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/**
 * Copyright (c) 2016-present, Yann Collet, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of https://github.com/facebook/zstd.
 *
 * 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").
 */

/* ***************************************************************
*  Tuning parameters
*****************************************************************/
/*!
*  MAXWINDOWSIZE_DEFAULT :
*  maximum window size accepted by DStream, by default.
*  Frames requiring more memory will be rejected.
*/
#ifndef ZSTD_MAXWINDOWSIZE_DEFAULT
#define ZSTD_MAXWINDOWSIZE_DEFAULT ((1 << ZSTD_WINDOWLOG_MAX) + 1) /* defined within zstd.h */
#endif

/*-*******************************************************
*  Dependencies
*********************************************************/
#include "fse.h"
#include "huf.h"
#include "mem.h" /* low level memory routines */
#include "zstd_internal.h"
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/string.h> /* memcpy, memmove, memset */

#define ZSTD_PREFETCH(ptr) __builtin_prefetch(ptr, 0, 0)

/*-*************************************
*  Macros
***************************************/
#define ZSTD_isError ERR_isError /* for inlining */
#define FSE_isError ERR_isError
#define HUF_isError ERR_isError

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

/*-*************************************************************
*   Context management
***************************************************************/
typedef enum {
	ZSTDds_getFrameHeaderSize,
	ZSTDds_decodeFrameHeader,
	ZSTDds_decodeBlockHeader,
	ZSTDds_decompressBlock,
	ZSTDds_decompressLastBlock,
	ZSTDds_checkChecksum,
	ZSTDds_decodeSkippableHeader,
	ZSTDds_skipFrame
} ZSTD_dStage;

typedef struct {
	FSE_DTable LLTable[FSE_DTABLE_SIZE_U32(LLFSELog)];
	FSE_DTable OFTable[FSE_DTABLE_SIZE_U32(OffFSELog)];
	FSE_DTable MLTable[FSE_DTABLE_SIZE_U32(MLFSELog)];
	HUF_DTable hufTable[HUF_DTABLE_SIZE(HufLog)]; /* can accommodate HUF_decompress4X */
	U64 workspace[HUF_DECOMPRESS_WORKSPACE_SIZE_U32 / 2];
	U32 rep[ZSTD_REP_NUM];
} ZSTD_entropyTables_t;

struct ZSTD_DCtx_s {
	const FSE_DTable *LLTptr;
	const FSE_DTable *MLTptr;
	const FSE_DTable *OFTptr;
	const HUF_DTable *HUFptr;
	ZSTD_entropyTables_t entropy;
	const void *previousDstEnd; /* detect continuity */
	const void *base;	   /* start of curr segment */
	const void *vBase;	  /* virtual start of previous segment if it was just before curr one */
	const void *dictEnd;	/* end of previous segment */
	size_t expected;
	ZSTD_frameParams fParams;
	blockType_e bType; /* used in ZSTD_decompressContinue(), to transfer blockType between header decoding and block decoding stages */
	ZSTD_dStage stage;
	U32 litEntropy;
	U32 fseEntropy;
	struct xxh64_state xxhState;
	size_t headerSize;
	U32 dictID;
	const BYTE *litPtr;
	ZSTD_customMem customMem;
	size_t litSize;
	size_t rleSize;
	BYTE litBuffer[ZSTD_BLOCKSIZE_ABSOLUTEMAX + WILDCOPY_OVERLENGTH];
	BYTE headerBuffer[ZSTD_FRAMEHEADERSIZE_MAX];
}; /* typedef'd to ZSTD_DCtx within "zstd.h" */