private Stream PrivDecompress(Stream inFile)
{
if (!IsLz77Compressed(inFile))
{
return(inFile);
}
inFile.Seek(0L, SeekOrigin.Begin);
uint num1 = 0;
Headers.HeaderType headerType = Headers.DetectHeader(inFile);
byte[] buffer = new byte[8];
inFile.Seek((long)headerType, SeekOrigin.Begin);
inFile.Read(buffer, 0, 8);
if ((int)Shared.Swap(BitConverter.ToUInt32(buffer, 0)) != (int)lz77Magic)
{
inFile.Dispose();
throw new Exception("Invaild Magic!");
}
if (buffer[4] != 16)
{
inFile.Dispose();
throw new Exception("Unsupported Compression Type!");
}
uint num2 = BitConverter.ToUInt32(buffer, 4) >> 8;
for (int index = 0; index < 4078; ++index)
{
textBuffer[index] = 223;
}
int num3 = 4078;
uint num4 = 7;
int num5 = 7;
MemoryStream memoryStream = new MemoryStream();
label_10:
while (true)
{
num4 <<= 1;
++num5;
if (num5 == 8)
{
int num6;
if ((num6 = inFile.ReadByte()) != -1)
{
num4 = (uint)num6;
num5 = 0;
}
else
{
goto label_24;
}
}
if (((int)num4 & 128) == 0)
{
int num6;
if ((num6 = inFile.ReadByte()) != inFile.Length - 1L)
{
if (num1 < num2)
{
memoryStream.WriteByte((byte)num6);
}
ushort[] textBuffer = this.textBuffer;
int index = num3;
int num7 = index + 1;
int num8 = (byte)num6;
textBuffer[index] = (ushort)num8;
num3 = num7 & 4095;
++num1;
}
else
{
goto label_24;
}
}
else
{
break;
}
}
int num9;
int num10;
if ((num9 = inFile.ReadByte()) != -1 && (num10 = inFile.ReadByte()) != -1)
{
int num6 = num10 | num9 << 8 & 3840;
int num7 = (num9 >> 4 & 15) + 2;
for (int index1 = 0; index1 <= num7; ++index1)
{
int num8 = this.textBuffer[num3 - num6 - 1 & 4095];
if (num1 < num2)
{
memoryStream.WriteByte((byte)num8);
}
ushort[] textBuffer = this.textBuffer;
int index2 = num3;
int num11 = index2 + 1;
int num12 = (byte)num8;
textBuffer[index2] = (ushort)num12;
num3 = num11 & 4095;
++num1;
}
goto label_10;
}
label_24:
return(memoryStream);
}
/// <summary>
/// Checks whether a file is Lz77 compressed or not.
/// </summary>
/// <param name="file"></param>
/// <returns></returns>
public static bool IsLz77Compressed(byte[] file)
{
Headers.HeaderType headerType = Headers.DetectHeader(file);
return((int)Shared.Swap(BitConverter.ToUInt32(file, (int)headerType)) == (int)lz77Magic);
}
private Stream decompress(Stream inFile)
{
if (!Lz77.IsLz77Compressed(inFile))
{
return(inFile);
}
inFile.Seek(0, SeekOrigin.Begin);
int i, j, k, r, c, z;
uint flags, decompressedSize, currentSize = 0;
Headers.HeaderType h = Headers.DetectHeader(inFile);
byte[] temp = new byte[8];
inFile.Seek((int)h, SeekOrigin.Begin);
inFile.Read(temp, 0, 8);
if (Shared.Swap(BitConverter.ToUInt32(temp, 0)) != lz77Magic)
{
inFile.Dispose(); throw new Exception("Invaild Magic!");
}
if (temp[4] != 0x10)
{
inFile.Dispose(); throw new Exception("Unsupported Compression Type!");
}
decompressedSize = (BitConverter.ToUInt32(temp, 4)) >> 8;
for (i = 0; i < N - F; i++)
{
textBuffer[i] = 0xdf;
}
r = N - F; flags = 7; z = 7;
MemoryStream outFile = new MemoryStream();
while (true)
{
flags <<= 1;
z++;
if (z == 8)
{
if ((c = inFile.ReadByte()) == -1)
{
break;
}
flags = (uint)c;
z = 0;
}
if ((flags & 0x80) == 0)
{
if ((c = inFile.ReadByte()) == inFile.Length - 1)
{
break;
}
if (currentSize < decompressedSize)
{
outFile.WriteByte((byte)c);
}
textBuffer[r++] = (byte)c;
r &= (N - 1);
currentSize++;
}
else
{
if ((i = inFile.ReadByte()) == -1)
{
break;
}
if ((j = inFile.ReadByte()) == -1)
{
break;
}
j = j | ((i << 8) & 0xf00);
i = ((i >> 4) & 0x0f) + threshold;
for (k = 0; k <= i; k++)
{
c = textBuffer[(r - j - 1) & (N - 1)];
if (currentSize < decompressedSize)
{
outFile.WriteByte((byte)c);
}
textBuffer[r++] = (byte)c; r &= (N - 1); currentSize++;
}
}
}
return(outFile);
}
