tor-browser

lz4frame.c (91373B)

---

/*
* 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 v1.6.1 .
* This library rely upon memory management capabilities (malloc, free)
* provided either by <stdlib.h>,
* or redirected towards another library of user's choice
* (see Memory Routines below).
*/


/*-************************************
*  Compiler Options
**************************************/
#include <limits.h>
#ifdef _MSC_VER    /* Visual Studio */
#  pragma warning(disable : 4127)   /* disable: C4127: conditional expression is constant */
#endif


/*-************************************
*  Tuning parameters
**************************************/
/*
* LZ4F_HEAPMODE :
* Control how LZ4F_compressFrame allocates the Compression State,
* either on stack (0:default, fastest), or in memory heap (1:requires malloc()).
*/
#ifndef LZ4F_HEAPMODE
#  define LZ4F_HEAPMODE 0
#endif


/*-************************************
*  Library declarations
**************************************/
#define LZ4F_STATIC_LINKING_ONLY
#include "lz4frame.h"
#define LZ4_STATIC_LINKING_ONLY
#include "lz4.h"
#define LZ4_HC_STATIC_LINKING_ONLY
#include "lz4hc.h"
#define XXH_STATIC_LINKING_ONLY
#include "xxhash.h"


/*-************************************
*  Memory routines
**************************************/
/*
* User may redirect invocations of
* malloc(), calloc() and free()
* towards another library or solution of their choice
* by modifying below section.
**/

#include <string.h>   /* memset, memcpy, memmove */
#ifndef LZ4_SRC_INCLUDED  /* avoid redefinition when sources are coalesced */
#  define MEM_INIT(p,v,s)   memset((p),(v),(s))
#endif

#ifndef LZ4_SRC_INCLUDED   /* avoid redefinition when sources are coalesced */
#  include <stdlib.h>   /* malloc, calloc, free */
#  define ALLOC(s)          malloc(s)
#  define ALLOC_AND_ZERO(s) calloc(1,(s))
#  define FREEMEM(p)        free(p)
#endif

static void* LZ4F_calloc(size_t s, LZ4F_CustomMem cmem)
{
   /* custom calloc defined : use it */
   if (cmem.customCalloc != NULL) {
       return cmem.customCalloc(cmem.opaqueState, s);
   }
   /* nothing defined : use default <stdlib.h>'s calloc() */
   if (cmem.customAlloc == NULL) {
       return ALLOC_AND_ZERO(s);
   }
   /* only custom alloc defined : use it, and combine it with memset() */
   {   void* const p = cmem.customAlloc(cmem.opaqueState, s);
       if (p != NULL) MEM_INIT(p, 0, s);
       return p;
}   }

static void* LZ4F_malloc(size_t s, LZ4F_CustomMem cmem)
{
   /* custom malloc defined : use it */
   if (cmem.customAlloc != NULL) {
       return cmem.customAlloc(cmem.opaqueState, s);
   }
   /* nothing defined : use default <stdlib.h>'s malloc() */
   return ALLOC(s);
}

static void LZ4F_free(void* p, LZ4F_CustomMem cmem)
{
   if (p == NULL) return;
   if (cmem.customFree != NULL) {
       /* custom allocation defined : use it */
       cmem.customFree(cmem.opaqueState, p);
       return;
   }
   /* nothing defined : use default <stdlib.h>'s free() */
   FREEMEM(p);
}


/*-************************************
*  Debug
**************************************/
#if defined(LZ4_DEBUG) && (LZ4_DEBUG>=1)
#  include <assert.h>
#else
#  ifndef assert
#    define assert(condition) ((void)0)
#  endif
#endif

#define LZ4F_STATIC_ASSERT(c)    { enum { LZ4F_static_assert = 1/(int)(!!(c)) }; }   /* use only *after* variable declarations */

#if defined(LZ4_DEBUG) && (LZ4_DEBUG>=2) && !defined(DEBUGLOG)
#  include <stdio.h>
static int g_debuglog_enable = 1;
#  define DEBUGLOG(l, ...) {                                  \
               if ((g_debuglog_enable) && (l<=LZ4_DEBUG)) {  \
                   fprintf(stderr, __FILE__ " (%i): ", __LINE__ );  \
                   fprintf(stderr, __VA_ARGS__);             \
                   fprintf(stderr, " \n");                   \
           }   }
#else
#  define DEBUGLOG(l, ...)      {}    /* disabled */
#endif


/*-************************************
*  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 endianness & alignment issues */
static U32 LZ4F_readLE32 (const void* src)
{
   const BYTE* const srcPtr = (const BYTE*)src;
   U32 value32 = srcPtr[0];
   value32 |= ((U32)srcPtr[1])<< 8;
   value32 |= ((U32)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
**************************************/
#ifndef LZ4_SRC_INCLUDED   /* avoid double definition */
#  define KB *(1<<10)
#  define MB *(1<<20)
#  define GB *(1<<30)
#endif

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

#define LZ4F_BLOCKUNCOMPRESSED_FLAG 0x80000000U
#define LZ4F_BLOCKSIZEID_DEFAULT LZ4F_max64KB

static const size_t minFHSize = LZ4F_HEADER_SIZE_MIN;   /*  7 */
static const size_t maxFHSize = LZ4F_HEADER_SIZE_MAX;   /* 19 */
static const size_t BHSize = LZ4F_BLOCK_HEADER_SIZE;  /* block header : size, and compress flag */
static const size_t BFSize = LZ4F_BLOCK_CHECKSUM_SIZE;  /* block footer : checksum (optional) */


/*-************************************
*  Structures and local types
**************************************/

typedef enum { LZ4B_COMPRESSED, LZ4B_UNCOMPRESSED} LZ4F_BlockCompressMode_e;
typedef enum { ctxNone, ctxFast, ctxHC } LZ4F_CtxType_e;

typedef struct LZ4F_cctx_s
{
   LZ4F_CustomMem cmem;
   LZ4F_preferences_t prefs;
   U32    version;
   U32    cStage;     /* 0 : compression uninitialized ; 1 : initialized, can compress */
   const LZ4F_CDict* cdict;
   size_t maxBlockSize;
   size_t maxBufferSize;
   BYTE*  tmpBuff;    /* internal buffer, for streaming */
   BYTE*  tmpIn;      /* starting position of data compress within internal buffer (>= tmpBuff) */
   size_t tmpInSize;  /* amount of data to compress after tmpIn */
   U64    totalInSize;
   XXH32_state_t xxh;
   void*  lz4CtxPtr;
   U16    lz4CtxAlloc; /* sized for: 0 = none, 1 = lz4 ctx, 2 = lz4hc ctx */
   U16    lz4CtxType;  /* in use as: 0 = none, 1 = lz4 ctx, 2 = lz4hc ctx */
   LZ4F_BlockCompressMode_e  blockCompressMode;
} 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;
}

LZ4F_errorCodes LZ4F_getErrorCode(size_t functionResult)
{
   if (!LZ4F_isError(functionResult)) return LZ4F_OK_NoError;
   return (LZ4F_errorCodes)(-(ptrdiff_t)functionResult);
}

static LZ4F_errorCode_t LZ4F_returnErrorCode(LZ4F_errorCodes code)
{
   /* A compilation error here means sizeof(ptrdiff_t) is not large enough */
   LZ4F_STATIC_ASSERT(sizeof(ptrdiff_t) >= sizeof(size_t));
   return (LZ4F_errorCode_t)-(ptrdiff_t)code;
}

#define RETURN_ERROR(e) return LZ4F_returnErrorCode(LZ4F_ERROR_ ## e)

#define RETURN_ERROR_IF(c,e) do {  \
       if (c) {                   \
           DEBUGLOG(3, "Error: " #c); \
           RETURN_ERROR(e);       \
       }                          \
   } while (0)

#define FORWARD_IF_ERROR(r) do { if (LZ4F_isError(r)) return (r); } while (0)

unsigned LZ4F_getVersion(void) { return LZ4F_VERSION; }

int LZ4F_compressionLevel_max(void) { return LZ4HC_CLEVEL_MAX; }

size_t LZ4F_getBlockSize(LZ4F_blockSizeID_t blockSizeID)
{
   static const size_t blockSizes[4] = { 64 KB, 256 KB, 1 MB, 4 MB };

   if (blockSizeID == 0) blockSizeID = LZ4F_BLOCKSIZEID_DEFAULT;
   if (blockSizeID < LZ4F_max64KB || blockSizeID > LZ4F_max4MB)
       RETURN_ERROR(maxBlockSize_invalid);
   {   int const blockSizeIdx = (int)blockSizeID - (int)LZ4F_max64KB;
       return blockSizes[blockSizeIdx];
}   }

/*-************************************
*  Private functions
**************************************/
#define MIN(a,b)   ( (a) < (b) ? (a) : (b) )

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


/*-************************************
*  Simple-pass 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;
}

/*! LZ4F_compressBound_internal() :
*  Provides dstCapacity given a srcSize to guarantee operation success in worst case situations.
*  prefsPtr is optional : if NULL is provided, preferences will be set to cover worst case scenario.
* @return is always the same for a srcSize and prefsPtr, so it can be relied upon to size reusable buffers.
*  When srcSize==0, LZ4F_compressBound() provides an upper bound for LZ4F_flush() and LZ4F_compressEnd() operations.
*/
static size_t LZ4F_compressBound_internal(size_t srcSize,
                                   const LZ4F_preferences_t* preferencesPtr,
                                         size_t alreadyBuffered)
{
   LZ4F_preferences_t prefsNull = LZ4F_INIT_PREFERENCES;
   prefsNull.frameInfo.contentChecksumFlag = LZ4F_contentChecksumEnabled;   /* worst case */
   prefsNull.frameInfo.blockChecksumFlag = LZ4F_blockChecksumEnabled;   /* worst case */
   {   const LZ4F_preferences_t* const prefsPtr = (preferencesPtr==NULL) ? &prefsNull : preferencesPtr;
       U32 const flush = prefsPtr->autoFlush | (srcSize==0);
       LZ4F_blockSizeID_t const blockID = prefsPtr->frameInfo.blockSizeID;
       size_t const blockSize = LZ4F_getBlockSize(blockID);
       size_t const maxBuffered = blockSize - 1;
       size_t const bufferedSize = MIN(alreadyBuffered, maxBuffered);
       size_t const maxSrcSize = srcSize + bufferedSize;
       unsigned const nbFullBlocks = (unsigned)(maxSrcSize / blockSize);
       size_t const partialBlockSize = maxSrcSize & (blockSize-1);
       size_t const lastBlockSize = flush ? partialBlockSize : 0;
       unsigned const nbBlocks = nbFullBlocks + (lastBlockSize>0);

       size_t const blockCRCSize = BFSize * prefsPtr->frameInfo.blockChecksumFlag;
       size_t const frameEnd = BHSize + (prefsPtr->frameInfo.contentChecksumFlag*BFSize);

       return ((BHSize + blockCRCSize) * nbBlocks) +
              (blockSize * nbFullBlocks) + lastBlockSize + frameEnd;
   }
}

size_t LZ4F_compressFrameBound(size_t srcSize, const LZ4F_preferences_t* preferencesPtr)
{
   LZ4F_preferences_t prefs;
   size_t const headerSize = maxFHSize;      /* max header size, including optional fields */

   if (preferencesPtr!=NULL) prefs = *preferencesPtr;
   else MEM_INIT(&prefs, 0, sizeof(prefs));
   prefs.autoFlush = 1;

   return headerSize + LZ4F_compressBound_internal(srcSize, &prefs, 0);;
}


/*! LZ4F_compressFrame_usingCDict() :
*  Compress srcBuffer using a dictionary, in a single step.
*  cdict can be NULL, in which case, no dictionary is used.
*  dstBuffer MUST be >= LZ4F_compressFrameBound(srcSize, preferencesPtr).
*  The LZ4F_preferences_t structure is optional : you may provide NULL as argument,
*  however, it's the only way to provide a dictID, so it's not recommended.
* @return : number of bytes written into dstBuffer,
*           or an error code if it fails (can be tested using LZ4F_isError())
*/
size_t LZ4F_compressFrame_usingCDict(LZ4F_cctx* cctx,
                                    void* dstBuffer, size_t dstCapacity,
                              const void* srcBuffer, size_t srcSize,
                              const LZ4F_CDict* cdict,
                              const LZ4F_preferences_t* preferencesPtr)
{
   LZ4F_preferences_t prefs;
   LZ4F_compressOptions_t options;
   BYTE* const dstStart = (BYTE*) dstBuffer;
   BYTE* dstPtr = dstStart;
   BYTE* const dstEnd = dstStart + dstCapacity;

   DEBUGLOG(4, "LZ4F_compressFrame_usingCDict (srcSize=%u)", (unsigned)srcSize);
   if (preferencesPtr!=NULL)
       prefs = *preferencesPtr;
   else
       MEM_INIT(&prefs, 0, sizeof(prefs));
   if (prefs.frameInfo.contentSize != 0)
       prefs.frameInfo.contentSize = (U64)srcSize;   /* auto-correct content size if selected (!=0) */

   prefs.frameInfo.blockSizeID = LZ4F_optimalBSID(prefs.frameInfo.blockSizeID, srcSize);
   prefs.autoFlush = 1;
   if (srcSize <= LZ4F_getBlockSize(prefs.frameInfo.blockSizeID))
       prefs.frameInfo.blockMode = LZ4F_blockIndependent;   /* only one block => no need for inter-block link */

   MEM_INIT(&options, 0, sizeof(options));
   options.stableSrc = 1;

   RETURN_ERROR_IF(dstCapacity < LZ4F_compressFrameBound(srcSize, &prefs), dstMaxSize_tooSmall);

   { size_t const headerSize = LZ4F_compressBegin_usingCDict(cctx, dstBuffer, dstCapacity, cdict, &prefs);  /* write header */
     FORWARD_IF_ERROR(headerSize);
     dstPtr += headerSize;   /* header size */ }

   assert(dstEnd >= dstPtr);
   { size_t const cSize = LZ4F_compressUpdate(cctx, dstPtr, (size_t)(dstEnd-dstPtr), srcBuffer, srcSize, &options);
     FORWARD_IF_ERROR(cSize);
     dstPtr += cSize; }

   assert(dstEnd >= dstPtr);
   { size_t const tailSize = LZ4F_compressEnd(cctx, dstPtr, (size_t)(dstEnd-dstPtr), &options);   /* flush last block, and generate suffix */
     FORWARD_IF_ERROR(tailSize);
     dstPtr += tailSize; }

   assert(dstEnd >= dstStart);
   return (size_t)(dstPtr - dstStart);
}


/*! LZ4F_compressFrame() :
*  Compress an entire srcBuffer into a valid LZ4 frame, in a single step.
*  dstBuffer MUST be >= LZ4F_compressFrameBound(srcSize, preferencesPtr).
*  The LZ4F_preferences_t structure is optional : you can provide NULL as argument. All preferences will be set to default.
* @return : number of bytes written into dstBuffer.
*           or 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)
{
   size_t result;
#if (LZ4F_HEAPMODE)
   LZ4F_cctx_t* cctxPtr;
   result = LZ4F_createCompressionContext(&cctxPtr, LZ4F_VERSION);
   FORWARD_IF_ERROR(result);
#else
   LZ4F_cctx_t cctx;
   LZ4_stream_t lz4ctx;
   LZ4F_cctx_t* const cctxPtr = &cctx;

   MEM_INIT(&cctx, 0, sizeof(cctx));
   cctx.version = LZ4F_VERSION;
   cctx.maxBufferSize = 5 MB;   /* mess with real buffer size to prevent dynamic allocation; works only because autoflush==1 & stableSrc==1 */
   if ( preferencesPtr == NULL
     || preferencesPtr->compressionLevel < LZ4HC_CLEVEL_MIN ) {
       LZ4_initStream(&lz4ctx, sizeof(lz4ctx));
       cctxPtr->lz4CtxPtr = &lz4ctx;
       cctxPtr->lz4CtxAlloc = 1;
       cctxPtr->lz4CtxType = ctxFast;
   }
#endif
   DEBUGLOG(4, "LZ4F_compressFrame");

   result = LZ4F_compressFrame_usingCDict(cctxPtr, dstBuffer, dstCapacity,
                                          srcBuffer, srcSize,
                                          NULL, preferencesPtr);

#if (LZ4F_HEAPMODE)
   LZ4F_freeCompressionContext(cctxPtr);
#else
   if ( preferencesPtr != NULL
     && preferencesPtr->compressionLevel >= LZ4HC_CLEVEL_MIN ) {
       LZ4F_free(cctxPtr->lz4CtxPtr, cctxPtr->cmem);
   }
#endif
   return result;
}


/*-***************************************************
*   Dictionary compression
*****************************************************/

struct LZ4F_CDict_s {
   LZ4F_CustomMem cmem;
   void* dictContent;
   LZ4_stream_t* fastCtx;
   LZ4_streamHC_t* HCCtx;
}; /* typedef'd to LZ4F_CDict within lz4frame_static.h */

LZ4F_CDict*
LZ4F_createCDict_advanced(LZ4F_CustomMem cmem, const void* dictBuffer, size_t dictSize)
{
   const char* dictStart = (const char*)dictBuffer;
   LZ4F_CDict* const cdict = (LZ4F_CDict*)LZ4F_malloc(sizeof(*cdict), cmem);
   DEBUGLOG(4, "LZ4F_createCDict_advanced");
   if (!cdict) return NULL;
   cdict->cmem = cmem;
   if (dictSize > 64 KB) {
       dictStart += dictSize - 64 KB;
       dictSize = 64 KB;
   }
   cdict->dictContent = LZ4F_malloc(dictSize, cmem);
   /* note: using @cmem to allocate => can't use default create */
   cdict->fastCtx = (LZ4_stream_t*)LZ4F_malloc(sizeof(LZ4_stream_t), cmem);
   cdict->HCCtx = (LZ4_streamHC_t*)LZ4F_malloc(sizeof(LZ4_streamHC_t), cmem);
   if (!cdict->dictContent || !cdict->fastCtx || !cdict->HCCtx) {
       LZ4F_freeCDict(cdict);
       return NULL;
   }
   memcpy(cdict->dictContent, dictStart, dictSize);
   LZ4_initStream(cdict->fastCtx, sizeof(LZ4_stream_t));
   LZ4_loadDictSlow(cdict->fastCtx, (const char*)cdict->dictContent, (int)dictSize);
   LZ4_initStreamHC(cdict->HCCtx, sizeof(LZ4_streamHC_t));
   /* note: we don't know at this point which compression level is going to be used
    * as a consequence, HCCtx is created for the more common HC mode */
   LZ4_setCompressionLevel(cdict->HCCtx, LZ4HC_CLEVEL_DEFAULT);
   LZ4_loadDictHC(cdict->HCCtx, (const char*)cdict->dictContent, (int)dictSize);
   return cdict;
}

/*! LZ4F_createCDict() :
*  When compressing multiple messages / blocks with the same dictionary, it's recommended to load it just once.
*  LZ4F_createCDict() will create a digested dictionary, ready to start future compression operations without startup delay.
*  LZ4F_CDict can be created once and shared by multiple threads concurrently, since its usage is read-only.
* @dictBuffer can be released after LZ4F_CDict creation, since its content is copied within CDict
* @return : digested dictionary for compression, or NULL if failed */
LZ4F_CDict* LZ4F_createCDict(const void* dictBuffer, size_t dictSize)
{
   DEBUGLOG(4, "LZ4F_createCDict");
   return LZ4F_createCDict_advanced(LZ4F_defaultCMem, dictBuffer, dictSize);
}

void LZ4F_freeCDict(LZ4F_CDict* cdict)
{
   if (cdict==NULL) return;  /* support free on NULL */
   LZ4F_free(cdict->dictContent, cdict->cmem);
   LZ4F_free(cdict->fastCtx, cdict->cmem);
   LZ4F_free(cdict->HCCtx, cdict->cmem);
   LZ4F_free(cdict, cdict->cmem);
}


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

LZ4F_cctx*
LZ4F_createCompressionContext_advanced(LZ4F_CustomMem customMem, unsigned version)
{
   LZ4F_cctx* const cctxPtr =
       (LZ4F_cctx*)LZ4F_calloc(sizeof(LZ4F_cctx), customMem);
   if (cctxPtr==NULL) return NULL;

   cctxPtr->cmem = customMem;
   cctxPtr->version = version;
   cctxPtr->cStage = 0;   /* Uninitialized. Next stage : init cctx */

   return cctxPtr;
}

/*! 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 incompatible 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_cctx** LZ4F_compressionContextPtr, unsigned version)
{
   assert(LZ4F_compressionContextPtr != NULL); /* considered a violation of narrow contract */
   /* in case it nonetheless happen in production */
   RETURN_ERROR_IF(LZ4F_compressionContextPtr == NULL, parameter_null);

   *LZ4F_compressionContextPtr = LZ4F_createCompressionContext_advanced(LZ4F_defaultCMem, version);
   RETURN_ERROR_IF(*LZ4F_compressionContextPtr==NULL, allocation_failed);
   return LZ4F_OK_NoError;
}

LZ4F_errorCode_t LZ4F_freeCompressionContext(LZ4F_cctx* cctxPtr)
{
   if (cctxPtr != NULL) {  /* support free on NULL */
      LZ4F_free(cctxPtr->lz4CtxPtr, cctxPtr->cmem);  /* note: LZ4_streamHC_t and LZ4_stream_t are simple POD types */
      LZ4F_free(cctxPtr->tmpBuff, cctxPtr->cmem);
      LZ4F_free(cctxPtr, cctxPtr->cmem);
   }
   return LZ4F_OK_NoError;
}


/**
* This function prepares the internal LZ4(HC) stream for a new compression,
* resetting the context and attaching the dictionary, if there is one.
*
* It needs to be called at the beginning of each independent compression
* stream (i.e., at the beginning of a frame in blockLinked mode, or at the
* beginning of each block in blockIndependent mode).
*/
static void LZ4F_initStream(void* ctx,
                           const LZ4F_CDict* cdict,
                           int level,
                           LZ4F_blockMode_t blockMode) {
   if (level < LZ4HC_CLEVEL_MIN) {
       if (cdict || blockMode == LZ4F_blockLinked) {
           /* In these cases, we will call LZ4_compress_fast_continue(),
            * which needs an already reset context. Otherwise, we'll call a
            * one-shot API. The non-continued APIs internally perform their own
            * resets at the beginning of their calls, where they know what
            * tableType they need the context to be in. So in that case this
            * would be misguided / wasted work. */
           LZ4_resetStream_fast((LZ4_stream_t*)ctx);
           if (cdict)
               LZ4_attach_dictionary((LZ4_stream_t*)ctx, cdict->fastCtx);
       }
       /* In these cases, we'll call a one-shot API.
        * The non-continued APIs internally perform their own resets
        * at the beginning of their calls, where they know
        * which tableType they need the context to be in.
        * Therefore, a reset here would be wasted work. */
   } else {
       LZ4_resetStreamHC_fast((LZ4_streamHC_t*)ctx, level);
       if (cdict)
           LZ4_attach_HC_dictionary((LZ4_streamHC_t*)ctx, cdict->HCCtx);
   }
}

static int ctxTypeID_to_size(int ctxTypeID) {
   switch(ctxTypeID) {
   case 1:
       return LZ4_sizeofState();
   case 2:
       return LZ4_sizeofStateHC();
   default:
       return 0;
   }
}

/* LZ4F_compressBegin_internal()
* Note: only accepts @cdict _or_ @dictBuffer as non NULL.
*/
size_t LZ4F_compressBegin_internal(LZ4F_cctx* cctx,
                         void* dstBuffer, size_t dstCapacity,
                         const void* dictBuffer, size_t dictSize,
                         const LZ4F_CDict* cdict,
                         const LZ4F_preferences_t* preferencesPtr)
{
   LZ4F_preferences_t const prefNull = LZ4F_INIT_PREFERENCES;
   BYTE* const dstStart = (BYTE*)dstBuffer;
   BYTE* dstPtr = dstStart;

   RETURN_ERROR_IF(dstCapacity < maxFHSize, dstMaxSize_tooSmall);
   if (preferencesPtr == NULL) preferencesPtr = &prefNull;
   cctx->prefs = *preferencesPtr;

   /* cctx Management */
   {   U16 const ctxTypeID = (cctx->prefs.compressionLevel < LZ4HC_CLEVEL_MIN) ? 1 : 2;
       int requiredSize = ctxTypeID_to_size(ctxTypeID);
       int allocatedSize = ctxTypeID_to_size(cctx->lz4CtxAlloc);
       if (allocatedSize < requiredSize) {
           /* not enough space allocated */
           LZ4F_free(cctx->lz4CtxPtr, cctx->cmem);
           if (cctx->prefs.compressionLevel < LZ4HC_CLEVEL_MIN) {
               /* must take ownership of memory allocation,
                * in order to respect custom allocator contract */
               cctx->lz4CtxPtr = LZ4F_malloc(sizeof(LZ4_stream_t), cctx->cmem);
               if (cctx->lz4CtxPtr)
                   LZ4_initStream(cctx->lz4CtxPtr, sizeof(LZ4_stream_t));
           } else {
               cctx->lz4CtxPtr = LZ4F_malloc(sizeof(LZ4_streamHC_t), cctx->cmem);
               if (cctx->lz4CtxPtr)
                   LZ4_initStreamHC(cctx->lz4CtxPtr, sizeof(LZ4_streamHC_t));
           }
           RETURN_ERROR_IF(cctx->lz4CtxPtr == NULL, allocation_failed);
           cctx->lz4CtxAlloc = ctxTypeID;
           cctx->lz4CtxType = ctxTypeID;
       } else if (cctx->lz4CtxType != ctxTypeID) {
           /* otherwise, a sufficient buffer is already allocated,
            * but we need to reset it to the correct context type */
           if (cctx->prefs.compressionLevel < LZ4HC_CLEVEL_MIN) {
               LZ4_initStream((LZ4_stream_t*)cctx->lz4CtxPtr, sizeof(LZ4_stream_t));
           } else {
               LZ4_initStreamHC((LZ4_streamHC_t*)cctx->lz4CtxPtr, sizeof(LZ4_streamHC_t));
               LZ4_setCompressionLevel((LZ4_streamHC_t*)cctx->lz4CtxPtr, cctx->prefs.compressionLevel);
           }
           cctx->lz4CtxType = ctxTypeID;
   }   }

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

   {   size_t const requiredBuffSize = preferencesPtr->autoFlush ?
               ((cctx->prefs.frameInfo.blockMode == LZ4F_blockLinked) ? 64 KB : 0) :  /* only needs past data up to window size */
               cctx->maxBlockSize + ((cctx->prefs.frameInfo.blockMode == LZ4F_blockLinked) ? 128 KB : 0);

       if (cctx->maxBufferSize < requiredBuffSize) {
           cctx->maxBufferSize = 0;
           LZ4F_free(cctx->tmpBuff, cctx->cmem);
           cctx->tmpBuff = (BYTE*)LZ4F_malloc(requiredBuffSize, cctx->cmem);
           RETURN_ERROR_IF(cctx->tmpBuff == NULL, allocation_failed);
           cctx->maxBufferSize = requiredBuffSize;
   }   }
   cctx->tmpIn = cctx->tmpBuff;
   cctx->tmpInSize = 0;
   (void)XXH32_reset(&(cctx->xxh), 0);

   /* context init */
   cctx->cdict = cdict;
   if (cctx->prefs.frameInfo.blockMode == LZ4F_blockLinked) {
       /* frame init only for blockLinked : blockIndependent will be init at each block */
       LZ4F_initStream(cctx->lz4CtxPtr, cdict, cctx->prefs.compressionLevel, LZ4F_blockLinked);
   }
   if (preferencesPtr->compressionLevel >= LZ4HC_CLEVEL_MIN) {
       LZ4_favorDecompressionSpeed((LZ4_streamHC_t*)cctx->lz4CtxPtr, (int)preferencesPtr->favorDecSpeed);
   }
   if (dictBuffer) {
       assert(cdict == NULL);
       RETURN_ERROR_IF(dictSize > INT_MAX, parameter_invalid);
       if (cctx->lz4CtxType == ctxFast) {
           /* lz4 fast*/
           LZ4_loadDict((LZ4_stream_t*)cctx->lz4CtxPtr, (const char*)dictBuffer, (int)dictSize);
       } else {
           /* lz4hc */
           assert(cctx->lz4CtxType == ctxHC);
           LZ4_loadDictHC((LZ4_streamHC_t*)cctx->lz4CtxPtr, (const char*)dictBuffer, (int)dictSize);
       }
   }

   /* Stage 2 : Write Frame Header */

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

       /* FLG Byte */
       *dstPtr++ = (BYTE)(((1 & _2BITS) << 6)    /* Version('01') */
           + ((cctx->prefs.frameInfo.blockMode & _1BIT ) << 5)
           + ((cctx->prefs.frameInfo.blockChecksumFlag & _1BIT ) << 4)
           + ((unsigned)(cctx->prefs.frameInfo.contentSize > 0) << 3)
           + ((cctx->prefs.frameInfo.contentChecksumFlag & _1BIT ) << 2)
           +  (cctx->prefs.frameInfo.dictID > 0) );
       /* BD Byte */
       *dstPtr++ = (BYTE)((cctx->prefs.frameInfo.blockSizeID & _3BITS) << 4);
       /* Optional Frame content size field */
       if (cctx->prefs.frameInfo.contentSize) {
           LZ4F_writeLE64(dstPtr, cctx->prefs.frameInfo.contentSize);
           dstPtr += 8;
           cctx->totalInSize = 0;
       }
       /* Optional dictionary ID field */
       if (cctx->prefs.frameInfo.dictID) {
           LZ4F_writeLE32(dstPtr, cctx->prefs.frameInfo.dictID);
           dstPtr += 4;
       }
       /* Header CRC Byte */
       *dstPtr = LZ4F_headerChecksum(headerStart, (size_t)(dstPtr - headerStart));
       dstPtr++;
   }

   cctx->cStage = 1;   /* header written, now request input data block */
   return (size_t)(dstPtr - dstStart);
}

size_t LZ4F_compressBegin(LZ4F_cctx* cctx,
                         void* dstBuffer, size_t dstCapacity,
                         const LZ4F_preferences_t* preferencesPtr)
{
   return LZ4F_compressBegin_internal(cctx, dstBuffer, dstCapacity,
                                       NULL, 0,
                                       NULL, preferencesPtr);
}

/* LZ4F_compressBegin_usingDictOnce:
* Hidden implementation,
* employed for multi-threaded compression
* when frame defines linked blocks */
size_t LZ4F_compressBegin_usingDictOnce(LZ4F_cctx* cctx,
                         void* dstBuffer, size_t dstCapacity,
                         const void* dict, size_t dictSize,
                         const LZ4F_preferences_t* preferencesPtr)
{
   return LZ4F_compressBegin_internal(cctx, dstBuffer, dstCapacity,
                                       dict, dictSize,
                                       NULL, preferencesPtr);
}

size_t LZ4F_compressBegin_usingDict(LZ4F_cctx* cctx,
                         void* dstBuffer, size_t dstCapacity,
                         const void* dict, size_t dictSize,
                         const LZ4F_preferences_t* preferencesPtr)
{
   /* note : incorrect implementation :
    * this will only use the dictionary once,
    * instead of once *per* block when frames defines independent blocks */
   return LZ4F_compressBegin_usingDictOnce(cctx, dstBuffer, dstCapacity,
                                       dict, dictSize,
                                       preferencesPtr);
}

size_t LZ4F_compressBegin_usingCDict(LZ4F_cctx* cctx,
                         void* dstBuffer, size_t dstCapacity,
                         const LZ4F_CDict* cdict,
                         const LZ4F_preferences_t* preferencesPtr)
{
   return LZ4F_compressBegin_internal(cctx, dstBuffer, dstCapacity,
                                       NULL, 0,
                                      cdict, preferencesPtr);
}


/*  LZ4F_compressBound() :
* @return minimum capacity of dstBuffer for a given srcSize to handle worst case scenario.
*  LZ4F_preferences_t structure is optional : if NULL, preferences will be set to cover worst case scenario.
*  This function cannot fail.
*/
size_t LZ4F_compressBound(size_t srcSize, const LZ4F_preferences_t* preferencesPtr)
{
   if (preferencesPtr && preferencesPtr->autoFlush) {
       return LZ4F_compressBound_internal(srcSize, preferencesPtr, 0);
   }
   return LZ4F_compressBound_internal(srcSize, preferencesPtr, (size_t)-1);
}


typedef int (*compressFunc_t)(void* ctx, const char* src, char* dst, int srcSize, int dstSize, int level, const LZ4F_CDict* cdict);


/*! LZ4F_makeBlock():
*  compress a single block, add header and optional checksum.
*  assumption : dst buffer capacity is >= BHSize + srcSize + crcSize
*/
static size_t LZ4F_makeBlock(void* dst,
                      const void* src, size_t srcSize,
                            compressFunc_t compress, void* lz4ctx, int level,
                      const LZ4F_CDict* cdict,
                            LZ4F_blockChecksum_t crcFlag)
{
   BYTE* const cSizePtr = (BYTE*)dst;
   U32 cSize;
   assert(compress != NULL);
   cSize = (U32)compress(lz4ctx, (const char*)src, (char*)(cSizePtr+BHSize),
                         (int)(srcSize), (int)(srcSize-1),
                         level, cdict);

   if (cSize == 0 || cSize >= srcSize) {
       cSize = (U32)srcSize;
       LZ4F_writeLE32(cSizePtr, cSize | LZ4F_BLOCKUNCOMPRESSED_FLAG);
       memcpy(cSizePtr+BHSize, src, srcSize);
   } else {
       LZ4F_writeLE32(cSizePtr, cSize);
   }
   if (crcFlag) {
       U32 const crc32 = XXH32(cSizePtr+BHSize, cSize, 0);  /* checksum of compressed data */
       LZ4F_writeLE32(cSizePtr+BHSize+cSize, crc32);
   }
   return BHSize + cSize + ((U32)crcFlag)*BFSize;
}


static int LZ4F_compressBlock(void* ctx, const char* src, char* dst, int srcSize, int dstCapacity, int level, const LZ4F_CDict* cdict)
{
   int const acceleration = (level < 0) ? -level + 1 : 1;
   DEBUGLOG(5, "LZ4F_compressBlock (srcSize=%i)", srcSize);
   LZ4F_initStream(ctx, cdict, level, LZ4F_blockIndependent);
   if (cdict) {
       return LZ4_compress_fast_continue((LZ4_stream_t*)ctx, src, dst, srcSize, dstCapacity, acceleration);
   } else {
       return LZ4_compress_fast_extState_fastReset(ctx, src, dst, srcSize, dstCapacity, acceleration);
   }
}

static int LZ4F_compressBlock_continue(void* ctx, const char* src, char* dst, int srcSize, int dstCapacity, int level, const LZ4F_CDict* cdict)
{
   int const acceleration = (level < 0) ? -level + 1 : 1;
   (void)cdict; /* init once at beginning of frame */
   DEBUGLOG(5, "LZ4F_compressBlock_continue (srcSize=%i)", srcSize);
   return LZ4_compress_fast_continue((LZ4_stream_t*)ctx, src, dst, srcSize, dstCapacity, acceleration);
}

static int LZ4F_compressBlockHC(void* ctx, const char* src, char* dst, int srcSize, int dstCapacity, int level, const LZ4F_CDict* cdict)
{
   LZ4F_initStream(ctx, cdict, level, LZ4F_blockIndependent);
   if (cdict) {
       return LZ4_compress_HC_continue((LZ4_streamHC_t*)ctx, src, dst, srcSize, dstCapacity);
   }
   return LZ4_compress_HC_extStateHC_fastReset(ctx, src, dst, srcSize, dstCapacity, level);
}

static int LZ4F_compressBlockHC_continue(void* ctx, const char* src, char* dst, int srcSize, int dstCapacity, int level, const LZ4F_CDict* cdict)
{
   (void)level; (void)cdict; /* init once at beginning of frame */
   return LZ4_compress_HC_continue((LZ4_streamHC_t*)ctx, src, dst, srcSize, dstCapacity);
}

static int LZ4F_doNotCompressBlock(void* ctx, const char* src, char* dst, int srcSize, int dstCapacity, int level, const LZ4F_CDict* cdict)
{
   (void)ctx; (void)src; (void)dst; (void)srcSize; (void)dstCapacity; (void)level; (void)cdict;
   return 0;
}

static compressFunc_t LZ4F_selectCompression(LZ4F_blockMode_t blockMode, int level, LZ4F_BlockCompressMode_e  compressMode)
{
   if (compressMode == LZ4B_UNCOMPRESSED)
       return LZ4F_doNotCompressBlock;
   if (level < LZ4HC_CLEVEL_MIN) {
       if (blockMode == LZ4F_blockIndependent) return LZ4F_compressBlock;
       return LZ4F_compressBlock_continue;
   }
   if (blockMode == LZ4F_blockIndependent) return LZ4F_compressBlockHC;
   return LZ4F_compressBlockHC_continue;
}

/* Save history (up to 64KB) into @tmpBuff */
static int LZ4F_localSaveDict(LZ4F_cctx_t* cctxPtr)
{
   if (cctxPtr->prefs.compressionLevel < LZ4HC_CLEVEL_MIN)
       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;

static const LZ4F_compressOptions_t k_cOptionsNull = { 0, { 0, 0, 0 } };


/*! LZ4F_compressUpdateImpl() :
*  LZ4F_compressUpdate() can be called repetitively to compress as much data as necessary.
*  When successful, the function always entirely consumes @srcBuffer.
*  src data is either buffered or compressed into @dstBuffer.
*  If the block compression does not match the compression of the previous block, the old data is flushed
*  and operations continue with the new compression mode.
* @dstCapacity MUST be >= LZ4F_compressBound(srcSize, preferencesPtr) when block compression is turned on.
* @compressOptionsPtr is optional : provide NULL to mean "default".
* @return : the number of bytes written into dstBuffer. It can be zero, meaning input data was just buffered.
*           or an error code if it fails (which can be tested using LZ4F_isError())
*  After an error, the state is left in a UB state, and must be re-initialized.
*/
static size_t LZ4F_compressUpdateImpl(LZ4F_cctx* cctxPtr,
                    void* dstBuffer, size_t dstCapacity,
                    const void* srcBuffer, size_t srcSize,
                    const LZ4F_compressOptions_t* compressOptionsPtr,
                    LZ4F_BlockCompressMode_e blockCompression)
 {
   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 const compress = LZ4F_selectCompression(cctxPtr->prefs.frameInfo.blockMode, cctxPtr->prefs.compressionLevel, blockCompression);
   size_t bytesWritten;
   DEBUGLOG(4, "LZ4F_compressUpdate (srcSize=%zu)", srcSize);

   RETURN_ERROR_IF(cctxPtr->cStage != 1, compressionState_uninitialized);   /* state must be initialized and waiting for next block */
   if (dstCapacity < LZ4F_compressBound_internal(srcSize, &(cctxPtr->prefs), cctxPtr->tmpInSize))
       RETURN_ERROR(dstMaxSize_tooSmall);

   if (blockCompression == LZ4B_UNCOMPRESSED && dstCapacity < srcSize)
       RETURN_ERROR(dstMaxSize_tooSmall);

   /* flush currently written block, to continue with new block compression */
   if (cctxPtr->blockCompressMode != blockCompression) {
       bytesWritten = LZ4F_flush(cctxPtr, dstBuffer, dstCapacity, compressOptionsPtr);
       dstPtr += bytesWritten;
       cctxPtr->blockCompressMode = blockCompression;
   }

   if (compressOptionsPtr == NULL) compressOptionsPtr = &k_cOptionsNull;

   /* complete tmp buffer */
   if (cctxPtr->tmpInSize > 0) {   /* some data already within tmp buffer */
       size_t const sizeToCopy = blockSize - cctxPtr->tmpInSize;
       assert(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_makeBlock(dstPtr,
                                    cctxPtr->tmpIn, blockSize,
                                    compress, cctxPtr->lz4CtxPtr, cctxPtr->prefs.compressionLevel,
                                    cctxPtr->cdict,
                                    cctxPtr->prefs.frameInfo.blockChecksumFlag);
           if (cctxPtr->prefs.frameInfo.blockMode==LZ4F_blockLinked) cctxPtr->tmpIn += blockSize;
           cctxPtr->tmpInSize = 0;
   }   }

   while ((size_t)(srcEnd - srcPtr) >= blockSize) {
       /* compress full blocks */
       lastBlockCompressed = fromSrcBuffer;
       dstPtr += LZ4F_makeBlock(dstPtr,
                                srcPtr, blockSize,
                                compress, cctxPtr->lz4CtxPtr, cctxPtr->prefs.compressionLevel,
                                cctxPtr->cdict,
                                cctxPtr->prefs.frameInfo.blockChecksumFlag);
       srcPtr += blockSize;
   }

   if ((cctxPtr->prefs.autoFlush) && (srcPtr < srcEnd)) {
       /* autoFlush : remaining input (< blockSize) is compressed */
       lastBlockCompressed = fromSrcBuffer;
       dstPtr += LZ4F_makeBlock(dstPtr,
                                srcPtr, (size_t)(srcEnd - srcPtr),
                                compress, cctxPtr->lz4CtxPtr, cctxPtr->prefs.compressionLevel,
                                cctxPtr->cdict,
                                cctxPtr->prefs.frameInfo.blockChecksumFlag);
       srcPtr = srcEnd;
   }

   /* preserve dictionary within @tmpBuff whenever necessary */
   if ((cctxPtr->prefs.frameInfo.blockMode==LZ4F_blockLinked) && (lastBlockCompressed==fromSrcBuffer)) {
       /* linked blocks are only supported in compressed mode, see LZ4F_uncompressedUpdate */
       assert(blockCompression == LZ4B_COMPRESSED);
       if (compressOptionsPtr->stableSrc) {
           cctxPtr->tmpIn = cctxPtr->tmpBuff;  /* src is stable : dictionary remains in src across invocations */
       } else {
           int const realDictSize = LZ4F_localSaveDict(cctxPtr);
           assert(0 <= realDictSize && realDictSize <= 64 KB);
           cctxPtr->tmpIn = cctxPtr->tmpBuff + realDictSize;
       }
   }

   /* keep tmpIn within limits */
   if (!(cctxPtr->prefs.autoFlush)  /* no autoflush : there may be some data left within internal buffer */
     && (cctxPtr->tmpIn + blockSize) > (cctxPtr->tmpBuff + cctxPtr->maxBufferSize) )  /* not enough room to store next block */
   {
       /* only preserve 64KB within internal buffer. Ensures there is enough room for next block.
        * note: this situation necessarily implies lastBlockCompressed==fromTmpBuffer */
       int const realDictSize = LZ4F_localSaveDict(cctxPtr);
       cctxPtr->tmpIn = cctxPtr->tmpBuff + realDictSize;
       assert((cctxPtr->tmpIn + blockSize) <= (cctxPtr->tmpBuff + cctxPtr->maxBufferSize));
   }

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

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

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

/*! LZ4F_compressUpdate() :
*  LZ4F_compressUpdate() can be called repetitively to compress as much data as necessary.
*  When successful, the function always entirely consumes @srcBuffer.
*  src data is either buffered or compressed into @dstBuffer.
*  If previously an uncompressed block was written, buffered data is flushed
*  before appending compressed data is continued.
* @dstCapacity MUST be >= LZ4F_compressBound(srcSize, preferencesPtr).
* @compressOptionsPtr is optional : provide NULL to mean "default".
* @return : the number of bytes written into dstBuffer. It can be zero, meaning input data was just buffered.
*           or an error code if it fails (which can be tested using LZ4F_isError())
*  After an error, the state is left in a UB state, and must be re-initialized.
*/
size_t LZ4F_compressUpdate(LZ4F_cctx* cctxPtr,
                          void* dstBuffer, size_t dstCapacity,
                    const void* srcBuffer, size_t srcSize,
                    const LZ4F_compressOptions_t* compressOptionsPtr)
{
    return LZ4F_compressUpdateImpl(cctxPtr,
                                  dstBuffer, dstCapacity,
                                  srcBuffer, srcSize,
                                  compressOptionsPtr, LZ4B_COMPRESSED);
}

/*! LZ4F_uncompressedUpdate() :
*  Same as LZ4F_compressUpdate(), but requests blocks to be sent uncompressed.
*  This symbol is only supported when LZ4F_blockIndependent is used
* @dstCapacity MUST be >= LZ4F_compressBound(srcSize, preferencesPtr).
* @compressOptionsPtr is optional : provide NULL to mean "default".
* @return : the number of bytes written into dstBuffer. It can be zero, meaning input data was just buffered.
*           or an error code if it fails (which can be tested using LZ4F_isError())
*  After an error, the state is left in a UB state, and must be re-initialized.
*/
size_t LZ4F_uncompressedUpdate(LZ4F_cctx* cctxPtr,
                              void* dstBuffer, size_t dstCapacity,
                        const void* srcBuffer, size_t srcSize,
                        const LZ4F_compressOptions_t* compressOptionsPtr)
{
   return LZ4F_compressUpdateImpl(cctxPtr,
                                  dstBuffer, dstCapacity,
                                  srcBuffer, srcSize,
                                  compressOptionsPtr, LZ4B_UNCOMPRESSED);
}


/*! LZ4F_flush() :
*  When compressed data must be sent immediately, without waiting for a block to be filled,
*  invoke LZ4_flush(), which will immediately compress any remaining data stored within LZ4F_cctx.
*  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 LZ4F_cctx.
*  The function outputs an error code if it fails (can be tested using LZ4F_isError())
*  LZ4F_compressOptions_t* is optional. NULL is a valid argument.
*/
size_t LZ4F_flush(LZ4F_cctx* cctxPtr,
                 void* dstBuffer, size_t dstCapacity,
           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 */
   RETURN_ERROR_IF(cctxPtr->cStage != 1, compressionState_uninitialized);
   RETURN_ERROR_IF(dstCapacity < (cctxPtr->tmpInSize + BHSize + BFSize), dstMaxSize_tooSmall);
   (void)compressOptionsPtr;   /* not useful (yet) */

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

   /* compress tmp buffer */
   dstPtr += LZ4F_makeBlock(dstPtr,
                            cctxPtr->tmpIn, cctxPtr->tmpInSize,
                            compress, cctxPtr->lz4CtxPtr, cctxPtr->prefs.compressionLevel,
                            cctxPtr->cdict,
                            cctxPtr->prefs.frameInfo.blockChecksumFlag);
   assert(((void)"flush overflows dstBuffer!", (size_t)(dstPtr - dstStart) <= dstCapacity));

   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 const realDictSize = LZ4F_localSaveDict(cctxPtr);
       cctxPtr->tmpIn = cctxPtr->tmpBuff + realDictSize;
   }

   return (size_t)(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 an (optional) checksum.
*  LZ4F_compressOptions_t structure is optional : you can provide NULL as argument.
* @return: the number of bytes written into dstBuffer (necessarily >= 4 (endMark size))
*       or an error code if it fails (can be tested using LZ4F_isError())
*  The context can then be used again to compress a new frame, starting with LZ4F_compressBegin().
*/
size_t LZ4F_compressEnd(LZ4F_cctx* cctxPtr,
                       void* dstBuffer, size_t dstCapacity,
                 const LZ4F_compressOptions_t* compressOptionsPtr)
{
   BYTE* const dstStart = (BYTE*)dstBuffer;
   BYTE* dstPtr = dstStart;

   size_t const flushSize = LZ4F_flush(cctxPtr, dstBuffer, dstCapacity, compressOptionsPtr);
   DEBUGLOG(5,"LZ4F_compressEnd: dstCapacity=%u", (unsigned)dstCapacity);
   FORWARD_IF_ERROR(flushSize);
   dstPtr += flushSize;

   assert(flushSize <= dstCapacity);
   dstCapacity -= flushSize;

   RETURN_ERROR_IF(dstCapacity < 4, dstMaxSize_tooSmall);
   LZ4F_writeLE32(dstPtr, 0);
   dstPtr += 4;   /* endMark */

   if (cctxPtr->prefs.frameInfo.contentChecksumFlag == LZ4F_contentChecksumEnabled) {
       U32 const xxh = XXH32_digest(&(cctxPtr->xxh));
       RETURN_ERROR_IF(dstCapacity < 8, dstMaxSize_tooSmall);
       DEBUGLOG(5,"Writing 32-bit content checksum (0x%0X)", xxh);
       LZ4F_writeLE32(dstPtr, xxh);
       dstPtr+=4;   /* content Checksum */
   }

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

   if (cctxPtr->prefs.frameInfo.contentSize) {
       if (cctxPtr->prefs.frameInfo.contentSize != cctxPtr->totalInSize)
           RETURN_ERROR(frameSize_wrong);
   }

   return (size_t)(dstPtr - dstStart);
}


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

typedef enum {
   dstage_getFrameHeader=0, dstage_storeFrameHeader,
   dstage_init,
   dstage_getBlockHeader, dstage_storeBlockHeader,
   dstage_copyDirect, dstage_getBlockChecksum,
   dstage_getCBlock, dstage_storeCBlock,
   dstage_flushOut,
   dstage_getSuffix, dstage_storeSuffix,
   dstage_getSFrameSize, dstage_storeSFrameSize,
   dstage_skipSkippable
} dStage_t;

struct LZ4F_dctx_s {
   LZ4F_CustomMem cmem;
   LZ4F_frameInfo_t frameInfo;
   U32    version;
   dStage_t 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;
   XXH32_state_t blockChecksum;
   int    skipChecksum;
   BYTE   header[LZ4F_HEADER_SIZE_MAX];
};  /* typedef'd to LZ4F_dctx in lz4frame.h */


LZ4F_dctx* LZ4F_createDecompressionContext_advanced(LZ4F_CustomMem customMem, unsigned version)
{
   LZ4F_dctx* const dctx = (LZ4F_dctx*)LZ4F_calloc(sizeof(LZ4F_dctx), customMem);
   if (dctx == NULL) return NULL;

   dctx->cmem = customMem;
   dctx->version = version;
   return dctx;
}

/*! 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)
{
   assert(LZ4F_decompressionContextPtr != NULL);  /* violation of narrow contract */
   RETURN_ERROR_IF(LZ4F_decompressionContextPtr == NULL, parameter_null);  /* in case it nonetheless happen in production */

   *LZ4F_decompressionContextPtr = LZ4F_createDecompressionContext_advanced(LZ4F_defaultCMem, versionNumber);
   if (*LZ4F_decompressionContextPtr == NULL) {  /* failed allocation */
       RETURN_ERROR(allocation_failed);
   }
   return LZ4F_OK_NoError;
}

LZ4F_errorCode_t LZ4F_freeDecompressionContext(LZ4F_dctx* dctx)
{
   LZ4F_errorCode_t result = LZ4F_OK_NoError;
   if (dctx != NULL) {   /* can accept NULL input, like free() */
     result = (LZ4F_errorCode_t)dctx->dStage;
     LZ4F_free(dctx->tmpIn, dctx->cmem);
     LZ4F_free(dctx->tmpOutBuffer, dctx->cmem);
     LZ4F_free(dctx, dctx->cmem);
   }
   return result;
}


/*==---   Streaming Decompression operations   ---==*/
void LZ4F_resetDecompressionContext(LZ4F_dctx* dctx)
{
   DEBUGLOG(5, "LZ4F_resetDecompressionContext");
   dctx->dStage = dstage_getFrameHeader;
   dctx->dict = NULL;
   dctx->dictSize = 0;
   dctx->skipChecksum = 0;
   dctx->frameRemainingSize = 0;
}


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

   DEBUGLOG(5, "LZ4F_decodeHeader");
   /* need to decode header to get frameInfo */
   RETURN_ERROR_IF(srcSize < minFHSize, frameHeader_incomplete);   /* minimal frame header size */
   MEM_INIT(&(dctx->frameInfo), 0, sizeof(dctx->frameInfo));

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

   /* control magic number */
#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
   if (LZ4F_readLE32(srcPtr) != LZ4F_MAGICNUMBER) {
       DEBUGLOG(4, "frame header error : unknown magic number");
       RETURN_ERROR(frameType_unknown);
   }
#endif
   dctx->frameInfo.frameType = LZ4F_frame;

   /* Flags */
   {   U32 const FLG = srcPtr[4];
       U32 const version = (FLG>>6) & _2BITS;
       blockChecksumFlag = (FLG>>4) & _1BIT;
       blockMode = (FLG>>5) & _1BIT;
       contentSizeFlag = (FLG>>3) & _1BIT;
       contentChecksumFlag = (FLG>>2) & _1BIT;
       dictIDFlag = FLG & _1BIT;
       /* validate */
       if (((FLG>>1)&_1BIT) != 0) RETURN_ERROR(reservedFlag_set); /* Reserved bit */
       if (version != 1) RETURN_ERROR(headerVersion_wrong);       /* Version Number, only supported value */
   }
   DEBUGLOG(6, "contentSizeFlag: %u", contentSizeFlag);

   /* Frame Header Size */
   frameHeaderSize = minFHSize + (contentSizeFlag?8:0) + (dictIDFlag?4:0);

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

   {   U32 const BD = srcPtr[5];
       blockSizeID = (BD>>4) & _3BITS;
       /* validate */
       if (((BD>>7)&_1BIT) != 0) RETURN_ERROR(reservedFlag_set);   /* Reserved bit */
       if (blockSizeID < 4) RETURN_ERROR(maxBlockSize_invalid);    /* 4-7 only supported values for the time being */
       if (((BD>>0)&_4BITS) != 0) RETURN_ERROR(reservedFlag_set);  /* Reserved bits */
   }

   /* check header */
   assert(frameHeaderSize > 5);
#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
   {   BYTE const HC = LZ4F_headerChecksum(srcPtr+4, frameHeaderSize-5);
       RETURN_ERROR_IF(HC != srcPtr[frameHeaderSize-1], headerChecksum_invalid);
   }
#endif

   /* save */
   dctx->frameInfo.blockMode = (LZ4F_blockMode_t)blockMode;
   dctx->frameInfo.blockChecksumFlag = (LZ4F_blockChecksum_t)blockChecksumFlag;
   dctx->frameInfo.contentChecksumFlag = (LZ4F_contentChecksum_t)contentChecksumFlag;
   dctx->frameInfo.blockSizeID = (LZ4F_blockSizeID_t)blockSizeID;
   dctx->maxBlockSize = LZ4F_getBlockSize((LZ4F_blockSizeID_t)blockSizeID);
   if (contentSizeFlag) {
       dctx->frameRemainingSize = dctx->frameInfo.contentSize = LZ4F_readLE64(srcPtr+6);
   }
   if (dictIDFlag)
       dctx->frameInfo.dictID = LZ4F_readLE32(srcPtr + frameHeaderSize - 5);

   dctx->dStage = dstage_init;

   return frameHeaderSize;
}


/*! LZ4F_headerSize() :
* @return : size of frame header
*           or an error code, which can be tested using LZ4F_isError()
*/
size_t LZ4F_headerSize(const void* src, size_t srcSize)
{
   RETURN_ERROR_IF(src == NULL, srcPtr_wrong);

   /* minimal srcSize to determine header size */
   if (srcSize < LZ4F_MIN_SIZE_TO_KNOW_HEADER_LENGTH)
       RETURN_ERROR(frameHeader_incomplete);

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

   /* control magic number */
#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
   if (LZ4F_readLE32(src) != LZ4F_MAGICNUMBER)
       RETURN_ERROR(frameType_unknown);
#endif

   /* Frame Header Size */
   {   BYTE const FLG = ((const BYTE*)src)[4];
       U32 const contentSizeFlag = (FLG>>3) & _1BIT;
       U32 const dictIDFlag = FLG & _1BIT;
       return minFHSize + (contentSizeFlag?8:0) + (dictIDFlag?4:0);
   }
}

/*! LZ4F_getFrameInfo() :
*  This function extracts frame parameters (max blockSize, frame checksum, etc.).
*  Usage is optional. Objective is to provide relevant information for allocation purposes.
*  This function works in 2 situations :
*   - At the beginning of a new frame, in which case it will decode this information from `srcBuffer`, and start the decoding process.
*     Amount of input data provided must be large enough to successfully decode the frame header.
*     A header size is variable, but is guaranteed to be <= LZ4F_HEADER_SIZE_MAX bytes. It's possible to provide more input data than this minimum.
*   - After decoding has been started. In which case, no input is read, frame parameters are extracted from dctx.
*  The number of bytes consumed from srcBuffer will be updated within *srcSizePtr (necessarily <= original value).
*  Decompression must resume from (srcBuffer + *srcSizePtr).
* @return : an hint about how many srcSize bytes LZ4F_decompress() expects for next call,
*           or an error code which can be tested using LZ4F_isError()
*  note 1 : in case of error, dctx is not modified. Decoding operations can resume from where they stopped.
*  note 2 : frame parameters are *copied into* an already allocated LZ4F_frameInfo_t structure.
*/
LZ4F_errorCode_t LZ4F_getFrameInfo(LZ4F_dctx* dctx,
                                  LZ4F_frameInfo_t* frameInfoPtr,
                            const void* srcBuffer, size_t* srcSizePtr)
{
   LZ4F_STATIC_ASSERT(dstage_getFrameHeader < dstage_storeFrameHeader);
   if (dctx->dStage > dstage_storeFrameHeader) {
       /* frameInfo already decoded */
       size_t o=0, i=0;
       *srcSizePtr = 0;
       *frameInfoPtr = dctx->frameInfo;
       /* returns : recommended nb of bytes for LZ4F_decompress() */
       return LZ4F_decompress(dctx, NULL, &o, NULL, &i, NULL);
   } else {
       if (dctx->dStage == dstage_storeFrameHeader) {
           /* frame decoding already started, in the middle of header => automatic fail */
           *srcSizePtr = 0;
           RETURN_ERROR(frameDecoding_alreadyStarted);
       } else {
           size_t const hSize = LZ4F_headerSize(srcBuffer, *srcSizePtr);
           if (LZ4F_isError(hSize)) { *srcSizePtr=0; return hSize; }
           if (*srcSizePtr < hSize) {
               *srcSizePtr=0;
               RETURN_ERROR(frameHeader_incomplete);
           }

           {   size_t decodeResult = LZ4F_decodeHeader(dctx, srcBuffer, hSize);
               if (LZ4F_isError(decodeResult)) {
                   *srcSizePtr = 0;
               } else {
                   *srcSizePtr = decodeResult;
                   decodeResult = BHSize;   /* block header size */
               }
               *frameInfoPtr = dctx->frameInfo;
               return decodeResult;
   }   }   }
}


/* LZ4F_updateDict() :
* only used for LZ4F_blockLinked mode
* Condition : @dstPtr != NULL
*/
static void LZ4F_updateDict(LZ4F_dctx* dctx,
                     const BYTE* dstPtr, size_t dstSize, const BYTE* dstBufferStart,
                     unsigned withinTmp)
{
   assert(dstPtr != NULL);
   if (dctx->dictSize==0) dctx->dict = (const BYTE*)dstPtr;  /* will lead to prefix mode */
   assert(dctx->dict != NULL);

   if (dctx->dict + dctx->dictSize == dstPtr) {  /* prefix mode, everything within dstBuffer */
       dctx->dictSize += dstSize;
       return;
   }

   assert(dstPtr >= dstBufferStart);
   if ((size_t)(dstPtr - dstBufferStart) + dstSize >= 64 KB) {  /* history in dstBuffer becomes large enough to become dictionary */
       dctx->dict = (const BYTE*)dstBufferStart;
       dctx->dictSize = (size_t)(dstPtr - dstBufferStart) + dstSize;
       return;
   }

   assert(dstSize < 64 KB);   /* if dstSize >= 64 KB, dictionary would be set into dstBuffer directly */

   /* dstBuffer does not contain whole useful history (64 KB), so it must be saved within tmpOutBuffer */
   assert(dctx->tmpOutBuffer != NULL);

   if (withinTmp && (dctx->dict == dctx->tmpOutBuffer)) {   /* continue history within tmpOutBuffer */
       /* withinTmp expectation : content of [dstPtr,dstSize] is same as [dict+dictSize,dstSize], so we just extend it */
       assert(dctx->dict + dctx->dictSize == dctx->tmpOut + dctx->tmpOutStart);
       dctx->dictSize += dstSize;
       return;
   }

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

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

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

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

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


/*! LZ4F_decompress() :
*  Call this function repetitively to regenerate compressed data in 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 number of bytes read is < number of bytes provided, then 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.
*  Schematically, it's the size of the current (or remaining) compressed block + header of next block.
*  Respecting the hint provides a small boost to performance, since it allows less buffer shuffling.
*  Note that this is just a hint, and 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* dctx,
                      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 ? dstStart + *dstSizePtr : NULL;
   BYTE* dstPtr = dstStart;
   const BYTE* selectedIn = NULL;
   unsigned doAnotherStage = 1;
   size_t nextSrcSizeHint = 1;


   DEBUGLOG(5, "LZ4F_decompress: src[%p](%u) => dst[%p](%u)",
           srcBuffer, (unsigned)*srcSizePtr, dstBuffer, (unsigned)*dstSizePtr);
   if (dstBuffer == NULL) assert(*dstSizePtr == 0);
   MEM_INIT(&optionsNull, 0, sizeof(optionsNull));
   if (decompressOptionsPtr==NULL) decompressOptionsPtr = &optionsNull;
   *srcSizePtr = 0;
   *dstSizePtr = 0;
   assert(dctx != NULL);
   dctx->skipChecksum |= (decompressOptionsPtr->skipChecksums != 0); /* once set, disable for the remainder of the frame */

   /* behaves as a state machine */

   while (doAnotherStage) {

       switch(dctx->dStage)
       {

       case dstage_getFrameHeader:
           DEBUGLOG(6, "dstage_getFrameHeader");
           if ((size_t)(srcEnd-srcPtr) >= maxFHSize) {  /* enough to decode - shortcut */
               size_t const hSize = LZ4F_decodeHeader(dctx, srcPtr, (size_t)(srcEnd-srcPtr));  /* will update dStage appropriately */
               FORWARD_IF_ERROR(hSize);
               srcPtr += hSize;
               break;
           }
           dctx->tmpInSize = 0;
           if (srcEnd-srcPtr == 0) return minFHSize;   /* 0-size input */
           dctx->tmpInTarget = minFHSize;   /* minimum size to decode header */
           dctx->dStage = dstage_storeFrameHeader;
           /* fall-through */

       case dstage_storeFrameHeader:
           DEBUGLOG(6, "dstage_storeFrameHeader");
           {   size_t const sizeToCopy = MIN(dctx->tmpInTarget - dctx->tmpInSize, (size_t)(srcEnd - srcPtr));
               memcpy(dctx->header + dctx->tmpInSize, srcPtr, sizeToCopy);
               dctx->tmpInSize += sizeToCopy;
               srcPtr += sizeToCopy;
           }
           if (dctx->tmpInSize < dctx->tmpInTarget) {
               nextSrcSizeHint = (dctx->tmpInTarget - dctx->tmpInSize) + BHSize;   /* rest of header + nextBlockHeader */
               doAnotherStage = 0;   /* not enough src data, ask for some more */
               break;
           }
           FORWARD_IF_ERROR( LZ4F_decodeHeader(dctx, dctx->header, dctx->tmpInTarget) ); /* will update dStage appropriately */
           break;

       case dstage_init:
           DEBUGLOG(6, "dstage_init");
           if (dctx->frameInfo.contentChecksumFlag) (void)XXH32_reset(&(dctx->xxh), 0);
           /* internal buffers allocation */
           {   size_t const bufferNeeded = dctx->maxBlockSize
                   + ((dctx->frameInfo.blockMode==LZ4F_blockLinked) ? 128 KB : 0);
               if (bufferNeeded > dctx->maxBufferSize) {   /* tmp buffers too small */
                   dctx->maxBufferSize = 0;   /* ensure allocation will be re-attempted on next entry*/
                   LZ4F_free(dctx->tmpIn, dctx->cmem);
                   dctx->tmpIn = (BYTE*)LZ4F_malloc(dctx->maxBlockSize + BFSize /* block checksum */, dctx->cmem);
                   RETURN_ERROR_IF(dctx->tmpIn == NULL, allocation_failed);
                   LZ4F_free(dctx->tmpOutBuffer, dctx->cmem);
                   dctx->tmpOutBuffer= (BYTE*)LZ4F_malloc(bufferNeeded, dctx->cmem);
                   RETURN_ERROR_IF(dctx->tmpOutBuffer== NULL, allocation_failed);
                   dctx->maxBufferSize = bufferNeeded;
           }   }
           dctx->tmpInSize = 0;
           dctx->tmpInTarget = 0;
           dctx->tmpOut = dctx->tmpOutBuffer;
           dctx->tmpOutStart = 0;
           dctx->tmpOutSize = 0;

           dctx->dStage = dstage_getBlockHeader;
           /* fall-through */

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

           if (dctx->dStage == dstage_storeBlockHeader)   /* can be skipped */
       case dstage_storeBlockHeader:
           {   size_t const remainingInput = (size_t)(srcEnd - srcPtr);
               size_t const wantedData = BHSize - dctx->tmpInSize;
               size_t const sizeToCopy = MIN(wantedData, remainingInput);
               memcpy(dctx->tmpIn + dctx->tmpInSize, srcPtr, sizeToCopy);
               srcPtr += sizeToCopy;
               dctx->tmpInSize += sizeToCopy;

               if (dctx->tmpInSize < BHSize) {   /* not enough input for cBlockSize */
                   nextSrcSizeHint = BHSize - dctx->tmpInSize;
                   doAnotherStage  = 0;
                   break;
               }
               selectedIn = dctx->tmpIn;
           }   /* if (dctx->dStage == dstage_storeBlockHeader) */

       /* decode block header */
           {   U32 const blockHeader = LZ4F_readLE32(selectedIn);
               size_t const nextCBlockSize = blockHeader & 0x7FFFFFFFU;
               size_t const crcSize = dctx->frameInfo.blockChecksumFlag * BFSize;
               if (blockHeader==0) {  /* frameEnd signal, no more block */
                   DEBUGLOG(5, "end of frame");
                   dctx->dStage = dstage_getSuffix;
                   break;
               }
               if (nextCBlockSize > dctx->maxBlockSize) {
                   RETURN_ERROR(maxBlockSize_invalid);
               }
               if (blockHeader & LZ4F_BLOCKUNCOMPRESSED_FLAG) {
                   /* next block is uncompressed */
                   dctx->tmpInTarget = nextCBlockSize;
                   DEBUGLOG(5, "next block is uncompressed (size %u)", (U32)nextCBlockSize);
                   if (dctx->frameInfo.blockChecksumFlag) {
                       (void)XXH32_reset(&dctx->blockChecksum, 0);
                   }
                   dctx->dStage = dstage_copyDirect;
                   break;
               }
               /* next block is a compressed block */
               dctx->tmpInTarget = nextCBlockSize + crcSize;
               dctx->dStage = dstage_getCBlock;
               if (dstPtr==dstEnd || srcPtr==srcEnd) {
                   nextSrcSizeHint = BHSize + nextCBlockSize + crcSize;
                   doAnotherStage = 0;
               }
               break;
           }

       case dstage_copyDirect:   /* uncompressed block */
           DEBUGLOG(6, "dstage_copyDirect");
           {   size_t sizeToCopy;
               if (dstPtr == NULL) {
                   sizeToCopy = 0;
               } else {
                   size_t const minBuffSize = MIN((size_t)(srcEnd-srcPtr), (size_t)(dstEnd-dstPtr));
                   sizeToCopy = MIN(dctx->tmpInTarget, minBuffSize);
                   memcpy(dstPtr, srcPtr, sizeToCopy);
                   if (!dctx->skipChecksum) {
                       if (dctx->frameInfo.blockChecksumFlag) {
                           (void)XXH32_update(&dctx->blockChecksum, srcPtr, sizeToCopy);
                       }
                       if (dctx->frameInfo.contentChecksumFlag)
                           (void)XXH32_update(&dctx->xxh, srcPtr, sizeToCopy);
                   }
                   if (dctx->frameInfo.contentSize)
                       dctx->frameRemainingSize -= sizeToCopy;

                   /* history management (linked blocks only)*/
                   if (dctx->frameInfo.blockMode == LZ4F_blockLinked) {
                       LZ4F_updateDict(dctx, dstPtr, sizeToCopy, dstStart, 0);
                   }
                   srcPtr += sizeToCopy;
                   dstPtr += sizeToCopy;
               }
               if (sizeToCopy == dctx->tmpInTarget) {   /* all done */
                   if (dctx->frameInfo.blockChecksumFlag) {
                       dctx->tmpInSize = 0;
                       dctx->dStage = dstage_getBlockChecksum;
                   } else
                       dctx->dStage = dstage_getBlockHeader;  /* new block */
                   break;
               }
               dctx->tmpInTarget -= sizeToCopy;  /* need to copy more */
           }
           nextSrcSizeHint = dctx->tmpInTarget +
                           +(dctx->frameInfo.blockChecksumFlag ? BFSize : 0)
                           + BHSize /* next header size */;
           doAnotherStage = 0;
           break;

       /* check block checksum for recently transferred uncompressed block */
       case dstage_getBlockChecksum:
           DEBUGLOG(6, "dstage_getBlockChecksum");
           {   const void* crcSrc;
               if ((srcEnd-srcPtr >= 4) && (dctx->tmpInSize==0)) {
                   crcSrc = srcPtr;
                   srcPtr += 4;
               } else {
                   size_t const stillToCopy = 4 - dctx->tmpInSize;
                   size_t const sizeToCopy = MIN(stillToCopy, (size_t)(srcEnd-srcPtr));
                   memcpy(dctx->header + dctx->tmpInSize, srcPtr, sizeToCopy);
                   dctx->tmpInSize += sizeToCopy;
                   srcPtr += sizeToCopy;
                   if (dctx->tmpInSize < 4) {  /* all input consumed */
                       doAnotherStage = 0;
                       break;
                   }
                   crcSrc = dctx->header;
               }
               if (!dctx->skipChecksum) {
                   U32 const readCRC = LZ4F_readLE32(crcSrc);
                   U32 const calcCRC = XXH32_digest(&dctx->blockChecksum);
#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
                   DEBUGLOG(6, "compare block checksum");
                   if (readCRC != calcCRC) {
                       DEBUGLOG(4, "incorrect block checksum: %08X != %08X",
                               readCRC, calcCRC);
                       RETURN_ERROR(blockChecksum_invalid);
                   }
#else
                   (void)readCRC;
                   (void)calcCRC;
#endif
           }   }
           dctx->dStage = dstage_getBlockHeader;  /* new block */
           break;

       case dstage_getCBlock:
           DEBUGLOG(6, "dstage_getCBlock");
           if ((size_t)(srcEnd-srcPtr) < dctx->tmpInTarget) {
               dctx->tmpInSize = 0;
               dctx->dStage = dstage_storeCBlock;
               break;
           }
           /* input large enough to read full block directly */
           selectedIn = srcPtr;
           srcPtr += dctx->tmpInTarget;

           if (0)  /* always jump over next block */
       case dstage_storeCBlock:
           {   size_t const wantedData = dctx->tmpInTarget - dctx->tmpInSize;
               size_t const inputLeft = (size_t)(srcEnd-srcPtr);
               size_t const sizeToCopy = MIN(wantedData, inputLeft);
               memcpy(dctx->tmpIn + dctx->tmpInSize, srcPtr, sizeToCopy);
               dctx->tmpInSize += sizeToCopy;
               srcPtr += sizeToCopy;
               if (dctx->tmpInSize < dctx->tmpInTarget) { /* need more input */
                   nextSrcSizeHint = (dctx->tmpInTarget - dctx->tmpInSize)
                                   + (dctx->frameInfo.blockChecksumFlag ? BFSize : 0)
                                   + BHSize /* next header size */;
                   doAnotherStage = 0;
                   break;
               }
               selectedIn = dctx->tmpIn;
           }

           /* At this stage, input is large enough to decode a block */

           /* First, decode and control block checksum if it exists */
           if (dctx->frameInfo.blockChecksumFlag) {
               assert(dctx->tmpInTarget >= 4);
               dctx->tmpInTarget -= 4;
               assert(selectedIn != NULL);  /* selectedIn is defined at this stage (either srcPtr, or dctx->tmpIn) */
               {   U32 const readBlockCrc = LZ4F_readLE32(selectedIn + dctx->tmpInTarget);
                   U32 const calcBlockCrc = XXH32(selectedIn, dctx->tmpInTarget, 0);
#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
                   RETURN_ERROR_IF(readBlockCrc != calcBlockCrc, blockChecksum_invalid);
#else
                   (void)readBlockCrc;
                   (void)calcBlockCrc;
#endif
           }   }

           /* decode directly into destination buffer if there is enough room */
           if ( ((size_t)(dstEnd-dstPtr) >= dctx->maxBlockSize)
                /* unless the dictionary is stored in tmpOut:
                 * in which case it's faster to decode within tmpOut
                 * to benefit from prefix speedup */
             && !(dctx->dict!= NULL && (const BYTE*)dctx->dict + dctx->dictSize == dctx->tmpOut) )
           {
               const char* dict = (const char*)dctx->dict;
               size_t dictSize = dctx->dictSize;
               int decodedSize;
               assert(dstPtr != NULL);
               if (dict && dictSize > 1 GB) {
                   /* overflow control : dctx->dictSize is an int, avoid truncation / sign issues */
                   dict += dictSize - 64 KB;
                   dictSize = 64 KB;
               }
               decodedSize = LZ4_decompress_safe_usingDict(
                       (const char*)selectedIn, (char*)dstPtr,
                       (int)dctx->tmpInTarget, (int)dctx->maxBlockSize,
                       dict, (int)dictSize);
               RETURN_ERROR_IF(decodedSize < 0, decompressionFailed);
               if ((dctx->frameInfo.contentChecksumFlag) && (!dctx->skipChecksum))
                   XXH32_update(&(dctx->xxh), dstPtr, (size_t)decodedSize);
               if (dctx->frameInfo.contentSize)
                   dctx->frameRemainingSize -= (size_t)decodedSize;

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

               dstPtr += decodedSize;
               dctx->dStage = dstage_getBlockHeader;  /* end of block, let's get another one */
               break;
           }

           /* not enough place into dst : decode into tmpOut */

           /* manage dictionary */
           if (dctx->frameInfo.blockMode == LZ4F_blockLinked) {
               if (dctx->dict == dctx->tmpOutBuffer) {
                   /* truncate dictionary to 64 KB if too big */
                   if (dctx->dictSize > 128 KB) {
                       memcpy(dctx->tmpOutBuffer, dctx->dict + dctx->dictSize - 64 KB, 64 KB);
                       dctx->dictSize = 64 KB;
                   }
                   dctx->tmpOut = dctx->tmpOutBuffer + dctx->dictSize;
               } else {  /* dict not within tmpOut */
                   size_t const reservedDictSpace = MIN(dctx->dictSize, 64 KB);
                   dctx->tmpOut = dctx->tmpOutBuffer + reservedDictSpace;
           }   }

           /* Decode block into tmpOut */
           {   const char* dict = (const char*)dctx->dict;
               size_t dictSize = dctx->dictSize;
               int decodedSize;
               if (dict && dictSize > 1 GB) {
                   /* the dictSize param is an int, avoid truncation / sign issues */
                   dict += dictSize - 64 KB;
                   dictSize = 64 KB;
               }
               decodedSize = LZ4_decompress_safe_usingDict(
                       (const char*)selectedIn, (char*)dctx->tmpOut,
                       (int)dctx->tmpInTarget, (int)dctx->maxBlockSize,
                       dict, (int)dictSize);
               RETURN_ERROR_IF(decodedSize < 0, decompressionFailed);
               if (dctx->frameInfo.contentChecksumFlag && !dctx->skipChecksum)
                   XXH32_update(&(dctx->xxh), dctx->tmpOut, (size_t)decodedSize);
               if (dctx->frameInfo.contentSize)
                   dctx->frameRemainingSize -= (size_t)decodedSize;
               dctx->tmpOutSize = (size_t)decodedSize;
               dctx->tmpOutStart = 0;
               dctx->dStage = dstage_flushOut;
           }
           /* fall-through */

       case dstage_flushOut:  /* flush decoded data from tmpOut to dstBuffer */
           DEBUGLOG(6, "dstage_flushOut");
           if (dstPtr != NULL) {
               size_t const sizeToCopy = MIN(dctx->tmpOutSize - dctx->tmpOutStart, (size_t)(dstEnd-dstPtr));
               memcpy(dstPtr, dctx->tmpOut + dctx->tmpOutStart, sizeToCopy);

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

               dctx->tmpOutStart += sizeToCopy;
               dstPtr += sizeToCopy;
           }
           if (dctx->tmpOutStart == dctx->tmpOutSize) { /* all flushed */
               dctx->dStage = dstage_getBlockHeader;  /* get next block */
               break;
           }
           /* could not flush everything : stop there, just request a block header */
           doAnotherStage = 0;
           nextSrcSizeHint = BHSize;
           break;

       case dstage_getSuffix:
           RETURN_ERROR_IF(dctx->frameRemainingSize, frameSize_wrong);   /* incorrect frame size decoded */
           if (!dctx->frameInfo.contentChecksumFlag) {  /* no checksum, frame is completed */
               nextSrcSizeHint = 0;
               LZ4F_resetDecompressionContext(dctx);
               doAnotherStage = 0;
               break;
           }
           if ((srcEnd - srcPtr) < 4) {  /* not enough size for entire CRC */
               dctx->tmpInSize = 0;
               dctx->dStage = dstage_storeSuffix;
           } else {
               selectedIn = srcPtr;
               srcPtr += 4;
           }

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

       /* case dstage_checkSuffix: */   /* no direct entry, avoid initialization risks */
           if (!dctx->skipChecksum) {
               U32 const readCRC = LZ4F_readLE32(selectedIn);
               U32 const resultCRC = XXH32_digest(&(dctx->xxh));
               DEBUGLOG(4, "frame checksum: stored 0x%0X vs 0x%0X processed", readCRC, resultCRC);
#ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
               RETURN_ERROR_IF(readCRC != resultCRC, contentChecksum_invalid);
#else
               (void)readCRC;
               (void)resultCRC;
#endif
           }
           nextSrcSizeHint = 0;
           LZ4F_resetDecompressionContext(dctx);
           doAnotherStage = 0;
           break;

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

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

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

       case dstage_skipSkippable:
           {   size_t const skipSize = MIN(dctx->tmpInTarget, (size_t)(srcEnd-srcPtr));
               srcPtr += skipSize;
               dctx->tmpInTarget -= skipSize;
               doAnotherStage = 0;
               nextSrcSizeHint = dctx->tmpInTarget;
               if (nextSrcSizeHint) break;  /* still more to skip */
               /* frame fully skipped : prepare context for a new frame */
               LZ4F_resetDecompressionContext(dctx);
               break;
           }
       }   /* switch (dctx->dStage) */
   }   /* while (doAnotherStage) */

   /* preserve history within tmpOut whenever necessary */
   LZ4F_STATIC_ASSERT((unsigned)dstage_init == 2);
   if ( (dctx->frameInfo.blockMode==LZ4F_blockLinked)  /* next block will use up to 64KB from previous ones */
     && (dctx->dict != dctx->tmpOutBuffer)             /* dictionary is not already within tmp */
     && (dctx->dict != NULL)                           /* dictionary exists */
     && (!decompressOptionsPtr->stableDst)             /* cannot rely on dst data to remain there for next call */
     && ((unsigned)(dctx->dStage)-2 < (unsigned)(dstage_getSuffix)-2) )  /* valid stages : [init ... getSuffix[ */
   {
       if (dctx->dStage == dstage_flushOut) {
           size_t const preserveSize = (size_t)(dctx->tmpOut - dctx->tmpOutBuffer);
           size_t copySize = 64 KB - dctx->tmpOutSize;
           const BYTE* oldDictEnd = dctx->dict + dctx->dictSize - dctx->tmpOutStart;
           if (dctx->tmpOutSize > 64 KB) copySize = 0;
           if (copySize > preserveSize) copySize = preserveSize;
           assert(dctx->tmpOutBuffer != NULL);

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

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

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

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

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

/*! LZ4F_decompress_usingDict() :
*  Same as LZ4F_decompress(), using a predefined dictionary.
*  Dictionary is used "in place", without any preprocessing.
*  It must remain accessible throughout the entire frame decoding.
*/
size_t LZ4F_decompress_usingDict(LZ4F_dctx* dctx,
                      void* dstBuffer, size_t* dstSizePtr,
                      const void* srcBuffer, size_t* srcSizePtr,
                      const void* dict, size_t dictSize,
                      const LZ4F_decompressOptions_t* decompressOptionsPtr)
{
   if (dctx->dStage <= dstage_init) {
       dctx->dict = (const BYTE*)dict;
       dctx->dictSize = dictSize;
   }
   return LZ4F_decompress(dctx, dstBuffer, dstSizePtr,
                          srcBuffer, srcSizePtr,
                          decompressOptionsPtr);
}