/* * bitstream * Part of FSE library * header file (to include) * Copyright (C) 2013-2016, Yann Collet. * * BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php) * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions are * met: * *   * Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. *   * Redistributions in binary form must reproduce the above * copyright notice, this list of conditions and the following disclaimer * in the documentation and/or other materials provided with the * distribution. * * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. * * This program is free software; you can redistribute it and/or modify it under * the terms of the GNU General Public License version 2 as published by the * Free Software Foundation. This program is dual-licensed; you may select * either version 2 of the GNU General Public License ("GPL") or BSD license * ("BSD"). * * You can contact the author at : * - Source repository : https://github.com/Cyan4973/FiniteStateEntropy */#ifndef BITSTREAM_H_MODULE#define BITSTREAM_H_MODULE /**  This API consists of small unitary functions, which must be inlined for best performance.*  Since link-time-optimization is not available for all compilers,*  these functions are defined into a .h to be included.*/ /*-*****************************************  Dependencies******************************************/#include "error_private.h" /* error codes and messages */#include "mem.h"	   /* unaligned access routines */ /*=========================================*  Target specific=========================================*/#define STREAM_ACCUMULATOR_MIN_32 25#define STREAM_ACCUMULATOR_MIN_64 57#define STREAM_ACCUMULATOR_MIN ((U32)(ZSTD_32bits() ? STREAM_ACCUMULATOR_MIN_32 : STREAM_ACCUMULATOR_MIN_64)) /*-*******************************************  bitStream encoding API (write forward)********************************************//* bitStream can mix input from multiple sources.*  A critical property of these streams is that they encode and decode in **reverse** direction.*  So the first bit sequence you add will be the last to be read, like a LIFO stack.*/typedef struct {	size_t bitContainer;	int bitPos;	char *startPtr;	char *ptr;	char *endPtr;} BIT_CStream_t; ZSTD_STATIC size_t BIT_initCStream(BIT_CStream_t *bitC, void *dstBuffer, size_t dstCapacity);ZSTD_STATIC void BIT_addBits(BIT_CStream_t *bitC, size_t value, unsigned nbBits);ZSTD_STATIC void BIT_flushBits(BIT_CStream_t *bitC);ZSTD_STATIC size_t BIT_closeCStream(BIT_CStream_t *bitC); /* Start with initCStream, providing the size of buffer to write into.*  bitStream will never write outside of this buffer.*  `dstCapacity` must be >= sizeof(bitD->bitContainer), otherwise @return will be an error code.**  bits are first added to a local register.*  Local register is size_t, hence 64-bits on 64-bits systems, or 32-bits on 32-bits systems.*  Writing data into memory is an explicit operation, performed by the flushBits function.*  Hence keep track how many bits are potentially stored into local register to avoid register overflow.*  After a flushBits, a maximum of 7 bits might still be stored into local register.**  Avoid storing elements of more than 24 bits if you want compatibility with 32-bits bitstream readers.**  Last operation is to close the bitStream.*  The function returns the final size of CStream in bytes.*  If data couldn't fit into `dstBuffer`, it will return a 0 ( == not storable)*/ /*-*********************************************  bitStream decoding API (read backward)**********************************************/typedef struct {	size_t bitContainer;	unsigned bitsConsumed;	const char *ptr;	const char *start;} BIT_DStream_t; typedef enum {	BIT_DStream_unfinished = 0,	BIT_DStream_endOfBuffer = 1,	BIT_DStream_completed = 2,	BIT_DStream_overflow = 3} BIT_DStream_status; /* result of BIT_reloadDStream() *//* 1,2,4,8 would be better for bitmap combinations, but slows down performance a bit ... :( */ ZSTD_STATIC size_t BIT_initDStream(BIT_DStream_t *bitD, const void *srcBuffer, size_t srcSize);ZSTD_STATIC size_t BIT_readBits(BIT_DStream_t *bitD, unsigned nbBits);ZSTD_STATIC BIT_DStream_status BIT_reloadDStream(BIT_DStream_t *bitD);ZSTD_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 explicitly reloaded from memory by the BIT_reloadDStream() method.*  A reload guarantee a minimum of ((8*sizeof(bitD->bitContainer))-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******************************************/ZSTD_STATIC void BIT_addBitsFast(BIT_CStream_t *bitC, size_t value, unsigned nbBits);/* faster, but works only if value is "clean", meaning all high bits above nbBits are 0 */ ZSTD_STATIC void BIT_flushBitsFast(BIT_CStream_t *bitC);/* unsafe version; does not check buffer overflow */ ZSTD_STATIC size_t BIT_readBitsFast(BIT_DStream_t *bitD, unsigned nbBits);/* faster, but works only if nbBits >= 1 */ /*-***************************************************************  Internal functions****************************************************************/ZSTD_STATIC unsigned BIT_highbit32(register U32 val) { return 31 - __builtin_clz(val); } /*=====    Local Constants   =====*/static const unsigned BIT_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, 0x3FFFFFF}; /* up to 26 bits */ /*-***************************************************************  bitStream encoding****************************************************************//*! BIT_initCStream() : *  `dstCapacity` must be > sizeof(void*) *  @return : 0 if success,			  otherwise an error code (can be tested using ERR_isError() ) */ZSTD_STATIC size_t BIT_initCStream(BIT_CStream_t *bitC, void *startPtr, size_t dstCapacity){	bitC->bitContainer = 0;	bitC->bitPos = 0;	bitC->startPtr = (char *)startPtr;	bitC->ptr = bitC->startPtr;	bitC->endPtr = bitC->startPtr + dstCapacity - sizeof(bitC->ptr);	if (dstCapacity <= sizeof(bitC->ptr))		return ERROR(dstSize_tooSmall);	return 0;} /*! BIT_addBits() :	can add up to 26 bits into `bitC`.	Does not check for register overflow ! */ZSTD_STATIC void BIT_addBits(BIT_CStream_t *bitC, size_t value, unsigned nbBits){	bitC->bitContainer |= (value & BIT_mask[nbBits]) << bitC->bitPos;	bitC->bitPos += nbBits;} /*! BIT_addBitsFast() : *  works only if `value` is _clean_, meaning all high bits above nbBits are 0 */ZSTD_STATIC void BIT_addBitsFast(BIT_CStream_t *bitC, size_t value, unsigned nbBits){	bitC->bitContainer |= value << bitC->bitPos;	bitC->bitPos += nbBits;} /*! BIT_flushBitsFast() : *  unsafe version; does not check buffer overflow */ZSTD_STATIC void BIT_flushBitsFast(BIT_CStream_t *bitC){	size_t const nbBytes = bitC->bitPos >> 3;	ZSTD_writeLEST(bitC->ptr, bitC->bitContainer);	bitC->ptr += nbBytes;	bitC->bitPos &= 7;	bitC->bitContainer >>= nbBytes * 8; /* if bitPos >= sizeof(bitContainer)*8 --> undefined behavior */} /*! BIT_flushBits() : *  safe version; check for buffer overflow, and prevents it. *  note : does not signal buffer overflow. This will be revealed later on using BIT_closeCStream() */ZSTD_STATIC void BIT_flushBits(BIT_CStream_t *bitC){	size_t const nbBytes = bitC->bitPos >> 3;	ZSTD_writeLEST(bitC->ptr, bitC->bitContainer);	bitC->ptr += nbBytes;	if (bitC->ptr > bitC->endPtr)		bitC->ptr = bitC->endPtr;	bitC->bitPos &= 7;	bitC->bitContainer >>= nbBytes * 8; /* if bitPos >= sizeof(bitContainer)*8 --> undefined behavior */} /*! BIT_closeCStream() : *  @return : size of CStream, in bytes,			  or 0 if it could not fit into dstBuffer */ZSTD_STATIC size_t BIT_closeCStream(BIT_CStream_t *bitC){	BIT_addBitsFast(bitC, 1, 1); /* endMark */	BIT_flushBits(bitC); 	if (bitC->ptr >= bitC->endPtr)		return 0; /* doesn't fit within authorized budget : cancel */ 	return (bitC->ptr - bitC->startPtr) + (bitC->bitPos > 0);} /*-********************************************************* bitStream decoding**********************************************************//*! BIT_initDStream() :*   Initialize a BIT_DStream_t.*   `bitD` : a pointer to an already allocated BIT_DStream_t structure.*   `srcSize` must be the *exact* size of the bitStream, in bytes.*   @return : size of stream (== srcSize) or an errorCode if a problem is detected*/ZSTD_STATIC size_t BIT_initDStream(BIT_DStream_t *bitD, const void *srcBuffer, size_t srcSize){	if (srcSize < 1) {		memset(bitD, 0, sizeof(*bitD));		return ERROR(srcSize_wrong);	} 	if (srcSize >= sizeof(bitD->bitContainer)) { /* normal case */		bitD->start = (const char *)srcBuffer;		bitD->ptr = (const char *)srcBuffer + srcSize - sizeof(bitD->bitContainer);		bitD->bitContainer = ZSTD_readLEST(bitD->ptr);		{			BYTE const lastByte = ((const BYTE *)srcBuffer)[srcSize - 1];			bitD->bitsConsumed = lastByte ? 8 - BIT_highbit32(lastByte) : 0; /* ensures bitsConsumed is always set */			if (lastByte == 0)				return ERROR(GENERIC); /* endMark not present */		}	} else {		bitD->start = (const char *)srcBuffer;		bitD->ptr = bitD->start;		bitD->bitContainer = *(const BYTE *)(bitD->start);		switch (srcSize) {		case 7: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[6]) << (sizeof(bitD->bitContainer) * 8 - 16);			/* fall through */		case 6: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[5]) << (sizeof(bitD->bitContainer) * 8 - 24);			/* fall through */		case 5: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[4]) << (sizeof(bitD->bitContainer) * 8 - 32);			/* fall through */		case 4: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[3]) << 24;			/* fall through */		case 3: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[2]) << 16;			/* fall through */		case 2: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[1]) << 8;		default:;		}		{			BYTE const lastByte = ((const BYTE *)srcBuffer)[srcSize - 1];			bitD->bitsConsumed = lastByte ? 8 - BIT_highbit32(lastByte) : 0;			if (lastByte == 0)				return ERROR(GENERIC); /* endMark not present */		}		bitD->bitsConsumed += (U32)(sizeof(bitD->bitContainer) - srcSize) * 8;	} 	return srcSize;} ZSTD_STATIC size_t BIT_getUpperBits(size_t bitContainer, U32 const start) { return bitContainer >> start; } ZSTD_STATIC size_t BIT_getMiddleBits(size_t bitContainer, U32 const start, U32 const nbBits) { return (bitContainer >> start) & BIT_mask[nbBits]; } ZSTD_STATIC size_t BIT_getLowerBits(size_t bitContainer, U32 const nbBits) { return bitContainer & BIT_mask[nbBits]; } /*! BIT_lookBits() : *  Provides next n bits from local register. *  local register is not modified. *  On 32-bits, maxNbBits==24. *  On 64-bits, maxNbBits==56. *  @return : value extracted */ZSTD_STATIC size_t BIT_lookBits(const BIT_DStream_t *bitD, U32 nbBits){	U32 const bitMask = sizeof(bitD->bitContainer) * 8 - 1;	return ((bitD->bitContainer << (bitD->bitsConsumed & bitMask)) >> 1) >> ((bitMask - nbBits) & bitMask);} /*! BIT_lookBitsFast() :*   unsafe version; only works only if nbBits >= 1 */ZSTD_STATIC size_t BIT_lookBitsFast(const BIT_DStream_t *bitD, U32 nbBits){	U32 const bitMask = sizeof(bitD->bitContainer) * 8 - 1;	return (bitD->bitContainer << (bitD->bitsConsumed & bitMask)) >> (((bitMask + 1) - nbBits) & bitMask);} ZSTD_STATIC void BIT_skipBits(BIT_DStream_t *bitD, U32 nbBits) { bitD->bitsConsumed += nbBits; } /*! BIT_readBits() : *  Read (consume) next n bits from local register and update. *  Pay attention to not read more than nbBits contained into local register. *  @return : extracted value. */ZSTD_STATIC size_t BIT_readBits(BIT_DStream_t *bitD, U32 nbBits){	size_t const value = BIT_lookBits(bitD, nbBits);	BIT_skipBits(bitD, nbBits);	return value;} /*! BIT_readBitsFast() :*   unsafe version; only works only if nbBits >= 1 */ZSTD_STATIC size_t BIT_readBitsFast(BIT_DStream_t *bitD, U32 nbBits){	size_t const value = BIT_lookBitsFast(bitD, nbBits);	BIT_skipBits(bitD, nbBits);	return value;} /*! BIT_reloadDStream() :*   Refill `bitD` from buffer previously set in BIT_initDStream() .*   This function is safe, it guarantees it will not read beyond src buffer.*   @return : status of `BIT_DStream_t` internal register.			  if status == BIT_DStream_unfinished, internal register is filled with >= (sizeof(bitD->bitContainer)*8 - 7) bits */ZSTD_STATIC BIT_DStream_status BIT_reloadDStream(BIT_DStream_t *bitD){	if (bitD->bitsConsumed > (sizeof(bitD->bitContainer) * 8)) /* should not happen => corruption detected */		return BIT_DStream_overflow; 	if (bitD->ptr >= bitD->start + sizeof(bitD->bitContainer)) {		bitD->ptr -= bitD->bitsConsumed >> 3;		bitD->bitsConsumed &= 7;		bitD->bitContainer = ZSTD_readLEST(bitD->ptr);		return BIT_DStream_unfinished;	}	if (bitD->ptr == bitD->start) {		if (bitD->bitsConsumed < sizeof(bitD->bitContainer) * 8)			return BIT_DStream_endOfBuffer;		return BIT_DStream_completed;	}	{		U32 nbBytes = bitD->bitsConsumed >> 3;		BIT_DStream_status result = BIT_DStream_unfinished;		if (bitD->ptr - nbBytes < bitD->start) {			nbBytes = (U32)(bitD->ptr - bitD->start); /* ptr > start */			result = BIT_DStream_endOfBuffer;		}		bitD->ptr -= nbBytes;		bitD->bitsConsumed -= nbBytes * 8;		bitD->bitContainer = ZSTD_readLEST(bitD->ptr); /* reminder : srcSize > sizeof(bitD) */		return result;	}} /*! BIT_endOfDStream() :*   @return Tells if DStream has exactly reached its end (all bits consumed).*/ZSTD_STATIC unsigned BIT_endOfDStream(const BIT_DStream_t *DStream){	return ((DStream->ptr == DStream->start) && (DStream->bitsConsumed == sizeof(DStream->bitContainer) * 8));} #endif /* BITSTREAM_H_MODULE */