private static void LZ4_memcpy_using_offset(byte *dstPtr, byte *srcPtr, byte *dstEnd, size_t offset)
{
var v = stackalloc byte[8];
Assert(dstEnd >= dstPtr + MINMATCH);
// Mem.Poke4(dstPtr, 0); /* silence an msan warning when offset==0 */
switch (offset)
{
case 1:
Mem.ZBlk(v, *srcPtr, 8);
break;
case 2:
Mem.Copy2(v, srcPtr);
Mem.Copy2(&v[2], srcPtr);
Mem.Copy4(&v[4], &v[0]);
break;
case 4:
Mem.Copy4(v, srcPtr);
Mem.Copy4(&v[4], srcPtr);
break;
default:
LZ4_memcpy_using_offset_base(dstPtr, srcPtr, dstEnd, offset);
return;
}
Mem.Copy8(dstPtr, v);
dstPtr += 8;
while (dstPtr < dstEnd)
{
Mem.Copy8(dstPtr, v);
dstPtr += 8;
}
}
private static void LZ4_memcpy_using_offset_base(
byte *dstPtr, byte *srcPtr, byte *dstEnd, uint offset)
{
if (offset < 8)
{
dstPtr[0] = srcPtr[0];
dstPtr[1] = srcPtr[1];
dstPtr[2] = srcPtr[2];
dstPtr[3] = srcPtr[3];
srcPtr += inc32table[offset];
Mem.Copy4(dstPtr + 4, srcPtr);
srcPtr -= dec64table[offset];
dstPtr += 8;
}
else
{
Mem.Copy8(dstPtr, srcPtr);
dstPtr += 8;
srcPtr += 8;
}
Mem.WildCopy8(dstPtr, srcPtr, dstEnd);
}
public static int LZ4_decompress_generic(
byte *src,
byte *dst,
int srcSize,
int outputSize,
bool endOnInput, // endCondition_directive
bool partialDecoding, // earlyEnd_directive
dict_directive dict,
byte *lowPrefix,
byte *dictStart,
size_t dictSize)
{
if (src == null)
{
return(-1);
}
{
byte *ip = (byte *)src;
byte *iend = ip + srcSize;
byte *op = (byte *)dst;
byte *oend = op + outputSize;
byte *cpy;
byte *dictEnd = (dictStart == null) ? null : dictStart + dictSize;
bool safeDecode = endOnInput;
bool checkOffset = ((safeDecode) && (dictSize < (int)(64 * KB)));
/* Set up the "end" pointers for the shortcut. */
byte *shortiend = iend - (endOnInput ? 14 : 8) /*maxLL*/ - 2 /*offset*/;
byte *shortoend = oend - (endOnInput ? 14 : 8) /*maxLL*/ - 18 /*maxML*/;
byte * match;
size_t offset;
uint token;
size_t length;
/* Special cases */
Assert(lowPrefix <= op);
if ((endOnInput) && ((outputSize == 0)))
{
/* Empty output buffer */
if (partialDecoding)
{
return(0);
}
return(((srcSize == 1) && (*ip == 0)) ? 0 : -1);
}
if ((!endOnInput) && ((outputSize == 0)))
{
return(*ip == 0 ? 1 : -1);
}
if ((endOnInput) && (srcSize == 0))
{
return(-1);
}
/* Main Loop : decode remaining sequences where output < FASTLOOP_SAFE_DISTANCE */
while (true)
{
token = *ip++;
length = (size_t)(token >> ML_BITS); /* literal length */
Assert(!endOnInput || ip <= iend); /* ip < iend before the increment */
/* A two-stage shortcut for the most common case:
* 1) If the literal length is 0..14, and there is enough space,
* enter the shortcut and copy 16 bytes on behalf of the literals
* (in the fast mode, only 8 bytes can be safely copied this way).
* 2) Further if the match length is 4..18, copy 18 bytes in a similar
* manner; but we ensure that there's enough space in the output for
* those 18 bytes earlier, upon entering the shortcut (in other words,
* there is a combined check for both stages).
*/
if ((endOnInput ? length != RUN_MASK : length <= 8)
/* strictly "less than" on input, to re-enter the loop with at least one byte */
&& ((!endOnInput || ip < shortiend) & (op <= shortoend)))
{
/* Copy the literals */
if (endOnInput)
{
Mem.Copy16(op, ip);
}
else
{
Mem.Copy8(op, ip);
}
// Mem.Copy(op, ip, endOnInput ? 16 : 8);
op += length;
ip += length;
/* The second stage: prepare for match copying, decode full info.
* If it doesn't work out, the info won't be wasted. */
length = token & ML_MASK; /* match length */
offset = Mem.Peek2(ip);
ip += 2;
match = op - offset;
Assert(match <= op); /* check overflow */
/* Do not deal with overlapping matches. */
if ((length != ML_MASK) &&
(offset >= 8) &&
(dict == dict_directive.withPrefix64k || match >= lowPrefix))
{
/* Copy the match. */
Mem.Copy18(op, match);
op += length + MINMATCH;
/* Both stages worked, load the next token. */
continue;
}
/* The second stage didn't work out, but the info is ready.
* Propel it right to the point of match copying. */
goto _copy_match;
}
/* decode literal length */
if (length == RUN_MASK)
{
variable_length_error error = variable_length_error.ok;
length += LZ4_readVLE(&ip, iend - RUN_MASK, endOnInput, endOnInput, &error);
if (error == variable_length_error.initial_error)
{
goto _output_error;
}
if ((safeDecode) && ((op) + length < (op)))
{
goto _output_error;
} /* overflow detection */
if ((safeDecode) && ((ip) + length < (ip)))
{
goto _output_error;
} /* overflow detection */
}
/* copy literals */
cpy = op + length;
if (((endOnInput) && ((cpy > oend - MFLIMIT) ||
(ip + length > iend - (2 + 1 + LASTLITERALS)))) ||
((!endOnInput) && (cpy > oend - WILDCOPYLENGTH)))
{
/* We've either hit the input parsing restriction or the output parsing restriction.
* If we've hit the input parsing condition then this must be the last sequence.
* If we've hit the output parsing condition then we are either using partialDecoding
* or we've hit the output parsing condition.
*/
if (partialDecoding)
{
/* Since we are partial decoding we may be in this block because of the output parsing
* restriction, which is not valid since the output buffer is allowed to be undersized.
*/
Assert(endOnInput);
/* If we're in this block because of the input parsing condition, then we must be on the
* last sequence (or invalid), so we must check that we exactly consume the input.
*/
if ((ip + length > iend - (2 + 1 + LASTLITERALS)) &&
(ip + length != iend))
{
goto _output_error;
}
Assert(ip + length <= iend);
/* We are finishing in the middle of a literals segment.
* Break after the copy.
*/
if (cpy > oend)
{
cpy = oend;
Assert(op <= oend);
length = (size_t)(oend - op);
}
Assert(ip + length <= iend);
}
else
{
/* We must be on the last sequence because of the parsing limitations so check
* that we exactly regenerate the original size (must be exact when !endOnInput).
*/
if ((!endOnInput) && (cpy != oend))
{
goto _output_error;
}
/* We must be on the last sequence (or invalid) because of the parsing limitations
* so check that we exactly consume the input and don't overrun the output buffer.
*/
if ((endOnInput) && ((ip + length != iend) || (cpy > oend)))
{
goto _output_error;
}
}
Mem.Move(op, ip, (int)length); /* supports overlapping memory regions, which only matters for in-place decompression scenarios */
ip += length;
op += length;
/* Necessarily EOF when !partialDecoding. When partialDecoding
* it is EOF if we've either filled the output buffer or hit
* the input parsing restriction.
*/
if (!partialDecoding || (cpy == oend) || (ip == iend))
{
break;
}
}
else
{
Mem.WildCopy8(
op, ip, cpy); /* may overwrite up to WILDCOPYLENGTH beyond cpy */
ip += length;
op = cpy;
}
/* get offset */
offset = Mem.Peek2(ip);
ip += 2;
match = op - offset;
/* get matchlength */
length = token & ML_MASK;
_copy_match:
if (length == ML_MASK)
{
variable_length_error error = variable_length_error.ok;
length += LZ4_readVLE(
&ip, iend - LASTLITERALS + 1, endOnInput, false, &error);
if (error != variable_length_error.ok)
{
goto _output_error;
}
if ((safeDecode) && ((op) + length < op))
{
goto _output_error; /* overflow detection */
}
}
length += MINMATCH;
if ((checkOffset) && ((match + dictSize < lowPrefix)))
{
goto _output_error; /* Error : offset outside buffers */
}
/* match starting within external dictionary */
if ((dict == dict_directive.usingExtDict) && (match < lowPrefix))
{
if ((op + length > oend - LASTLITERALS))
{
if (partialDecoding)
{
length = MIN(length, (size_t)(oend - op));
}
else
{
goto _output_error; /* doesn't respect parsing restriction */
}
}
if (length <= (size_t)(lowPrefix - match))
{
/* match fits entirely within external dictionary : just copy */
Mem.Move(op, dictEnd - (lowPrefix - match), (int)length);
op += length;
}
else
{
/* match stretches into both external dictionary and current block */
size_t copySize = (size_t)(lowPrefix - match);
size_t restSize = length - copySize;
Mem.Copy(op, dictEnd - copySize, (int)copySize);
op += copySize;
if (restSize > (size_t)(op - lowPrefix))
{
/* overlap copy */
byte *endOfMatch = op + restSize;
byte *copyFrom = lowPrefix;
while (op < endOfMatch)
{
*op++ = *copyFrom++;
}
}
else
{
Mem.Copy(op, lowPrefix, (int)restSize);
op += restSize;
}
}
continue;
}
Assert(match >= lowPrefix);
/* copy match within block */
cpy = op + length;
/* partialDecoding : may end anywhere within the block */
Assert(op <= oend);
if (partialDecoding && (cpy > oend - MATCH_SAFEGUARD_DISTANCE))
{
size_t mlen = MIN(length, (size_t)(oend - op));
byte * matchEnd = match + mlen;
byte * copyEnd = op + mlen;
if (matchEnd > op)
{
/* overlap copy */
while (op < copyEnd)
{
*op++ = *match++;
}
}
else
{
Mem.Copy(op, match, (int)mlen);
}
op = copyEnd;
if (op == oend)
{
break;
}
continue;
}
if ((offset < 8))
{
// Mem.Poke4(op, 0); /* silence msan warning when offset==0 */
op[0] = match[0];
op[1] = match[1];
op[2] = match[2];
op[3] = match[3];
match += inc32table[offset];
Mem.Copy4(op + 4, match);
match -= dec64table[offset];
}
else
{
Mem.Copy8(op, match);
match += 8;
}
op += 8;
if ((cpy > oend - MATCH_SAFEGUARD_DISTANCE))
{
byte *oCopyLimit = oend - (WILDCOPYLENGTH - 1);
if (cpy > oend - LASTLITERALS)
{
goto _output_error;
} /* Error : last LASTLITERALS bytes must be literals (uncompressed) */
if (op < oCopyLimit)
{
Mem.WildCopy8(op, match, oCopyLimit);
match += oCopyLimit - op;
op = oCopyLimit;
}
while (op < cpy)
{
*op++ = *match++;
}
}
else
{
Mem.Copy8(op, match);
if (length > 16)
{
Mem.WildCopy8(op + 8, match + 8, cpy);
}
}
op = cpy; /* wildcopy correction */
}
/* end of decoding */
if (endOnInput)
{
return((int)(((byte *)op) - dst)); /* Nb of output bytes decoded */
}
else
{
return((int)(((byte *)ip) - src)); /* Nb of input bytes read */
}
/* Overflow error detected */
_output_error:
return((int)(-(((byte *)ip) - src)) - 1);
}
}
