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(LZ4): decompression routine moved to separate class.

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This commit is contained in:
morkt 2017-04-05 18:33:35 +04:00
parent 90564a52a8
commit e98a6a2fca
1 changed files with 91 additions and 88 deletions
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179
ArcFormats/Lz4Stream.cs
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@ -73,7 +73,7 @@ namespace GameRes.Compression
{
int version = flags >> 6;
if (version != 1)
throw Lz4Stream.InvalidData();
throw Lz4Compressor.InvalidData();
IndependentBlocks = 0 != (flags & 0x20);
HasBlockChecksum = 0 != (flags & 0x10);
HasContentLength = 0 != (flags & 8);
@ -89,7 +89,7 @@ namespace GameRes.Compression
case 5: BlockSize = 0x40000; break;
case 6: BlockSize = 0x100000; break;
case 7: BlockSize = 0x400000; break;
default: throw Lz4Stream.InvalidData();
default: throw Lz4Compressor.InvalidData();
}
}
}
@ -173,7 +173,7 @@ namespace GameRes.Compression
m_block = new byte[m_block_size];
if (m_block_size != BaseStream.Read (m_block, 0, m_block_size))
throw new EndOfStreamException();
m_data_size = DecompressBlock();
m_data_size = Lz4Compressor.DecompressBlock (m_block, m_block_size, m_data, m_data.Length);
if (m_info.HasBlockChecksum)
ReadChecksum();
}
@ -187,91 +187,6 @@ namespace GameRes.Compression
// XXX checksum is ignored
}
const int MinMatch = 4;
const int LastLiterals = 5;
const int MFLimit = 12;
const int MatchLengthBits = 4;
const int MatchLengthMask = 0xF;
const int RunMask = 0xF;
int DecompressBlock ()
{
int src = 0;
int iend = m_block_size;
int dst = 0;
int oend = m_data.Length;
for (;;)
{
/* get literal length */
int token = m_block[src++];
int length = token >> MatchLengthBits;
if (RunMask == length)
{
int n;
do
{
n = m_block[src++];
length += n;
}
while ((src < iend - RunMask) && (0xFF == n));
if (dst + length < dst || src + length < src) // overflow detection
throw InvalidData();
}
/* copy literals */
int copy_end = dst + length;
if ((copy_end > oend - MFLimit) || (src + length > iend - (3+LastLiterals)))
{
if ((src + length != iend) || copy_end > oend)
throw InvalidData();
Buffer.BlockCopy (m_block, src, m_data, dst, length);
src += length;
dst += length;
break;
}
Buffer.BlockCopy (m_block, src, m_data, dst, length);
src += length;
dst = copy_end;
/* get offset */
int offset = LittleEndian.ToUInt16 (m_block, src);
src += 2;
int match = dst - offset;
if (match < 0)
throw InvalidData();
/* get matchlength */
length = token & MatchLengthMask;
if (MatchLengthMask == length)
{
int n;
do
{
n = m_block[src++];
if (src > iend - LastLiterals)
throw InvalidData();
length += n;
}
while (0xFF == n);
if (dst + length < dst) // overflow detection
throw InvalidData();
}
length += MinMatch;
/* copy match within block */
Binary.CopyOverlapped (m_data, match, dst, length);
dst += length;
}
return dst; // number of output bytes decoded
}
internal static InvalidDataException InvalidData ()
{
return new InvalidDataException ("Invalid LZ4 compressed stream.");
}
#region Not supported IO.Stream methods
public override bool CanSeek { get { return false; } }
public override long Length
@ -294,4 +209,92 @@ namespace GameRes.Compression
}
#endregion
}
public class Lz4Compressor
{
const int MinMatch = 4;
const int LastLiterals = 5;
const int MFLimit = 12;
const int MatchLengthBits = 4;
const int MatchLengthMask = 0xF;
const int RunMask = 0xF;
public static int DecompressBlock (byte[] block, int block_size, byte[] output, int output_size)
{
int src = 0;
int iend = block_size;
int dst = 0;
int oend = output_size;
for (;;)
{
/* get literal length */
int token = block[src++];
int length = token >> MatchLengthBits;
if (RunMask == length)
{
int n;
do
{
n = block[src++];
length += n;
}
while ((src < iend - RunMask) && (0xFF == n));
if (dst + length < dst || src + length < src) // overflow detection
throw InvalidData();
}
/* copy literals */
int copy_end = dst + length;
if ((copy_end > oend - MFLimit) || (src + length > iend - (3+LastLiterals)))
{
if ((src + length != iend) || copy_end > oend)
throw InvalidData();
Buffer.BlockCopy (block, src, output, dst, length);
src += length;
dst += length;
break;
}
Buffer.BlockCopy (block, src, output, dst, length);
src += length;
dst = copy_end;
/* get offset */
int offset = LittleEndian.ToUInt16 (block, src);
src += 2;
int match = dst - offset;
if (match < 0)
throw InvalidData();
/* get matchlength */
length = token & MatchLengthMask;
if (MatchLengthMask == length)
{
int n;
do
{
n = block[src++];
if (src > iend - LastLiterals)
throw InvalidData();
length += n;
}
while (0xFF == n);
if (dst + length < dst) // overflow detection
throw InvalidData();
}
length += MinMatch;
/* copy match within block */
Binary.CopyOverlapped (output, match, dst, length);
dst += length;
}
return dst; // number of output bytes decoded
}
internal static InvalidDataException InvalidData ()
{
return new InvalidDataException ("Invalid LZ4 compressed stream.");
}
}
}