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374 lines
15 KiB
374 lines
15 KiB
/*
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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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*
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* BSD 2-Clause License (http://www.opensource.org/licenses/bsd-license.php)
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*
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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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*
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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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*
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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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*
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* This program is free software; you can redistribute it and/or modify it under
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* the terms of the GNU General Public License version 2 as published by the
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* Free Software Foundation. This program is dual-licensed; you may select
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* either version 2 of the GNU General Public License ("GPL") or BSD license
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* ("BSD").
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*
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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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/*
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* This API consists of small unitary functions, which must be inlined for best performance.
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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 "error_private.h" /* error codes and messages */
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#include "mem.h" /* unaligned access routines */
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/*=========================================
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* Target specific
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=========================================*/
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#define STREAM_ACCUMULATOR_MIN_32 25
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#define STREAM_ACCUMULATOR_MIN_64 57
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#define STREAM_ACCUMULATOR_MIN ((U32)(ZSTD_32bits() ? STREAM_ACCUMULATOR_MIN_32 : STREAM_ACCUMULATOR_MIN_64))
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/*-******************************************
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* bitStream encoding API (write forward)
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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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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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ZSTD_STATIC size_t BIT_initCStream(BIT_CStream_t *bitC, void *dstBuffer, size_t dstCapacity);
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ZSTD_STATIC void BIT_addBits(BIT_CStream_t *bitC, size_t value, unsigned nbBits);
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ZSTD_STATIC void BIT_flushBits(BIT_CStream_t *bitC);
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ZSTD_STATIC size_t BIT_closeCStream(BIT_CStream_t *bitC);
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/* Start with 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(bitD->bitContainer), 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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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 {
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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
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} 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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ZSTD_STATIC size_t BIT_initDStream(BIT_DStream_t *bitD, const void *srcBuffer, size_t srcSize);
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ZSTD_STATIC size_t BIT_readBits(BIT_DStream_t *bitD, unsigned nbBits);
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ZSTD_STATIC BIT_DStream_status BIT_reloadDStream(BIT_DStream_t *bitD);
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ZSTD_STATIC unsigned BIT_endOfDStream(const BIT_DStream_t *bitD);
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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(bitD->bitContainer))-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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ZSTD_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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ZSTD_STATIC void BIT_flushBitsFast(BIT_CStream_t *bitC);
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/* unsafe version; does not check buffer overflow */
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ZSTD_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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* Internal functions
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****************************************************************/
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ZSTD_STATIC unsigned BIT_highbit32(register U32 val) { return 31 - __builtin_clz(val); }
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/*===== Local Constants =====*/
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static const unsigned BIT_mask[] = {0, 1, 3, 7, 0xF, 0x1F, 0x3F, 0x7F, 0xFF,
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0x1FF, 0x3FF, 0x7FF, 0xFFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF, 0x1FFFF,
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0x3FFFF, 0x7FFFF, 0xFFFFF, 0x1FFFFF, 0x3FFFFF, 0x7FFFFF, 0xFFFFFF, 0x1FFFFFF, 0x3FFFFFF}; /* up to 26 bits */
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/*-**************************************************************
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* bitStream encoding
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****************************************************************/
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/*! BIT_initCStream() :
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* `dstCapacity` must be > sizeof(void*)
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* @return : 0 if success,
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otherwise an error code (can be tested using ERR_isError() ) */
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ZSTD_STATIC size_t BIT_initCStream(BIT_CStream_t *bitC, void *startPtr, size_t dstCapacity)
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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 + dstCapacity - sizeof(bitC->ptr);
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if (dstCapacity <= sizeof(bitC->ptr))
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return ERROR(dstSize_tooSmall);
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return 0;
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}
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/*! BIT_addBits() :
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can add up to 26 bits into `bitC`.
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Does not check for register overflow ! */
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ZSTD_STATIC void BIT_addBits(BIT_CStream_t *bitC, size_t value, unsigned nbBits)
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{
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bitC->bitContainer |= (value & BIT_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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ZSTD_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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ZSTD_STATIC void BIT_flushBitsFast(BIT_CStream_t *bitC)
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{
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size_t const nbBytes = bitC->bitPos >> 3;
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ZSTD_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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/*! BIT_flushBits() :
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* safe version; check for buffer overflow, and prevents it.
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* note : does not signal buffer overflow. This will be revealed later on using BIT_closeCStream() */
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ZSTD_STATIC void BIT_flushBits(BIT_CStream_t *bitC)
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{
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size_t const nbBytes = bitC->bitPos >> 3;
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ZSTD_writeLEST(bitC->ptr, bitC->bitContainer);
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bitC->ptr += nbBytes;
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if (bitC->ptr > bitC->endPtr)
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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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* @return : size of CStream, in bytes,
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or 0 if it could not fit into dstBuffer */
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ZSTD_STATIC size_t BIT_closeCStream(BIT_CStream_t *bitC)
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{
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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)
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return 0; /* doesn't fit within authorized budget : cancel */
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return (bitC->ptr - bitC->startPtr) + (bitC->bitPos > 0);
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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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* `srcSize` must be the *exact* size of the bitStream, in bytes.
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* @return : size of stream (== srcSize) or an errorCode if a problem is detected
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*/
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ZSTD_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) {
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memset(bitD, 0, sizeof(*bitD));
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return ERROR(srcSize_wrong);
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}
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if (srcSize >= sizeof(bitD->bitContainer)) { /* normal case */
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bitD->start = (const char *)srcBuffer;
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bitD->ptr = (const char *)srcBuffer + srcSize - sizeof(bitD->bitContainer);
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bitD->bitContainer = ZSTD_readLEST(bitD->ptr);
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{
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BYTE const lastByte = ((const BYTE *)srcBuffer)[srcSize - 1];
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bitD->bitsConsumed = lastByte ? 8 - BIT_highbit32(lastByte) : 0; /* ensures bitsConsumed is always set */
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if (lastByte == 0)
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return ERROR(GENERIC); /* endMark not present */
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}
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} else {
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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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case 7: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[6]) << (sizeof(bitD->bitContainer) * 8 - 16);
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case 6: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[5]) << (sizeof(bitD->bitContainer) * 8 - 24);
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case 5: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[4]) << (sizeof(bitD->bitContainer) * 8 - 32);
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case 4: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[3]) << 24;
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case 3: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[2]) << 16;
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case 2: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[1]) << 8;
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default:;
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}
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{
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BYTE const lastByte = ((const BYTE *)srcBuffer)[srcSize - 1];
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bitD->bitsConsumed = lastByte ? 8 - BIT_highbit32(lastByte) : 0;
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if (lastByte == 0)
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return ERROR(GENERIC); /* endMark not present */
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}
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bitD->bitsConsumed += (U32)(sizeof(bitD->bitContainer) - srcSize) * 8;
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}
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return srcSize;
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}
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ZSTD_STATIC size_t BIT_getUpperBits(size_t bitContainer, U32 const start) { return bitContainer >> start; }
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ZSTD_STATIC size_t BIT_getMiddleBits(size_t bitContainer, U32 const start, U32 const nbBits) { return (bitContainer >> start) & BIT_mask[nbBits]; }
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ZSTD_STATIC size_t BIT_getLowerBits(size_t bitContainer, U32 const nbBits) { return bitContainer & BIT_mask[nbBits]; }
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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.
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* On 32-bits, maxNbBits==24.
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* On 64-bits, maxNbBits==56.
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* @return : value extracted
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*/
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ZSTD_STATIC size_t BIT_lookBits(const BIT_DStream_t *bitD, U32 nbBits)
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{
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U32 const 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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ZSTD_STATIC size_t BIT_lookBitsFast(const BIT_DStream_t *bitD, U32 nbBits)
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{
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U32 const 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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ZSTD_STATIC void BIT_skipBits(BIT_DStream_t *bitD, U32 nbBits) { bitD->bitsConsumed += nbBits; }
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/*! BIT_readBits() :
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* Read (consume) next n bits from local register and update.
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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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ZSTD_STATIC size_t BIT_readBits(BIT_DStream_t *bitD, U32 nbBits)
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{
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size_t const 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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ZSTD_STATIC size_t BIT_readBitsFast(BIT_DStream_t *bitD, U32 nbBits)
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{
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size_t const 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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/*! BIT_reloadDStream() :
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* Refill `bitD` from buffer previously set in BIT_initDStream() .
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* This function is safe, it guarantees it will not read beyond src buffer.
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* @return : status of `BIT_DStream_t` internal register.
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if status == BIT_DStream_unfinished, internal register is filled with >= (sizeof(bitD->bitContainer)*8 - 7) bits */
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ZSTD_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 not happen => corruption detected */
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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 = ZSTD_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)
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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 = ZSTD_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 exactly reached its end (all bits consumed).
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*/
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ZSTD_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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#endif /* BITSTREAM_H_MODULE */
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