in subversion/libsvn_subr/lz4/lz4.c [1099:1258]
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 when no prefix */
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 unsigned dec32table[] = {0, 1, 2, 1, 4, 4, 4, 4};
const int dec64table[] = {0, 0, 0, -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 : decode sequences */
while (1) {
size_t length;
const BYTE* match;
size_t offset;
/* get literal length */
unsigned const 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((uptrval)(op)+length<(uptrval)(op))) goto _output_error; /* overflow detection */
if ((safeDecode) && unlikely((uptrval)(ip)+length<(uptrval)(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-WILDCOPYLENGTH)) )
{
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 */
offset = LZ4_readLE16(ip); ip+=2;
match = op - offset;
if ((checkOffset) && (unlikely(match < lowLimit))) goto _output_error; /* Error : offset outside buffers */
LZ4_write32(op, (U32)offset); /* costs ~1%; silence an msan warning when offset==0 */
/* get matchlength */
length = token & ML_MASK;
if (length == ML_MASK) {
unsigned s;
do {
s = *ip++;
if ((endOnInput) && (ip > iend-LASTLITERALS)) goto _output_error;
length += s;
} while (s==255);
if ((safeDecode) && unlikely((uptrval)(op)+length<(uptrval)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 */
memmove(op, dictEnd - (lowPrefix-match), length);
op += length;
} else {
/* match encompass external dictionary and current block */
size_t const copySize = (size_t)(lowPrefix-match);
size_t const restSize = length - copySize;
memcpy(op, dictEnd - copySize, copySize);
op += copySize;
if (restSize > (size_t)(op-lowPrefix)) { /* overlap copy */
BYTE* const endOfMatch = op + restSize;
const BYTE* copyFrom = lowPrefix;
while (op < endOfMatch) *op++ = *copyFrom++;
} else {
memcpy(op, lowPrefix, restSize);
op += restSize;
} }
continue;
}
/* copy match within block */
cpy = op + length;
if (unlikely(offset<8)) {
const int dec64 = dec64table[offset];
op[0] = match[0];
op[1] = match[1];
op[2] = match[2];
op[3] = match[3];
match += dec32table[offset];
memcpy(op+4, match, 4);
match -= dec64;
} else { LZ4_copy8(op, match); match+=8; }
op += 8;
if (unlikely(cpy>oend-12)) {
BYTE* const oCopyLimit = oend-(WILDCOPYLENGTH-1);
if (cpy > oend-LASTLITERALS) goto _output_error; /* Error : last LASTLITERALS bytes must be literals (uncompressed) */
if (op < oCopyLimit) {
LZ4_wildCopy(op, match, oCopyLimit);
match += oCopyLimit - op;
op = oCopyLimit;
}
while (op<cpy) *op++ = *match++;
} else {
LZ4_copy8(op, match);
if (length>16) LZ4_wildCopy(op+8, match+8, 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;
}