private static int LZ4_decompress_generic <TEndCondition, TEarlyEnd, TDict, TEndian>(
ref byte *src,
ref byte *dst,
int srcSize,
int outputSize, /* If TEndCondition==EndOnInputSize, this value is `dstCapacity` */
int targetOutputSize, /* only used if TEarlyEnd==Partial*/
byte *lowPrefix, /* always <= dst, == dst when no prefix */
byte *dictStart, /* only if TDict==UsingExtDict */
uint dictSize) /* note : = 0 if TDict==NoDict */
where TEndCondition : struct, IEndCondition
where TEarlyEnd : struct, IEarlyEnd
where TDict : struct, IDict
where TEndian : struct, IEndian
{
var ip = src;
var iend = ip + srcSize;
var op = dst;
var oend = op + outputSize;
var oexit = op + targetOutputSize;
var dictEnd = dictStart + dictSize;
/* Set up the "end" pointers for the shortcut. */
var shortiend = iend - (typeof(TEndCondition) == typeof(EndOnInputSize) ? 14 : 8) /*maxLL*/ - 2 /*offset*/;
var shortoend = oend - (typeof(TEndCondition) == typeof(EndOnInputSize) ? 14 : 8) /*maxLL*/ - 18 /*maxML*/;
Debug.WriteLine($"LZ4_decompress_generic (srcSize:{srcSize})");
/* Special cases */
if (typeof(TEarlyEnd) == typeof(Partial) && oexit > oend - MFLIMIT)
{
oexit = oend - MFLIMIT; /* targetOutputSize too high => just decode everything */
}
if (typeof(TEndCondition) == typeof(EndOnInputSize) && outputSize == 0)
{
return(srcSize == 1 && *ip == 0 ? 0 : -1); /* Empty output buffer */
}
if (typeof(TEndCondition) == typeof(EndOnOutputSize) && outputSize == 0)
{
return(*ip == 0 ? 1 : -1);
}
if (typeof(TEndCondition) == typeof(EndOnInputSize) && srcSize == 0)
{
return(-1);
}
/* Main Loop : decode sequences */
byte *cpy;
while (true)
{
byte * match;
ushort offset;
var token = *ip++;
var length = token >> ML_BITS; /* literal length */
assert(typeof(TEndCondition) != typeof(EndOnInputSize) || 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 ((typeof(TEndCondition) == typeof(EndOnInputSize) ? length != RUN_MASK : length <= 8)
/* strictly "less than" on input, to re-enter the loop with at least one byte */
&& (typeof(TEndCondition) != typeof(EndOnInputSize) || ip < shortiend) & (op <= shortoend))
{
/* Copy the literals */
if (typeof(TEndCondition) == typeof(EndOnInputSize))
{
Mem.Copy16(op, ip);
}
else
{
Mem.Copy8(op, ip);
}
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 = LZ4_readLE16 <TEndian>(ip);
ip += 2;
match = op - offset;
/* Do not deal with overlapping matches. */
if (length != ML_MASK &&
offset >= 8 &&
(typeof(TDict) == typeof(WithPrefix64K) || match >= lowPrefix))
{
/* Copy the match. */
Unsafe.CopyBlock(op, match, 18);
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)
{
byte s;
if (typeof(TEndCondition) == typeof(EndOnInputSize))
{
if (ip >= iend - RUN_MASK)
{
goto _output_error; /* overflow detection */
}
do
{
s = *ip++;
length += s;
} while (ip < iend - RUN_MASK && s == 255);
if (op + length < op || ip + length < ip)
{
goto _output_error; /* overflow detection */
}
}
else
{
do
{
s = *ip++;
length += s;
} while (s == 255);
}
}
/* copy literals */
cpy = op + length;
if (typeof(TEndCondition) == typeof(EndOnInputSize) && (cpy > (typeof(TEarlyEnd) == typeof(Partial) ? oexit : oend - MFLIMIT) || ip + length > iend - (2 + 1 + LASTLITERALS)) ||
typeof(TEndCondition) == typeof(EndOnOutputSize) && cpy > oend - WILDCOPYLENGTH)
{
if (typeof(TEarlyEnd) == typeof(Partial))
{
if (cpy > oend)
{
goto _output_error; /* Error : write attempt beyond end of output buffer */
}
if (typeof(TEndCondition) == typeof(EndOnInputSize) && ip + length > iend)
{
goto _output_error; /* Error : read attempt beyond end of input buffer */
}
}
else
{
if (typeof(TEndCondition) != typeof(EndOnInputSize) && cpy != oend)
{
goto _output_error; /* Error : block decoding must stop exactly there */
}
if (typeof(TEndCondition) == typeof(EndOnInputSize) && (ip + length != iend || cpy > oend))
{
goto _output_error; /* Error : input must be consumed */
}
}
Unsafe.CopyBlock(op, ip, (uint)length);
ip += length;
op += length;
break; /* Necessarily EOF, due to parsing restrictions */
}
Mem.WildCopy(op, ip, cpy);
ip += length;
op = cpy;
/* get offset */
offset = LZ4_readLE16 <TEndian>(ip);
ip += 2;
match = op - offset;
/* get matchlength */
length = token & ML_MASK;
_copy_match:
if (typeof(TEndCondition) == typeof(EndOnInputSize) && dictSize < _64KB && !(match + dictSize < lowPrefix))
{
goto _output_error; /* Error : offset outside buffers */
}
Mem.Write(op, (uint)offset); /* costs ~1%; silence an msan warning when offset==0 */
if (length == ML_MASK)
{
byte s;
do
{
s = *ip++;
if (typeof(TEndCondition) == typeof(EndOnInputSize) && ip > iend - LASTLITERALS)
{
goto _output_error;
}
length += s;
} while (s == 255);
if (typeof(TEndCondition) == typeof(EndOnInputSize) && op + length < op)
{
goto _output_error; /* overflow detection */
}
}
length += MINMATCH;
/* check external dictionary */
if (typeof(TDict) == typeof(UsingExtDict) && match < lowPrefix)
{
if (op + length > oend - LASTLITERALS)
{
goto _output_error; /* doesn't respect parsing restriction */
}
if (length <= lowPrefix - match)
{
/* match can be copied as a single segment from external dictionary */
Platform.Move(op, dictEnd - (lowPrefix - match), length);
op += length;
}
else
{
/* match encompass external dictionary and current block */
var copySize = (uint)(lowPrefix - match);
var restSize = (uint)length - copySize;
Unsafe.CopyBlock(op, dictEnd - copySize, copySize);
op += copySize;
if (restSize > (uint)(op - lowPrefix))
{ /* overlap copy */
var endOfMatch = op + restSize;
var copyFrom = lowPrefix;
while (op < endOfMatch)
{
*op++ = *copyFrom++;
}
}
else
{
Unsafe.CopyBlock(op, lowPrefix, restSize);
op += restSize;
}
}
continue;
}
/* copy match within block */
cpy = op + length;
if (offset < 8)
{
op[0] = match[0];
op[1] = match[1];
op[2] = match[2];
op[3] = match[3];
match += inc32table[offset];
Unsafe.CopyBlock(op + 4, match, 4);
match -= dec64table[offset];
}
else
{
Unsafe.CopyBlock(op, match, 8);
match += 8;
}
op += 8;
if (cpy > oend - 12)
{
var oCopyLimit = oend - (WILDCOPYLENGTH - 1);
if (cpy > oend - LASTLITERALS)
{
goto _output_error; /* Error : last LASTLITERALS bytes must be literals (uncompressed) */
}
if (op < oCopyLimit)
{
Mem.WildCopy(op, match, oCopyLimit);
match += oCopyLimit - op;
op = oCopyLimit;
}
while (op < cpy)
{
*op++ = *match++;
}
}
else
{
Mem.Copy8(op, match);
if (length > 16)
{
Mem.WildCopy(op + 8, match + 8, cpy);
}
}
op = cpy; /* correction */
}
var wrote = (int)(op - dst);
var read = (int)(ip - src);
dst += wrote;
src += read;
/* end of decoding */
if (typeof(TEndCondition) == typeof(EndOnInputSize))
{
return(wrote); /* Nb of output bytes decoded */
}
return(read); /* Nb of input bytes read */
/* Overflow error detected */
_output_error:
return((int)(-(ip - src)) - 1);
}
public static int LZ4_decompress_generic(
byte *src,
byte *dst,
int srcSize,
int outputSize,
endCondition_directive endOnInput,
earlyEnd_directive partialDecoding,
int targetOutputSize,
dict_directive dict,
byte *lowPrefix,
byte *dictStart,
int dictSize)
{
var ip = src;
var iend = ip + srcSize;
var op = dst;
var oend = op + outputSize;
var oexit = op + targetOutputSize;
var dictEnd = dictStart + dictSize;
var safeDecode = endOnInput == endCondition_directive.endOnInputSize;
var checkOffset = safeDecode && dictSize < 64 * KB;
if (partialDecoding != earlyEnd_directive.full && oexit > oend - MFLIMIT)
{
oexit = oend - MFLIMIT;
}
if (endOnInput == endCondition_directive.endOnInputSize && outputSize == 0)
{
return(srcSize == 1 && *ip == 0 ? 0 : -1);
}
if (endOnInput != endCondition_directive.endOnInputSize && outputSize == 0)
{
return(*ip == 0 ? 1 : -1);
}
for (;;)
{
int length;
uint token = *ip++;
if (ip + 14 + 2 <= iend &&
op + 14 + 18 <= oend &&
token < 15 << ML_BITS &&
(token & ML_MASK) != 15)
{
var ll = (int)(token >> ML_BITS);
int off = Mem.Peek16(ip + ll);
var matchPtr = op + ll - off;
if (off >= 18 && matchPtr >= lowPrefix)
{
var ml = (int)((token & ML_MASK) + MINMATCH);
Mem.Copy16(op, ip);
op += ll;
ip += ll + 2;
Mem.Copy18(op, matchPtr);
op += ml;
continue;
}
}
if ((length = (int)(token >> ML_BITS)) == RUN_MASK)
{
uint s;
do
{
s = *ip++;
length += (int)s;
}while (
(endOnInput != endCondition_directive.endOnInputSize || ip < iend - RUN_MASK) &&
s == 255);
if (safeDecode && op + length < op)
{
goto _output_error;
}
if (safeDecode && ip + length < ip)
{
goto _output_error;
}
}
var cpy = op + length;
if (endOnInput == endCondition_directive.endOnInputSize &&
(
cpy > (partialDecoding == earlyEnd_directive.partial ? oexit : oend - MFLIMIT) ||
ip + length > iend - (2 + 1 + LASTLITERALS)
) ||
endOnInput != endCondition_directive.endOnInputSize && cpy > oend - WILDCOPYLENGTH)
{
if (partialDecoding == earlyEnd_directive.partial)
{
if (cpy > oend)
{
goto _output_error;
}
if (endOnInput == endCondition_directive.endOnInputSize && ip + length > iend)
{
goto _output_error;
}
}
else
{
if (endOnInput != endCondition_directive.endOnInputSize && cpy != oend)
{
goto _output_error;
}
if (endOnInput == endCondition_directive.endOnInputSize &&
(ip + length != iend || cpy > oend))
{
goto _output_error;
}
}
Mem.Copy(op, ip, length);
ip += length;
op += length;
break;
}
Mem.WildCopy(op, ip, cpy);
ip += length;
op = cpy;
int offset = Mem.Peek16(ip);
ip += 2;
var match = op - offset;
if (checkOffset && match + dictSize < lowPrefix)
{
goto _output_error;
}
Mem.Poke32(op, (uint)offset);
length = (int)(token & ML_MASK);
if (length == ML_MASK)
{
uint s;
do
{
s = *ip++;
if ((endOnInput == endCondition_directive.endOnInputSize) && (ip > iend - LASTLITERALS))
{
goto _output_error;
}
length += (int)s;
}while (s == 255);
if (safeDecode && op + length < op)
{
goto _output_error;
}
}
length += MINMATCH;
if (dict == dict_directive.usingExtDict && match < lowPrefix)
{
if (op + length > oend - LASTLITERALS)
{
goto _output_error;
}
if (length <= lowPrefix - match)
{
Mem.Move(op, dictEnd - (lowPrefix - match), length);
op += length;
}
else
{
var copySize = (int)(lowPrefix - match);
var restSize = length - copySize;
Mem.Copy(op, dictEnd - copySize, copySize);
op += copySize;
if (restSize > (int)(op - lowPrefix))
{
var endOfMatch = op + restSize;
var copyFrom = lowPrefix;
while (op < endOfMatch)
{
*op++ = *copyFrom++;
}
}
else
{
Mem.Copy(op, lowPrefix, restSize);
op += restSize;
}
}
continue;
}
cpy = op + length;
if (offset < 8)
{
op[0] = match[0];
op[1] = match[1];
op[2] = match[2];
op[3] = match[3];
match += inc32table[offset];
Mem.Copy(op + 4, match, 4);
match -= dec64table[offset];
}
else
{
Mem.Copy8(op, match);
match += 8;
}
op += 8;
if (cpy > oend - 12)
{
var oCopyLimit = oend - (WILDCOPYLENGTH - 1);
if (cpy > oend - LASTLITERALS)
{
goto _output_error;
}
if (op < oCopyLimit)
{
Mem.WildCopy(op, match, oCopyLimit);
match += oCopyLimit - op;
op = oCopyLimit;
}
while (op < cpy)
{
*op++ = *match++;
}
}
else
{
Mem.Copy8(op, match);
if (length > 16)
{
Mem.WildCopy(op + 8, match + 8, cpy);
}
}
op = cpy; /* correction */
}
/* end of decoding */
if (endOnInput == endCondition_directive.endOnInputSize)
{
return((int)(op - dst)); /* Nb of output bytes decoded */
}
return((int)(ip - src)); /* Nb of input bytes read */
/* Overflow error detected */
_output_error:
return((int)-(ip - src) - 1);
}
