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