private bool DecodeWindow()
{
int num = delta.ReadByte();
if (num == -1)
{
return(false);
}
int num2 = -1;
bool flag = (num & 4) == 4;
num &= 0xFB;
Stream stream;
switch (num & 3)
{
case 0:
stream = null;
break;
case 1:
if (original == null)
{
throw new VcdiffFormatException("Source stream requested by delta but not provided by caller.");
}
stream = original;
break;
case 2:
stream = output;
num2 = (int)output.Position;
break;
case 3:
throw new VcdiffFormatException("Invalid window indicator - bits 0 and 1 both set.");
default:
throw new VcdiffFormatException("Invalid window indicator - bits 3-7 not all zero.");
}
byte[] array = null;
int num3 = 0;
if (stream != null)
{
num3 = IOHelper.ReadBigEndian7BitEncodedInt(delta);
int num4 = IOHelper.ReadBigEndian7BitEncodedInt(delta);
stream.Position = num4;
array = IOHelper.CheckedReadBytes(stream, num3);
if (num2 != -1)
{
stream.Position = num2;
}
}
IOHelper.ReadBigEndian7BitEncodedInt(delta);
int num5 = IOHelper.ReadBigEndian7BitEncodedInt(delta);
byte[] array2 = new byte[num5];
MemoryStream memoryStream = new MemoryStream(array2, writable: true);
if (IOHelper.CheckedReadByte(delta) != 0)
{
throw new VcdiffFormatException("VcdiffDecoder is unable to handle compressed delta sections.");
}
int size = IOHelper.ReadBigEndian7BitEncodedInt(delta);
int size2 = IOHelper.ReadBigEndian7BitEncodedInt(delta);
int size3 = IOHelper.ReadBigEndian7BitEncodedInt(delta);
if (flag)
{
IOHelper.CheckedReadBytes(delta, 4);
}
byte[] array3 = IOHelper.CheckedReadBytes(delta, size);
byte[] buffer = IOHelper.CheckedReadBytes(delta, size2);
byte[] addresses = IOHelper.CheckedReadBytes(delta, size3);
int num6 = 0;
MemoryStream memoryStream2 = new MemoryStream(buffer, writable: false);
cache.Reset(addresses);
while (true)
{
int num7 = memoryStream2.ReadByte();
if (num7 == -1)
{
break;
}
for (int i = 0; i < 2; i++)
{
Instruction instruction = codeTable[num7, i];
int num8 = instruction.Size;
if (num8 == 0 && instruction.Type != 0)
{
num8 = IOHelper.ReadBigEndian7BitEncodedInt(memoryStream2);
}
switch (instruction.Type)
{
case InstructionType.Add:
memoryStream.Write(array3, num6, num8);
num6 += num8;
break;
case InstructionType.Copy:
{
int num9 = cache.DecodeAddress((int)memoryStream.Position + num3, instruction.Mode);
if (array != null && num9 < array.Length)
{
memoryStream.Write(array, num9, num8);
break;
}
num9 -= num3;
if (num9 + num8 < memoryStream.Position)
{
memoryStream.Write(array2, num9, num8);
break;
}
for (int k = 0; k < num8; k++)
{
memoryStream.WriteByte(array2[num9++]);
}
break;
}
case InstructionType.Run:
{
byte value = array3[num6++];
for (int j = 0; j < num8; j++)
{
memoryStream.WriteByte(value);
}
break;
}
default:
throw new VcdiffFormatException("Invalid instruction type found.");
case InstructionType.NoOp:
break;
}
}
}
output.Write(array2, 0, num5);
adler.Update(array2, 0, num5);
return(true);
}