From c4f608a39b8dbfd105320e4f15f1a2114e652200 Mon Sep 17 00:00:00 2001
From: goyuken <goyuken@4bbf4f03-6f44-549e-7e59-35d4b0962838>
Date: Sun, 19 Apr 2015 13:55:47 +0000
Subject: [PATCH] "Correct" IPS applier to resize file if it tries to write off
 end.  I'm not sure what the spec behavior is, but this works for at least one
 file in the wild.

---
 BizHawk.Client.Common/IPS.cs     | 20 ++++++++++++++------
 BizHawk.Client.Common/RomGame.cs |  2 +-
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/BizHawk.Client.Common/IPS.cs b/BizHawk.Client.Common/IPS.cs
index 621ebe6a40..ccc9122b4f 100644
--- a/BizHawk.Client.Common/IPS.cs
+++ b/BizHawk.Client.Common/IPS.cs
@@ -5,7 +5,7 @@ namespace BizHawk.Client.Common
 {
 	public static class IPS
 	{
-		public static void Patch(byte[] rom, Stream patch)
+		public static byte[] Patch(byte[] rom, Stream patch)
 		{
 			var ipsHeader = new byte[5];
 			patch.Read(ipsHeader, 0, 5);
@@ -16,32 +16,40 @@ namespace BizHawk.Client.Common
 				if (ipsHeader[i] != header[i])
 				{
 					Console.WriteLine("Patch file specified is invalid.");
-					return;
+					return null;
 				}
 			}
 
 			// header verified, loop over patch entries
 			uint EOF = ('E' * 0x10000 + 'O' * 0x100 + 'F');
 
+			var ret = new MemoryStream(rom.Length);
+			ret.Write(rom, 0, rom.Length);
+
 			while (true)
 			{
 				uint offset = Read24(patch);
-				if (offset == EOF) return;
+				if (offset == EOF)
+					return ret.ToArray();
 				ushort size = Read16(patch);
 
+				ret.Seek(offset, SeekOrigin.Begin);
+
 				if (size != 0) // non-RLE patch
 				{
 					var patchData = new byte[size];
 					patch.Read(patchData, 0, size);
-					for (int i = 0; i < size; i++)
-						rom[offset++] = patchData[i];
+
+					ret.Write(patchData, 0, patchData.Length);
 				}
 				else // RLE patch
 				{
 					size = Read16(patch);
 					byte value = (byte)patch.ReadByte();
 					for (int i = 0; i < size; i++)
-						rom[offset++] = value;
+					{
+						ret.WriteByte(value);
+					}
 				}
 			}
 		}
diff --git a/BizHawk.Client.Common/RomGame.cs b/BizHawk.Client.Common/RomGame.cs
index 8c526cb2fd..8e4cbdcc1f 100644
--- a/BizHawk.Client.Common/RomGame.cs
+++ b/BizHawk.Client.Common/RomGame.cs
@@ -90,7 +90,7 @@ namespace BizHawk.Client.Common
 					patchFile.BindFirstOf("IPS");
 					if (patchFile.IsBound)
 					{
-						IPS.Patch(RomData, patchFile.GetStream());
+						RomData = IPS.Patch(RomData, patchFile.GetStream());
 					}
 				}
 			}