FreeBSD/Linux Kernel Cross Reference
sys/contrib/zstd/lib/decompress/zstd_decompress.c

     /*
      * Copyright (c) Yann Collet, Facebook, Inc.
      * All rights reserved.
      *
      * This source code is licensed under both the BSD-style license (found in the
      * LICENSE file in the root directory of this source tree) and the GPLv2 (found
      * in the COPYING file in the root directory of this source tree).
      * You may select, at your option, one of the above-listed licenses.
      */
    
    
    /* ***************************************************************
    *  Tuning parameters
    *****************************************************************/
    /*!
     * HEAPMODE :
     * Select how default decompression function ZSTD_decompress() allocates its context,
     * on stack (0), or into heap (1, default; requires malloc()).
     * Note that functions with explicit context such as ZSTD_decompressDCtx() are unaffected.
     */
    #ifndef ZSTD_HEAPMODE
    #  define ZSTD_HEAPMODE 1
    #endif
    
    /*!
    *  LEGACY_SUPPORT :
    *  if set to 1+, ZSTD_decompress() can decode older formats (v0.1+)
    */
    #ifndef ZSTD_LEGACY_SUPPORT
    #  define ZSTD_LEGACY_SUPPORT 0
    #endif
    
    /*!
     *  MAXWINDOWSIZE_DEFAULT :
     *  maximum window size accepted by DStream __by default__.
     *  Frames requiring more memory will be rejected.
     *  It's possible to set a different limit using ZSTD_DCtx_setMaxWindowSize().
     */
    #ifndef ZSTD_MAXWINDOWSIZE_DEFAULT
    #  define ZSTD_MAXWINDOWSIZE_DEFAULT (((U32)1 << ZSTD_WINDOWLOG_LIMIT_DEFAULT) + 1)
    #endif
    
    /*!
     *  NO_FORWARD_PROGRESS_MAX :
     *  maximum allowed nb of calls to ZSTD_decompressStream()
     *  without any forward progress
     *  (defined as: no byte read from input, and no byte flushed to output)
     *  before triggering an error.
     */
    #ifndef ZSTD_NO_FORWARD_PROGRESS_MAX
    #  define ZSTD_NO_FORWARD_PROGRESS_MAX 16
    #endif
    
    
    /*-*******************************************************
    *  Dependencies
    *********************************************************/
    #include "../common/zstd_deps.h"   /* ZSTD_memcpy, ZSTD_memmove, ZSTD_memset */
    #include "../common/mem.h"         /* low level memory routines */
    #define FSE_STATIC_LINKING_ONLY
    #include "../common/fse.h"
    #define HUF_STATIC_LINKING_ONLY
    #include "../common/huf.h"
    #include "../common/xxhash.h" /* XXH64_reset, XXH64_update, XXH64_digest, XXH64 */
    #include "../common/zstd_internal.h"  /* blockProperties_t */
    #include "zstd_decompress_internal.h"   /* ZSTD_DCtx */
    #include "zstd_ddict.h"  /* ZSTD_DDictDictContent */
    #include "zstd_decompress_block.h"   /* ZSTD_decompressBlock_internal */
    
    #if defined(ZSTD_LEGACY_SUPPORT) && (ZSTD_LEGACY_SUPPORT>=1)
    #  include "../legacy/zstd_legacy.h"
    #endif
    
    
    
    /*************************************
     * Multiple DDicts Hashset internals *
     *************************************/
    
    #define DDICT_HASHSET_MAX_LOAD_FACTOR_COUNT_MULT 4
    #define DDICT_HASHSET_MAX_LOAD_FACTOR_SIZE_MULT 3   /* These two constants represent SIZE_MULT/COUNT_MULT load factor without using a float.
                                                         * Currently, that means a 0.75 load factor.
                                                         * So, if count * COUNT_MULT / size * SIZE_MULT != 0, then we've exceeded
                                                         * the load factor of the ddict hash set.
                                                         */
    
    #define DDICT_HASHSET_TABLE_BASE_SIZE 64
    #define DDICT_HASHSET_RESIZE_FACTOR 2
    
    /* Hash function to determine starting position of dict insertion within the table
     * Returns an index between [0, hashSet->ddictPtrTableSize]
     */
    static size_t ZSTD_DDictHashSet_getIndex(const ZSTD_DDictHashSet* hashSet, U32 dictID) {
        const U64 hash = XXH64(&dictID, sizeof(U32), 0);
        /* DDict ptr table size is a multiple of 2, use size - 1 as mask to get index within [0, hashSet->ddictPtrTableSize) */
        return hash & (hashSet->ddictPtrTableSize - 1);
    }
    
    /* Adds DDict to a hashset without resizing it.
    * If inserting a DDict with a dictID that already exists in the set, replaces the one in the set.
    * Returns 0 if successful, or a zstd error code if something went wrong.
    */
   static size_t ZSTD_DDictHashSet_emplaceDDict(ZSTD_DDictHashSet* hashSet, const ZSTD_DDict* ddict) {
       const U32 dictID = ZSTD_getDictID_fromDDict(ddict);
       size_t idx = ZSTD_DDictHashSet_getIndex(hashSet, dictID);
       const size_t idxRangeMask = hashSet->ddictPtrTableSize - 1;
       RETURN_ERROR_IF(hashSet->ddictPtrCount == hashSet->ddictPtrTableSize, GENERIC, "Hash set is full!");
       DEBUGLOG(4, "Hashed index: for dictID: %u is %zu", dictID, idx);
       while (hashSet->ddictPtrTable[idx] != NULL) {
           /* Replace existing ddict if inserting ddict with same dictID */
           if (ZSTD_getDictID_fromDDict(hashSet->ddictPtrTable[idx]) == dictID) {
               DEBUGLOG(4, "DictID already exists, replacing rather than adding");
               hashSet->ddictPtrTable[idx] = ddict;
               return 0;
           }
           idx &= idxRangeMask;
           idx++;
       }
       DEBUGLOG(4, "Final idx after probing for dictID %u is: %zu", dictID, idx);
       hashSet->ddictPtrTable[idx] = ddict;
       hashSet->ddictPtrCount++;
       return 0;
   }
   
   /* Expands hash table by factor of DDICT_HASHSET_RESIZE_FACTOR and
    * rehashes all values, allocates new table, frees old table.
    * Returns 0 on success, otherwise a zstd error code.
    */
   static size_t ZSTD_DDictHashSet_expand(ZSTD_DDictHashSet* hashSet, ZSTD_customMem customMem) {
       size_t newTableSize = hashSet->ddictPtrTableSize * DDICT_HASHSET_RESIZE_FACTOR;
       const ZSTD_DDict** newTable = (const ZSTD_DDict**)ZSTD_customCalloc(sizeof(ZSTD_DDict*) * newTableSize, customMem);
       const ZSTD_DDict** oldTable = hashSet->ddictPtrTable;
       size_t oldTableSize = hashSet->ddictPtrTableSize;
       size_t i;
   
       DEBUGLOG(4, "Expanding DDict hash table! Old size: %zu new size: %zu", oldTableSize, newTableSize);
       RETURN_ERROR_IF(!newTable, memory_allocation, "Expanded hashset allocation failed!");
       hashSet->ddictPtrTable = newTable;
       hashSet->ddictPtrTableSize = newTableSize;
       hashSet->ddictPtrCount = 0;
       for (i = 0; i < oldTableSize; ++i) {
           if (oldTable[i] != NULL) {
               FORWARD_IF_ERROR(ZSTD_DDictHashSet_emplaceDDict(hashSet, oldTable[i]), "");
           }
       }
       ZSTD_customFree((void*)oldTable, customMem);
       DEBUGLOG(4, "Finished re-hash");
       return 0;
   }
   
   /* Fetches a DDict with the given dictID
    * Returns the ZSTD_DDict* with the requested dictID. If it doesn't exist, then returns NULL.
    */
   static const ZSTD_DDict* ZSTD_DDictHashSet_getDDict(ZSTD_DDictHashSet* hashSet, U32 dictID) {
       size_t idx = ZSTD_DDictHashSet_getIndex(hashSet, dictID);
       const size_t idxRangeMask = hashSet->ddictPtrTableSize - 1;
       DEBUGLOG(4, "Hashed index: for dictID: %u is %zu", dictID, idx);
       for (;;) {
           size_t currDictID = ZSTD_getDictID_fromDDict(hashSet->ddictPtrTable[idx]);
           if (currDictID == dictID || currDictID == 0) {
               /* currDictID == 0 implies a NULL ddict entry */
               break;
           } else {
               idx &= idxRangeMask;    /* Goes to start of table when we reach the end */
               idx++;
           }
       }
       DEBUGLOG(4, "Final idx after probing for dictID %u is: %zu", dictID, idx);
       return hashSet->ddictPtrTable[idx];
   }
   
   /* Allocates space for and returns a ddict hash set
    * The hash set's ZSTD_DDict* table has all values automatically set to NULL to begin with.
    * Returns NULL if allocation failed.
    */
   static ZSTD_DDictHashSet* ZSTD_createDDictHashSet(ZSTD_customMem customMem) {
       ZSTD_DDictHashSet* ret = (ZSTD_DDictHashSet*)ZSTD_customMalloc(sizeof(ZSTD_DDictHashSet), customMem);
       DEBUGLOG(4, "Allocating new hash set");
       if (!ret)
           return NULL;
       ret->ddictPtrTable = (const ZSTD_DDict**)ZSTD_customCalloc(DDICT_HASHSET_TABLE_BASE_SIZE * sizeof(ZSTD_DDict*), customMem);
       if (!ret->ddictPtrTable) {
           ZSTD_customFree(ret, customMem);
           return NULL;
       }
       ret->ddictPtrTableSize = DDICT_HASHSET_TABLE_BASE_SIZE;
       ret->ddictPtrCount = 0;
       return ret;
   }
   
   /* Frees the table of ZSTD_DDict* within a hashset, then frees the hashset itself.
    * Note: The ZSTD_DDict* within the table are NOT freed.
    */
   static void ZSTD_freeDDictHashSet(ZSTD_DDictHashSet* hashSet, ZSTD_customMem customMem) {
       DEBUGLOG(4, "Freeing ddict hash set");
       if (hashSet && hashSet->ddictPtrTable) {
           ZSTD_customFree((void*)hashSet->ddictPtrTable, customMem);
       }
       if (hashSet) {
           ZSTD_customFree(hashSet, customMem);
       }
   }
   
   /* Public function: Adds a DDict into the ZSTD_DDictHashSet, possibly triggering a resize of the hash set.
    * Returns 0 on success, or a ZSTD error.
    */
   static size_t ZSTD_DDictHashSet_addDDict(ZSTD_DDictHashSet* hashSet, const ZSTD_DDict* ddict, ZSTD_customMem customMem) {
       DEBUGLOG(4, "Adding dict ID: %u to hashset with - Count: %zu Tablesize: %zu", ZSTD_getDictID_fromDDict(ddict), hashSet->ddictPtrCount, hashSet->ddictPtrTableSize);
       if (hashSet->ddictPtrCount * DDICT_HASHSET_MAX_LOAD_FACTOR_COUNT_MULT / hashSet->ddictPtrTableSize * DDICT_HASHSET_MAX_LOAD_FACTOR_SIZE_MULT != 0) {
           FORWARD_IF_ERROR(ZSTD_DDictHashSet_expand(hashSet, customMem), "");
       }
       FORWARD_IF_ERROR(ZSTD_DDictHashSet_emplaceDDict(hashSet, ddict), "");
       return 0;
   }
   
   /*-*************************************************************
   *   Context management
   ***************************************************************/
   size_t ZSTD_sizeof_DCtx (const ZSTD_DCtx* dctx)
   {
       if (dctx==NULL) return 0;   /* support sizeof NULL */
       return sizeof(*dctx)
              + ZSTD_sizeof_DDict(dctx->ddictLocal)
              + dctx->inBuffSize + dctx->outBuffSize;
   }
   
   size_t ZSTD_estimateDCtxSize(void) { return sizeof(ZSTD_DCtx); }
   
   
   static size_t ZSTD_startingInputLength(ZSTD_format_e format)
   {
       size_t const startingInputLength = ZSTD_FRAMEHEADERSIZE_PREFIX(format);
       /* only supports formats ZSTD_f_zstd1 and ZSTD_f_zstd1_magicless */
       assert( (format == ZSTD_f_zstd1) || (format == ZSTD_f_zstd1_magicless) );
       return startingInputLength;
   }
   
   static void ZSTD_DCtx_resetParameters(ZSTD_DCtx* dctx)
   {
       assert(dctx->streamStage == zdss_init);
       dctx->format = ZSTD_f_zstd1;
       dctx->maxWindowSize = ZSTD_MAXWINDOWSIZE_DEFAULT;
       dctx->outBufferMode = ZSTD_bm_buffered;
       dctx->forceIgnoreChecksum = ZSTD_d_validateChecksum;
       dctx->refMultipleDDicts = ZSTD_rmd_refSingleDDict;
   }
   
   static void ZSTD_initDCtx_internal(ZSTD_DCtx* dctx)
   {
       dctx->staticSize  = 0;
       dctx->ddict       = NULL;
       dctx->ddictLocal  = NULL;
       dctx->dictEnd     = NULL;
       dctx->ddictIsCold = 0;
       dctx->dictUses = ZSTD_dont_use;
       dctx->inBuff      = NULL;
       dctx->inBuffSize  = 0;
       dctx->outBuffSize = 0;
       dctx->streamStage = zdss_init;
   #if defined(ZSTD_LEGACY_SUPPORT) && (ZSTD_LEGACY_SUPPORT>=1)
       dctx->legacyContext = NULL;
       dctx->previousLegacyVersion = 0;
   #endif
       dctx->noForwardProgress = 0;
       dctx->oversizedDuration = 0;
   #if DYNAMIC_BMI2
       dctx->bmi2 = ZSTD_cpuSupportsBmi2();
   #endif
       dctx->ddictSet = NULL;
       ZSTD_DCtx_resetParameters(dctx);
   #ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
       dctx->dictContentEndForFuzzing = NULL;
   #endif
   }
   
   ZSTD_DCtx* ZSTD_initStaticDCtx(void *workspace, size_t workspaceSize)
   {
       ZSTD_DCtx* const dctx = (ZSTD_DCtx*) workspace;
   
       if ((size_t)workspace & 7) return NULL;  /* 8-aligned */
       if (workspaceSize < sizeof(ZSTD_DCtx)) return NULL;  /* minimum size */
   
       ZSTD_initDCtx_internal(dctx);
       dctx->staticSize = workspaceSize;
       dctx->inBuff = (char*)(dctx+1);
       return dctx;
   }
   
   static ZSTD_DCtx* ZSTD_createDCtx_internal(ZSTD_customMem customMem) {
       if ((!customMem.customAlloc) ^ (!customMem.customFree)) return NULL;
   
       {   ZSTD_DCtx* const dctx = (ZSTD_DCtx*)ZSTD_customMalloc(sizeof(*dctx), customMem);
           if (!dctx) return NULL;
           dctx->customMem = customMem;
           ZSTD_initDCtx_internal(dctx);
           return dctx;
       }
   }
   
   ZSTD_DCtx* ZSTD_createDCtx_advanced(ZSTD_customMem customMem)
   {
       return ZSTD_createDCtx_internal(customMem);
   }
   
   ZSTD_DCtx* ZSTD_createDCtx(void)
   {
       DEBUGLOG(3, "ZSTD_createDCtx");
       return ZSTD_createDCtx_internal(ZSTD_defaultCMem);
   }
   
   static void ZSTD_clearDict(ZSTD_DCtx* dctx)
   {
       ZSTD_freeDDict(dctx->ddictLocal);
       dctx->ddictLocal = NULL;
       dctx->ddict = NULL;
       dctx->dictUses = ZSTD_dont_use;
   }
   
   size_t ZSTD_freeDCtx(ZSTD_DCtx* dctx)
   {
       if (dctx==NULL) return 0;   /* support free on NULL */
       RETURN_ERROR_IF(dctx->staticSize, memory_allocation, "not compatible with static DCtx");
       {   ZSTD_customMem const cMem = dctx->customMem;
           ZSTD_clearDict(dctx);
           ZSTD_customFree(dctx->inBuff, cMem);
           dctx->inBuff = NULL;
   #if defined(ZSTD_LEGACY_SUPPORT) && (ZSTD_LEGACY_SUPPORT >= 1)
           if (dctx->legacyContext)
               ZSTD_freeLegacyStreamContext(dctx->legacyContext, dctx->previousLegacyVersion);
   #endif
           if (dctx->ddictSet) {
               ZSTD_freeDDictHashSet(dctx->ddictSet, cMem);
               dctx->ddictSet = NULL;
           }
           ZSTD_customFree(dctx, cMem);
           return 0;
       }
   }
   
   /* no longer useful */
   void ZSTD_copyDCtx(ZSTD_DCtx* dstDCtx, const ZSTD_DCtx* srcDCtx)
   {
       size_t const toCopy = (size_t)((char*)(&dstDCtx->inBuff) - (char*)dstDCtx);
       ZSTD_memcpy(dstDCtx, srcDCtx, toCopy);  /* no need to copy workspace */
   }
   
   /* Given a dctx with a digested frame params, re-selects the correct ZSTD_DDict based on
    * the requested dict ID from the frame. If there exists a reference to the correct ZSTD_DDict, then
    * accordingly sets the ddict to be used to decompress the frame.
    *
    * If no DDict is found, then no action is taken, and the ZSTD_DCtx::ddict remains as-is.
    *
    * ZSTD_d_refMultipleDDicts must be enabled for this function to be called.
    */
   static void ZSTD_DCtx_selectFrameDDict(ZSTD_DCtx* dctx) {
       assert(dctx->refMultipleDDicts && dctx->ddictSet);
       DEBUGLOG(4, "Adjusting DDict based on requested dict ID from frame");
       if (dctx->ddict) {
           const ZSTD_DDict* frameDDict = ZSTD_DDictHashSet_getDDict(dctx->ddictSet, dctx->fParams.dictID);
           if (frameDDict) {
               DEBUGLOG(4, "DDict found!");
               ZSTD_clearDict(dctx);
               dctx->dictID = dctx->fParams.dictID;
               dctx->ddict = frameDDict;
               dctx->dictUses = ZSTD_use_indefinitely;
           }
       }
   }
   
   
   /*-*************************************************************
    *   Frame header decoding
    ***************************************************************/
   
   /*! ZSTD_isFrame() :
    *  Tells if the content of `buffer` starts with a valid Frame Identifier.
    *  Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0.
    *  Note 2 : Legacy Frame Identifiers are considered valid only if Legacy Support is enabled.
    *  Note 3 : Skippable Frame Identifiers are considered valid. */
   unsigned ZSTD_isFrame(const void* buffer, size_t size)
   {
       if (size < ZSTD_FRAMEIDSIZE) return 0;
       {   U32 const magic = MEM_readLE32(buffer);
           if (magic == ZSTD_MAGICNUMBER) return 1;
           if ((magic & ZSTD_MAGIC_SKIPPABLE_MASK) == ZSTD_MAGIC_SKIPPABLE_START) return 1;
       }
   #if defined(ZSTD_LEGACY_SUPPORT) && (ZSTD_LEGACY_SUPPORT >= 1)
       if (ZSTD_isLegacy(buffer, size)) return 1;
   #endif
       return 0;
   }
   
   /*! ZSTD_isSkippableFrame() :
    *  Tells if the content of `buffer` starts with a valid Frame Identifier for a skippable frame.
    *  Note : Frame Identifier is 4 bytes. If `size < 4`, @return will always be 0.
    */
   unsigned ZSTD_isSkippableFrame(const void* buffer, size_t size)
   {
       if (size < ZSTD_FRAMEIDSIZE) return 0;
       {   U32 const magic = MEM_readLE32(buffer);
           if ((magic & ZSTD_MAGIC_SKIPPABLE_MASK) == ZSTD_MAGIC_SKIPPABLE_START) return 1;
       }
       return 0;
   }
   
   /** ZSTD_frameHeaderSize_internal() :
    *  srcSize must be large enough to reach header size fields.
    *  note : only works for formats ZSTD_f_zstd1 and ZSTD_f_zstd1_magicless.
    * @return : size of the Frame Header
    *           or an error code, which can be tested with ZSTD_isError() */
   static size_t ZSTD_frameHeaderSize_internal(const void* src, size_t srcSize, ZSTD_format_e format)
   {
       size_t const minInputSize = ZSTD_startingInputLength(format);
       RETURN_ERROR_IF(srcSize < minInputSize, srcSize_wrong, "");
   
       {   BYTE const fhd = ((const BYTE*)src)[minInputSize-1];
           U32 const dictID= fhd & 3;
           U32 const singleSegment = (fhd >> 5) & 1;
           U32 const fcsId = fhd >> 6;
           return minInputSize + !singleSegment
                + ZSTD_did_fieldSize[dictID] + ZSTD_fcs_fieldSize[fcsId]
                + (singleSegment && !fcsId);
       }
   }
   
   /** ZSTD_frameHeaderSize() :
    *  srcSize must be >= ZSTD_frameHeaderSize_prefix.
    * @return : size of the Frame Header,
    *           or an error code (if srcSize is too small) */
   size_t ZSTD_frameHeaderSize(const void* src, size_t srcSize)
   {
       return ZSTD_frameHeaderSize_internal(src, srcSize, ZSTD_f_zstd1);
   }
   
   
   /** ZSTD_getFrameHeader_advanced() :
    *  decode Frame Header, or require larger `srcSize`.
    *  note : only works for formats ZSTD_f_zstd1 and ZSTD_f_zstd1_magicless
    * @return : 0, `zfhPtr` is correctly filled,
    *          >0, `srcSize` is too small, value is wanted `srcSize` amount,
    *           or an error code, which can be tested using ZSTD_isError() */
   size_t ZSTD_getFrameHeader_advanced(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize, ZSTD_format_e format)
   {
       const BYTE* ip = (const BYTE*)src;
       size_t const minInputSize = ZSTD_startingInputLength(format);
   
       ZSTD_memset(zfhPtr, 0, sizeof(*zfhPtr));   /* not strictly necessary, but static analyzer do not understand that zfhPtr is only going to be read only if return value is zero, since they are 2 different signals */
       if (srcSize < minInputSize) return minInputSize;
       RETURN_ERROR_IF(src==NULL, GENERIC, "invalid parameter");
   
       if ( (format != ZSTD_f_zstd1_magicless)
         && (MEM_readLE32(src) != ZSTD_MAGICNUMBER) ) {
           if ((MEM_readLE32(src) & ZSTD_MAGIC_SKIPPABLE_MASK) == ZSTD_MAGIC_SKIPPABLE_START) {
               /* skippable frame */
               if (srcSize < ZSTD_SKIPPABLEHEADERSIZE)
                   return ZSTD_SKIPPABLEHEADERSIZE; /* magic number + frame length */
               ZSTD_memset(zfhPtr, 0, sizeof(*zfhPtr));
               zfhPtr->frameContentSize = MEM_readLE32((const char *)src + ZSTD_FRAMEIDSIZE);
               zfhPtr->frameType = ZSTD_skippableFrame;
               return 0;
           }
           RETURN_ERROR(prefix_unknown, "");
       }
   
       /* ensure there is enough `srcSize` to fully read/decode frame header */
       {   size_t const fhsize = ZSTD_frameHeaderSize_internal(src, srcSize, format);
           if (srcSize < fhsize) return fhsize;
           zfhPtr->headerSize = (U32)fhsize;
       }
   
       {   BYTE const fhdByte = ip[minInputSize-1];
           size_t pos = minInputSize;
           U32 const dictIDSizeCode = fhdByte&3;
           U32 const checksumFlag = (fhdByte>>2)&1;
           U32 const singleSegment = (fhdByte>>5)&1;
           U32 const fcsID = fhdByte>>6;
           U64 windowSize = 0;
           U32 dictID = 0;
           U64 frameContentSize = ZSTD_CONTENTSIZE_UNKNOWN;
           RETURN_ERROR_IF((fhdByte & 0x08) != 0, frameParameter_unsupported,
                           "reserved bits, must be zero");
   
           if (!singleSegment) {
               BYTE const wlByte = ip[pos++];
               U32 const windowLog = (wlByte >> 3) + ZSTD_WINDOWLOG_ABSOLUTEMIN;
               RETURN_ERROR_IF(windowLog > ZSTD_WINDOWLOG_MAX, frameParameter_windowTooLarge, "");
               windowSize = (1ULL << windowLog);
               windowSize += (windowSize >> 3) * (wlByte&7);
           }
           switch(dictIDSizeCode)
           {
               default:
                   assert(0);  /* impossible */
                   ZSTD_FALLTHROUGH;
               case 0 : break;
               case 1 : dictID = ip[pos]; pos++; break;
               case 2 : dictID = MEM_readLE16(ip+pos); pos+=2; break;
               case 3 : dictID = MEM_readLE32(ip+pos); pos+=4; break;
           }
           switch(fcsID)
           {
               default:
                   assert(0);  /* impossible */
                   ZSTD_FALLTHROUGH;
               case 0 : if (singleSegment) frameContentSize = ip[pos]; break;
               case 1 : frameContentSize = MEM_readLE16(ip+pos)+256; break;
               case 2 : frameContentSize = MEM_readLE32(ip+pos); break;
               case 3 : frameContentSize = MEM_readLE64(ip+pos); break;
           }
           if (singleSegment) windowSize = frameContentSize;
   
           zfhPtr->frameType = ZSTD_frame;
           zfhPtr->frameContentSize = frameContentSize;
           zfhPtr->windowSize = windowSize;
           zfhPtr->blockSizeMax = (unsigned) MIN(windowSize, ZSTD_BLOCKSIZE_MAX);
           zfhPtr->dictID = dictID;
           zfhPtr->checksumFlag = checksumFlag;
       }
       return 0;
   }
   
   /** ZSTD_getFrameHeader() :
    *  decode Frame Header, or require larger `srcSize`.
    *  note : this function does not consume input, it only reads it.
    * @return : 0, `zfhPtr` is correctly filled,
    *          >0, `srcSize` is too small, value is wanted `srcSize` amount,
    *           or an error code, which can be tested using ZSTD_isError() */
   size_t ZSTD_getFrameHeader(ZSTD_frameHeader* zfhPtr, const void* src, size_t srcSize)
   {
       return ZSTD_getFrameHeader_advanced(zfhPtr, src, srcSize, ZSTD_f_zstd1);
   }
   
   /** ZSTD_getFrameContentSize() :
    *  compatible with legacy mode
    * @return : decompressed size of the single frame pointed to be `src` if known, otherwise
    *         - ZSTD_CONTENTSIZE_UNKNOWN if the size cannot be determined
    *         - ZSTD_CONTENTSIZE_ERROR if an error occurred (e.g. invalid magic number, srcSize too small) */
   unsigned long long ZSTD_getFrameContentSize(const void *src, size_t srcSize)
   {
   #if defined(ZSTD_LEGACY_SUPPORT) && (ZSTD_LEGACY_SUPPORT >= 1)
       if (ZSTD_isLegacy(src, srcSize)) {
           unsigned long long const ret = ZSTD_getDecompressedSize_legacy(src, srcSize);
           return ret == 0 ? ZSTD_CONTENTSIZE_UNKNOWN : ret;
       }
   #endif
       {   ZSTD_frameHeader zfh;
           if (ZSTD_getFrameHeader(&zfh, src, srcSize) != 0)
               return ZSTD_CONTENTSIZE_ERROR;
           if (zfh.frameType == ZSTD_skippableFrame) {
               return 0;
           } else {
               return zfh.frameContentSize;
       }   }
   }
   
   static size_t readSkippableFrameSize(void const* src, size_t srcSize)
   {
       size_t const skippableHeaderSize = ZSTD_SKIPPABLEHEADERSIZE;
       U32 sizeU32;
   
       RETURN_ERROR_IF(srcSize < ZSTD_SKIPPABLEHEADERSIZE, srcSize_wrong, "");
   
       sizeU32 = MEM_readLE32((BYTE const*)src + ZSTD_FRAMEIDSIZE);
       RETURN_ERROR_IF((U32)(sizeU32 + ZSTD_SKIPPABLEHEADERSIZE) < sizeU32,
                       frameParameter_unsupported, "");
       {
           size_t const skippableSize = skippableHeaderSize + sizeU32;
           RETURN_ERROR_IF(skippableSize > srcSize, srcSize_wrong, "");
           return skippableSize;
       }
   }
   
   /*! ZSTD_readSkippableFrame() :
    * Retrieves a zstd skippable frame containing data given by src, and writes it to dst buffer.
    *
    * The parameter magicVariant will receive the magicVariant that was supplied when the frame was written,
    * i.e. magicNumber - ZSTD_MAGIC_SKIPPABLE_START.  This can be NULL if the caller is not interested
    * in the magicVariant.
    *
    * Returns an error if destination buffer is not large enough, or if the frame is not skippable.
    *
    * @return : number of bytes written or a ZSTD error.
    */
   ZSTDLIB_API size_t ZSTD_readSkippableFrame(void* dst, size_t dstCapacity, unsigned* magicVariant,
                                               const void* src, size_t srcSize)
   {
       U32 const magicNumber = MEM_readLE32(src);
       size_t skippableFrameSize = readSkippableFrameSize(src, srcSize);
       size_t skippableContentSize = skippableFrameSize - ZSTD_SKIPPABLEHEADERSIZE;
   
       /* check input validity */
       RETURN_ERROR_IF(!ZSTD_isSkippableFrame(src, srcSize), frameParameter_unsupported, "");
       RETURN_ERROR_IF(skippableFrameSize < ZSTD_SKIPPABLEHEADERSIZE || skippableFrameSize > srcSize, srcSize_wrong, "");
       RETURN_ERROR_IF(skippableContentSize > dstCapacity, dstSize_tooSmall, "");
   
       /* deliver payload */
       if (skippableContentSize > 0  && dst != NULL)
           ZSTD_memcpy(dst, (const BYTE *)src + ZSTD_SKIPPABLEHEADERSIZE, skippableContentSize);
       if (magicVariant != NULL)
           *magicVariant = magicNumber - ZSTD_MAGIC_SKIPPABLE_START;
       return skippableContentSize;
   }
   
   /** ZSTD_findDecompressedSize() :
    *  compatible with legacy mode
    *  `srcSize` must be the exact length of some number of ZSTD compressed and/or
    *      skippable frames
    *  @return : decompressed size of the frames contained */
   unsigned long long ZSTD_findDecompressedSize(const void* src, size_t srcSize)
   {
       unsigned long long totalDstSize = 0;
   
       while (srcSize >= ZSTD_startingInputLength(ZSTD_f_zstd1)) {
           U32 const magicNumber = MEM_readLE32(src);
   
           if ((magicNumber & ZSTD_MAGIC_SKIPPABLE_MASK) == ZSTD_MAGIC_SKIPPABLE_START) {
               size_t const skippableSize = readSkippableFrameSize(src, srcSize);
               if (ZSTD_isError(skippableSize)) {
                   return ZSTD_CONTENTSIZE_ERROR;
               }
               assert(skippableSize <= srcSize);
   
               src = (const BYTE *)src + skippableSize;
               srcSize -= skippableSize;
               continue;
           }
   
           {   unsigned long long const ret = ZSTD_getFrameContentSize(src, srcSize);
               if (ret >= ZSTD_CONTENTSIZE_ERROR) return ret;
   
               /* check for overflow */
               if (totalDstSize + ret < totalDstSize) return ZSTD_CONTENTSIZE_ERROR;
               totalDstSize += ret;
           }
           {   size_t const frameSrcSize = ZSTD_findFrameCompressedSize(src, srcSize);
               if (ZSTD_isError(frameSrcSize)) {
                   return ZSTD_CONTENTSIZE_ERROR;
               }
   
               src = (const BYTE *)src + frameSrcSize;
               srcSize -= frameSrcSize;
           }
       }  /* while (srcSize >= ZSTD_frameHeaderSize_prefix) */
   
       if (srcSize) return ZSTD_CONTENTSIZE_ERROR;
   
       return totalDstSize;
   }
   
   /** ZSTD_getDecompressedSize() :
    *  compatible with legacy mode
    * @return : decompressed size if known, 0 otherwise
                note : 0 can mean any of the following :
                      - frame content is empty
                      - decompressed size field is not present in frame header
                      - frame header unknown / not supported
                      - frame header not complete (`srcSize` too small) */
   unsigned long long ZSTD_getDecompressedSize(const void* src, size_t srcSize)
   {
       unsigned long long const ret = ZSTD_getFrameContentSize(src, srcSize);
       ZSTD_STATIC_ASSERT(ZSTD_CONTENTSIZE_ERROR < ZSTD_CONTENTSIZE_UNKNOWN);
       return (ret >= ZSTD_CONTENTSIZE_ERROR) ? 0 : ret;
   }
   
   
   /** ZSTD_decodeFrameHeader() :
    * `headerSize` must be the size provided by ZSTD_frameHeaderSize().
    * If multiple DDict references are enabled, also will choose the correct DDict to use.
    * @return : 0 if success, or an error code, which can be tested using ZSTD_isError() */
   static size_t ZSTD_decodeFrameHeader(ZSTD_DCtx* dctx, const void* src, size_t headerSize)
   {
       size_t const result = ZSTD_getFrameHeader_advanced(&(dctx->fParams), src, headerSize, dctx->format);
       if (ZSTD_isError(result)) return result;    /* invalid header */
       RETURN_ERROR_IF(result>0, srcSize_wrong, "headerSize too small");
   
       /* Reference DDict requested by frame if dctx references multiple ddicts */
       if (dctx->refMultipleDDicts == ZSTD_rmd_refMultipleDDicts && dctx->ddictSet) {
           ZSTD_DCtx_selectFrameDDict(dctx);
       }
   
   #ifndef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
       /* Skip the dictID check in fuzzing mode, because it makes the search
        * harder.
        */
       RETURN_ERROR_IF(dctx->fParams.dictID && (dctx->dictID != dctx->fParams.dictID),
                       dictionary_wrong, "");
   #endif
       dctx->validateChecksum = (dctx->fParams.checksumFlag && !dctx->forceIgnoreChecksum) ? 1 : 0;
       if (dctx->validateChecksum) XXH64_reset(&dctx->xxhState, 0);
       dctx->processedCSize += headerSize;
       return 0;
   }
   
   static ZSTD_frameSizeInfo ZSTD_errorFrameSizeInfo(size_t ret)
   {
       ZSTD_frameSizeInfo frameSizeInfo;
       frameSizeInfo.compressedSize = ret;
       frameSizeInfo.decompressedBound = ZSTD_CONTENTSIZE_ERROR;
       return frameSizeInfo;
   }
   
   static ZSTD_frameSizeInfo ZSTD_findFrameSizeInfo(const void* src, size_t srcSize)
   {
       ZSTD_frameSizeInfo frameSizeInfo;
       ZSTD_memset(&frameSizeInfo, 0, sizeof(ZSTD_frameSizeInfo));
   
   #if defined(ZSTD_LEGACY_SUPPORT) && (ZSTD_LEGACY_SUPPORT >= 1)
       if (ZSTD_isLegacy(src, srcSize))
           return ZSTD_findFrameSizeInfoLegacy(src, srcSize);
   #endif
   
       if ((srcSize >= ZSTD_SKIPPABLEHEADERSIZE)
           && (MEM_readLE32(src) & ZSTD_MAGIC_SKIPPABLE_MASK) == ZSTD_MAGIC_SKIPPABLE_START) {
           frameSizeInfo.compressedSize = readSkippableFrameSize(src, srcSize);
           assert(ZSTD_isError(frameSizeInfo.compressedSize) ||
                  frameSizeInfo.compressedSize <= srcSize);
           return frameSizeInfo;
       } else {
           const BYTE* ip = (const BYTE*)src;
           const BYTE* const ipstart = ip;
           size_t remainingSize = srcSize;
           size_t nbBlocks = 0;
           ZSTD_frameHeader zfh;
   
           /* Extract Frame Header */
           {   size_t const ret = ZSTD_getFrameHeader(&zfh, src, srcSize);
               if (ZSTD_isError(ret))
                   return ZSTD_errorFrameSizeInfo(ret);
               if (ret > 0)
                   return ZSTD_errorFrameSizeInfo(ERROR(srcSize_wrong));
           }
   
           ip += zfh.headerSize;
           remainingSize -= zfh.headerSize;
   
           /* Iterate over each block */
           while (1) {
               blockProperties_t blockProperties;
               size_t const cBlockSize = ZSTD_getcBlockSize(ip, remainingSize, &blockProperties);
               if (ZSTD_isError(cBlockSize))
                   return ZSTD_errorFrameSizeInfo(cBlockSize);
   
               if (ZSTD_blockHeaderSize + cBlockSize > remainingSize)
                   return ZSTD_errorFrameSizeInfo(ERROR(srcSize_wrong));
   
               ip += ZSTD_blockHeaderSize + cBlockSize;
               remainingSize -= ZSTD_blockHeaderSize + cBlockSize;
               nbBlocks++;
   
               if (blockProperties.lastBlock) break;
           }
   
           /* Final frame content checksum */
           if (zfh.checksumFlag) {
               if (remainingSize < 4)
                   return ZSTD_errorFrameSizeInfo(ERROR(srcSize_wrong));
               ip += 4;
           }
   
           frameSizeInfo.compressedSize = (size_t)(ip - ipstart);
           frameSizeInfo.decompressedBound = (zfh.frameContentSize != ZSTD_CONTENTSIZE_UNKNOWN)
                                           ? zfh.frameContentSize
                                           : nbBlocks * zfh.blockSizeMax;
           return frameSizeInfo;
       }
   }
   
   /** ZSTD_findFrameCompressedSize() :
    *  compatible with legacy mode
    *  `src` must point to the start of a ZSTD frame, ZSTD legacy frame, or skippable frame
    *  `srcSize` must be at least as large as the frame contained
    *  @return : the compressed size of the frame starting at `src` */
   size_t ZSTD_findFrameCompressedSize(const void *src, size_t srcSize)
   {
       ZSTD_frameSizeInfo const frameSizeInfo = ZSTD_findFrameSizeInfo(src, srcSize);
       return frameSizeInfo.compressedSize;
   }
   
   /** ZSTD_decompressBound() :
    *  compatible with legacy mode
    *  `src` must point to the start of a ZSTD frame or a skippeable frame
    *  `srcSize` must be at least as large as the frame contained
    *  @return : the maximum decompressed size of the compressed source
    */
   unsigned long long ZSTD_decompressBound(const void* src, size_t srcSize)
   {
       unsigned long long bound = 0;
       /* Iterate over each frame */
       while (srcSize > 0) {
           ZSTD_frameSizeInfo const frameSizeInfo = ZSTD_findFrameSizeInfo(src, srcSize);
           size_t const compressedSize = frameSizeInfo.compressedSize;
           unsigned long long const decompressedBound = frameSizeInfo.decompressedBound;
           if (ZSTD_isError(compressedSize) || decompressedBound == ZSTD_CONTENTSIZE_ERROR)
               return ZSTD_CONTENTSIZE_ERROR;
           assert(srcSize >= compressedSize);
           src = (const BYTE*)src + compressedSize;
           srcSize -= compressedSize;
           bound += decompressedBound;
       }
       return bound;
   }
   
   
   /*-*************************************************************
    *   Frame decoding
    ***************************************************************/
   
   /** ZSTD_insertBlock() :
    *  insert `src` block into `dctx` history. Useful to track uncompressed blocks. */
   size_t ZSTD_insertBlock(ZSTD_DCtx* dctx, const void* blockStart, size_t blockSize)
   {
       DEBUGLOG(5, "ZSTD_insertBlock: %u bytes", (unsigned)blockSize);
       ZSTD_checkContinuity(dctx, blockStart, blockSize);
       dctx->previousDstEnd = (const char*)blockStart + blockSize;
       return blockSize;
   }
   
   
   static size_t ZSTD_copyRawBlock(void* dst, size_t dstCapacity,
                             const void* src, size_t srcSize)
   {
       DEBUGLOG(5, "ZSTD_copyRawBlock");
       RETURN_ERROR_IF(srcSize > dstCapacity, dstSize_tooSmall, "");
       if (dst == NULL) {
           if (srcSize == 0) return 0;
           RETURN_ERROR(dstBuffer_null, "");
       }
       ZSTD_memcpy(dst, src, srcSize);
       return srcSize;
   }
   
   static size_t ZSTD_setRleBlock(void* dst, size_t dstCapacity,
                                  BYTE b,
                                  size_t regenSize)
   {
       RETURN_ERROR_IF(regenSize > dstCapacity, dstSize_tooSmall, "");
       if (dst == NULL) {
           if (regenSize == 0) return 0;
           RETURN_ERROR(dstBuffer_null, "");
       }
       ZSTD_memset(dst, b, regenSize);
       return regenSize;
   }
   
   static void ZSTD_DCtx_trace_end(ZSTD_DCtx const* dctx, U64 uncompressedSize, U64 compressedSize, unsigned streaming)
   {
   #if ZSTD_TRACE
       if (dctx->traceCtx && ZSTD_trace_decompress_end != NULL) {
           ZSTD_Trace trace;
           ZSTD_memset(&trace, 0, sizeof(trace));
           trace.version = ZSTD_VERSION_NUMBER;
           trace.streaming = streaming;
           if (dctx->ddict) {
               trace.dictionaryID = ZSTD_getDictID_fromDDict(dctx->ddict);
               trace.dictionarySize = ZSTD_DDict_dictSize(dctx->ddict);
               trace.dictionaryIsCold = dctx->ddictIsCold;
           }
           trace.uncompressedSize = (size_t)uncompressedSize;
           trace.compressedSize = (size_t)compressedSize;
           trace.dctx = dctx;
           ZSTD_trace_decompress_end(dctx->traceCtx, &trace);
       }
   #else
       (void)dctx;
       (void)uncompressedSize;
       (void)compressedSize;
       (void)streaming;
   #endif
   }
   
   
   /*! ZSTD_decompressFrame() :
    * @dctx must be properly initialized
    *  will update *srcPtr and *srcSizePtr,
    *  to make *srcPtr progress by one frame. */
   static size_t ZSTD_decompressFrame(ZSTD_DCtx* dctx,
                                      void* dst, size_t dstCapacity,
                                const void** srcPtr, size_t *srcSizePtr)
   {
       const BYTE* const istart = (const BYTE*)(*srcPtr);
       const BYTE* ip = istart;
       BYTE* const ostart = (BYTE*)dst;
       BYTE* const oend = dstCapacity != 0 ? ostart + dstCapacity : ostart;
       BYTE* op = ostart;
       size_t remainingSrcSize = *srcSizePtr;
   
       DEBUGLOG(4, "ZSTD_decompressFrame (srcSize:%i)", (int)*srcSizePtr);
   
       /* check */
       RETURN_ERROR_IF(
           remainingSrcSize < ZSTD_FRAMEHEADERSIZE_MIN(dctx->format)+ZSTD_blockHeaderSize,
           srcSize_wrong, "");
   
       /* Frame Header */
       {   size_t const frameHeaderSize = ZSTD_frameHeaderSize_internal(
                   ip, ZSTD_FRAMEHEADERSIZE_PREFIX(dctx->format), dctx->format);
           if (ZSTD_isError(frameHeaderSize)) return frameHeaderSize;
           RETURN_ERROR_IF(remainingSrcSize < frameHeaderSize+ZSTD_blockHeaderSize,
                           srcSize_wrong, "");
           FORWARD_IF_ERROR( ZSTD_decodeFrameHeader(dctx, ip, frameHeaderSize) , "");
           ip += frameHeaderSize; remainingSrcSize -= frameHeaderSize;
       }
   
       /* Loop on each block */
       while (1) {
           size_t decodedSize;
           blockProperties_t blockProperties;
           size_t const cBlockSize = ZSTD_getcBlockSize(ip, remainingSrcSize, &blockProperties);
           if (ZSTD_isError(cBlockSize)) return cBlockSize;
   
           ip += ZSTD_blockHeaderSize;
           remainingSrcSize -= ZSTD_blockHeaderSize;
           RETURN_ERROR_IF(cBlockSize > remainingSrcSize, srcSize_wrong, "");
   
           switch(blockProperties.blockType)
           {
           case bt_compressed:
               decodedSize = ZSTD_decompressBlock_internal(dctx, op, (size_t)(oend-op), ip, cBlockSize, /* frame */ 1, not_streaming);
               break;
           case bt_raw :
               decodedSize = ZSTD_copyRawBlock(op, (size_t)(oend-op), ip, cBlockSize);
               break;
           case bt_rle :
               decodedSize = ZSTD_setRleBlock(op, (size_t)(oend-op), *ip, blockProperties.origSize);
               break;
           case bt_reserved :
           default:
               RETURN_ERROR(corruption_detected, "invalid block type");
           }
   
           if (ZSTD_isError(decodedSize)) return decodedSize;
           if (dctx->validateChecksum)
               XXH64_update(&dctx->xxhState, op, decodedSize);
           if (decodedSize != 0)
               op += decodedSize;
           assert(ip != NULL);
           ip += cBlockSize;
           remainingSrcSize -= cBlockSize;
           if (blockProperties.lastBlock) break;
       }
   
       if (dctx->fParams.frameContentSize != ZSTD_CONTENTSIZE_UNKNOWN) {
           RETURN_ERROR_IF((U64)(op-ostart) != dctx->fParams.frameContentSize,
                           corruption_detected, "");
       }
       if (dctx->fParams.checksumFlag) { /* Frame content checksum verification */
           RETURN_ERROR_IF(remainingSrcSize<4, checksum_wrong, "");
           if (!dctx->forceIgnoreChecksum) {
               U32 const checkCalc = (U32)XXH64_digest(&dctx->xxhState);
               U32 checkRead;
               checkRead = MEM_readLE32(ip);
               RETURN_ERROR_IF(checkRead != checkCalc, checksum_wrong, "");
           }
           ip += 4;
           remainingSrcSize -= 4;
       }
       ZSTD_DCtx_trace_end(dctx, (U64)(op-ostart), (U64)(ip-istart), /* streaming */ 0);
       /* Allow caller to get size read */
       *srcPtr = ip;
       *srcSizePtr = remainingSrcSize;
       return (size_t)(op-ostart);
   }
   
   static size_t ZSTD_decompressMultiFrame(ZSTD_DCtx* dctx,
                                           void* dst, size_t dstCapacity,
                                     const void* src, size_t srcSize,
                                     const void* dict, size_t dictSize,
                                     const ZSTD_DDict* ddict)
   {
       void* const dststart = dst;
       int moreThan1Frame = 0;
   
       DEBUGLOG(5, "ZSTD_decompressMultiFrame");
       assert(dict==NULL || ddict==NULL);  /* either dict or ddict set, not both */
   
       if (ddict) {
           dict = ZSTD_DDict_dictContent(ddict);
           dictSize = ZSTD_DDict_dictSize(ddict);
       }
   
       while (srcSize >= ZSTD_startingInputLength(dctx->format)) {
   
   #if defined(ZSTD_LEGACY_SUPPORT) && (ZSTD_LEGACY_SUPPORT >= 1)
           if (ZSTD_isLegacy(src, srcSize)) {
               size_t decodedSize;
               size_t const frameSize = ZSTD_findFrameCompressedSizeLegacy(src, srcSize);
               if (ZSTD_isError(frameSize)) return frameSize;
               RETURN_ERROR_IF(dctx->staticSize, memory_allocation,
                   "legacy support is not compatible with static dctx");
   
               decodedSize = ZSTD_decompressLegacy(dst, dstCapacity, src, frameSize, dict, dictSize);
               if (ZSTD_isError(decodedSize)) return decodedSize;
   
               assert(decodedSize <= dstCapacity);
               dst = (BYTE*)dst + decodedSize;
               dstCapacity -= decodedSize;
   
               src = (const BYTE*)src + frameSize;
               srcSize -= frameSize;
  
              continue;
          }
  #endif
  
          {   U32 const magicNumber = MEM_readLE32(src);
              DEBUGLOG(4, "reading magic number %08X (expecting %08X)",
                          (unsigned)magicNumber, ZSTD_MAGICNUMBER);
              if ((magicNumber & ZSTD_MAGIC_SKIPPABLE_MASK) == ZSTD_MAGIC_SKIPPABLE_START) {
                  size_t const skippableSize = readSkippableFrameSize(src, srcSize);
                  FORWARD_IF_ERROR(skippableSize, "readSkippableFrameSize failed");
                  assert(skippableSize <= srcSize);
  
                  src = (const BYTE *)src + skippableSize;
                  srcSize -= skippableSize;
                  continue;
          }   }
  
          if (ddict) {
              /* we were called from ZSTD_decompress_usingDDict */
              FORWARD_IF_ERROR(ZSTD_decompressBegin_usingDDict(dctx, ddict), "");
          } else {
              /* this will initialize correctly with no dict if dict == NULL, so
               * use this in all cases but ddict */
              FORWARD_IF_ERROR(ZSTD_decompressBegin_usingDict(dctx, dict, dictSize), "");
          }
          ZSTD_checkContinuity(dctx, dst, dstCapacity);
  
          {   const size_t res = ZSTD_decompressFrame(dctx, dst, dstCapacity,
                                                      &src, &srcSize);
              RETURN_ERROR_IF(
                  (ZSTD_getErrorCode(res) == ZSTD_error_prefix_unknown)
               && (moreThan1Frame==1),
                  srcSize_wrong,
                  "At least one frame successfully completed, "
                  "but following bytes are garbage: "
                  "it's more likely to be a srcSize error, "
                  "specifying more input bytes than size of frame(s). "
                  "Note: one could be unlucky, it might be a corruption error instead, "
                  "happening right at the place where we expect zstd magic bytes. "
                  "But this is _much_ less likely than a srcSize field error.");
              if (ZSTD_isError(res)) return res;
              assert(res <= dstCapacity);
              if (res != 0)
                  dst = (BYTE*)dst + res;
              dstCapacity -= res;
          }
          moreThan1Frame = 1;
      }  /* while (srcSize >= ZSTD_frameHeaderSize_prefix) */
  
      RETURN_ERROR_IF(srcSize, srcSize_wrong, "input not entirely consumed");
  
      return (size_t)((BYTE*)dst - (BYTE*)dststart);
  }
  
  size_t ZSTD_decompress_usingDict(ZSTD_DCtx* dctx,
                                   void* dst, size_t dstCapacity,
                             const void* src, size_t srcSize,
                             const void* dict, size_t dictSize)
  {
      return ZSTD_decompressMultiFrame(dctx, dst, dstCapacity, src, srcSize, dict, dictSize, NULL);
  }
  
  
  static ZSTD_DDict const* ZSTD_getDDict(ZSTD_DCtx* dctx)
  {
      switch (dctx->dictUses) {
      default:
          assert(0 /* Impossible */);
          ZSTD_FALLTHROUGH;
      case ZSTD_dont_use:
          ZSTD_clearDict(dctx);
          return NULL;
      case ZSTD_use_indefinitely:
          return dctx->ddict;
      case ZSTD_use_once:
          dctx->dictUses = ZSTD_dont_use;
          return dctx->ddict;
      }
  }
  
  size_t ZSTD_decompressDCtx(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize)
  {
      return ZSTD_decompress_usingDDict(dctx, dst, dstCapacity, src, srcSize, ZSTD_getDDict(dctx));
  }
  
  
  size_t ZSTD_decompress(void* dst, size_t dstCapacity, const void* src, size_t srcSize)
  {
  #if defined(ZSTD_HEAPMODE) && (ZSTD_HEAPMODE>=1)
      size_t regenSize;
      ZSTD_DCtx* const dctx =  ZSTD_createDCtx_internal(ZSTD_defaultCMem);
      RETURN_ERROR_IF(dctx==NULL, memory_allocation, "NULL pointer!");
      regenSize = ZSTD_decompressDCtx(dctx, dst, dstCapacity, src, srcSize);
      ZSTD_freeDCtx(dctx);
      return regenSize;
  #else   /* stack mode */
      ZSTD_DCtx dctx;
      ZSTD_initDCtx_internal(&dctx);
      return ZSTD_decompressDCtx(&dctx, dst, dstCapacity, src, srcSize);
  #endif
  }
  
  
  /*-**************************************
  *   Advanced Streaming Decompression API
  *   Bufferless and synchronous
  ****************************************/
  size_t ZSTD_nextSrcSizeToDecompress(ZSTD_DCtx* dctx) { return dctx->expected; }
  
  /**
   * Similar to ZSTD_nextSrcSizeToDecompress(), but when when a block input can be streamed,
   * we allow taking a partial block as the input. Currently only raw uncompressed blocks can
   * be streamed.
   *
   * For blocks that can be streamed, this allows us to reduce the latency until we produce
   * output, and avoid copying the input.
   *
   * @param inputSize - The total amount of input that the caller currently has.
   */
  static size_t ZSTD_nextSrcSizeToDecompressWithInputSize(ZSTD_DCtx* dctx, size_t inputSize) {
      if (!(dctx->stage == ZSTDds_decompressBlock || dctx->stage == ZSTDds_decompressLastBlock))
          return dctx->expected;
      if (dctx->bType != bt_raw)
          return dctx->expected;
      return BOUNDED(1, inputSize, dctx->expected);
  }
  
  ZSTD_nextInputType_e ZSTD_nextInputType(ZSTD_DCtx* dctx) {
      switch(dctx->stage)
      {
      default:   /* should not happen */
          assert(0);
          ZSTD_FALLTHROUGH;
      case ZSTDds_getFrameHeaderSize:
          ZSTD_FALLTHROUGH;
      case ZSTDds_decodeFrameHeader:
          return ZSTDnit_frameHeader;
      case ZSTDds_decodeBlockHeader:
          return ZSTDnit_blockHeader;
      case ZSTDds_decompressBlock:
          return ZSTDnit_block;
      case ZSTDds_decompressLastBlock:
          return ZSTDnit_lastBlock;
      case ZSTDds_checkChecksum:
          return ZSTDnit_checksum;
      case ZSTDds_decodeSkippableHeader:
          ZSTD_FALLTHROUGH;
      case ZSTDds_skipFrame:
          return ZSTDnit_skippableFrame;
      }
  }
  
  static int ZSTD_isSkipFrame(ZSTD_DCtx* dctx) { return dctx->stage == ZSTDds_skipFrame; }
  
  /** ZSTD_decompressContinue() :
   *  srcSize : must be the exact nb of bytes expected (see ZSTD_nextSrcSizeToDecompress())
   *  @return : nb of bytes generated into `dst` (necessarily <= `dstCapacity)
   *            or an error code, which can be tested using ZSTD_isError() */
  size_t ZSTD_decompressContinue(ZSTD_DCtx* dctx, void* dst, size_t dstCapacity, const void* src, size_t srcSize)
  {
      DEBUGLOG(5, "ZSTD_decompressContinue (srcSize:%u)", (unsigned)srcSize);
      /* Sanity check */
      RETURN_ERROR_IF(srcSize != ZSTD_nextSrcSizeToDecompressWithInputSize(dctx, srcSize), srcSize_wrong, "not allowed");
      ZSTD_checkContinuity(dctx, dst, dstCapacity);
  
      dctx->processedCSize += srcSize;
  
      switch (dctx->stage)
      {
      case ZSTDds_getFrameHeaderSize :
          assert(src != NULL);
          if (dctx->format == ZSTD_f_zstd1) {  /* allows header */
              assert(srcSize >= ZSTD_FRAMEIDSIZE);  /* to read skippable magic number */
              if ((MEM_readLE32(src) & ZSTD_MAGIC_SKIPPABLE_MASK) == ZSTD_MAGIC_SKIPPABLE_START) {        /* skippable frame */
                  ZSTD_memcpy(dctx->headerBuffer, src, srcSize);
                  dctx->expected = ZSTD_SKIPPABLEHEADERSIZE - srcSize;  /* remaining to load to get full skippable frame header */
                  dctx->stage = ZSTDds_decodeSkippableHeader;
                  return 0;
          }   }
          dctx->headerSize = ZSTD_frameHeaderSize_internal(src, srcSize, dctx->format);
          if (ZSTD_isError(dctx->headerSize)) return dctx->headerSize;
          ZSTD_memcpy(dctx->headerBuffer, src, srcSize);
          dctx->expected = dctx->headerSize - srcSize;
          dctx->stage = ZSTDds_decodeFrameHeader;
          return 0;
  
      case ZSTDds_decodeFrameHeader:
          assert(src != NULL);
          ZSTD_memcpy(dctx->headerBuffer + (dctx->headerSize - srcSize), src, srcSize);
          FORWARD_IF_ERROR(ZSTD_decodeFrameHeader(dctx, dctx->headerBuffer, dctx->headerSize), "");
          dctx->expected = ZSTD_blockHeaderSize;
          dctx->stage = ZSTDds_decodeBlockHeader;
          return 0;
  
      case ZSTDds_decodeBlockHeader:
          {   blockProperties_t bp;
              size_t const cBlockSize = ZSTD_getcBlockSize(src, ZSTD_blockHeaderSize, &bp);
              if (ZSTD_isError(cBlockSize)) return cBlockSize;
              RETURN_ERROR_IF(cBlockSize > dctx->fParams.blockSizeMax, corruption_detected, "Block Size Exceeds Maximum");
              dctx->expected = cBlockSize;
              dctx->bType = bp.blockType;
              dctx->rleSize = bp.origSize;
              if (cBlockSize) {
                  dctx->stage = bp.lastBlock ? ZSTDds_decompressLastBlock : ZSTDds_decompressBlock;
                  return 0;
              }
              /* empty block */
              if (bp.lastBlock) {
                  if (dctx->fParams.checksumFlag) {
                      dctx->expected = 4;
                      dctx->stage = ZSTDds_checkChecksum;
                  } else {
                      dctx->expected = 0; /* end of frame */
                      dctx->stage = ZSTDds_getFrameHeaderSize;
                  }
              } else {
                  dctx->expected = ZSTD_blockHeaderSize;  /* jump to next header */
                  dctx->stage = ZSTDds_decodeBlockHeader;
              }
              return 0;
          }
  
      case ZSTDds_decompressLastBlock:
      case ZSTDds_decompressBlock:
          DEBUGLOG(5, "ZSTD_decompressContinue: case ZSTDds_decompressBlock");
          {   size_t rSize;
              switch(dctx->bType)
              {
              case bt_compressed:
                  DEBUGLOG(5, "ZSTD_decompressContinue: case bt_compressed");
                  rSize = ZSTD_decompressBlock_internal(dctx, dst, dstCapacity, src, srcSize, /* frame */ 1, is_streaming);
                  dctx->expected = 0;  /* Streaming not supported */
                  break;
              case bt_raw :
                  assert(srcSize <= dctx->expected);
                  rSize = ZSTD_copyRawBlock(dst, dstCapacity, src, srcSize);
                  FORWARD_IF_ERROR(rSize, "ZSTD_copyRawBlock failed");
                  assert(rSize == srcSize);
                  dctx->expected -= rSize;
                  break;
              case bt_rle :
                  rSize = ZSTD_setRleBlock(dst, dstCapacity, *(const BYTE*)src, dctx->rleSize);
                  dctx->expected = 0;  /* Streaming not supported */
                  break;
              case bt_reserved :   /* should never happen */
              default:
                  RETURN_ERROR(corruption_detected, "invalid block type");
              }
              FORWARD_IF_ERROR(rSize, "");
              RETURN_ERROR_IF(rSize > dctx->fParams.blockSizeMax, corruption_detected, "Decompressed Block Size Exceeds Maximum");
              DEBUGLOG(5, "ZSTD_decompressContinue: decoded size from block : %u", (unsigned)rSize);
              dctx->decodedSize += rSize;
              if (dctx->validateChecksum) XXH64_update(&dctx->xxhState, dst, rSize);
              dctx->previousDstEnd = (char*)dst + rSize;
  
              /* Stay on the same stage until we are finished streaming the block. */
              if (dctx->expected > 0) {
                  return rSize;
              }
  
              if (dctx->stage == ZSTDds_decompressLastBlock) {   /* end of frame */
                  DEBUGLOG(4, "ZSTD_decompressContinue: decoded size from frame : %u", (unsigned)dctx->decodedSize);
                  RETURN_ERROR_IF(
                      dctx->fParams.frameContentSize != ZSTD_CONTENTSIZE_UNKNOWN
                   && dctx->decodedSize != dctx->fParams.frameContentSize,
                      corruption_detected, "");
                  if (dctx->fParams.checksumFlag) {  /* another round for frame checksum */
                      dctx->expected = 4;
                      dctx->stage = ZSTDds_checkChecksum;
                  } else {
                      ZSTD_DCtx_trace_end(dctx, dctx->decodedSize, dctx->processedCSize, /* streaming */ 1);
                      dctx->expected = 0;   /* ends here */
                      dctx->stage = ZSTDds_getFrameHeaderSize;
                  }
              } else {
                  dctx->stage = ZSTDds_decodeBlockHeader;
                  dctx->expected = ZSTD_blockHeaderSize;
              }
              return rSize;
          }
  
      case ZSTDds_checkChecksum:
          assert(srcSize == 4);  /* guaranteed by dctx->expected */
          {
              if (dctx->validateChecksum) {
                  U32 const h32 = (U32)XXH64_digest(&dctx->xxhState);
                  U32 const check32 = MEM_readLE32(src);
                  DEBUGLOG(4, "ZSTD_decompressContinue: checksum : calculated %08X :: %08X read", (unsigned)h32, (unsigned)check32);
                  RETURN_ERROR_IF(check32 != h32, checksum_wrong, "");
              }
              ZSTD_DCtx_trace_end(dctx, dctx->decodedSize, dctx->processedCSize, /* streaming */ 1);
              dctx->expected = 0;
              dctx->stage = ZSTDds_getFrameHeaderSize;
              return 0;
          }
  
      case ZSTDds_decodeSkippableHeader:
          assert(src != NULL);
          assert(srcSize <= ZSTD_SKIPPABLEHEADERSIZE);
          ZSTD_memcpy(dctx->headerBuffer + (ZSTD_SKIPPABLEHEADERSIZE - srcSize), src, srcSize);   /* complete skippable header */
          dctx->expected = MEM_readLE32(dctx->headerBuffer + ZSTD_FRAMEIDSIZE);   /* note : dctx->expected can grow seriously large, beyond local buffer size */
          dctx->stage = ZSTDds_skipFrame;
          return 0;
  
      case ZSTDds_skipFrame:
          dctx->expected = 0;
          dctx->stage = ZSTDds_getFrameHeaderSize;
          return 0;
  
      default:
          assert(0);   /* impossible */
          RETURN_ERROR(GENERIC, "impossible to reach");   /* some compiler require default to do something */
      }
  }
  
  
  static size_t ZSTD_refDictContent(ZSTD_DCtx* dctx, const void* dict, size_t dictSize)
  {
      dctx->dictEnd = dctx->previousDstEnd;
      dctx->virtualStart = (const char*)dict - ((const char*)(dctx->previousDstEnd) - (const char*)(dctx->prefixStart));
      dctx->prefixStart = dict;
      dctx->previousDstEnd = (const char*)dict + dictSize;
  #ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
      dctx->dictContentBeginForFuzzing = dctx->prefixStart;
      dctx->dictContentEndForFuzzing = dctx->previousDstEnd;
  #endif
      return 0;
  }
  
  /*! ZSTD_loadDEntropy() :
   *  dict : must point at beginning of a valid zstd dictionary.
   * @return : size of entropy tables read */
  size_t
  ZSTD_loadDEntropy(ZSTD_entropyDTables_t* entropy,
                    const void* const dict, size_t const dictSize)
  {
      const BYTE* dictPtr = (const BYTE*)dict;
      const BYTE* const dictEnd = dictPtr + dictSize;
  
      RETURN_ERROR_IF(dictSize <= 8, dictionary_corrupted, "dict is too small");
      assert(MEM_readLE32(dict) == ZSTD_MAGIC_DICTIONARY);   /* dict must be valid */
      dictPtr += 8;   /* skip header = magic + dictID */
  
      ZSTD_STATIC_ASSERT(offsetof(ZSTD_entropyDTables_t, OFTable) == offsetof(ZSTD_entropyDTables_t, LLTable) + sizeof(entropy->LLTable));
      ZSTD_STATIC_ASSERT(offsetof(ZSTD_entropyDTables_t, MLTable) == offsetof(ZSTD_entropyDTables_t, OFTable) + sizeof(entropy->OFTable));
      ZSTD_STATIC_ASSERT(sizeof(entropy->LLTable) + sizeof(entropy->OFTable) + sizeof(entropy->MLTable) >= HUF_DECOMPRESS_WORKSPACE_SIZE);
      {   void* const workspace = &entropy->LLTable;   /* use fse tables as temporary workspace; implies fse tables are grouped together */
          size_t const workspaceSize = sizeof(entropy->LLTable) + sizeof(entropy->OFTable) + sizeof(entropy->MLTable);
  #ifdef HUF_FORCE_DECOMPRESS_X1
          /* in minimal huffman, we always use X1 variants */
          size_t const hSize = HUF_readDTableX1_wksp(entropy->hufTable,
                                                  dictPtr, dictEnd - dictPtr,
                                                  workspace, workspaceSize);
  #else
          size_t const hSize = HUF_readDTableX2_wksp(entropy->hufTable,
                                                  dictPtr, (size_t)(dictEnd - dictPtr),
                                                  workspace, workspaceSize);
  #endif
          RETURN_ERROR_IF(HUF_isError(hSize), dictionary_corrupted, "");
          dictPtr += hSize;
      }
  
      {   short offcodeNCount[MaxOff+1];
          unsigned offcodeMaxValue = MaxOff, offcodeLog;
          size_t const offcodeHeaderSize = FSE_readNCount(offcodeNCount, &offcodeMaxValue, &offcodeLog, dictPtr, (size_t)(dictEnd-dictPtr));
          RETURN_ERROR_IF(FSE_isError(offcodeHeaderSize), dictionary_corrupted, "");
          RETURN_ERROR_IF(offcodeMaxValue > MaxOff, dictionary_corrupted, "");
          RETURN_ERROR_IF(offcodeLog > OffFSELog, dictionary_corrupted, "");
          ZSTD_buildFSETable( entropy->OFTable,
                              offcodeNCount, offcodeMaxValue,
                              OF_base, OF_bits,
                              offcodeLog,
                              entropy->workspace, sizeof(entropy->workspace),
                              /* bmi2 */0);
          dictPtr += offcodeHeaderSize;
      }
  
      {   short matchlengthNCount[MaxML+1];
          unsigned matchlengthMaxValue = MaxML, matchlengthLog;
          size_t const matchlengthHeaderSize = FSE_readNCount(matchlengthNCount, &matchlengthMaxValue, &matchlengthLog, dictPtr, (size_t)(dictEnd-dictPtr));
          RETURN_ERROR_IF(FSE_isError(matchlengthHeaderSize), dictionary_corrupted, "");
          RETURN_ERROR_IF(matchlengthMaxValue > MaxML, dictionary_corrupted, "");
          RETURN_ERROR_IF(matchlengthLog > MLFSELog, dictionary_corrupted, "");
          ZSTD_buildFSETable( entropy->MLTable,
                              matchlengthNCount, matchlengthMaxValue,
                              ML_base, ML_bits,
                              matchlengthLog,
                              entropy->workspace, sizeof(entropy->workspace),
                              /* bmi2 */ 0);
          dictPtr += matchlengthHeaderSize;
      }
  
      {   short litlengthNCount[MaxLL+1];
          unsigned litlengthMaxValue = MaxLL, litlengthLog;
          size_t const litlengthHeaderSize = FSE_readNCount(litlengthNCount, &litlengthMaxValue, &litlengthLog, dictPtr, (size_t)(dictEnd-dictPtr));
          RETURN_ERROR_IF(FSE_isError(litlengthHeaderSize), dictionary_corrupted, "");
          RETURN_ERROR_IF(litlengthMaxValue > MaxLL, dictionary_corrupted, "");
          RETURN_ERROR_IF(litlengthLog > LLFSELog, dictionary_corrupted, "");
          ZSTD_buildFSETable( entropy->LLTable,
                              litlengthNCount, litlengthMaxValue,
                              LL_base, LL_bits,
                              litlengthLog,
                              entropy->workspace, sizeof(entropy->workspace),
                              /* bmi2 */ 0);
          dictPtr += litlengthHeaderSize;
      }
  
      RETURN_ERROR_IF(dictPtr+12 > dictEnd, dictionary_corrupted, "");
      {   int i;
          size_t const dictContentSize = (size_t)(dictEnd - (dictPtr+12));
          for (i=0; i<3; i++) {
              U32 const rep = MEM_readLE32(dictPtr); dictPtr += 4;
              RETURN_ERROR_IF(rep==0 || rep > dictContentSize,
                              dictionary_corrupted, "");
              entropy->rep[i] = rep;
      }   }
  
      return (size_t)(dictPtr - (const BYTE*)dict);
  }
  
  static size_t ZSTD_decompress_insertDictionary(ZSTD_DCtx* dctx, const void* dict, size_t dictSize)
  {
      if (dictSize < 8) return ZSTD_refDictContent(dctx, dict, dictSize);
      {   U32 const magic = MEM_readLE32(dict);
          if (magic != ZSTD_MAGIC_DICTIONARY) {
              return ZSTD_refDictContent(dctx, dict, dictSize);   /* pure content mode */
      }   }
      dctx->dictID = MEM_readLE32((const char*)dict + ZSTD_FRAMEIDSIZE);
  
      /* load entropy tables */
      {   size_t const eSize = ZSTD_loadDEntropy(&dctx->entropy, dict, dictSize);
          RETURN_ERROR_IF(ZSTD_isError(eSize), dictionary_corrupted, "");
          dict = (const char*)dict + eSize;
          dictSize -= eSize;
      }
      dctx->litEntropy = dctx->fseEntropy = 1;
  
      /* reference dictionary content */
      return ZSTD_refDictContent(dctx, dict, dictSize);
  }
  
  size_t ZSTD_decompressBegin(ZSTD_DCtx* dctx)
  {
      assert(dctx != NULL);
  #if ZSTD_TRACE
      dctx->traceCtx = (ZSTD_trace_decompress_begin != NULL) ? ZSTD_trace_decompress_begin(dctx) : 0;
  #endif
      dctx->expected = ZSTD_startingInputLength(dctx->format);  /* dctx->format must be properly set */
      dctx->stage = ZSTDds_getFrameHeaderSize;
      dctx->processedCSize = 0;
      dctx->decodedSize = 0;
      dctx->previousDstEnd = NULL;
      dctx->prefixStart = NULL;
      dctx->virtualStart = NULL;
      dctx->dictEnd = NULL;
      dctx->entropy.hufTable[0] = (HUF_DTable)((HufLog)*0x1000001);  /* cover both little and big endian */
      dctx->litEntropy = dctx->fseEntropy = 0;
      dctx->dictID = 0;
      dctx->bType = bt_reserved;
      ZSTD_STATIC_ASSERT(sizeof(dctx->entropy.rep) == sizeof(repStartValue));
      ZSTD_memcpy(dctx->entropy.rep, repStartValue, sizeof(repStartValue));  /* initial repcodes */
      dctx->LLTptr = dctx->entropy.LLTable;
      dctx->MLTptr = dctx->entropy.MLTable;
      dctx->OFTptr = dctx->entropy.OFTable;
      dctx->HUFptr = dctx->entropy.hufTable;
      return 0;
  }
  
  size_t ZSTD_decompressBegin_usingDict(ZSTD_DCtx* dctx, const void* dict, size_t dictSize)
  {
      FORWARD_IF_ERROR( ZSTD_decompressBegin(dctx) , "");
      if (dict && dictSize)
          RETURN_ERROR_IF(
              ZSTD_isError(ZSTD_decompress_insertDictionary(dctx, dict, dictSize)),
              dictionary_corrupted, "");
      return 0;
  }
  
  
  /* ======   ZSTD_DDict   ====== */
  
  size_t ZSTD_decompressBegin_usingDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict)
  {
      DEBUGLOG(4, "ZSTD_decompressBegin_usingDDict");
      assert(dctx != NULL);
      if (ddict) {
          const char* const dictStart = (const char*)ZSTD_DDict_dictContent(ddict);
          size_t const dictSize = ZSTD_DDict_dictSize(ddict);
          const void* const dictEnd = dictStart + dictSize;
          dctx->ddictIsCold = (dctx->dictEnd != dictEnd);
          DEBUGLOG(4, "DDict is %s",
                      dctx->ddictIsCold ? "~cold~" : "hot!");
      }
      FORWARD_IF_ERROR( ZSTD_decompressBegin(dctx) , "");
      if (ddict) {   /* NULL ddict is equivalent to no dictionary */
          ZSTD_copyDDictParameters(dctx, ddict);
      }
      return 0;
  }
  
  /*! ZSTD_getDictID_fromDict() :
   *  Provides the dictID stored within dictionary.
   *  if @return == 0, the dictionary is not conformant with Zstandard specification.
   *  It can still be loaded, but as a content-only dictionary. */
  unsigned ZSTD_getDictID_fromDict(const void* dict, size_t dictSize)
  {
      if (dictSize < 8) return 0;
      if (MEM_readLE32(dict) != ZSTD_MAGIC_DICTIONARY) return 0;
      return MEM_readLE32((const char*)dict + ZSTD_FRAMEIDSIZE);
  }
  
  /*! ZSTD_getDictID_fromFrame() :
   *  Provides the dictID required to decompress frame stored within `src`.
   *  If @return == 0, the dictID could not be decoded.
   *  This could for one of the following reasons :
   *  - The frame does not require a dictionary (most common case).
   *  - The frame was built with dictID intentionally removed.
   *    Needed dictionary is a hidden information.
   *    Note : this use case also happens when using a non-conformant dictionary.
   *  - `srcSize` is too small, and as a result, frame header could not be decoded.
   *    Note : possible if `srcSize < ZSTD_FRAMEHEADERSIZE_MAX`.
   *  - This is not a Zstandard frame.
   *  When identifying the exact failure cause, it's possible to use
   *  ZSTD_getFrameHeader(), which will provide a more precise error code. */
  unsigned ZSTD_getDictID_fromFrame(const void* src, size_t srcSize)
  {
      ZSTD_frameHeader zfp = { 0, 0, 0, ZSTD_frame, 0, 0, 0 };
      size_t const hError = ZSTD_getFrameHeader(&zfp, src, srcSize);
      if (ZSTD_isError(hError)) return 0;
      return zfp.dictID;
  }
  
  
  /*! ZSTD_decompress_usingDDict() :
  *   Decompression using a pre-digested Dictionary
  *   Use dictionary without significant overhead. */
  size_t ZSTD_decompress_usingDDict(ZSTD_DCtx* dctx,
                                    void* dst, size_t dstCapacity,
                              const void* src, size_t srcSize,
                              const ZSTD_DDict* ddict)
  {
      /* pass content and size in case legacy frames are encountered */
      return ZSTD_decompressMultiFrame(dctx, dst, dstCapacity, src, srcSize,
                                       NULL, 0,
                                       ddict);
  }
  
  
  /*=====================================
  *   Streaming decompression
  *====================================*/
  
  ZSTD_DStream* ZSTD_createDStream(void)
  {
      DEBUGLOG(3, "ZSTD_createDStream");
      return ZSTD_createDCtx_internal(ZSTD_defaultCMem);
  }
  
  ZSTD_DStream* ZSTD_initStaticDStream(void *workspace, size_t workspaceSize)
  {
      return ZSTD_initStaticDCtx(workspace, workspaceSize);
  }
  
  ZSTD_DStream* ZSTD_createDStream_advanced(ZSTD_customMem customMem)
  {
      return ZSTD_createDCtx_internal(customMem);
  }
  
  size_t ZSTD_freeDStream(ZSTD_DStream* zds)
  {
      return ZSTD_freeDCtx(zds);
  }
  
  
  /* ***  Initialization  *** */
  
  size_t ZSTD_DStreamInSize(void)  { return ZSTD_BLOCKSIZE_MAX + ZSTD_blockHeaderSize; }
  size_t ZSTD_DStreamOutSize(void) { return ZSTD_BLOCKSIZE_MAX; }
  
  size_t ZSTD_DCtx_loadDictionary_advanced(ZSTD_DCtx* dctx,
                                     const void* dict, size_t dictSize,
                                           ZSTD_dictLoadMethod_e dictLoadMethod,
                                           ZSTD_dictContentType_e dictContentType)
  {
      RETURN_ERROR_IF(dctx->streamStage != zdss_init, stage_wrong, "");
      ZSTD_clearDict(dctx);
      if (dict && dictSize != 0) {
          dctx->ddictLocal = ZSTD_createDDict_advanced(dict, dictSize, dictLoadMethod, dictContentType, dctx->customMem);
          RETURN_ERROR_IF(dctx->ddictLocal == NULL, memory_allocation, "NULL pointer!");
          dctx->ddict = dctx->ddictLocal;
          dctx->dictUses = ZSTD_use_indefinitely;
      }
      return 0;
  }
  
  size_t ZSTD_DCtx_loadDictionary_byReference(ZSTD_DCtx* dctx, const void* dict, size_t dictSize)
  {
      return ZSTD_DCtx_loadDictionary_advanced(dctx, dict, dictSize, ZSTD_dlm_byRef, ZSTD_dct_auto);
  }
  
  size_t ZSTD_DCtx_loadDictionary(ZSTD_DCtx* dctx, const void* dict, size_t dictSize)
  {
      return ZSTD_DCtx_loadDictionary_advanced(dctx, dict, dictSize, ZSTD_dlm_byCopy, ZSTD_dct_auto);
  }
  
  size_t ZSTD_DCtx_refPrefix_advanced(ZSTD_DCtx* dctx, const void* prefix, size_t prefixSize, ZSTD_dictContentType_e dictContentType)
  {
      FORWARD_IF_ERROR(ZSTD_DCtx_loadDictionary_advanced(dctx, prefix, prefixSize, ZSTD_dlm_byRef, dictContentType), "");
      dctx->dictUses = ZSTD_use_once;
      return 0;
  }
  
  size_t ZSTD_DCtx_refPrefix(ZSTD_DCtx* dctx, const void* prefix, size_t prefixSize)
  {
      return ZSTD_DCtx_refPrefix_advanced(dctx, prefix, prefixSize, ZSTD_dct_rawContent);
  }
  
  
  /* ZSTD_initDStream_usingDict() :
   * return : expected size, aka ZSTD_startingInputLength().
   * this function cannot fail */
  size_t ZSTD_initDStream_usingDict(ZSTD_DStream* zds, const void* dict, size_t dictSize)
  {
      DEBUGLOG(4, "ZSTD_initDStream_usingDict");
      FORWARD_IF_ERROR( ZSTD_DCtx_reset(zds, ZSTD_reset_session_only) , "");
      FORWARD_IF_ERROR( ZSTD_DCtx_loadDictionary(zds, dict, dictSize) , "");
      return ZSTD_startingInputLength(zds->format);
  }
  
  /* note : this variant can't fail */
  size_t ZSTD_initDStream(ZSTD_DStream* zds)
  {
      DEBUGLOG(4, "ZSTD_initDStream");
      return ZSTD_initDStream_usingDDict(zds, NULL);
  }
  
  /* ZSTD_initDStream_usingDDict() :
   * ddict will just be referenced, and must outlive decompression session
   * this function cannot fail */
  size_t ZSTD_initDStream_usingDDict(ZSTD_DStream* dctx, const ZSTD_DDict* ddict)
  {
      FORWARD_IF_ERROR( ZSTD_DCtx_reset(dctx, ZSTD_reset_session_only) , "");
      FORWARD_IF_ERROR( ZSTD_DCtx_refDDict(dctx, ddict) , "");
      return ZSTD_startingInputLength(dctx->format);
  }
  
  /* ZSTD_resetDStream() :
   * return : expected size, aka ZSTD_startingInputLength().
   * this function cannot fail */
  size_t ZSTD_resetDStream(ZSTD_DStream* dctx)
  {
      FORWARD_IF_ERROR(ZSTD_DCtx_reset(dctx, ZSTD_reset_session_only), "");
      return ZSTD_startingInputLength(dctx->format);
  }
  
  
  size_t ZSTD_DCtx_refDDict(ZSTD_DCtx* dctx, const ZSTD_DDict* ddict)
  {
      RETURN_ERROR_IF(dctx->streamStage != zdss_init, stage_wrong, "");
      ZSTD_clearDict(dctx);
      if (ddict) {
          dctx->ddict = ddict;
          dctx->dictUses = ZSTD_use_indefinitely;
          if (dctx->refMultipleDDicts == ZSTD_rmd_refMultipleDDicts) {
              if (dctx->ddictSet == NULL) {
                  dctx->ddictSet = ZSTD_createDDictHashSet(dctx->customMem);
                  if (!dctx->ddictSet) {
                      RETURN_ERROR(memory_allocation, "Failed to allocate memory for hash set!");
                  }
              }
              assert(!dctx->staticSize);  /* Impossible: ddictSet cannot have been allocated if static dctx */
              FORWARD_IF_ERROR(ZSTD_DDictHashSet_addDDict(dctx->ddictSet, ddict, dctx->customMem), "");
          }
      }
      return 0;
  }
  
  /* ZSTD_DCtx_setMaxWindowSize() :
   * note : no direct equivalence in ZSTD_DCtx_setParameter,
   * since this version sets windowSize, and the other sets windowLog */
  size_t ZSTD_DCtx_setMaxWindowSize(ZSTD_DCtx* dctx, size_t maxWindowSize)
  {
      ZSTD_bounds const bounds = ZSTD_dParam_getBounds(ZSTD_d_windowLogMax);
      size_t const min = (size_t)1 << bounds.lowerBound;
      size_t const max = (size_t)1 << bounds.upperBound;
      RETURN_ERROR_IF(dctx->streamStage != zdss_init, stage_wrong, "");
      RETURN_ERROR_IF(maxWindowSize < min, parameter_outOfBound, "");
      RETURN_ERROR_IF(maxWindowSize > max, parameter_outOfBound, "");
      dctx->maxWindowSize = maxWindowSize;
      return 0;
  }
  
  size_t ZSTD_DCtx_setFormat(ZSTD_DCtx* dctx, ZSTD_format_e format)
  {
      return ZSTD_DCtx_setParameter(dctx, ZSTD_d_format, (int)format);
  }
  
  ZSTD_bounds ZSTD_dParam_getBounds(ZSTD_dParameter dParam)
  {
      ZSTD_bounds bounds = { 0, 0, 0 };
      switch(dParam) {
          case ZSTD_d_windowLogMax:
              bounds.lowerBound = ZSTD_WINDOWLOG_ABSOLUTEMIN;
              bounds.upperBound = ZSTD_WINDOWLOG_MAX;
              return bounds;
          case ZSTD_d_format:
              bounds.lowerBound = (int)ZSTD_f_zstd1;
              bounds.upperBound = (int)ZSTD_f_zstd1_magicless;
              ZSTD_STATIC_ASSERT(ZSTD_f_zstd1 < ZSTD_f_zstd1_magicless);
              return bounds;
          case ZSTD_d_stableOutBuffer:
              bounds.lowerBound = (int)ZSTD_bm_buffered;
              bounds.upperBound = (int)ZSTD_bm_stable;
              return bounds;
          case ZSTD_d_forceIgnoreChecksum:
              bounds.lowerBound = (int)ZSTD_d_validateChecksum;
              bounds.upperBound = (int)ZSTD_d_ignoreChecksum;
              return bounds;
          case ZSTD_d_refMultipleDDicts:
              bounds.lowerBound = (int)ZSTD_rmd_refSingleDDict;
              bounds.upperBound = (int)ZSTD_rmd_refMultipleDDicts;
              return bounds;
          default:;
      }
      bounds.error = ERROR(parameter_unsupported);
      return bounds;
  }
  
  /* ZSTD_dParam_withinBounds:
   * @return 1 if value is within dParam bounds,
   * 0 otherwise */
  static int ZSTD_dParam_withinBounds(ZSTD_dParameter dParam, int value)
  {
      ZSTD_bounds const bounds = ZSTD_dParam_getBounds(dParam);
      if (ZSTD_isError(bounds.error)) return 0;
      if (value < bounds.lowerBound) return 0;
      if (value > bounds.upperBound) return 0;
      return 1;
  }
  
  #define CHECK_DBOUNDS(p,v) {                \
      RETURN_ERROR_IF(!ZSTD_dParam_withinBounds(p, v), parameter_outOfBound, ""); \
  }
  
  size_t ZSTD_DCtx_getParameter(ZSTD_DCtx* dctx, ZSTD_dParameter param, int* value)
  {
      switch (param) {
          case ZSTD_d_windowLogMax:
              *value = (int)ZSTD_highbit32((U32)dctx->maxWindowSize);
              return 0;
          case ZSTD_d_format:
              *value = (int)dctx->format;
              return 0;
          case ZSTD_d_stableOutBuffer:
              *value = (int)dctx->outBufferMode;
              return 0;
          case ZSTD_d_forceIgnoreChecksum:
              *value = (int)dctx->forceIgnoreChecksum;
              return 0;
          case ZSTD_d_refMultipleDDicts:
              *value = (int)dctx->refMultipleDDicts;
              return 0;
          default:;
      }
      RETURN_ERROR(parameter_unsupported, "");
  }
  
  size_t ZSTD_DCtx_setParameter(ZSTD_DCtx* dctx, ZSTD_dParameter dParam, int value)
  {
      RETURN_ERROR_IF(dctx->streamStage != zdss_init, stage_wrong, "");
      switch(dParam) {
          case ZSTD_d_windowLogMax:
              if (value == 0) value = ZSTD_WINDOWLOG_LIMIT_DEFAULT;
              CHECK_DBOUNDS(ZSTD_d_windowLogMax, value);
              dctx->maxWindowSize = ((size_t)1) << value;
              return 0;
          case ZSTD_d_format:
              CHECK_DBOUNDS(ZSTD_d_format, value);
              dctx->format = (ZSTD_format_e)value;
              return 0;
          case ZSTD_d_stableOutBuffer:
              CHECK_DBOUNDS(ZSTD_d_stableOutBuffer, value);
              dctx->outBufferMode = (ZSTD_bufferMode_e)value;
              return 0;
          case ZSTD_d_forceIgnoreChecksum:
              CHECK_DBOUNDS(ZSTD_d_forceIgnoreChecksum, value);
              dctx->forceIgnoreChecksum = (ZSTD_forceIgnoreChecksum_e)value;
              return 0;
          case ZSTD_d_refMultipleDDicts:
              CHECK_DBOUNDS(ZSTD_d_refMultipleDDicts, value);
              if (dctx->staticSize != 0) {
                  RETURN_ERROR(parameter_unsupported, "Static dctx does not support multiple DDicts!");
              }
              dctx->refMultipleDDicts = (ZSTD_refMultipleDDicts_e)value;
              return 0;
          default:;
      }
      RETURN_ERROR(parameter_unsupported, "");
  }
  
  size_t ZSTD_DCtx_reset(ZSTD_DCtx* dctx, ZSTD_ResetDirective reset)
  {
      if ( (reset == ZSTD_reset_session_only)
        || (reset == ZSTD_reset_session_and_parameters) ) {
          dctx->streamStage = zdss_init;
          dctx->noForwardProgress = 0;
      }
      if ( (reset == ZSTD_reset_parameters)
        || (reset == ZSTD_reset_session_and_parameters) ) {
          RETURN_ERROR_IF(dctx->streamStage != zdss_init, stage_wrong, "");
          ZSTD_clearDict(dctx);
          ZSTD_DCtx_resetParameters(dctx);
      }
      return 0;
  }
  
  
  size_t ZSTD_sizeof_DStream(const ZSTD_DStream* dctx)
  {
      return ZSTD_sizeof_DCtx(dctx);
  }
  
  size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long long frameContentSize)
  {
      size_t const blockSize = (size_t) MIN(windowSize, ZSTD_BLOCKSIZE_MAX);
      /* space is needed to store the litbuffer after the output of a given block without stomping the extDict of a previous run, as well as to cover both windows against wildcopy*/
      unsigned long long const neededRBSize = windowSize + blockSize + ZSTD_BLOCKSIZE_MAX + (WILDCOPY_OVERLENGTH * 2);
      unsigned long long const neededSize = MIN(frameContentSize, neededRBSize);
      size_t const minRBSize = (size_t) neededSize;
      RETURN_ERROR_IF((unsigned long long)minRBSize != neededSize,
                      frameParameter_windowTooLarge, "");
      return minRBSize;
  }
  
  size_t ZSTD_estimateDStreamSize(size_t windowSize)
  {
      size_t const blockSize = MIN(windowSize, ZSTD_BLOCKSIZE_MAX);
      size_t const inBuffSize = blockSize;  /* no block can be larger */
      size_t const outBuffSize = ZSTD_decodingBufferSize_min(windowSize, ZSTD_CONTENTSIZE_UNKNOWN);
      return ZSTD_estimateDCtxSize() + inBuffSize + outBuffSize;
  }
  
  size_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize)
  {
      U32 const windowSizeMax = 1U << ZSTD_WINDOWLOG_MAX;   /* note : should be user-selectable, but requires an additional parameter (or a dctx) */
      ZSTD_frameHeader zfh;
      size_t const err = ZSTD_getFrameHeader(&zfh, src, srcSize);
      if (ZSTD_isError(err)) return err;
      RETURN_ERROR_IF(err>0, srcSize_wrong, "");
      RETURN_ERROR_IF(zfh.windowSize > windowSizeMax,
                      frameParameter_windowTooLarge, "");
      return ZSTD_estimateDStreamSize((size_t)zfh.windowSize);
  }
  
  
  /* *****   Decompression   ***** */
  
  static int ZSTD_DCtx_isOverflow(ZSTD_DStream* zds, size_t const neededInBuffSize, size_t const neededOutBuffSize)
  {
      return (zds->inBuffSize + zds->outBuffSize) >= (neededInBuffSize + neededOutBuffSize) * ZSTD_WORKSPACETOOLARGE_FACTOR;
  }
  
  static void ZSTD_DCtx_updateOversizedDuration(ZSTD_DStream* zds, size_t const neededInBuffSize, size_t const neededOutBuffSize)
  {
      if (ZSTD_DCtx_isOverflow(zds, neededInBuffSize, neededOutBuffSize))
          zds->oversizedDuration++;
      else
          zds->oversizedDuration = 0;
  }
  
  static int ZSTD_DCtx_isOversizedTooLong(ZSTD_DStream* zds)
  {
      return zds->oversizedDuration >= ZSTD_WORKSPACETOOLARGE_MAXDURATION;
  }
  
  /* Checks that the output buffer hasn't changed if ZSTD_obm_stable is used. */
  static size_t ZSTD_checkOutBuffer(ZSTD_DStream const* zds, ZSTD_outBuffer const* output)
  {
      ZSTD_outBuffer const expect = zds->expectedOutBuffer;
      /* No requirement when ZSTD_obm_stable is not enabled. */
      if (zds->outBufferMode != ZSTD_bm_stable)
          return 0;
      /* Any buffer is allowed in zdss_init, this must be the same for every other call until
       * the context is reset.
       */
      if (zds->streamStage == zdss_init)
          return 0;
      /* The buffer must match our expectation exactly. */
      if (expect.dst == output->dst && expect.pos == output->pos && expect.size == output->size)
          return 0;
      RETURN_ERROR(dstBuffer_wrong, "ZSTD_d_stableOutBuffer enabled but output differs!");
  }
  
  /* Calls ZSTD_decompressContinue() with the right parameters for ZSTD_decompressStream()
   * and updates the stage and the output buffer state. This call is extracted so it can be
   * used both when reading directly from the ZSTD_inBuffer, and in buffered input mode.
   * NOTE: You must break after calling this function since the streamStage is modified.
   */
  static size_t ZSTD_decompressContinueStream(
              ZSTD_DStream* zds, char** op, char* oend,
              void const* src, size_t srcSize) {
      int const isSkipFrame = ZSTD_isSkipFrame(zds);
      if (zds->outBufferMode == ZSTD_bm_buffered) {
          size_t const dstSize = isSkipFrame ? 0 : zds->outBuffSize - zds->outStart;
          size_t const decodedSize = ZSTD_decompressContinue(zds,
                  zds->outBuff + zds->outStart, dstSize, src, srcSize);
          FORWARD_IF_ERROR(decodedSize, "");
          if (!decodedSize && !isSkipFrame) {
              zds->streamStage = zdss_read;
          } else {
              zds->outEnd = zds->outStart + decodedSize;
              zds->streamStage = zdss_flush;
          }
      } else {
          /* Write directly into the output buffer */
          size_t const dstSize = isSkipFrame ? 0 : (size_t)(oend - *op);
          size_t const decodedSize = ZSTD_decompressContinue(zds, *op, dstSize, src, srcSize);
          FORWARD_IF_ERROR(decodedSize, "");
          *op += decodedSize;
          /* Flushing is not needed. */
          zds->streamStage = zdss_read;
          assert(*op <= oend);
          assert(zds->outBufferMode == ZSTD_bm_stable);
      }
      return 0;
  }
  
  size_t ZSTD_decompressStream(ZSTD_DStream* zds, ZSTD_outBuffer* output, ZSTD_inBuffer* input)
  {
      const char* const src = (const char*)input->src;
      const char* const istart = input->pos != 0 ? src + input->pos : src;
      const char* const iend = input->size != 0 ? src + input->size : src;
      const char* ip = istart;
      char* const dst = (char*)output->dst;
      char* const ostart = output->pos != 0 ? dst + output->pos : dst;
      char* const oend = output->size != 0 ? dst + output->size : dst;
      char* op = ostart;
      U32 someMoreWork = 1;
  
      DEBUGLOG(5, "ZSTD_decompressStream");
      RETURN_ERROR_IF(
          input->pos > input->size,
          srcSize_wrong,
          "forbidden. in: pos: %u   vs size: %u",
          (U32)input->pos, (U32)input->size);
      RETURN_ERROR_IF(
          output->pos > output->size,
          dstSize_tooSmall,
          "forbidden. out: pos: %u   vs size: %u",
          (U32)output->pos, (U32)output->size);
      DEBUGLOG(5, "input size : %u", (U32)(input->size - input->pos));
      FORWARD_IF_ERROR(ZSTD_checkOutBuffer(zds, output), "");
  
      while (someMoreWork) {
          switch(zds->streamStage)
          {
          case zdss_init :
              DEBUGLOG(5, "stage zdss_init => transparent reset ");
              zds->streamStage = zdss_loadHeader;
              zds->lhSize = zds->inPos = zds->outStart = zds->outEnd = 0;
  #if defined(ZSTD_LEGACY_SUPPORT) && (ZSTD_LEGACY_SUPPORT>=1)
              zds->legacyVersion = 0;
  #endif
              zds->hostageByte = 0;
              zds->expectedOutBuffer = *output;
              ZSTD_FALLTHROUGH;
  
          case zdss_loadHeader :
              DEBUGLOG(5, "stage zdss_loadHeader (srcSize : %u)", (U32)(iend - ip));
  #if defined(ZSTD_LEGACY_SUPPORT) && (ZSTD_LEGACY_SUPPORT>=1)
              if (zds->legacyVersion) {
                  RETURN_ERROR_IF(zds->staticSize, memory_allocation,
                      "legacy support is incompatible with static dctx");
                  {   size_t const hint = ZSTD_decompressLegacyStream(zds->legacyContext, zds->legacyVersion, output, input);
                      if (hint==0) zds->streamStage = zdss_init;
                      return hint;
              }   }
  #endif
              {   size_t const hSize = ZSTD_getFrameHeader_advanced(&zds->fParams, zds->headerBuffer, zds->lhSize, zds->format);
                  if (zds->refMultipleDDicts && zds->ddictSet) {
                      ZSTD_DCtx_selectFrameDDict(zds);
                  }
                  DEBUGLOG(5, "header size : %u", (U32)hSize);
                  if (ZSTD_isError(hSize)) {
  #if defined(ZSTD_LEGACY_SUPPORT) && (ZSTD_LEGACY_SUPPORT>=1)
                      U32 const legacyVersion = ZSTD_isLegacy(istart, iend-istart);
                      if (legacyVersion) {
                          ZSTD_DDict const* const ddict = ZSTD_getDDict(zds);
                          const void* const dict = ddict ? ZSTD_DDict_dictContent(ddict) : NULL;
                          size_t const dictSize = ddict ? ZSTD_DDict_dictSize(ddict) : 0;
                          DEBUGLOG(5, "ZSTD_decompressStream: detected legacy version v0.%u", legacyVersion);
                          RETURN_ERROR_IF(zds->staticSize, memory_allocation,
                              "legacy support is incompatible with static dctx");
                          FORWARD_IF_ERROR(ZSTD_initLegacyStream(&zds->legacyContext,
                                      zds->previousLegacyVersion, legacyVersion,
                                      dict, dictSize), "");
                          zds->legacyVersion = zds->previousLegacyVersion = legacyVersion;
                          {   size_t const hint = ZSTD_decompressLegacyStream(zds->legacyContext, legacyVersion, output, input);
                              if (hint==0) zds->streamStage = zdss_init;   /* or stay in stage zdss_loadHeader */
                              return hint;
                      }   }
  #endif
                      return hSize;   /* error */
                  }
                  if (hSize != 0) {   /* need more input */
                      size_t const toLoad = hSize - zds->lhSize;   /* if hSize!=0, hSize > zds->lhSize */
                      size_t const remainingInput = (size_t)(iend-ip);
                      assert(iend >= ip);
                      if (toLoad > remainingInput) {   /* not enough input to load full header */
                          if (remainingInput > 0) {
                              ZSTD_memcpy(zds->headerBuffer + zds->lhSize, ip, remainingInput);
                              zds->lhSize += remainingInput;
                          }
                          input->pos = input->size;
                          return (MAX((size_t)ZSTD_FRAMEHEADERSIZE_MIN(zds->format), hSize) - zds->lhSize) + ZSTD_blockHeaderSize;   /* remaining header bytes + next block header */
                      }
                      assert(ip != NULL);
                      ZSTD_memcpy(zds->headerBuffer + zds->lhSize, ip, toLoad); zds->lhSize = hSize; ip += toLoad;
                      break;
              }   }
  
              /* check for single-pass mode opportunity */
              if (zds->fParams.frameContentSize != ZSTD_CONTENTSIZE_UNKNOWN
                  && zds->fParams.frameType != ZSTD_skippableFrame
                  && (U64)(size_t)(oend-op) >= zds->fParams.frameContentSize) {
                  size_t const cSize = ZSTD_findFrameCompressedSize(istart, (size_t)(iend-istart));
                  if (cSize <= (size_t)(iend-istart)) {
                      /* shortcut : using single-pass mode */
                      size_t const decompressedSize = ZSTD_decompress_usingDDict(zds, op, (size_t)(oend-op), istart, cSize, ZSTD_getDDict(zds));
                      if (ZSTD_isError(decompressedSize)) return decompressedSize;
                      DEBUGLOG(4, "shortcut to single-pass ZSTD_decompress_usingDDict()")
                      ip = istart + cSize;
                      op += decompressedSize;
                      zds->expected = 0;
                      zds->streamStage = zdss_init;
                      someMoreWork = 0;
                      break;
              }   }
  
              /* Check output buffer is large enough for ZSTD_odm_stable. */
              if (zds->outBufferMode == ZSTD_bm_stable
                  && zds->fParams.frameType != ZSTD_skippableFrame
                  && zds->fParams.frameContentSize != ZSTD_CONTENTSIZE_UNKNOWN
                  && (U64)(size_t)(oend-op) < zds->fParams.frameContentSize) {
                  RETURN_ERROR(dstSize_tooSmall, "ZSTD_obm_stable passed but ZSTD_outBuffer is too small");
              }
  
              /* Consume header (see ZSTDds_decodeFrameHeader) */
              DEBUGLOG(4, "Consume header");
              FORWARD_IF_ERROR(ZSTD_decompressBegin_usingDDict(zds, ZSTD_getDDict(zds)), "");
  
              if ((MEM_readLE32(zds->headerBuffer) & ZSTD_MAGIC_SKIPPABLE_MASK) == ZSTD_MAGIC_SKIPPABLE_START) {  /* skippable frame */
                  zds->expected = MEM_readLE32(zds->headerBuffer + ZSTD_FRAMEIDSIZE);
                  zds->stage = ZSTDds_skipFrame;
              } else {
                  FORWARD_IF_ERROR(ZSTD_decodeFrameHeader(zds, zds->headerBuffer, zds->lhSize), "");
                  zds->expected = ZSTD_blockHeaderSize;
                  zds->stage = ZSTDds_decodeBlockHeader;
              }
  
              /* control buffer memory usage */
              DEBUGLOG(4, "Control max memory usage (%u KB <= max %u KB)",
                          (U32)(zds->fParams.windowSize >>10),
                          (U32)(zds->maxWindowSize >> 10) );
              zds->fParams.windowSize = MAX(zds->fParams.windowSize, 1U << ZSTD_WINDOWLOG_ABSOLUTEMIN);
              RETURN_ERROR_IF(zds->fParams.windowSize > zds->maxWindowSize,
                              frameParameter_windowTooLarge, "");
  
              /* Adapt buffer sizes to frame header instructions */
              {   size_t const neededInBuffSize = MAX(zds->fParams.blockSizeMax, 4 /* frame checksum */);
                  size_t const neededOutBuffSize = zds->outBufferMode == ZSTD_bm_buffered
                          ? ZSTD_decodingBufferSize_min(zds->fParams.windowSize, zds->fParams.frameContentSize)
                          : 0;
  
                  ZSTD_DCtx_updateOversizedDuration(zds, neededInBuffSize, neededOutBuffSize);
  
                  {   int const tooSmall = (zds->inBuffSize < neededInBuffSize) || (zds->outBuffSize < neededOutBuffSize);
                      int const tooLarge = ZSTD_DCtx_isOversizedTooLong(zds);
  
                      if (tooSmall || tooLarge) {
                          size_t const bufferSize = neededInBuffSize + neededOutBuffSize;
                          DEBUGLOG(4, "inBuff  : from %u to %u",
                                      (U32)zds->inBuffSize, (U32)neededInBuffSize);
                          DEBUGLOG(4, "outBuff : from %u to %u",
                                      (U32)zds->outBuffSize, (U32)neededOutBuffSize);
                          if (zds->staticSize) {  /* static DCtx */
                              DEBUGLOG(4, "staticSize : %u", (U32)zds->staticSize);
                              assert(zds->staticSize >= sizeof(ZSTD_DCtx));  /* controlled at init */
                              RETURN_ERROR_IF(
                                  bufferSize > zds->staticSize - sizeof(ZSTD_DCtx),
                                  memory_allocation, "");
                          } else {
                              ZSTD_customFree(zds->inBuff, zds->customMem);
                              zds->inBuffSize = 0;
                              zds->outBuffSize = 0;
                              zds->inBuff = (char*)ZSTD_customMalloc(bufferSize, zds->customMem);
                              RETURN_ERROR_IF(zds->inBuff == NULL, memory_allocation, "");
                          }
                          zds->inBuffSize = neededInBuffSize;
                          zds->outBuff = zds->inBuff + zds->inBuffSize;
                          zds->outBuffSize = neededOutBuffSize;
              }   }   }
              zds->streamStage = zdss_read;
              ZSTD_FALLTHROUGH;
  
          case zdss_read:
              DEBUGLOG(5, "stage zdss_read");
              {   size_t const neededInSize = ZSTD_nextSrcSizeToDecompressWithInputSize(zds, (size_t)(iend - ip));
                  DEBUGLOG(5, "neededInSize = %u", (U32)neededInSize);
                  if (neededInSize==0) {  /* end of frame */
                      zds->streamStage = zdss_init;
                      someMoreWork = 0;
                      break;
                  }
                  if ((size_t)(iend-ip) >= neededInSize) {  /* decode directly from src */
                      FORWARD_IF_ERROR(ZSTD_decompressContinueStream(zds, &op, oend, ip, neededInSize), "");
                      ip += neededInSize;
                      /* Function modifies the stage so we must break */
                      break;
              }   }
              if (ip==iend) { someMoreWork = 0; break; }   /* no more input */
              zds->streamStage = zdss_load;
              ZSTD_FALLTHROUGH;
  
          case zdss_load:
              {   size_t const neededInSize = ZSTD_nextSrcSizeToDecompress(zds);
                  size_t const toLoad = neededInSize - zds->inPos;
                  int const isSkipFrame = ZSTD_isSkipFrame(zds);
                  size_t loadedSize;
                  /* At this point we shouldn't be decompressing a block that we can stream. */
                  assert(neededInSize == ZSTD_nextSrcSizeToDecompressWithInputSize(zds, iend - ip));
                  if (isSkipFrame) {
                      loadedSize = MIN(toLoad, (size_t)(iend-ip));
                  } else {
                      RETURN_ERROR_IF(toLoad > zds->inBuffSize - zds->inPos,
                                      corruption_detected,
                                      "should never happen");
                      loadedSize = ZSTD_limitCopy(zds->inBuff + zds->inPos, toLoad, ip, (size_t)(iend-ip));
                  }
                  ip += loadedSize;
                  zds->inPos += loadedSize;
                  if (loadedSize < toLoad) { someMoreWork = 0; break; }   /* not enough input, wait for more */
  
                  /* decode loaded input */
                  zds->inPos = 0;   /* input is consumed */
                  FORWARD_IF_ERROR(ZSTD_decompressContinueStream(zds, &op, oend, zds->inBuff, neededInSize), "");
                  /* Function modifies the stage so we must break */
                  break;
              }
          case zdss_flush:
              {   size_t const toFlushSize = zds->outEnd - zds->outStart;
                  size_t const flushedSize = ZSTD_limitCopy(op, (size_t)(oend-op), zds->outBuff + zds->outStart, toFlushSize);
                  op += flushedSize;
                  zds->outStart += flushedSize;
                  if (flushedSize == toFlushSize) {  /* flush completed */
                      zds->streamStage = zdss_read;
                      if ( (zds->outBuffSize < zds->fParams.frameContentSize)
                        && (zds->outStart + zds->fParams.blockSizeMax > zds->outBuffSize) ) {
                          DEBUGLOG(5, "restart filling outBuff from beginning (left:%i, needed:%u)",
                                  (int)(zds->outBuffSize - zds->outStart),
                                  (U32)zds->fParams.blockSizeMax);
                          zds->outStart = zds->outEnd = 0;
                      }
                      break;
              }   }
              /* cannot complete flush */
              someMoreWork = 0;
              break;
  
          default:
              assert(0);    /* impossible */
              RETURN_ERROR(GENERIC, "impossible to reach");   /* some compiler require default to do something */
      }   }
  
      /* result */
      input->pos = (size_t)(ip - (const char*)(input->src));
      output->pos = (size_t)(op - (char*)(output->dst));
  
      /* Update the expected output buffer for ZSTD_obm_stable. */
      zds->expectedOutBuffer = *output;
  
      if ((ip==istart) && (op==ostart)) {  /* no forward progress */
          zds->noForwardProgress ++;
          if (zds->noForwardProgress >= ZSTD_NO_FORWARD_PROGRESS_MAX) {
              RETURN_ERROR_IF(op==oend, dstSize_tooSmall, "");
              RETURN_ERROR_IF(ip==iend, srcSize_wrong, "");
              assert(0);
          }
      } else {
          zds->noForwardProgress = 0;
      }
      {   size_t nextSrcSizeHint = ZSTD_nextSrcSizeToDecompress(zds);
          if (!nextSrcSizeHint) {   /* frame fully decoded */
              if (zds->outEnd == zds->outStart) {  /* output fully flushed */
                  if (zds->hostageByte) {
                      if (input->pos >= input->size) {
                          /* can't release hostage (not present) */
                          zds->streamStage = zdss_read;
                          return 1;
                      }
                      input->pos++;  /* release hostage */
                  }   /* zds->hostageByte */
                  return 0;
              }  /* zds->outEnd == zds->outStart */
              if (!zds->hostageByte) { /* output not fully flushed; keep last byte as hostage; will be released when all output is flushed */
                  input->pos--;   /* note : pos > 0, otherwise, impossible to finish reading last block */
                  zds->hostageByte=1;
              }
              return 1;
          }  /* nextSrcSizeHint==0 */
          nextSrcSizeHint += ZSTD_blockHeaderSize * (ZSTD_nextInputType(zds) == ZSTDnit_block);   /* preload header of next block */
          assert(zds->inPos <= nextSrcSizeHint);
          nextSrcSizeHint -= zds->inPos;   /* part already loaded*/
          return nextSrcSizeHint;
      }
  }
  
  size_t ZSTD_decompressStream_simpleArgs (
                              ZSTD_DCtx* dctx,
                              void* dst, size_t dstCapacity, size_t* dstPos,
                        const void* src, size_t srcSize, size_t* srcPos)
  {
      ZSTD_outBuffer output = { dst, dstCapacity, *dstPos };
      ZSTD_inBuffer  input  = { src, srcSize, *srcPos };
      /* ZSTD_compress_generic() will check validity of dstPos and srcPos */
      size_t const cErr = ZSTD_decompressStream(dctx, &output, &input);
      *dstPos = output.pos;
      *srcPos = input.pos;
      return cErr;
  }

Cache object: 0d55ae31283771a7aba6bbb14ddbc8b8