private byte[] Decompress(byte[] buffer, int decompressedLength)
{
if (decompressedLength == 0)
{
return(buffer); // Uncompressed data
}
// Skip header and checksum
using (var compressed = new MemoryStream(buffer, 2, buffer.Length - 6))
{
var result = new byte[decompressedLength];
using (var deflate = new DeflateStream(compressed, CompressionMode.Decompress, true))
{
deflate.Read(result, 0, decompressedLength);
}
// Adler-32 checksum
var checksum = BitConverter.ToUInt32(BitConverter.GetBytes(Checksum.Adler32(result)).Reverse().ToArray(), 0);
var original = BitConverter.ToUInt32(buffer, buffer.Length - 4);
if (checksum != original)
{
throw new MyRawException("Checksum failure in compressed data stream.");
}
return(result);
}
}
// Since DeflateStream doesn't add the zlib init header and post-data checksum, we have to do
// some trickery.
private byte[] Compress(byte[] buffer)
{
using (var compressed = new MemoryStream())
{
// Header
compressed.WriteByte(0x78);
compressed.WriteByte(0x9c);
using (var deflate = new DeflateStream(compressed, CompressionMode.Compress, true))
{
deflate.Write(buffer, 0, buffer.Length);
}
// Adler-32 checksum
var checksum = Checksum.Adler32(buffer);
foreach (var b in BitConverter.GetBytes(checksum).Reverse())
{
compressed.WriteByte(b);
}
return(compressed.ToArray());
}
}
