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376 lines
14 KiB
C
376 lines
14 KiB
C
/* ******************************************************************
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bitstream
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Part of FSE library
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header file (to include)
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Copyright (C) 2013-2016, Yann Collet.
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BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are
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met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above
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copyright notice, this list of conditions and the following disclaimer
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in the documentation and/or other materials provided with the
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distribution.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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You can contact the author at :
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- Source repository : https://github.com/Cyan4973/FiniteStateEntropy
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****************************************************************** */
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#ifndef BITSTREAM_H_MODULE
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#define BITSTREAM_H_MODULE
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#if defined (__cplusplus)
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extern "C" {
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#endif
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/*
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* This API consists of small unitary functions, which highly benefit from being inlined.
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* Since link-time-optimization is not available for all compilers,
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* these functions are defined into a .h to be included.
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*/
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/*-****************************************
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* Dependencies
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******************************************/
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#include "mem.h" /* unaligned access routines */
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#include "error_private.h" /* error codes and messages */
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/*-******************************************
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* bitStream encoding API (write forward)
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********************************************/
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/*!
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* bitStream can mix input from multiple sources.
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* A critical property of these streams is that they encode and decode in **reverse** direction.
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* So the first bit sequence you add will be the last to be read, like a LIFO stack.
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*/
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typedef struct
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{
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size_t bitContainer;
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int bitPos;
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char* startPtr;
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char* ptr;
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char* endPtr;
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} BIT_CStream_t;
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MEM_STATIC size_t BIT_initCStream(BIT_CStream_t* bitC, void* dstBuffer, size_t dstCapacity);
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MEM_STATIC void BIT_addBits(BIT_CStream_t* bitC, size_t value, unsigned nbBits);
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MEM_STATIC void BIT_flushBits(BIT_CStream_t* bitC);
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MEM_STATIC size_t BIT_closeCStream(BIT_CStream_t* bitC);
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/*!
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* Start by initCStream, providing the size of buffer to write into.
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* bitStream will never write outside of this buffer.
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* @dstCapacity must be >= sizeof(size_t), otherwise @return will be an error code.
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*
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* bits are first added to a local register.
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* Local register is size_t, hence 64-bits on 64-bits systems, or 32-bits on 32-bits systems.
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* Writing data into memory is an explicit operation, performed by the flushBits function.
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* Hence keep track how many bits are potentially stored into local register to avoid register overflow.
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* After a flushBits, a maximum of 7 bits might still be stored into local register.
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*
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* Avoid storing elements of more than 24 bits if you want compatibility with 32-bits bitstream readers.
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*
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* Last operation is to close the bitStream.
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* The function returns the final size of CStream in bytes.
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* If data couldn't fit into @dstBuffer, it will return a 0 ( == not storable)
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*/
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/*-********************************************
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* bitStream decoding API (read backward)
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**********************************************/
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typedef struct
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{
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size_t bitContainer;
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unsigned bitsConsumed;
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const char* ptr;
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const char* start;
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} BIT_DStream_t;
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typedef enum { BIT_DStream_unfinished = 0,
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BIT_DStream_endOfBuffer = 1,
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BIT_DStream_completed = 2,
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BIT_DStream_overflow = 3 } BIT_DStream_status; /* result of BIT_reloadDStream() */
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/* 1,2,4,8 would be better for bitmap combinations, but slows down performance a bit ... :( */
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MEM_STATIC size_t BIT_initDStream(BIT_DStream_t* bitD, const void* srcBuffer, size_t srcSize);
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MEM_STATIC size_t BIT_readBits(BIT_DStream_t* bitD, unsigned nbBits);
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MEM_STATIC BIT_DStream_status BIT_reloadDStream(BIT_DStream_t* bitD);
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MEM_STATIC unsigned BIT_endOfDStream(const BIT_DStream_t* bitD);
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/*!
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* Start by invoking BIT_initDStream().
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* A chunk of the bitStream is then stored into a local register.
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* Local register size is 64-bits on 64-bits systems, 32-bits on 32-bits systems (size_t).
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* You can then retrieve bitFields stored into the local register, **in reverse order**.
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* Local register is explicitly reloaded from memory by the BIT_reloadDStream() method.
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* A reload guarantee a minimum of ((8*sizeof(size_t))-7) bits when its result is BIT_DStream_unfinished.
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* Otherwise, it can be less than that, so proceed accordingly.
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* Checking if DStream has reached its end can be performed with BIT_endOfDStream()
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*/
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/*-****************************************
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* unsafe API
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******************************************/
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MEM_STATIC void BIT_addBitsFast(BIT_CStream_t* bitC, size_t value, unsigned nbBits);
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/* faster, but works only if value is "clean", meaning all high bits above nbBits are 0 */
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MEM_STATIC void BIT_flushBitsFast(BIT_CStream_t* bitC);
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/* unsafe version; does not check buffer overflow */
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MEM_STATIC size_t BIT_readBitsFast(BIT_DStream_t* bitD, unsigned nbBits);
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/* faster, but works only if nbBits >= 1 */
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/*-**************************************************************
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* Helper functions
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****************************************************************/
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MEM_STATIC unsigned BIT_highbit32 (register U32 val)
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{
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# if defined(_MSC_VER) /* Visual */
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unsigned long r=0;
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_BitScanReverse ( &r, val );
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return (unsigned) r;
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# elif defined(__GNUC__) && (__GNUC__ >= 3) /* Use GCC Intrinsic */
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return 31 - __builtin_clz (val);
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# else /* Software version */
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static const unsigned DeBruijnClz[32] = { 0, 9, 1, 10, 13, 21, 2, 29, 11, 14, 16, 18, 22, 25, 3, 30, 8, 12, 20, 28, 15, 17, 24, 7, 19, 27, 23, 6, 26, 5, 4, 31 };
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U32 v = val;
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unsigned r;
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v |= v >> 1;
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v |= v >> 2;
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v |= v >> 4;
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v |= v >> 8;
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v |= v >> 16;
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r = DeBruijnClz[ (U32) (v * 0x07C4ACDDU) >> 27];
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return r;
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# endif
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}
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/*-**************************************************************
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* bitStream encoding
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****************************************************************/
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MEM_STATIC size_t BIT_initCStream(BIT_CStream_t* bitC, void* startPtr, size_t maxSize)
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{
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bitC->bitContainer = 0;
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bitC->bitPos = 0;
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bitC->startPtr = (char*)startPtr;
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bitC->ptr = bitC->startPtr;
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bitC->endPtr = bitC->startPtr + maxSize - sizeof(bitC->ptr);
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if (maxSize < sizeof(bitC->ptr)) return ERROR(dstSize_tooSmall);
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return 0;
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}
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MEM_STATIC void BIT_addBits(BIT_CStream_t* bitC, size_t value, unsigned nbBits)
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{
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static const unsigned mask[] = { 0, 1, 3, 7, 0xF, 0x1F, 0x3F, 0x7F, 0xFF, 0x1FF, 0x3FF, 0x7FF, 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF, 0x1FFFF, 0x3FFFF, 0x7FFFF, 0xFFFFF, 0x1FFFFF, 0x3FFFFF, 0x7FFFFF, 0xFFFFFF, 0x1FFFFFF }; /* up to 25 bits */
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bitC->bitContainer |= (value & mask[nbBits]) << bitC->bitPos;
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bitC->bitPos += nbBits;
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}
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/*! BIT_addBitsFast
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* works only if `value` is _clean_, meaning all high bits above nbBits are 0 */
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MEM_STATIC void BIT_addBitsFast(BIT_CStream_t* bitC, size_t value, unsigned nbBits)
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{
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bitC->bitContainer |= value << bitC->bitPos;
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bitC->bitPos += nbBits;
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}
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/*! BIT_flushBitsFast
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* unsafe version; does not check buffer overflow */
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MEM_STATIC void BIT_flushBitsFast(BIT_CStream_t* bitC)
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{
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size_t nbBytes = bitC->bitPos >> 3;
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MEM_writeLEST(bitC->ptr, bitC->bitContainer);
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bitC->ptr += nbBytes;
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bitC->bitPos &= 7;
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bitC->bitContainer >>= nbBytes*8; /* if bitPos >= sizeof(bitContainer)*8 --> undefined behavior */
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}
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MEM_STATIC void BIT_flushBits(BIT_CStream_t* bitC)
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{
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size_t nbBytes = bitC->bitPos >> 3;
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MEM_writeLEST(bitC->ptr, bitC->bitContainer);
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bitC->ptr += nbBytes;
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if (bitC->ptr > bitC->endPtr) bitC->ptr = bitC->endPtr;
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bitC->bitPos &= 7;
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bitC->bitContainer >>= nbBytes*8; /* if bitPos >= sizeof(bitContainer)*8 --> undefined behavior */
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}
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/*! BIT_closeCStream
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* @result : size of CStream, in bytes, or 0 if it cannot fit into dstBuffer */
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MEM_STATIC size_t BIT_closeCStream(BIT_CStream_t* bitC)
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{
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char* endPtr;
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BIT_addBitsFast(bitC, 1, 1); /* endMark */
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BIT_flushBits(bitC);
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if (bitC->ptr >= bitC->endPtr) /* too close to buffer's end */
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return 0; /* not storable */
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endPtr = bitC->ptr;
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endPtr += bitC->bitPos > 0; /* remaining bits (incomplete byte) */
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return (endPtr - bitC->startPtr);
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}
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/*-********************************************************
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* bitStream decoding
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**********************************************************/
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/*!BIT_initDStream
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* Initialize a BIT_DStream_t.
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* @bitD : a pointer to an already allocated BIT_DStream_t structure
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* @srcBuffer must point at the beginning of a bitStream
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* @srcSize must be the exact size of the bitStream
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* @result : size of stream (== srcSize) or an errorCode if a problem is detected
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*/
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MEM_STATIC size_t BIT_initDStream(BIT_DStream_t* bitD, const void* srcBuffer, size_t srcSize)
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{
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if (srcSize < 1) { memset(bitD, 0, sizeof(*bitD)); return ERROR(srcSize_wrong); }
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if (srcSize >= sizeof(size_t)) { /* normal case */
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U32 contain32;
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bitD->start = (const char*)srcBuffer;
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bitD->ptr = (const char*)srcBuffer + srcSize - sizeof(size_t);
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bitD->bitContainer = MEM_readLEST(bitD->ptr);
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contain32 = ((const BYTE*)srcBuffer)[srcSize-1];
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if (contain32 == 0) return ERROR(GENERIC); /* endMark not present */
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bitD->bitsConsumed = 8 - BIT_highbit32(contain32);
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} else {
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U32 contain32;
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bitD->start = (const char*)srcBuffer;
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bitD->ptr = bitD->start;
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bitD->bitContainer = *(const BYTE*)(bitD->start);
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switch(srcSize)
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{
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case 7: bitD->bitContainer += (size_t)(((const BYTE*)(bitD->start))[6]) << (sizeof(size_t)*8 - 16);
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case 6: bitD->bitContainer += (size_t)(((const BYTE*)(bitD->start))[5]) << (sizeof(size_t)*8 - 24);
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case 5: bitD->bitContainer += (size_t)(((const BYTE*)(bitD->start))[4]) << (sizeof(size_t)*8 - 32);
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case 4: bitD->bitContainer += (size_t)(((const BYTE*)(bitD->start))[3]) << 24;
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case 3: bitD->bitContainer += (size_t)(((const BYTE*)(bitD->start))[2]) << 16;
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case 2: bitD->bitContainer += (size_t)(((const BYTE*)(bitD->start))[1]) << 8;
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default:;
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}
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contain32 = ((const BYTE*)srcBuffer)[srcSize-1];
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if (contain32 == 0) return ERROR(GENERIC); /* endMark not present */
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bitD->bitsConsumed = 8 - BIT_highbit32(contain32);
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bitD->bitsConsumed += (U32)(sizeof(size_t) - srcSize)*8;
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}
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return srcSize;
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}
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/*!BIT_lookBits
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* Provides next n bits from local register
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* local register is not modified (bits are still present for next read/look)
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* On 32-bits, maxNbBits==25
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* On 64-bits, maxNbBits==57
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* @return : value extracted
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*/
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MEM_STATIC size_t BIT_lookBits(BIT_DStream_t* bitD, U32 nbBits)
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{
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const U32 bitMask = sizeof(bitD->bitContainer)*8 - 1;
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return ((bitD->bitContainer << (bitD->bitsConsumed & bitMask)) >> 1) >> ((bitMask-nbBits) & bitMask);
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}
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/*! BIT_lookBitsFast :
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* unsafe version; only works only if nbBits >= 1 */
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MEM_STATIC size_t BIT_lookBitsFast(BIT_DStream_t* bitD, U32 nbBits)
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{
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const U32 bitMask = sizeof(bitD->bitContainer)*8 - 1;
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return (bitD->bitContainer << (bitD->bitsConsumed & bitMask)) >> (((bitMask+1)-nbBits) & bitMask);
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}
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MEM_STATIC void BIT_skipBits(BIT_DStream_t* bitD, U32 nbBits)
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{
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bitD->bitsConsumed += nbBits;
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}
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/*!BIT_readBits
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* Read next n bits from local register.
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* pay attention to not read more than nbBits contained into local register.
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* @return : extracted value.
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*/
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MEM_STATIC size_t BIT_readBits(BIT_DStream_t* bitD, U32 nbBits)
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{
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size_t value = BIT_lookBits(bitD, nbBits);
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BIT_skipBits(bitD, nbBits);
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return value;
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}
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/*!BIT_readBitsFast :
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* unsafe version; only works only if nbBits >= 1 */
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MEM_STATIC size_t BIT_readBitsFast(BIT_DStream_t* bitD, U32 nbBits)
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{
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size_t value = BIT_lookBitsFast(bitD, nbBits);
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BIT_skipBits(bitD, nbBits);
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return value;
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}
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MEM_STATIC BIT_DStream_status BIT_reloadDStream(BIT_DStream_t* bitD)
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{
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if (bitD->bitsConsumed > (sizeof(bitD->bitContainer)*8)) /* should never happen */
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return BIT_DStream_overflow;
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if (bitD->ptr >= bitD->start + sizeof(bitD->bitContainer)) {
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bitD->ptr -= bitD->bitsConsumed >> 3;
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bitD->bitsConsumed &= 7;
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bitD->bitContainer = MEM_readLEST(bitD->ptr);
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return BIT_DStream_unfinished;
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}
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if (bitD->ptr == bitD->start) {
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if (bitD->bitsConsumed < sizeof(bitD->bitContainer)*8) return BIT_DStream_endOfBuffer;
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return BIT_DStream_completed;
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}
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{
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U32 nbBytes = bitD->bitsConsumed >> 3;
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BIT_DStream_status result = BIT_DStream_unfinished;
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if (bitD->ptr - nbBytes < bitD->start) {
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nbBytes = (U32)(bitD->ptr - bitD->start); /* ptr > start */
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result = BIT_DStream_endOfBuffer;
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}
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bitD->ptr -= nbBytes;
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bitD->bitsConsumed -= nbBytes*8;
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bitD->bitContainer = MEM_readLEST(bitD->ptr); /* reminder : srcSize > sizeof(bitD) */
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return result;
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}
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}
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/*! BIT_endOfDStream
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* @return Tells if DStream has reached its exact end
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*/
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MEM_STATIC unsigned BIT_endOfDStream(const BIT_DStream_t* DStream)
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{
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return ((DStream->ptr == DStream->start) && (DStream->bitsConsumed == sizeof(DStream->bitContainer)*8));
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}
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#if defined (__cplusplus)
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}
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#endif
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#endif /* BITSTREAM_H_MODULE */
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