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ext/zstd/lib/decompress/zstd_decompress_block.c  view on Meta::CPAN

/*
 * Copyright (c) 2016-present, 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.
 */

/* zstd_decompress_block :
 * this module takes care of decompressing _compressed_ block */

/*-*******************************************************
*  Dependencies
*********************************************************/
#include <string.h>      /* memcpy, memmove, memset */
#include "compiler.h"    /* prefetch */
#include "cpu.h"         /* bmi2 */
#include "mem.h"         /* low level memory routines */
#define FSE_STATIC_LINKING_ONLY
#include "fse.h"
#define HUF_STATIC_LINKING_ONLY
#include "huf.h"
#include "zstd_internal.h"
#include "zstd_decompress_internal.h"   /* ZSTD_DCtx */
#include "zstd_ddict.h"  /* ZSTD_DDictDictContent */
#include "zstd_decompress_block.h"

/*_*******************************************************
*  Macros
**********************************************************/

/* These two optional macros force the use one way or another of the two
 * ZSTD_decompressSequences implementations. You can't force in both directions
 * at the same time.
 */
#if defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT) && \
    defined(ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG)
#error "Cannot force the use of the short and the long ZSTD_decompressSequences variants!"
#endif


/*_*******************************************************
*  Memory operations
**********************************************************/
static void ZSTD_copy4(void* dst, const void* src) { memcpy(dst, src, 4); }


/*-*************************************************************
 *   Block decoding
 ***************************************************************/

/*! ZSTD_getcBlockSize() :
 *  Provides the size of compressed block from block header `src` */
size_t ZSTD_getcBlockSize(const void* src, size_t srcSize,
                          blockProperties_t* bpPtr)
{
    RETURN_ERROR_IF(srcSize < ZSTD_blockHeaderSize, srcSize_wrong);

    {   U32 const cBlockHeader = MEM_readLE24(src);
        U32 const cSize = cBlockHeader >> 3;
        bpPtr->lastBlock = cBlockHeader & 1;
        bpPtr->blockType = (blockType_e)((cBlockHeader >> 1) & 3);
        bpPtr->origSize = cSize;   /* only useful for RLE */
        if (bpPtr->blockType == bt_rle) return 1;
        RETURN_ERROR_IF(bpPtr->blockType == bt_reserved, corruption_detected);
        return cSize;
    }
}


/* Hidden declaration for fullbench */
size_t ZSTD_decodeLiteralsBlock(ZSTD_DCtx* dctx,
                          const void* src, size_t srcSize);
/*! ZSTD_decodeLiteralsBlock() :
 * @return : nb of bytes read from src (< srcSize )
 *  note : symbol not declared but exposed for fullbench */
size_t ZSTD_decodeLiteralsBlock(ZSTD_DCtx* dctx,
                          const void* src, size_t srcSize)   /* note : srcSize < BLOCKSIZE */
{
    DEBUGLOG(5, "ZSTD_decodeLiteralsBlock");
    RETURN_ERROR_IF(srcSize < MIN_CBLOCK_SIZE, corruption_detected);

    {   const BYTE* const istart = (const BYTE*) src;
        symbolEncodingType_e const litEncType = (symbolEncodingType_e)(istart[0] & 3);

        switch(litEncType)
        {
        case set_repeat:
            DEBUGLOG(5, "set_repeat flag : re-using stats from previous compressed literals block");