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-rw-r--r--lib/zstd/common/bitstream.h437
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diff --git a/lib/zstd/common/bitstream.h b/lib/zstd/common/bitstream.h
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+++ b/lib/zstd/common/bitstream.h
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+/* ******************************************************************
+ * 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);
+ return (bitContainer >> (start & regMask)) & BIT_mask[nbBits];
+}
+
+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 */
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-01 10:18:27 +0000