public static byte[] Compress(ByteArrayStream target)
{
var commands = new List <byte>();
var data = new List <byte>();
var copyData = 0;
while (!target.AtEnd)
{
var term = target.GetBytes(0x11);
var copyOutput = 0;
var copyOffset = -1;
while (term.Length >= 3)
{
var(found, address) = target.FindLastInWindow(term, target.Address - 256, target.Address + term.Length - 1);
if (found)
{
copyOutput = term.Length - 2;
copyOffset = target.Address - address - 1;
break;
}
term = target.GetBytes(term.Length - 1);
}
if (copyOutput == 0)
{
if (copyData == 0xf)
{
commands.Add((byte)copyData);
copyData = 1;
}
else
{
copyData++;
}
data.Add(target.Byte());
}
else
{
commands.Add((byte)((copyOutput << 4) + copyData));
commands.Add((byte)copyOffset);
copyData = 0;
target.Address += term.Length;
}
}
// Add last copy data command
if (copyData != 0)
{
commands.Add((byte)copyData);
}
// Add terminating command
commands.Add(0);
var output = new ByteArrayStream(commands.Count + data.Count + 2);
var dataOffset = commands.Count;
if (dataOffset > 0xffff)
{
throw new Exception($"{nameof(dataOffset)} cannot be larger than 0xffff. {nameof(commands)} is too large");
}
output.Word((ushort)dataOffset);
output.Write(commands);
output.Write(data);
return(output.Buffer);
}
