize;
        dctxPtr->dStage = dstage_storeHeader;
        return srcSize;
    }

    BD = srcPtr[5];
    blockSizeID = (BD>>4) & _3BITS;

    /* validate */
    if (version != 1) return err0r(LZ4F_ERROR_headerVersion_wrong);        /* Version Number, only supported value */
    if (blockChecksumFlag != 0) return err0r(LZ4F_ERROR_blockChecksum_unsupported); /* Not supported for the time being */
    if (((FLG>>0)&_2BITS) != 0) return err0r(LZ4F_ERROR_reservedFlag_set); /* Reserved bits */
    if (((BD>>7)&_1BIT) != 0) return err0r(LZ4F_ERROR_reservedFlag_set);   /* Reserved bit */
    if (blockSizeID < 4) return err0r(LZ4F_ERROR_maxBlockSize_invalid);    /* 4-7 only supported values for the time being */
    if (((BD>>0)&_4BITS) != 0) return err0r(LZ4F_ERROR_reservedFlag_set);  /* Reserved bits */

    /* check */
    HC = LZ4F_headerChecksum(srcPtr+4, frameHeaderSize-5);
    if (HC != srcPtr[frameHeaderSize-1]) return err0r(LZ4F_ERROR_headerChecksum_invalid);   /* Bad header checksum error */

    /* save */
    dctxPtr->frameInfo.blockMode = (LZ4F_blockMode_t)blockMode;
    dctxPtr->frameInfo.contentChecksumFlag = (LZ4F_contentChecksum_t)contentChecksumFlag;
    dctxPtr->frameInfo.blockSizeID = (LZ4F_blockSizeID_t)blockSizeID;
    dctxPtr->maxBlockSize = LZ4F_getBlockSize(blockSizeID);
    if (contentSizeFlag)
        dctxPtr->frameRemainingSize = dctxPtr->frameInfo.contentSize = LZ4F_readLE64(srcPtr+6);

    /* init */
    if (contentChecksumFlag) XXH32_reset(&(dctxPtr->xxh), 0);

    /* alloc */
    bufferNeeded = dctxPtr->maxBlockSize + ((dctxPtr->frameInfo.blockMode==LZ4F_blockLinked) * 128 KB);
    if (bufferNeeded > dctxPtr->maxBufferSize) {   /* tmp buffers too small */
        FREEMEM(dctxPtr->tmpIn);
        FREEMEM(dctxPtr->tmpOutBuffer);
        dctxPtr->maxBufferSize = bufferNeeded;
        dctxPtr->tmpIn = (BYTE*)ALLOCATOR(dctxPtr->maxBlockSize);
        if (dctxPtr->tmpIn == NULL) return err0r(LZ4F_ERROR_GENERIC);
        dctxPtr->tmpOutBuffer= (BYTE*)ALLOCATOR(dctxPtr->maxBufferSize);
        if (dctxPtr->tmpOutBuffer== NULL) return err0r(LZ4F_ERROR_GENERIC);
    }
    dctxPtr->tmpInSize = 0;
    dctxPtr->tmpInTarget = 0;
    dctxPtr->dict = dctxPtr->tmpOutBuffer;
    dctxPtr->dictSize = 0;
    dctxPtr->tmpOut = dctxPtr->tmpOutBuffer;
    dctxPtr->tmpOutStart = 0;
    dctxPtr->tmpOutSize = 0;

    dctxPtr->dStage = dstage_getCBlockSize;

    return frameHeaderSize;
}


/*! LZ4F_getFrameInfo() :
*   Decodes frame header information, such as blockSize. Usage is optional.
*   The objective is to extract header information before receiving decompressed data, typically for allocation purposes.
*   LZ4F_getFrameInfo() can also be used *after* starting decompression, on a valid LZ4F_decompressionContext_t.
*   The number of bytes consumed from srcBuffer will be provided within *srcSizePtr (necessarily <= original value).
*   Decompression must resume from where it stopped (srcBuffer + *srcSizePtr)
*   @return : hint of the better `srcSize` to use for next call to LZ4F_decompress,
*             or an error code which can be tested using LZ4F_isError().
*/
LZ4F_errorCode_t LZ4F_getFrameInfo(LZ4F_dctx* dctxPtr, LZ4F_frameInfo_t* frameInfoPtr,
                                   const void* srcBuffer, size_t* srcSizePtr)
{
    if (dctxPtr->dStage > dstage_storeHeader) {  /* note : requires dstage_* header related to be at beginning of enum */
        /* frameInfo already decoded */
        size_t o=0, i=0;
        *srcSizePtr = 0;
        *frameInfoPtr = dctxPtr->frameInfo;
        return LZ4F_decompress(dctxPtr, NULL, &o, NULL, &i, NULL);  /* returns : recommended nb of bytes for LZ4F_decompress() */
    } else {
        size_t nextSrcSize, o=0;
        size_t const hSize = LZ4F_headerSize(srcBuffer, *srcSizePtr);
        if (LZ4F_isError(hSize)) { *srcSizePtr=0; return hSize; }
        if (*srcSizePtr < hSize) { *srcSizePtr=0; return err0r(LZ4F_ERROR_frameHeader_incomplete); }

        *srcSizePtr = hSize;
        nextSrcSize = LZ4F_decompress(dctxPtr, NULL, &o, srcBuffer, srcSizePtr, NULL);
        if (dctxPtr->dStage <= dstage_storeHeader) return err0r(LZ4F_ERROR_frameHeader_incomplete); /* should not happen, already checked */
        *frameInfoPtr = dctxPtr->frameInfo;
        return nextSrcSize;
    }
}


/* trivial redirector, for common prototype */
static int LZ4F_decompress_safe (const char* source, char* dest, int compressedSize, int maxDecompressedSize, const char* dictStart, int dictSize)
{
    (void)dictStart; (void)dictSize;
    return LZ4_decompress_safe (source, dest, compressedSize, maxDecompressedSize);
}


static void LZ4F_updateDict(LZ4F_dctx* dctxPtr, const BYTE* dstPtr, size_t dstSize, const BYTE* dstPtr0, unsigned withinTmp)
{
    if (dctxPtr->dictSize==0)
        dctxPtr->dict = (const BYTE*)dstPtr;   /* priority to dictionary continuity */

    if (dctxPtr->dict + dctxPtr->dictSize == dstPtr) {  /* dictionary continuity */
        dctxPtr->dictSize += dstSize;
        return;
    }

    if (dstPtr - dstPtr0 + dstSize >= 64 KB) {  /* dstBuffer large enough to become dictionary */
        dctxPtr->dict = (const BYTE*)dstPtr0;
        dctxPtr->dictSize = dstPtr - dstPtr0 + dstSize;
        return;
    }

    if ((withinTmp) && (dctxPtr->dict == dctxPtr->tmpOutBuffer)) {
        /* assumption : dctxPtr->dict + dctxPtr->dictSize == dctxPtr->tmpOut + dctxPtr->tmpOutStart */
        dctxPtr->dictSize += dstSize;
        return;
    }

    if (withinTmp) { /* copy relevant dict portion in front of tmpOut within tmpOutBuffer */
        size_t preserveSize = dctxPtr->tmpOut - dctxPtr->tmpOutBuffer;
        size_t copySize = 64 KB - dctxPtr->tmpOutSize;
        const BYTE* oldDictEnd = dctxPtr->dict + dctxPtr->dictSize - dctxPtr->tmpOutStart;
        if (dctxPtr->tmpOutSize > 64 KB) copySize = 0;
        if (copySize > preserveSize) copySize = preserveSize;

        memcpy(dctxPtr->tmpOutBuffer + preserveSize - copySize, oldDictEnd - copySize, copySize);

        dctxPtr->dict = dctxPtr->tmpOutBuffer;
        dctxPtr->dictSize = preserveSize + dctxPtr->tmpOutStart + dstSize;
        return;
    }

    if (dctxPtr->dict == dctxPtr->tmpOutBuffer) {    /* copy dst into tmp to complete dict */
        if (dctxPtr->dictSize + dstSize > dctxPtr->maxBufferSize) {  /* tmp buffer not large enough */
            size_t preserveSize = 64 KB - dstSize;   /* note : dstSize < 64 KB */
            memcpy(dctxPtr->tmpOutBuffer, dctxPtr->dict + dctxPtr->dictSize - preserveSize, preserveSize);
            dctxPtr->dictSize = preserveSize;
        }
        memcpy(dctxPtr->tmpOutBuffer + dctxPtr->dictSize, dstPtr, dstSize);
        dctxPtr->dictSize += dstSize;
        return;
    }

    /* join dict & dest into tmp */
    {   size_t preserveSize = 64 KB - dstSize;   /* note : dstSize < 64 KB */
        if (preserveSize > dctxPtr->dictSize) preserveSize = dctxPtr->dictSize;
        memcpy(dctxPtr->tmpOutBuffer, dctxPtr->dict + dctxPtr->dictSize - preserveSize, preserveSize);
        memcpy(dctxPtr->tmpOutBuffer + preserveSize, dstPtr, dstSize);
        dctxPtr->dict = dctxPtr->tmpOutBuffer;
        dctxPtr->dictSize = preserveSize + dstSize;
    }
}



/*! LZ4F_decompress() :
* Call this function repetitively to regenerate data compressed within srcBuffer.
* The function will attempt to decode up to *srcSizePtr bytes from srcBuffer, into dstBuffer of capacity *dstSizePtr.
*
* The number of bytes regenerated into dstBuffer will be provided within *dstSizePtr (necessarily <= original value).
*
* The number of bytes effectively read from srcBuffer will be provided within *srcSizePtr (necessarily <= original value).
* If the number of bytes read is < number of bytes provided, then the decompression operation is not complete.
* Remaining data will have to be presented again in a subsequent invocation.
*
* The function result is an hint of the better srcSize to use for next call to LZ4F_decompress.
* Basically, it's the size of the current (or remaining) compressed block + header of next block.
* Respecting the hint provides some boost to performance, since it allows less buffer shuffling.
* Note that this is just a hint, it's always possible to any srcSize value.
* When a frame is fully decoded, @return will be 0.
* If decompression failed, @return is an error code which can be tested using LZ4F_isError().
*/
size_t LZ4F_decompress(LZ4F_dctx* dctxPtr,
                       void* dstBuffer, size_t* dstSizePtr,
                       const void* srcBuffer, size_t* srcSizePtr,
                       const LZ4F_decompressOptions_t* decompressOptionsPtr)
{
    LZ4F_decompressOptions_t optionsNull;
    const BYTE* const srcStart = (const BYTE*)srcBuffer;
    const BYTE* const srcEnd = srcStart + *srcSizePtr;
    const BYTE* srcPtr = srcStart;
    BYTE* const dstStart = (BYTE*)dstBuffer;
    BYTE* const dstEnd = dstStart + *dstSizePtr;
    BYTE* dstPtr = dstStart;
    const BYTE* selectedIn = NULL;
    unsigned doAnotherStage = 1;
    size_t nextSrcSizeHint = 1;


    memset(&optionsNull, 0, sizeof(optionsNull));
    if (decompressOptionsPtr==NULL) decompressOptionsPtr = &optionsNull;
    *srcSizePtr = 0;
    *dstSizePtr = 0;

    /* programmed as a state machine */

    while (doAnotherStage) {

        switch(dctxPtr->dStage)
        {

        case dstage_getHeader:
            if ((size_t)(srcEnd-srcPtr) >= maxFHSize) {  /* enough to decode - shortcut */
                LZ4F_errorCode_t const hSize = LZ4F_decodeHeader(dctxPtr, srcPtr, srcEnd-srcPtr);
                if (LZ4F_isError(hSize)) return hSize;
                srcPtr += hSize;
                break;
            }
            dctxPtr->tmpInSize = 0;
            dctxPtr->tmpInTarget = minFHSize;   /* minimum to attempt decode */
            dctxPtr->dStage = dstage_storeHeader;
            /* pass-through */

        case dstage_storeHeader:
            {   size_t sizeToCopy = dctxPtr->tmpInTarget - dctxPtr->tmpInSize;
                if (sizeToCopy > (size_t)(srcEnd - srcPtr)) sizeToCopy =  srcEnd - srcPtr;
                memcpy(dctxPtr->header + dctxPtr->tmpInSize, srcPtr, sizeToCopy);
                dctxPtr->tmpInSize += sizeToCopy;
                srcPtr += sizeToCopy;
                if (dctxPtr->tmpInSize < dctxPtr->tmpInTarget) {
                    nextSrcSizeHint = (dctxPtr->tmpInTarget - dctxPtr->tmpInSize) + BHSize;   /* rest of header + nextBlockHeader */
                    doAnotherStage = 0;   /* not enough src data, ask for some more */
                    break;
                }
                {   LZ4F_errorCode_t const hSize = LZ4F_decodeHeader(dctxPtr, dctxPtr->header, dctxPtr->tmpInTarget);
                    if (LZ4F_isError(hSize)) return hSize;
                }
                break;
            }

        case dstage_getCBlockSize:
            if ((size_t)(srcEnd - srcPtr) >= BHSize) {
                selectedIn = srcPtr;
                srcPtr += BHSize;
            } else {
                /* not enough input to read cBlockSize field */
                dctxPtr->tmpInSize = 0;
                dctxPtr->dStage = dstage_storeCBlockSize;
            }

            if (dctxPtr->dStage == dstage_storeCBlockSize)   /* can be skipped */
        case dstage_storeCBlockSize:
            {   size_t sizeToCopy = BHSize - dctxPtr->tmpInSize;
                if (sizeToCopy > (size_t)(srcEnd - srcPtr)) sizeToCopy = srcEnd - srcPtr;
                memcpy(dctxPtr->tmpIn + dctxPtr->tmpInSize, srcPtr, sizeToCopy);
                srcPtr += sizeToCopy;
                dctxPtr->tmpInSize += sizeToCopy;
                if (dctxPtr->tmpInSize < BHSize) {   /* not enough input to get full cBlockSize; wait for more */
                    nextSrcSizeHint = BHSize - dctxPtr->tmpInSize;
                    doAnotherStage  = 0;
                    break;
                }
                selectedIn = dctxPtr->tmpIn;
            }

        /* case dstage_decodeCBlockSize: */   /* no more direct access, to prevent scan-build warning */
            {   size_t const nextCBlockSize = LZ4F_readLE32(selectedIn) & 0x7FFFFFFFU;
                if (nextCBlockSize==0) {  /* frameEnd signal, no more CBlock */
                    dctxPtr->dStage = dstage_getSuffix;
                    break;
                }
                if (nextCBlockSize > dctxPtr->maxBlockSize) return err0r(LZ4F_ERROR_GENERIC);   /* invalid cBlockSize */
                dctxPtr->tmpInTarget = nextCBlockSize;
                if (LZ4F_readLE32(selectedIn) & LZ4F_BLOCKUNCOMPRESSED_FLAG) {
                    dctxPtr->dStage = dstage_copyDirect;
                    break;
                }
                dctxPtr->dStage = dstage_getCBlock;
                if (dstPtr==dstEnd) {
                    nextSrcSizeHint = nextCBlockSize + BHSize;
                    doAnotherStage = 0;
                }
                break;
            }

        case dstage_copyDirect:   /* uncompressed block */
            {   size_t sizeToCopy = dctxPtr->tmpInTarget;
                if ((size_t)(srcEnd-srcPtr) < sizeToCopy) sizeToCopy = srcEnd - srcPtr;  /* not enough input to read full block */
                if ((size_t)(dstEnd-dstPtr) < sizeToCopy) sizeToCopy = dstEnd - dstPtr;
                memcpy(dstPtr, srcPtr, sizeToCopy);
                if (dctxPtr->frameInfo.contentChecksumFlag) XXH32_update(&(dctxPtr->xxh), srcPtr, sizeToCopy);
                if (dctxPtr->frameInfo.contentSize) dctxPtr->frameRemainingSize -= sizeToCopy;

                /* dictionary management */
                if (dctxPtr->frameInfo.blockMode==LZ4F_blockLinked)
                    LZ4F_updateDict(dctxPtr, dstPtr, sizeToCopy, dstStart, 0);

                srcPtr += sizeToCopy;
                dstPtr += sizeToCopy;
                if (sizeToCopy == dctxPtr->tmpInTarget) {  /* all copied */
                    dctxPtr->dStage = dstage_getCBlockSize;
                    break;
                }
                dctxPtr->tmpInTarget -= sizeToCopy;   /* still need to copy more */
                nextSrcSizeHint = dctxPtr->tmpInTarget + BHSize;
                doAnotherStage = 0;
                break;
            }

        case dstage_getCBlock:   /* entry from dstage_decodeCBlockSize */
            if ((size_t)(srcEnd-srcPtr) < dctxPtr->tmpInTarget) {
                dctxPtr->tmpInSize = 0;
                dctxPtr->dStage = dstage_storeCBlock;
                break;
            }
            selectedIn = srcPtr;
            srcPtr += dctxPtr->tmpInTarget;
            dctxPtr->dStage = dstage_decodeCBlock;
            break;

        case dstage_storeCBlock:
            {   size_t sizeToCopy = dctxPtr->tmpInTarget - dctxPtr->tmpInSize;
                if (sizeToCopy > (size_t)(srcEnd-srcPtr)) sizeToCopy = srcEnd-srcPtr;
                memcpy(dctxPtr->tmpIn + dctxPtr->tmpInSize, srcPtr, sizeToCopy);
                dctxPtr->tmpInSize += sizeToCopy;
                srcPtr += sizeToCopy;
                if (dctxPtr->tmpInSize < dctxPtr->tmpInTarget) { /* need more input */
                    nextSrcSizeHint = (dctxPtr->tmpInTarget - dctxPtr->tmpInSize) + BHSize;
                    doAnotherStage=0;
                    break;
                }
                selectedIn = dctxPtr->tmpIn;
                dctxPtr->dStage = dstage_decodeCBlock;
                /* pass-through */
            }

        case dstage_decodeCBlock:
            if ((size_t)(dstEnd-dstPtr) < dctxPtr->maxBlockSize)   /* not enough place into dst : decode into tmpOut */
                dctxPtr->dStage = dstage_decodeCBlock_intoTmp;
            else
                dctxPtr->dStage = dstage_decodeCBlock_intoDst;
            break;

        case dstage_decodeCBlock_intoDst:
            {   int (*decoder)(const char*, char*, int, int, const char*, int);
                int decodedSize;

                if (dctxPtr->frameInfo.blockMode == LZ4F_blockLinked)
                    decoder = LZ4_decompress_safe_usingDict;
                else
                    decoder = LZ4F_decompress_safe;

                decodedSize = decoder((const char*)selectedIn, (char*)dstPtr, (int)dctxPtr->tmpInTarget, (int)dctxPtr->maxBlockSize, (const char*)dctxPtr->dict, (int)dctxPtr->dictSize);
                if (decodedSize < 0) return err0r(LZ4F_ERROR_GENERIC);   /* decompression failed */
                if (dctxPtr->frameInfo.contentChecksumFlag) XXH32_update(&(dctxPtr->xxh), dstPtr, decodedSize);
                if (dctxPtr->frameInfo.contentSize) dctxPtr->frameRemainingSize -= decodedSize;

                /* dictionary management */
                if (dctxPtr->frameInfo.blockMode==LZ4F_blockLinked)
                    LZ4F_updateDict(dctxPtr, dstPtr, decodedSize, dstStart, 0);

                dstPtr += decodedSize;
                dctxPtr->dStage = dstage_getCBlockSize;
                break;
            }

        case dstage_decodeCBlock_intoTmp:
            /* not enough place into dst : decode into tmpOut */
            {   int (*decoder)(const char*, char*, int, int, const char*, int);
                int decodedSize;

                if (dctxPtr->frameInfo.blockMode == LZ4F_blockLinked)
                    decoder = LZ4_decompress_safe_usingDict;
                else
                    decoder = LZ4F_decompress_safe;

                /* ensure enough place for tmpOut */
                if (dctxPtr->frameInfo.blockMode == LZ4F_blockLinked) {
                    if (dctxPtr->dict == dctxPtr->tmpOutBuffer) {
                        if (dctxPtr->dictSize > 128 KB) {
                            memcpy(dctxPtr->tmpOutBuffer, dctxPtr->dict + dctxPtr->dictSize - 64 KB, 64 KB);
                            dctxPtr->dictSize = 64 KB;
                        }
                        dctxPtr->tmpOut = dctxPtr->tmpOutBuffer + dctxPtr->dictSize;
                    } else {  /* dict not within tmp */
                        size_t reservedDictSpace = dctxPtr->dictSize;
                        if (reservedDictSpace > 64 KB) reservedDictSpace = 64 KB;
                        dctxPtr->tmpOut = dctxPtr->tmpOutBuffer + reservedDictSpace;
                    }
                }

                /* Decode */
                decodedSize = decoder((const char*)selectedIn, (char*)dctxPtr->tmpOut, (int)dctxPtr->tmpInTarget, (int)dctxPtr->maxBlockSize, (const char*)dctxPtr->dict, (int)dctxPtr->dictSize);
                if (decodedSize < 0) return err0r(LZ4F_ERROR_decompressionFailed);   /* decompression failed */
                if (dctxPtr->frameInfo.contentChecksumFlag) XXH32_update(&(dctxPtr->xxh), dctxPtr->tmpOut, decodedSize);
                if (dctxPtr->frameInfo.contentSize) dctxPtr->frameRemainingSize -= decodedSize;
                dctxPtr->tmpOutSize = decodedSize;
                dctxPtr->tmpOutStart = 0;
                dctxPtr->dStage = dstage_flushOut;
                break;
            }

        case dstage_flushOut:  /* flush decoded data from tmpOut to dstBuffer */
            {   size_t sizeToCopy = dctxPtr->tmpOutSize - dctxPtr->tmpOutStart;
                if (sizeToCopy > (size_t)(dstEnd-dstPtr)) sizeToCopy = dstEnd-dstPtr;
                memcpy(dstPtr, dctxPtr->tmpOut + dctxPtr->tmpOutStart, sizeToCopy);

                /* dictionary management */
                if (dctxPtr->frameInfo.blockMode==LZ4F_blockLinked)
                    LZ4F_updateDict(dctxPtr, dstPtr, sizeToCopy, dstStart, 1);

                dctxPtr->tmpOutStart += sizeToCopy;
                dstPtr += sizeToCopy;

                /* end of flush ? */
                if (dctxPtr->tmpOutStart == dctxPtr->tmpOutSize) {
                    dctxPtr->dStage = dstage_getCBlockSize;
                    break;
                }
                nextSrcSizeHint = BHSize;
                doAnotherStage = 0;   /* still some data to flush */
                break;
            }

        case dstage_getSuffix:
            {   size_t const suffixSize = dctxPtr->frameInfo.contentChecksumFlag * 4;
                if (dctxPtr->frameRemainingSize) return err0r(LZ4F_ERROR_frameSize_wrong);   /* incorrect frame size decoded */
                if (suffixSize == 0) {  /* frame completed */
                    nextSrcSizeHint = 0;
                    dctxPtr->dStage = dstage_getHeader;
                    doAnotherStage = 0;
                    break;
                }
                if ((srcEnd - srcPtr) < 4) {  /* not enough size for entire CRC */
                    dctxPtr->tmpInSize = 0;
                    dctxPtr->dStage = dstage_storeSuffix;
                } else {
                    selectedIn = srcPtr;
                    srcPtr += 4;
                }
            }

            if (dctxPtr->dStage == dstage_storeSuffix)   /* can be skipped */
        case dstage_storeSuffix:
            {
                size_t sizeToCopy = 4 - dctxPtr->tmpInSize;
                if (sizeToCopy > (size_t)(srcEnd - srcPtr)) sizeToCopy = srcEnd - srcPtr;
                memcpy(dctxPtr->tmpIn + dctxPtr->tmpInSize, srcPtr, sizeToCopy);
                srcPtr += sizeToCopy;
                dctxPtr->tmpInSize += sizeToCopy;
                if (dctxPtr->tmpInSize < 4) { /* not enough input to read complete suffix */
                    nextSrcSizeHint = 4 - dctxPtr->tmpInSize;
                    doAnotherStage=0;
                    break;
                }
                selectedIn = dctxPtr->tmpIn;
            }

        /* case dstage_checkSuffix: */   /* no direct call, to avoid scan-build warning */
            {   U32 const readCRC = LZ4F_readLE32(selectedIn);
                U32 const resultCRC = XXH32_digest(&(dctxPtr->xxh));
                if (readCRC != resultCRC) return err0r(LZ4F_ERROR_contentChecksum_invalid);
                nextSrcSizeHint = 0;
                dctxPtr->dStage = dstage_getHeader;
                doAnotherStage = 0;
                break;
            }

        case dstage_getSFrameSize:
            if ((srcEnd - srcPtr) >= 4) {
                selectedIn = srcPtr;
                srcPtr += 4;
            } else {
                /* not enough input to read cBlockSize field */
                dctxPtr->tmpInSize = 4;
                dctxPtr->tmpInTarget = 8;
                dctxPtr->dStage = dstage_storeSFrameSize;
            }

            if (dctxPtr->dStage == dstage_storeSFrameSize)
        case dstage_storeSFrameSize:
            {
                size_t sizeToCopy = dctxPtr->tmpInTarget - dctxPtr->tmpInSize;
                if (sizeToCopy > (size_t)(srcEnd - srcPtr)) sizeToCopy = srcEnd - srcPtr;
                memcpy(dctxPtr->header + dctxPtr->tmpInSize, srcPtr, sizeToCopy);
                srcPtr += sizeToCopy;
                dctxPtr->tmpInSize += sizeToCopy;
                if (dctxPtr->tmpInSize < dctxPtr->tmpInTarget) { /* not enough input to get full sBlockSize; wait for more */
                    nextSrcSizeHint = dctxPtr->tmpInTarget - dctxPtr->tmpInSize;
                    doAnotherStage = 0;
                    break;
                }
                selectedIn = dctxPtr->header + 4;
            }

        /* case dstage_decodeSFrameSize: */   /* no direct access */
            {   size_t const SFrameSize = LZ4F_readLE32(selectedIn);
                dctxPtr->frameInfo.contentSize = SFrameSize;
                dctxPtr->tmpInTarget = SFrameSize;
                dctxPtr->dStage = dstage_skipSkippable;
                break;
            }

        case dstage_skipSkippable:
            {   size_t skipSize = dctxPtr->tmpInTarget;
                if (skipSize > (size_t)(srcEnd-srcPtr)) skipSize = srcEnd-srcPtr;
                srcPtr += skipSize;
                dctxPtr->tmpInTarget -= skipSize;
                doAnotherStage = 0;
                nextSrcSizeHint = dctxPtr->tmpInTarget;
                if (nextSrcSizeHint) break;
                dctxPtr->dStage = dstage_getHeader;
                break;
            }
        }
    }

    /* preserve dictionary within tmp if necessary */
    if ( (dctxPtr->frameInfo.blockMode==LZ4F_blockLinked)
        &&(dctxPtr->dict != dctxPtr->tmpOutBuffer)
        &&(!decompressOptionsPtr->stableDst)
        &&((unsigned)(dctxPtr->dStage-1) < (unsigned)(dstage_getSuffix-1))
        )
    {
        if (dctxPtr->dStage == dstage_flushOut) {
            size_t preserveSize = dctxPtr->tmpOut - dctxPtr->tmpOutBuffer;
            size_t copySize = 64 KB - dctxPtr->tmpOutSize;
            const BYTE* oldDictEnd = dctxPtr->dict + dctxPtr->dictSize - dctxPtr->tmpOutStart;
            if (dctxPtr->tmpOutSize > 64 KB) copySize = 0;
            if (copySize > preserveSize) copySize = preserveSize;

            memcpy(dctxPtr->tmpOutBuffer + preserveSize - copySize, oldDictEnd - copySize, copySize);

            dctxPtr->dict = dctxPtr->tmpOutBuffer;
            dctxPtr->dictSize = preserveSize + dctxPtr->tmpOutStart;
        } else {
            size_t newDictSize = dctxPtr->dictSize;
            const BYTE* oldDictEnd = dctxPtr->dict + dctxPtr->dictSize;
            if ((newDictSize) > 64 KB) newDictSize = 64 KB;

            memcpy(dctxPtr->tmpOutBuffer, oldDictEnd - newDictSize, newDictSize);

            dctxPtr->dict = dctxPtr->tmpOutBuffer;
            dctxPtr->dictSize = newDictSize;
            dctxPtr->tmpOut = dctxPtr->tmpOutBuffer + newDictSize;
        }
    }

    *srcSizePtr = (srcPtr - srcStart);
    *dstSizePtr = (dstPtr - dstStart);
    return nextSrcSizeHint;
}