in subversion/libsvn_subr/lz4/lz4.c [469:666]
FORCE_INLINE int LZ4_compress_generic(
LZ4_stream_t_internal* const cctx,
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)
{
const BYTE* ip = (const BYTE*) source;
const BYTE* base;
const BYTE* lowLimit;
const BYTE* const lowRefLimit = ip - cctx->dictSize;
const BYTE* const dictionary = cctx->dictionary;
const BYTE* const dictEnd = dictionary + cctx->dictSize;
const ptrdiff_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;
/* Init conditions */
if ((U32)inputSize > (U32)LZ4_MAX_INPUT_SIZE) return 0; /* Unsupported inputSize, too large (or negative) */
switch(dict)
{
case noDict:
default:
base = (const BYTE*)source;
lowLimit = (const BYTE*)source;
break;
case withPrefix64k:
base = (const BYTE*)source - cctx->currentOffset;
lowLimit = (const BYTE*)source - cctx->dictSize;
break;
case usingExtDict:
base = (const BYTE*)source - cctx->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, cctx->hashTable, tableType, base);
ip++; forwardH = LZ4_hashPosition(ip, tableType);
/* Main Loop */
for ( ; ; ) {
ptrdiff_t refDelta = 0;
const BYTE* match;
BYTE* token;
/* Find a match */
{ const BYTE* forwardIp = ip;
unsigned step = 1;
unsigned searchMatchNb = acceleration << LZ4_skipTrigger;
do {
U32 const h = forwardH;
ip = forwardIp;
forwardIp += step;
step = (searchMatchNb++ >> LZ4_skipTrigger);
if (unlikely(forwardIp > mflimit)) goto _last_literals;
match = LZ4_getPositionOnHash(h, cctx->hashTable, 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, cctx->hashTable, 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 Literals */
{ unsigned const litLength = (unsigned)(ip - anchor);
token = op++;
if ((outputLimited) && /* Check output buffer overflow */
(unlikely(op + litLength + (2 + 1 + LASTLITERALS) + (litLength/255) > olimit)))
return 0;
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 matchCode;
if ((dict==usingExtDict) && (lowLimit==dictionary)) {
const BYTE* limit;
match += refDelta;
limit = ip + (dictEnd-match);
if (limit > matchlimit) limit = matchlimit;
matchCode = LZ4_count(ip+MINMATCH, match+MINMATCH, limit);
ip += MINMATCH + matchCode;
if (ip==limit) {
unsigned const more = LZ4_count(ip, (const BYTE*)source, matchlimit);
matchCode += more;
ip += more;
}
} else {
matchCode = LZ4_count(ip+MINMATCH, match+MINMATCH, matchlimit);
ip += MINMATCH + matchCode;
}
if ( outputLimited && /* Check output buffer overflow */
(unlikely(op + (1 + LASTLITERALS) + (matchCode>>8) > olimit)) )
return 0;
if (matchCode >= ML_MASK) {
*token += ML_MASK;
matchCode -= ML_MASK;
LZ4_write32(op, 0xFFFFFFFF);
while (matchCode >= 4*255) op+=4, LZ4_write32(op, 0xFFFFFFFF), matchCode -= 4*255;
op += matchCode / 255;
*op++ = (BYTE)(matchCode % 255);
} else
*token += (BYTE)(matchCode);
}
anchor = ip;
/* Test end of chunk */
if (ip > mflimit) break;
/* Fill table */
LZ4_putPosition(ip-2, cctx->hashTable, tableType, base);
/* Test next position */
match = LZ4_getPosition(ip, cctx->hashTable, tableType, base);
if (dict==usingExtDict) {
if (match < (const BYTE*)source) {
refDelta = dictDelta;
lowLimit = dictionary;
} else {
refDelta = 0;
lowLimit = (const BYTE*)source;
} }
LZ4_putPosition(ip, cctx->hashTable, 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 */
{ size_t const lastRun = (size_t)(iend - anchor);
if ( (outputLimited) && /* Check output buffer overflow */
((op - (BYTE*)dest) + lastRun + 1 + ((lastRun+255-RUN_MASK)/255) > (U32)maxOutputSize) )
return 0;
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);
}