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OpenRA/OpenRA.Mods.Cnc/FileFormats/XORDeltaCompression.cs
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Initial commit: OpenRA game engine
Fork from OpenRA/OpenRA with one-click launch script (start-ra.cmd)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
2026-01-10 21:46:54 +08:00

83 lines
1.9 KiB
C#

#region Copyright & License Information
/*
* Copyright (c) The OpenRA Developers and Contributors
* This file is part of OpenRA, which is free software. It is made
* available to you under the terms of the GNU General Public License
* as published by the Free Software Foundation, either version 3 of
* the License, or (at your option) any later version. For more
* information, see COPYING.
*/
#endregion
using OpenRA.Mods.Common.FileFormats;
namespace OpenRA.Mods.Cnc.FileFormats
{
// Data that is to be XORed against another set of data (aka Format40)
public static class XORDeltaCompression
{
public static int DecodeInto(byte[] src, byte[] dest, int srcOffset)
{
var ctx = new FastByteReader(src, srcOffset);
var destIndex = 0;
while (true)
{
var i = ctx.ReadByte();
if ((i & 0x80) == 0)
{
var count = i & 0x7F;
if (count == 0)
{
// case 6
count = ctx.ReadByte();
var value = ctx.ReadByte();
for (var end = destIndex + count; destIndex < end; destIndex++)
dest[destIndex] ^= value;
}
else
{
// case 5
for (var end = destIndex + count; destIndex < end; destIndex++)
dest[destIndex] ^= ctx.ReadByte();
}
}
else
{
var count = i & 0x7F;
if (count == 0)
{
count = ctx.ReadWord();
if (count == 0)
return destIndex;
if ((count & 0x8000) == 0)
{
// case 2
destIndex += count & 0x7FFF;
}
else if ((count & 0x4000) == 0)
{
// case 3
for (var end = destIndex + (count & 0x3FFF); destIndex < end; destIndex++)
dest[destIndex] ^= ctx.ReadByte();
}
else
{
// case 4
var value = ctx.ReadByte();
for (var end = destIndex + (count & 0x3FFF); destIndex < end; destIndex++)
dest[destIndex] ^= value;
}
}
else
{
// case 1
destIndex += count;
}
}
}
}
}
}