464 lines
18 KiB
C++
464 lines
18 KiB
C++
/* ******************************************************************
|
|
* 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
|
|
|
|
#if defined (__cplusplus)
|
|
extern "C" {
|
|
#endif
|
|
/*
|
|
* 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
|
|
=========================================*/
|
|
#ifndef ZSTD_NO_INTRINSICS
|
|
# if defined(__BMI__) && defined(__GNUC__)
|
|
# include <immintrin.h> /* support for bextr (experimental) */
|
|
# elif defined(__ICCARM__)
|
|
# include <intrinsics.h>
|
|
# endif
|
|
#endif
|
|
|
|
#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 defined(_MSC_VER) /* Visual */
|
|
# if STATIC_BMI2 == 1
|
|
return _lzcnt_u32(val) ^ 31;
|
|
# else
|
|
unsigned long r = 0;
|
|
return _BitScanReverse(&r, val) ? (unsigned)r : 0;
|
|
# endif
|
|
# elif defined(__GNUC__) && (__GNUC__ >= 3) /* Use GCC Intrinsic */
|
|
return __builtin_clz (val) ^ 31;
|
|
# elif defined(__ICCARM__) /* IAR Intrinsic */
|
|
return 31 - __CLZ(val);
|
|
# 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);
|
|
/* 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;
|
|
/* fall-through */
|
|
|
|
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);
|
|
return (bitContainer >> (start & regMask)) & BIT_mask[nbBits];
|
|
}
|
|
|
|
MEM_STATIC FORCE_INLINE_ATTR size_t BIT_getLowerBits(size_t bitContainer, U32 const nbBits)
|
|
{
|
|
#if defined(STATIC_BMI2) && STATIC_BMI2 == 1
|
|
return _bzhi_u64(bitContainer, nbBits);
|
|
#else
|
|
assert(nbBits < BIT_MASK_SIZE);
|
|
return bitContainer & BIT_mask[nbBits];
|
|
#endif
|
|
}
|
|
|
|
/*! 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));
|
|
}
|
|
|
|
#if defined (__cplusplus)
|
|
}
|
|
#endif
|
|
|
|
#endif /* BITSTREAM_H_MODULE */
|