in src/lz4.c [435:654]
FORCE_INLINE int LZ4_compress_generic(
void* const ctx,
const char* const source,
char* const dest,
const int inputSize,
const int maxOutputSize,
const limitedOutput_directive outputLimited,
const tableType_t tableType,
const dict_directive dict,
const dictIssue_directive dictIssue,
const U32 acceleration)
{
LZ4_stream_t_internal* const dictPtr = (LZ4_stream_t_internal*)ctx;
const BYTE* ip = (const BYTE*) source;
const BYTE* base;
const BYTE* lowLimit;
const BYTE* const lowRefLimit = ip - dictPtr->dictSize;
const BYTE* const dictionary = dictPtr->dictionary;
const BYTE* const dictEnd = dictionary + dictPtr->dictSize;
const size_t dictDelta = dictEnd - (const BYTE*)source;
const BYTE* anchor = (const BYTE*) source;
const BYTE* const iend = ip + inputSize;
const BYTE* const mflimit = iend - MFLIMIT;
const BYTE* const matchlimit = iend - LASTLITERALS;
BYTE* op = (BYTE*) dest;
BYTE* const olimit = op + maxOutputSize;
U32 forwardH;
size_t refDelta=0;
/* Init conditions */
if ((U32)inputSize > (U32)LZ4_MAX_INPUT_SIZE) return 0; /* Unsupported input size, too large (or negative) */
switch(dict)
{
case noDict:
default:
base = (const BYTE*)source;
lowLimit = (const BYTE*)source;
break;
case withPrefix64k:
base = (const BYTE*)source - dictPtr->currentOffset;
lowLimit = (const BYTE*)source - dictPtr->dictSize;
break;
case usingExtDict:
base = (const BYTE*)source - dictPtr->currentOffset;
lowLimit = (const BYTE*)source;
break;
}
if ((tableType == byU16) && (inputSize>=LZ4_64Klimit)) return 0; /* Size too large (not within 64K limit) */
if (inputSize<LZ4_minLength) goto _last_literals; /* Input too small, no compression (all literals) */
/* First Byte */
LZ4_putPosition(ip, ctx, tableType, base);
ip++; forwardH = LZ4_hashPosition(ip, tableType);
/* Main Loop */
for ( ; ; )
{
const BYTE* match;
BYTE* token;
{
const BYTE* forwardIp = ip;
unsigned step = 1;
unsigned searchMatchNb = acceleration << LZ4_skipTrigger;
/* Find a match */
do {
U32 h = forwardH;
ip = forwardIp;
forwardIp += step;
step = (searchMatchNb++ >> LZ4_skipTrigger);
if (unlikely(forwardIp > mflimit)) goto _last_literals;
match = LZ4_getPositionOnHash(h, ctx, tableType, base);
if (dict==usingExtDict)
{
if (match<(const BYTE*)source)
{
refDelta = dictDelta;
lowLimit = dictionary;
}
else
{
refDelta = 0;
lowLimit = (const BYTE*)source;
}
}
forwardH = LZ4_hashPosition(forwardIp, tableType);
LZ4_putPositionOnHash(ip, h, ctx, tableType, base);
} while ( ((dictIssue==dictSmall) ? (match < lowRefLimit) : 0)
|| ((tableType==byU16) ? 0 : (match + MAX_DISTANCE < ip))
|| (LZ4_read32(match+refDelta) != LZ4_read32(ip)) );
}
/* Catch up */
while ((ip>anchor) && (match+refDelta > lowLimit) && (unlikely(ip[-1]==match[refDelta-1]))) { ip--; match--; }
{
/* Encode Literal length */
unsigned litLength = (unsigned)(ip - anchor);
token = op++;
if ((outputLimited) && (unlikely(op + litLength + (2 + 1 + LASTLITERALS) + (litLength/255) > olimit)))
return 0; /* Check output limit */
if (litLength>=RUN_MASK)
{
int len = (int)litLength-RUN_MASK;
*token=(RUN_MASK<<ML_BITS);
for(; len >= 255 ; len-=255) *op++ = 255;
*op++ = (BYTE)len;
}
else *token = (BYTE)(litLength<<ML_BITS);
/* Copy Literals */
LZ4_wildCopy(op, anchor, op+litLength);
op+=litLength;
}
_next_match:
/* Encode Offset */
LZ4_writeLE16(op, (U16)(ip-match)); op+=2;
/* Encode MatchLength */
{
unsigned matchLength;
if ((dict==usingExtDict) && (lowLimit==dictionary))
{
const BYTE* limit;
match += refDelta;
limit = ip + (dictEnd-match);
if (limit > matchlimit) limit = matchlimit;
matchLength = LZ4_count(ip+MINMATCH, match+MINMATCH, limit);
ip += MINMATCH + matchLength;
if (ip==limit)
{
unsigned more = LZ4_count(ip, (const BYTE*)source, matchlimit);
matchLength += more;
ip += more;
}
}
else
{
matchLength = LZ4_count(ip+MINMATCH, match+MINMATCH, matchlimit);
ip += MINMATCH + matchLength;
}
if ((outputLimited) && (unlikely(op + (1 + LASTLITERALS) + (matchLength>>8) > olimit)))
return 0; /* Check output limit */
if (matchLength>=ML_MASK)
{
*token += ML_MASK;
matchLength -= ML_MASK;
for (; matchLength >= 510 ; matchLength-=510) { *op++ = 255; *op++ = 255; }
if (matchLength >= 255) { matchLength-=255; *op++ = 255; }
*op++ = (BYTE)matchLength;
}
else *token += (BYTE)(matchLength);
}
anchor = ip;
/* Test end of chunk */
if (ip > mflimit) break;
/* Fill table */
LZ4_putPosition(ip-2, ctx, tableType, base);
/* Test next position */
match = LZ4_getPosition(ip, ctx, tableType, base);
if (dict==usingExtDict)
{
if (match<(const BYTE*)source)
{
refDelta = dictDelta;
lowLimit = dictionary;
}
else
{
refDelta = 0;
lowLimit = (const BYTE*)source;
}
}
LZ4_putPosition(ip, ctx, tableType, base);
if ( ((dictIssue==dictSmall) ? (match>=lowRefLimit) : 1)
&& (match+MAX_DISTANCE>=ip)
&& (LZ4_read32(match+refDelta)==LZ4_read32(ip)) )
{ token=op++; *token=0; goto _next_match; }
/* Prepare next loop */
forwardH = LZ4_hashPosition(++ip, tableType);
}
_last_literals:
/* Encode Last Literals */
{
const size_t lastRun = (size_t)(iend - anchor);
if ((outputLimited) && ((op - (BYTE*)dest) + lastRun + 1 + ((lastRun+255-RUN_MASK)/255) > (U32)maxOutputSize))
return 0; /* Check output limit */
if (lastRun >= RUN_MASK)
{
size_t accumulator = lastRun - RUN_MASK;
*op++ = RUN_MASK << ML_BITS;
for(; accumulator >= 255 ; accumulator-=255) *op++ = 255;
*op++ = (BYTE) accumulator;
}
else
{
*op++ = (BYTE)(lastRun<<ML_BITS);
}
memcpy(op, anchor, lastRun);
op += lastRun;
}
/* End */
return (int) (((char*)op)-dest);
}