Fix D2 shp parsing and make it a proper frame source.

OpenRA.FileFormats/Graphics/SpriteSource.cs

@@ -28,7 +28,7 @@ namespace OpenRA.FileFormats
 		IEnumerable<ISpriteFrame> Frames { get; }
 	}
 
-	public enum SpriteType { Unknown, ShpTD, ShpTS, TmpTD, TmpRA, R8 }
+	public enum SpriteType { Unknown, ShpTD, ShpTS, ShpD2, TmpTD, TmpRA, R8 }
 	public static class SpriteSource
 	{
 		static bool IsTmpRA(Stream s)
@@ -129,6 +129,44 @@ namespace OpenRA.FileFormats
 			return b == 0x20 || b == 0x40 || b == 0x80;
 		}
 
+		static bool IsShpD2(Stream s)
+		{
+			var start = s.Position;
+
+			// First word is the image count
+			var imageCount = s.ReadUInt16();
+			if (imageCount == 0)
+			{
+				s.Position = start;
+				return false;
+			}
+
+			// Test for two vs four byte offset
+			var testOffset = s.ReadUInt32();
+			var offsetSize = (testOffset & 0xFF0000) > 0 ? 2 : 4;
+
+			// Last offset should point to the end of file
+			var finalOffset = start + 2 + offsetSize * imageCount;
+			if (finalOffset > s.Length)
+			{
+				s.Position = start;
+				return false;
+			}
+
+			s.Position = finalOffset;
+			var eof = offsetSize == 2 ? s.ReadUInt16() : s.ReadUInt32();
+			if (eof + 2 != s.Length)
+			{
+				s.Position = start;
+				return false;
+			}
+
+			// Check the format flag on the first frame
+			var b = s.ReadUInt16();
+			s.Position = start;
+			return b == 5 || b <= 3;
+		}
+
 		static bool IsR8(Stream s)
 		{
 			var start = s.Position;
@@ -165,6 +203,9 @@ namespace OpenRA.FileFormats
 			if (IsTmpTD(s))
 				return SpriteType.TmpTD;
 
+			if (IsShpD2(s))
+				return SpriteType.ShpD2;
+
 			return SpriteType.Unknown;
 		}
 
@@ -183,6 +224,8 @@ namespace OpenRA.FileFormats
 					return new TmpRAReader(s);
 				case SpriteType.TmpTD:
 					return new TmpTDReader(s);
+				case SpriteType.ShpD2:
+					return new ShpD2Reader(s);
 				case SpriteType.Unknown:
 				default:
 					throw new InvalidDataException(filename + " is not a valid sprite file");