ext/zstdruby/libzstd/legacy/zstd_v02.c in zstd-ruby-1.3.2.0 vs ext/zstdruby/libzstd/legacy/zstd_v02.c in zstd-ruby-1.3.3.0

- old
+ new

@@ -328,22 +328,10 @@ MEM_STATIC size_t BIT_readBits(BIT_DStream_t* bitD, unsigned nbBits); MEM_STATIC BIT_DStream_status BIT_reloadDStream(BIT_DStream_t* bitD); MEM_STATIC unsigned BIT_endOfDStream(const BIT_DStream_t* bitD); -/* -* Start by invoking BIT_initDStream(). -* A chunk of the bitStream is then stored into a local register. -* Local register size is 64-bits on 64-bits systems, 32-bits on 32-bits systems (size_t). -* You can then retrieve bitFields stored into the local register, **in reverse order**. -* Local register is manually filled from memory by the BIT_reloadDStream() method. -* A reload guarantee a minimum of ((8*sizeof(size_t))-7) bits when its result is BIT_DStream_unfinished. -* Otherwise, it can be less than that, so proceed accordingly. -* Checking if DStream has reached its end can be performed with BIT_endOfDStream() -*/ - - /****************************************** * unsafe API ******************************************/ MEM_STATIC size_t BIT_readBitsFast(BIT_DStream_t* bitD, unsigned nbBits); /* faster, but works only if nbBits >= 1 */ @@ -351,11 +339,11 @@ /**************************************************************** * Helper functions ****************************************************************/ -MEM_STATIC unsigned BIT_highbit32 (register U32 val) +MEM_STATIC unsigned BIT_highbit32 (U32 val) { # if defined(_MSC_VER) /* Visual */ unsigned long r=0; _BitScanReverse ( &r, val ); return (unsigned) r; @@ -425,17 +413,10 @@ } return srcSize; } -/*!BIT_lookBits - * Provides next n bits from local register - * local register is not modified (bits are still present for next read/look) - * On 32-bits, maxNbBits==25 - * On 64-bits, maxNbBits==57 - * @return : value extracted - */ MEM_STATIC size_t BIT_lookBits(BIT_DStream_t* bitD, U32 nbBits) { const U32 bitMask = sizeof(bitD->bitContainer)*8 - 1; return ((bitD->bitContainer << (bitD->bitsConsumed & bitMask)) >> 1) >> ((bitMask-nbBits) & bitMask); } @@ -451,15 +432,10 @@ MEM_STATIC void BIT_skipBits(BIT_DStream_t* bitD, U32 nbBits) { bitD->bitsConsumed += nbBits; } -/*!BIT_readBits - * Read next n bits from local register. - * pay attention to not read more than nbBits contained into local register. - * @return : extracted value. - */ MEM_STATIC size_t BIT_readBits(BIT_DStream_t* bitD, U32 nbBits) { size_t value = BIT_lookBits(bitD, nbBits); BIT_skipBits(bitD, nbBits); return value; @@ -692,58 +668,9 @@ static void FSE_initDState(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD, const FSE_DTable* dt); static unsigned char FSE_decodeSymbol(FSE_DState_t* DStatePtr, BIT_DStream_t* bitD); static unsigned FSE_endOfDState(const FSE_DState_t* DStatePtr); - -/* -Let's now decompose FSE_decompress_usingDTable() into its unitary components. -You will decode FSE-encoded symbols from the bitStream, -and also any other bitFields you put in, **in reverse order**. - -You will need a few variables to track your bitStream. They are : - -BIT_DStream_t DStream; // Stream context -FSE_DState_t DState; // State context. Multiple ones are possible -FSE_DTable* DTablePtr; // Decoding table, provided by FSE_buildDTable() - -The first thing to do is to init the bitStream. - errorCode = BIT_initDStream(&DStream, srcBuffer, srcSize); - -You should then retrieve your initial state(s) -(in reverse flushing order if you have several ones) : - errorCode = FSE_initDState(&DState, &DStream, DTablePtr); - -You can then decode your data, symbol after symbol. -For information the maximum number of bits read by FSE_decodeSymbol() is 'tableLog'. -Keep in mind that symbols are decoded in reverse order, like a LIFO stack (last in, first out). - unsigned char symbol = FSE_decodeSymbol(&DState, &DStream); - -You can retrieve any bitfield you eventually stored into the bitStream (in reverse order) -Note : maximum allowed nbBits is 25, for 32-bits compatibility - size_t bitField = BIT_readBits(&DStream, nbBits); - -All above operations only read from local register (which size depends on size_t). -Refueling the register from memory is manually performed by the reload method. - endSignal = FSE_reloadDStream(&DStream); - -BIT_reloadDStream() result tells if there is still some more data to read from DStream. -BIT_DStream_unfinished : there is still some data left into the DStream. -BIT_DStream_endOfBuffer : Dstream reached end of buffer. Its container may no longer be completely filled. -BIT_DStream_completed : Dstream reached its exact end, corresponding in general to decompression completed. -BIT_DStream_tooFar : Dstream went too far. Decompression result is corrupted. - -When reaching end of buffer (BIT_DStream_endOfBuffer), progress slowly, notably if you decode multiple symbols per loop, -to properly detect the exact end of stream. -After each decoded symbol, check if DStream is fully consumed using this simple test : - BIT_reloadDStream(&DStream) >= BIT_DStream_completed - -When it's done, verify decompression is fully completed, by checking both DStream and the relevant states. -Checking if DStream has reached its end is performed by : - BIT_endOfDStream(&DStream); -Check also the states. There might be some symbols left there, if some high probability ones (>50%) are possible. - FSE_endOfDState(&DState); -*/ /****************************************** * FSE unsafe API ******************************************/