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Diffstat (limited to 'lib/zstd/common/bitstream.h')
| -rw-r--r-- | lib/zstd/common/bitstream.h | 446 |
1 files changed, 446 insertions, 0 deletions
diff --git a/lib/zstd/common/bitstream.h b/lib/zstd/common/bitstream.h new file mode 100644 index 000000000000..feef3a1b1d60 --- /dev/null +++ b/lib/zstd/common/bitstream.h @@ -0,0 +1,446 @@ +/* ****************************************************************** + * bitstream + * Part of FSE library + * Copyright (c) Yann Collet, Facebook, Inc. + * + * You can contact the author at : + * - Source repository : https://github.com/Cyan4973/FiniteStateEntropy + * + * This source code is licensed under both the BSD-style license (found in the + * LICENSE file in the root directory of this source tree) and the GPLv2 (found + * in the COPYING file in the root directory of this source tree). + * You may select, at your option, one of the above-listed licenses. +****************************************************************** */ +#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 "mem.h" /* unaligned access routines */ +#include "compiler.h" /* UNLIKELY() */ +#include "debug.h" /* assert(), DEBUGLOG(), RAWLOG() */ +#include "error_private.h" /* error codes and messages */ + + +/*========================================= +* Target specific +=========================================*/ + +#define STREAM_ACCUMULATOR_MIN_32 25 +#define STREAM_ACCUMULATOR_MIN_64 57 +#define STREAM_ACCUMULATOR_MIN ((U32)(MEM_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; + unsigned bitPos; + char* startPtr; + char* ptr; + char* endPtr; +} BIT_CStream_t; + +MEM_STATIC size_t BIT_initCStream(BIT_CStream_t* bitC, void* dstBuffer, size_t dstCapacity); +MEM_STATIC void BIT_addBits(BIT_CStream_t* bitC, size_t value, unsigned nbBits); +MEM_STATIC void BIT_flushBits(BIT_CStream_t* bitC); +MEM_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; + const char* limitPtr; +} 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 ... :( */ + +MEM_STATIC size_t BIT_initDStream(BIT_DStream_t* bitD, const void* srcBuffer, size_t srcSize); +MEM_STATIC size_t BIT_readBits(BIT_DStream_t* bitD, unsigned nbBits); +MEM_STATIC BIT_DStream_status BIT_reloadDStream(BIT_DStream_t* bitD); +MEM_STATIC unsigned BIT_endOfDStream(const BIT_DStream_t* bitD); + + +/* Start by invoking BIT_initDStream(). +* A chunk of the bitStream is then stored into a local register. +* Local register size is 64-bits on 64-bits systems, 32-bits on 32-bits systems (size_t). +* You can then retrieve bitFields stored into the local register, **in reverse order**. +* Local register is 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 +******************************************/ +MEM_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 */ + +MEM_STATIC void BIT_flushBitsFast(BIT_CStream_t* bitC); +/* unsafe version; does not check buffer overflow */ + +MEM_STATIC size_t BIT_readBitsFast(BIT_DStream_t* bitD, unsigned nbBits); +/* faster, but works only if nbBits >= 1 */ + + + +/*-************************************************************** +* Internal functions +****************************************************************/ +MEM_STATIC unsigned BIT_highbit32 (U32 val) +{ + assert(val != 0); + { +# if (__GNUC__ >= 3) /* Use GCC Intrinsic */ + return __builtin_clz (val) ^ 31; +# else /* Software version */ + 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 }; + U32 v = val; + v |= v >> 1; + v |= v >> 2; + v |= v >> 4; + v |= v >> 8; + v |= v >> 16; + return DeBruijnClz[ (U32) (v * 0x07C4ACDDU) >> 27]; +# endif + } +} + +/*===== 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, 0x7FFFFFF, 0xFFFFFFF, 0x1FFFFFFF, + 0x3FFFFFFF, 0x7FFFFFFF}; /* up to 31 bits */ +#define BIT_MASK_SIZE (sizeof(BIT_mask) / sizeof(BIT_mask[0])) + +/*-************************************************************** +* bitStream encoding +****************************************************************/ +/*! BIT_initCStream() : + * `dstCapacity` must be > sizeof(size_t) + * @return : 0 if success, + * otherwise an error code (can be tested using ERR_isError()) */ +MEM_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->bitContainer); + if (dstCapacity <= sizeof(bitC->bitContainer)) return ERROR(dstSize_tooSmall); + return 0; +} + +/*! BIT_addBits() : + * can add up to 31 bits into `bitC`. + * Note : does not check for register overflow ! */ +MEM_STATIC void BIT_addBits(BIT_CStream_t* bitC, + size_t value, unsigned nbBits) +{ + DEBUG_STATIC_ASSERT(BIT_MASK_SIZE == 32); + assert(nbBits < BIT_MASK_SIZE); + assert(nbBits + bitC->bitPos < sizeof(bitC->bitContainer) * 8); + 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 */ +MEM_STATIC void BIT_addBitsFast(BIT_CStream_t* bitC, + size_t value, unsigned nbBits) +{ + assert((value>>nbBits) == 0); + assert(nbBits + bitC->bitPos < sizeof(bitC->bitContainer) * 8); + bitC->bitContainer |= value << bitC->bitPos; + bitC->bitPos += nbBits; +} + +/*! BIT_flushBitsFast() : + * assumption : bitContainer has not overflowed + * unsafe version; does not check buffer overflow */ +MEM_STATIC void BIT_flushBitsFast(BIT_CStream_t* bitC) +{ + size_t const nbBytes = bitC->bitPos >> 3; + assert(bitC->bitPos < sizeof(bitC->bitContainer) * 8); + assert(bitC->ptr <= bitC->endPtr); + MEM_writeLEST(bitC->ptr, bitC->bitContainer); + bitC->ptr += nbBytes; + bitC->bitPos &= 7; + bitC->bitContainer >>= nbBytes*8; +} + +/*! BIT_flushBits() : + * assumption : bitContainer has not overflowed + * safe version; check for buffer overflow, and prevents it. + * note : does not signal buffer overflow. + * overflow will be revealed later on using BIT_closeCStream() */ +MEM_STATIC void BIT_flushBits(BIT_CStream_t* bitC) +{ + size_t const nbBytes = bitC->bitPos >> 3; + assert(bitC->bitPos < sizeof(bitC->bitContainer) * 8); + assert(bitC->ptr <= bitC->endPtr); + MEM_writeLEST(bitC->ptr, bitC->bitContainer); + bitC->ptr += nbBytes; + if (bitC->ptr > bitC->endPtr) bitC->ptr = bitC->endPtr; + bitC->bitPos &= 7; + bitC->bitContainer >>= nbBytes*8; +} + +/*! BIT_closeCStream() : + * @return : size of CStream, in bytes, + * or 0 if it could not fit into dstBuffer */ +MEM_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; /* overflow detected */ + 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 + */ +MEM_STATIC size_t BIT_initDStream(BIT_DStream_t* bitD, const void* srcBuffer, size_t srcSize) +{ + if (srcSize < 1) { ZSTD_memset(bitD, 0, sizeof(*bitD)); return ERROR(srcSize_wrong); } + + bitD->start = (const char*)srcBuffer; + bitD->limitPtr = bitD->start + sizeof(bitD->bitContainer); + + if (srcSize >= sizeof(bitD->bitContainer)) { /* normal case */ + bitD->ptr = (const char*)srcBuffer + srcSize - sizeof(bitD->bitContainer); + bitD->bitContainer = MEM_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->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); + ZSTD_FALLTHROUGH; + + case 6: bitD->bitContainer += (size_t)(((const BYTE*)(srcBuffer))[5]) << (sizeof(bitD->bitContainer)*8 - 24); + ZSTD_FALLTHROUGH; + + case 5: bitD->bitContainer += (size_t)(((const BYTE*)(srcBuffer))[4]) << (sizeof(bitD->bitContainer)*8 - 32); + ZSTD_FALLTHROUGH; + + case 4: bitD->bitContainer += (size_t)(((const BYTE*)(srcBuffer))[3]) << 24; + ZSTD_FALLTHROUGH; + + case 3: bitD->bitContainer += (size_t)(((const BYTE*)(srcBuffer))[2]) << 16; + ZSTD_FALLTHROUGH; + + case 2: bitD->bitContainer += (size_t)(((const BYTE*)(srcBuffer))[1]) << 8; + ZSTD_FALLTHROUGH; + + default: break; + } + { BYTE const lastByte = ((const BYTE*)srcBuffer)[srcSize-1]; + bitD->bitsConsumed = lastByte ? 8 - BIT_highbit32(lastByte) : 0; + if (lastByte == 0) return ERROR(corruption_detected); /* endMark not present */ + } + bitD->bitsConsumed += (U32)(sizeof(bitD->bitContainer) - srcSize)*8; + } + + return srcSize; +} + +MEM_STATIC FORCE_INLINE_ATTR size_t BIT_getUpperBits(size_t bitContainer, U32 const start) +{ + return bitContainer >> start; +} + +MEM_STATIC FORCE_INLINE_ATTR size_t BIT_getMiddleBits(size_t bitContainer, U32 const start, U32 const nbBits) +{ + U32 const regMask = sizeof(bitContainer)*8 - 1; + /* if start > regMask, bitstream is corrupted, and result is undefined */ + assert(nbBits < BIT_MASK_SIZE); + /* x86 transform & ((1 << nbBits) - 1) to bzhi instruction, it is better + * than accessing memory. When bmi2 instruction is not present, we consider + * such cpus old (pre-Haswell, 2013) and their performance is not of that + * importance. + */ +#if defined(__x86_64__) || defined(_M_X86) + return (bitContainer >> (start & regMask)) & ((((U64)1) << nbBits) - 1); +#else + return (bitContainer >> (start & regMask)) & BIT_mask[nbBits]; +#endif +} + +MEM_STATIC FORCE_INLINE_ATTR size_t BIT_getLowerBits(size_t bitContainer, U32 const nbBits) +{ + assert(nbBits < BIT_MASK_SIZE); + 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 */ +MEM_STATIC FORCE_INLINE_ATTR size_t BIT_lookBits(const BIT_DStream_t* bitD, U32 nbBits) +{ + /* arbitrate between double-shift and shift+mask */ +#if 1 + /* if bitD->bitsConsumed + nbBits > sizeof(bitD->bitContainer)*8, + * bitstream is likely corrupted, and result is undefined */ + return BIT_getMiddleBits(bitD->bitContainer, (sizeof(bitD->bitContainer)*8) - bitD->bitsConsumed - nbBits, nbBits); +#else + /* this code path is slower on my os-x laptop */ + U32 const regMask = sizeof(bitD->bitContainer)*8 - 1; + return ((bitD->bitContainer << (bitD->bitsConsumed & regMask)) >> 1) >> ((regMask-nbBits) & regMask); +#endif +} + +/*! BIT_lookBitsFast() : + * unsafe version; only works if nbBits >= 1 */ +MEM_STATIC size_t BIT_lookBitsFast(const BIT_DStream_t* bitD, U32 nbBits) +{ + U32 const regMask = sizeof(bitD->bitContainer)*8 - 1; + assert(nbBits >= 1); + return (bitD->bitContainer << (bitD->bitsConsumed & regMask)) >> (((regMask+1)-nbBits) & regMask); +} + +MEM_STATIC FORCE_INLINE_ATTR 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. */ +MEM_STATIC FORCE_INLINE_ATTR size_t BIT_readBits(BIT_DStream_t* bitD, unsigned 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 */ +MEM_STATIC size_t BIT_readBitsFast(BIT_DStream_t* bitD, unsigned nbBits) +{ + size_t const value = BIT_lookBitsFast(bitD, nbBits); + assert(nbBits >= 1); + BIT_skipBits(bitD, nbBits); + return value; +} + +/*! BIT_reloadDStreamFast() : + * Similar to BIT_reloadDStream(), but with two differences: + * 1. bitsConsumed <= sizeof(bitD->bitContainer)*8 must hold! + * 2. Returns BIT_DStream_overflow when bitD->ptr < bitD->limitPtr, at this + * point you must use BIT_reloadDStream() to reload. + */ +MEM_STATIC BIT_DStream_status BIT_reloadDStreamFast(BIT_DStream_t* bitD) +{ + if (UNLIKELY(bitD->ptr < bitD->limitPtr)) + return BIT_DStream_overflow; + assert(bitD->bitsConsumed <= sizeof(bitD->bitContainer)*8); + bitD->ptr -= bitD->bitsConsumed >> 3; + bitD->bitsConsumed &= 7; + bitD->bitContainer = MEM_readLEST(bitD->ptr); + return BIT_DStream_unfinished; +} + +/*! 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. + * when status == BIT_DStream_unfinished, internal register is filled with at least 25 or 57 bits */ +MEM_STATIC BIT_DStream_status BIT_reloadDStream(BIT_DStream_t* bitD) +{ + if (bitD->bitsConsumed > (sizeof(bitD->bitContainer)*8)) /* overflow detected, like end of stream */ + return BIT_DStream_overflow; + + if (bitD->ptr >= bitD->limitPtr) { + return BIT_reloadDStreamFast(bitD); + } + if (bitD->ptr == bitD->start) { + if (bitD->bitsConsumed < sizeof(bitD->bitContainer)*8) return BIT_DStream_endOfBuffer; + return BIT_DStream_completed; + } + /* start < ptr < limitPtr */ + { 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 = MEM_readLEST(bitD->ptr); /* reminder : srcSize > sizeof(bitD->bitContainer), otherwise bitD->ptr == bitD->start */ + return result; + } +} + +/*! BIT_endOfDStream() : + * @return : 1 if DStream has _exactly_ reached its end (all bits consumed). + */ +MEM_STATIC unsigned BIT_endOfDStream(const BIT_DStream_t* DStream) +{ + return ((DStream->ptr == DStream->start) && (DStream->bitsConsumed == sizeof(DStream->bitContainer)*8)); +} + + +#endif /* BITSTREAM_H_MODULE */ |