Commit e0c1b49f authored by Nick Terrell's avatar Nick Terrell
Browse files

lib: zstd: Upgrade to latest upstream zstd version 1.4.10 

Upgrade to the latest upstream zstd version 1.4.10.

This patch is 100% generated from upstream zstd commit 20821a46f412 [0].

This patch is very large because it is transitioning from the custom
kernel zstd to using upstream directly. The new zstd follows upstreams
file structure which is different. Future update patches will be much
smaller because they will only contain the changes from one upstream
zstd release.

As an aid for review I've created a commit [1] that shows the diff
between upstream zstd as-is (which doesn't compile), and the zstd
code imported in this patch. The verion of zstd in this patch is
generated from upstream with changes applied by automation to replace
upstreams libc dependencies, remove unnecessary portability macros,
replace `/**` comments with `/*` comments, and use the kernel's xxhash
instead of bundling it.

The benefits of this patch are as follows:
1. Using upstream directly with automated script to generate kernel
   code. This allows us to update the kernel every upstream release, so
   the kernel gets the latest bug fixes and performance improvements,
   and doesn't get 3 years out of date again. The automation and the
   translated code are tested every upstream commit to ensure it
   continues to work.
2. Upgrades from a custom zstd based on 1.3.1 to 1.4.10, getting 3 years
   of performance improvements and bug fixes. On x86_64 I've measured
   15% faster BtrFS and SquashFS decompression+read speeds, 35% faster
   kernel decompression, and 30% faster ZRAM decompression+read speeds.
3. Zstd-1.4.10 supports negative compression levels, which allow zstd to
   match or subsume lzo's performance.
4. Maintains the same kernel-specific wrapper API, so no callers have to
   be modified with zstd version updates.

One concern that was brought up was stack usage. Upstream zstd had
already removed most of its heavy stack usage functions, but I just
removed the last functions that allocate arrays on the stack. I've
measured the high water mark for both compression and decompression
before and after this patch. Decompression is approximately neutral,
using about 1.2KB of stack space. Compression levels up to 3 regressed
from 1.4KB -> 1.6KB, and higher compression levels regressed from 1.5KB
-> 2KB. We've added unit tests upstream to prevent further regression.
I believe that this is a reasonable increase, and if it does end up
causing problems, this commit can be cleanly reverted, because it only
touches zstd.

I chose the bulk update instead of replaying upstream commits because
there have been ~3500 upstream commits since the 1.3.1 release, zstd
wasn't ready to be used in the kernel as-is before a month ago, and not
all upstream zstd commits build. The bulk update preserves bisectablity
because bugs can be bisected to the zstd version update. At that point
the update can be reverted, and we can work with upstream to find and
fix the bug.

Note that upstream zstd release 1.4.10 doesn't exist yet. I have cut a
staging branch at 20821a46f412 [0] and will apply any changes requested
to the staging branch. Once we're ready to merge this update I will cut
a zstd release at the commit we merge, so we have a known zstd release
in the kernel.

The implementation of the kernel API is contained in
zstd_compress_module.c and zstd_decompress_module.c.

[0] https://github.com/facebook/zstd/commit/20821a46f4122f9abd7c7b245d28162dde8129c9
[1] https://github.com/terrelln/linux/commit/e0fa481d0e3df26918da0a13749740a1f6777574



Signed-off-by: default avatarNick Terrell <terrelln@fb.com>
Tested By: Paul Jones <paul@pauljones.id.au>
Tested-by: default avatarOleksandr Natalenko <oleksandr@natalenko.name>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com> # LLVM/Clang v13.0.0 on x86-64
Tested-by: default avatarJean-Denis Girard <jd.girard@sysnux.pf>
parent 2479b523

include/linux/zstd.h

+10 −3
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0-only */

/* SPDX-License-Identifier: GPL-2.0+ OR BSD-3-Clause */

/*

 * Copyright (c) Yann Collet, Facebook, Inc.

 * All rights reserved.
@@ -22,6 +22,7 @@ 


/* ======   Dependency   ====== */

#include <linux/types.h>

#include <linux/zstd_errors.h>

#include <linux/zstd_lib.h>



/* ======   Helper Functions   ====== */
@@ -417,12 +418,18 @@ size_t zstd_find_frame_compressed_size(const void *src, size_t src_size); 


/**

 * struct zstd_frame_params - zstd frame parameters stored in the frame header

 * @frameContentSize: The frame content size, or 0 if not present.

 * @frameContentSize: The frame content size, or ZSTD_CONTENTSIZE_UNKNOWN if not

 *                    present.

 * @windowSize:       The window size, or 0 if the frame is a skippable frame.

 * @blockSizeMax:     The maximum block size.

 * @frameType:        The frame type (zstd or skippable)

 * @headerSize:       The size of the frame header.

 * @dictID:           The dictionary id, or 0 if not present.

 * @checksumFlag:     Whether a checksum was used.

 *

 * See zstd_lib.h.

 */

typedef ZSTD_frameParams zstd_frame_header;

typedef ZSTD_frameHeader zstd_frame_header;



/**

 * zstd_get_frame_header() - extracts parameters from a zstd or skippable frame

include/linux/zstd_errors.h

0 → 100644
+77 −0
Original line number Diff line number Diff line 
/*

 * Copyright (c) Yann Collet, Facebook, Inc.

 * All rights reserved.

 *

 * 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 ZSTD_ERRORS_H_398273423

#define ZSTD_ERRORS_H_398273423





/*===== dependency =====*/

#include <linux/types.h>   /* size_t */





/* =====   ZSTDERRORLIB_API : control library symbols visibility   ===== */

#define ZSTDERRORLIB_VISIBILITY 

#define ZSTDERRORLIB_API ZSTDERRORLIB_VISIBILITY



/*-*********************************************

 *  Error codes list

 *-*********************************************

 *  Error codes _values_ are pinned down since v1.3.1 only.

 *  Therefore, don't rely on values if you may link to any version < v1.3.1.

 *

 *  Only values < 100 are considered stable.

 *

 *  note 1 : this API shall be used with static linking only.

 *           dynamic linking is not yet officially supported.

 *  note 2 : Prefer relying on the enum than on its value whenever possible

 *           This is the only supported way to use the error list < v1.3.1

 *  note 3 : ZSTD_isError() is always correct, whatever the library version.

 **********************************************/

typedef enum {

  ZSTD_error_no_error = 0,

  ZSTD_error_GENERIC  = 1,

  ZSTD_error_prefix_unknown                = 10,

  ZSTD_error_version_unsupported           = 12,

  ZSTD_error_frameParameter_unsupported    = 14,

  ZSTD_error_frameParameter_windowTooLarge = 16,

  ZSTD_error_corruption_detected = 20,

  ZSTD_error_checksum_wrong      = 22,

  ZSTD_error_dictionary_corrupted      = 30,

  ZSTD_error_dictionary_wrong          = 32,

  ZSTD_error_dictionaryCreation_failed = 34,

  ZSTD_error_parameter_unsupported   = 40,

  ZSTD_error_parameter_outOfBound    = 42,

  ZSTD_error_tableLog_tooLarge       = 44,

  ZSTD_error_maxSymbolValue_tooLarge = 46,

  ZSTD_error_maxSymbolValue_tooSmall = 48,

  ZSTD_error_stage_wrong       = 60,

  ZSTD_error_init_missing      = 62,

  ZSTD_error_memory_allocation = 64,

  ZSTD_error_workSpace_tooSmall= 66,

  ZSTD_error_dstSize_tooSmall = 70,

  ZSTD_error_srcSize_wrong    = 72,

  ZSTD_error_dstBuffer_null   = 74,

  /* following error codes are __NOT STABLE__, they can be removed or changed in future versions */

  ZSTD_error_frameIndex_tooLarge = 100,

  ZSTD_error_seekableIO          = 102,

  ZSTD_error_dstBuffer_wrong     = 104,

  ZSTD_error_srcBuffer_wrong     = 105,

  ZSTD_error_maxCode = 120  /* never EVER use this value directly, it can change in future versions! Use ZSTD_isError() instead */

} ZSTD_ErrorCode;



/*! ZSTD_getErrorCode() :

    convert a `size_t` function result into a `ZSTD_ErrorCode` enum type,

    which can be used to compare with enum list published above */

ZSTDERRORLIB_API ZSTD_ErrorCode ZSTD_getErrorCode(size_t functionResult);

ZSTDERRORLIB_API const char* ZSTD_getErrorString(ZSTD_ErrorCode code);   /*< Same as ZSTD_getErrorName, but using a `ZSTD_ErrorCode` enum argument */







#endif /* ZSTD_ERRORS_H_398273423 */

include/linux/zstd_lib.h

+2321 −1046

File changed.

Preview size limit exceeded, changes collapsed.

lib/zstd/Makefile

+41 −5
Original line number Diff line number Diff line 
# SPDX-License-Identifier: GPL-2.0-only

# SPDX-License-Identifier: GPL-2.0+ OR BSD-3-Clause

# ################################################################

# Copyright (c) Facebook, Inc.

# All rights reserved.

#

# 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.

# ################################################################

obj-$(CONFIG_ZSTD_COMPRESS) += zstd_compress.o

obj-$(CONFIG_ZSTD_DECOMPRESS) += zstd_decompress.o



ccflags-y += -O3



zstd_compress-y := fse_compress.o huf_compress.o compress.o \

		   entropy_common.o fse_decompress.o zstd_common.o

zstd_decompress-y := huf_decompress.o decompress.o \

		     entropy_common.o fse_decompress.o zstd_common.o
 
zstd_compress-y := \

		zstd_compress_module.o \

		common/debug.o \

		common/entropy_common.o \

		common/error_private.o \

		common/fse_decompress.o \

		common/zstd_common.o \

		compress/fse_compress.o \

		compress/hist.o \

		compress/huf_compress.o \

		compress/zstd_compress.o \

		compress/zstd_compress_literals.o \

		compress/zstd_compress_sequences.o \

		compress/zstd_compress_superblock.o \

		compress/zstd_double_fast.o \

		compress/zstd_fast.o \

		compress/zstd_lazy.o \

		compress/zstd_ldm.o \

		compress/zstd_opt.o \



zstd_decompress-y := \

		zstd_decompress_module.o \

		common/debug.o \

		common/entropy_common.o \

		common/error_private.o \

		common/fse_decompress.o \

		common/zstd_common.o \

		decompress/huf_decompress.o \

		decompress/zstd_ddict.o \

		decompress/zstd_decompress.o \

		decompress/zstd_decompress_block.o \

lib/zstd/bitstream.h

deleted100644 → 0
+0 −380
Original line number Diff line number Diff line 
/*

 * 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);

			fallthrough;

		case 6: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[5]) << (sizeof(bitD->bitContainer) * 8 - 24);

			fallthrough;

		case 5: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[4]) << (sizeof(bitD->bitContainer) * 8 - 32);

			fallthrough;

		case 4: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[3]) << 24;

			fallthrough;

		case 3: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[2]) << 16;

			fallthrough;

		case 2: bitD->bitContainer += (size_t)(((const BYTE *)(srcBuffer))[1]) << 8;

			fallthrough;

		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 */