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lz4.c
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// SPDX-License-Identifier: BSD-2-Clause
/*
LZ4 - Fast LZ compression algorithm
Copyright (C) 2011-2015, Yann Collet.
You can contact the author at :
- LZ4 source repository : https://github.com/Cyan4973/lz4
- LZ4 public forum : https://groups.google.com/forum/#!forum/lz4c
*/
/**************************************
* Reading and writing into memory
**************************************/
/* customized version of memcpy, which may overwrite up to 7 bytes beyond dstEnd */
static void LZ4_wildCopy(void* dstPtr, const void* srcPtr, void* dstEnd)
{
BYTE* d = (BYTE*)dstPtr;
const BYTE* s = (const BYTE*)srcPtr;
BYTE* e = (BYTE*)dstEnd;
do { LZ4_copy8(d,s); d+=8; s+=8; } while (d<e);
}
/**************************************
* Common Constants
**************************************/
#define MINMATCH 4
#define COPYLENGTH 8
#define LASTLITERALS 5
#define MFLIMIT (COPYLENGTH+MINMATCH)
static const int LZ4_minLength = (MFLIMIT+1);
#define KB *(1 <<10)
#define MB *(1 <<20)
#define GB *(1U<<30)
#define MAXD_LOG 16
#define MAX_DISTANCE ((1 << MAXD_LOG) - 1)
#define ML_BITS 4
#define ML_MASK ((1U<<ML_BITS)-1)
#define RUN_BITS (8-ML_BITS)
#define RUN_MASK ((1U<<RUN_BITS)-1)
/**************************************
* Local Structures and types
**************************************/
typedef enum { noDict = 0, withPrefix64k, usingExtDict } dict_directive;
typedef enum { endOnOutputSize = 0, endOnInputSize = 1 } endCondition_directive;
typedef enum { full = 0, partial = 1 } earlyEnd_directive;
/*******************************
* Decompression functions
*******************************/
/*
* This generic decompression function cover all use cases.
* It shall be instantiated several times, using different sets of directives
* Note that it is essential this generic function is really inlined,
* in order to remove useless branches during compilation optimization.
*/
FORCE_INLINE int LZ4_decompress_generic(
const char* const source,
char* const dest,
int inputSize,
int outputSize, /* If endOnInput==endOnInputSize, this value is the max size of Output Buffer. */
int endOnInput, /* endOnOutputSize, endOnInputSize */
int partialDecoding, /* full, partial */
int targetOutputSize, /* only used if partialDecoding==partial */
int dict, /* noDict, withPrefix64k, usingExtDict */
const BYTE* const lowPrefix, /* == dest if dict == noDict */
const BYTE* const dictStart, /* only if dict==usingExtDict */
const size_t dictSize /* note : = 0 if noDict */
)
{
/* Local Variables */
const BYTE* ip = (const BYTE*) source;
const BYTE* const iend = ip + inputSize;
BYTE* op = (BYTE*) dest;
BYTE* const oend = op + outputSize;
BYTE* cpy;
BYTE* oexit = op + targetOutputSize;
const BYTE* const lowLimit = lowPrefix - dictSize;
const BYTE* const dictEnd = (const BYTE*)dictStart + dictSize;
const size_t dec32table[] = {4, 1, 2, 1, 4, 4, 4, 4};
const size_t dec64table[] = {0, 0, 0, (size_t)-1, 0, 1, 2, 3};
const int safeDecode = (endOnInput==endOnInputSize);
const int checkOffset = ((safeDecode) && (dictSize < (int)(64 KB)));
/* Special cases */
if ((partialDecoding) && (oexit> oend-MFLIMIT)) oexit = oend-MFLIMIT; /* targetOutputSize too high => decode everything */
if ((endOnInput) && (unlikely(outputSize==0))) return ((inputSize==1) && (*ip==0)) ? 0 : -1; /* Empty output buffer */
if ((!endOnInput) && (unlikely(outputSize==0))) return (*ip==0?1:-1);
/* Main Loop */
while (1)
{
unsigned token;
size_t length;
const BYTE* match;
/* get literal length */
token = *ip++;
if ((length=(token>>ML_BITS)) == RUN_MASK)
{
unsigned s;
do
{
s = *ip++;
length += s;
}
while (likely((endOnInput)?ip<iend-RUN_MASK:1) && (s==255));
if ((safeDecode) && unlikely((size_t)(op+length)<(size_t)(op))) goto _output_error; /* overflow detection */
if ((safeDecode) && unlikely((size_t)(ip+length)<(size_t)(ip))) goto _output_error; /* overflow detection */
}
/* copy literals */
cpy = op+length;
if (((endOnInput) && ((cpy>(partialDecoding?oexit:oend-MFLIMIT)) || (ip+length>iend-(2+1+LASTLITERALS))) )
|| ((!endOnInput) && (cpy>oend-COPYLENGTH)))
{
if (partialDecoding)
{
if (cpy > oend) goto _output_error; /* Error : write attempt beyond end of output buffer */
if ((endOnInput) && (ip+length > iend)) goto _output_error; /* Error : read attempt beyond end of input buffer */
}
else
{
if ((!endOnInput) && (cpy != oend)) goto _output_error; /* Error : block decoding must stop exactly there */
if ((endOnInput) && ((ip+length != iend) || (cpy > oend))) goto _output_error; /* Error : input must be consumed */
}
memcpy(op, ip, length);
ip += length;
op += length;
break; /* Necessarily EOF, due to parsing restrictions */
}
LZ4_wildCopy(op, ip, cpy);
ip += length; op = cpy;
/* get offset */
match = cpy - LZ4_readLE16(ip); ip+=2;
if ((checkOffset) && (unlikely(match < lowLimit))) goto _output_error; /* Error : offset outside destination buffer */
/* get matchlength */
length = token & ML_MASK;
if (length == ML_MASK)
{
unsigned s;
do
{
if ((endOnInput) && (ip > iend-LASTLITERALS)) goto _output_error;
s = *ip++;
length += s;
} while (s==255);
if ((safeDecode) && unlikely((size_t)(op+length)<(size_t)op)) goto _output_error; /* overflow detection */
}
length += MINMATCH;
/* check external dictionary */
if ((dict==usingExtDict) && (match < lowPrefix))
{
if (unlikely(op+length > oend-LASTLITERALS)) goto _output_error; /* doesn't respect parsing restriction */
if (length <= (size_t)(lowPrefix-match))
{
/* match can be copied as a single segment from external dictionary */
match = dictEnd - (lowPrefix-match);
memmove(op, match, length); op += length;
}
else
{
/* match encompass external dictionary and current segment */
size_t copySize = (size_t)(lowPrefix-match);
memcpy(op, dictEnd - copySize, copySize);
op += copySize;
copySize = length - copySize;
if (copySize > (size_t)(op-lowPrefix)) /* overlap within current segment */
{
BYTE* const endOfMatch = op + copySize;
const BYTE* copyFrom = lowPrefix;
while (op < endOfMatch) *op++ = *copyFrom++;
}
else
{
memcpy(op, lowPrefix, copySize);
op += copySize;
}
}
continue;
}
/* copy repeated sequence */
cpy = op + length;
if (unlikely((op-match)<8))
{
const size_t dec64 = dec64table[op-match];
op[0] = match[0];
op[1] = match[1];
op[2] = match[2];
op[3] = match[3];
match += dec32table[op-match];
LZ4_copy4(op+4, match);
op += 8; match -= dec64;
} else { LZ4_copy8(op, match); op+=8; match+=8; }
if (unlikely(cpy>oend-12))
{
if (cpy > oend-LASTLITERALS) goto _output_error; /* Error : last LASTLITERALS bytes must be literals */
if (op < oend-8)
{
LZ4_wildCopy(op, match, oend-8);
match += (oend-8) - op;
op = oend-8;
}
while (op<cpy) *op++ = *match++;
}
else
LZ4_wildCopy(op, match, cpy);
op=cpy; /* correction */
}
/* end of decoding */
if (endOnInput)
return (int) (((char*)op)-dest); /* Nb of output bytes decoded */
else
return (int) (((const char*)ip)-source); /* Nb of input bytes read */
/* Overflow error detected */
_output_error:
return (int) (-(((const char*)ip)-source))-1;
}