72 lines
1.5 KiB
C#
72 lines
1.5 KiB
C#
using System;
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using System.IO;
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namespace BizHawk.Client.Common
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{
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public static class IPS
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{
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public static byte[] Patch(byte[] rom, Stream patch)
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{
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var ipsHeader = new byte[5];
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patch.Read(ipsHeader, 0, 5);
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string header = "PATCH";
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for (int i = 0; i < 5; i++)
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{
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if (ipsHeader[i] != header[i])
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{
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Console.WriteLine("Patch file specified is invalid.");
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return null;
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}
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}
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// header verified, loop over patch entries
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uint EOF = ('E' * 0x10000 + 'O' * 0x100 + 'F');
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var ret = new MemoryStream(rom.Length);
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ret.Write(rom, 0, rom.Length);
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while (true)
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{
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uint offset = Read24(patch);
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if (offset == EOF)
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return ret.ToArray();
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ushort size = Read16(patch);
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ret.Seek(offset, SeekOrigin.Begin);
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if (size != 0) // non-RLE patch
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{
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var patchData = new byte[size];
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patch.Read(patchData, 0, size);
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ret.Write(patchData, 0, patchData.Length);
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}
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else // RLE patch
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{
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size = Read16(patch);
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byte value = (byte)patch.ReadByte();
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for (int i = 0; i < size; i++)
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{
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ret.WriteByte(value);
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}
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}
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}
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}
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private static ushort Read16(Stream patch)
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{
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int Upper = patch.ReadByte();
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int Lower = patch.ReadByte();
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return (ushort)(Upper * 0x100 + Lower);
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}
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private static uint Read24(Stream patch)
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{
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int Upper = patch.ReadByte();
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int Middle = patch.ReadByte();
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int Lower = patch.ReadByte();
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return (uint)(Upper * 0x10000 + Middle * 0x100 + Lower);
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}
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}
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} |