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Diffstat (limited to 'lib/zstd/bitstream.h')
| -rw-r--r-- | lib/zstd/bitstream.h | 374 |
1 files changed, 374 insertions, 0 deletions
diff --git a/lib/zstd/bitstream.h b/lib/zstd/bitstream.h new file mode 100644 index 0000000..a826b99 --- /dev/null +++ b/lib/zstd/bitstream.h @@ -0,0 +1,374 @@ +/* + * 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); + case 6: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[5]) << (sizeof(bitD->bitContainer) * 8 - 24); + case 5: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[4]) << (sizeof(bitD->bitContainer) * 8 - 32); + case 4: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[3]) << 24; + case 3: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[2]) << 16; + 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 */ |
