fm2 hash parsing

TASVideos.Parsers/Parsers/Fm2.cs

@@ -1,4 +1,6 @@
-namespace TASVideos.MovieParsers.Parsers;
+using System.Text;
+
+namespace TASVideos.MovieParsers.Parsers;
 
 [FileExtension("fm2")]
 internal class Fm2 : Parser, IParser
@@ -55,9 +57,43 @@ public async Task<IParseResult> Parse(Stream file, long length)
 			result.StartType = MovieStartType.Savestate;
 		}
 
+		var hashLine = header.GetValueFor(Keys.RomChecksum);
+		if (!string.IsNullOrWhiteSpace(hashLine))
+		{
+			var hashSplit = hashLine.Split(':');
+			var base64Line = hashSplit.Length == 2 ? hashSplit[1] : "";
+			if (!string.IsNullOrWhiteSpace(base64Line))
+			{
+				try
+				{
+					byte[] data = Convert.FromBase64String(base64Line);
+					string hash = BytesToHexString(data.AsSpan());
+					if (hash.Length == 32)
+					{
+						result.Hashes.Add(HashType.Md5, hash.ToLower());
+					}
+				}
+				catch
+				{
+					// Treat an invalid base64 hash as a missing hash
+				}
+			}
+		}
+
 		return result;
 	}
 
+	private static string BytesToHexString(ReadOnlySpan<byte> bytes)
+	{
+		StringBuilder sb = new(capacity: 2 * bytes.Length, maxCapacity: 2 * bytes.Length);
+		foreach (var b in bytes)
+		{
+			sb.Append($"{b:X2}");
+		}
+
+		return sb.ToString();
+	}
+
 	private static class Keys
 	{
 		public const string RerecordCount = "rerecordcount";
@@ -66,5 +102,6 @@ private static class Keys
 		public const string Length = "length";
 		public const string Fds = "fds";
 		public const string StartsFromSavestate = "savestate";
+		public const string RomChecksum = "romChecksum";
 	}
 }

tests/TASVideos.MovieParsers.Tests/Fm2ParserTests.cs

@@ -97,4 +97,20 @@ public async Task BinaryWithoutFrameCount()
 		AssertNoWarnings(result);
 		Assert.AreEqual(1, result.Errors.Count());
 	}
+
+	[TestMethod]
+	public async Task Hash()
+	{
+		var result = await _fm2Parser.Parse(Embedded("hash.fm2"), EmbeddedLength("hash.fm2"));
+		Assert.AreEqual(1, result.Hashes.Count);
+		Assert.AreEqual(HashType.Md5, result.Hashes.First().Key);
+		Assert.AreEqual("e9d82f825725c616b0be66ac85dc1b7a", result.Hashes.First().Value);
+	}
+
+	[TestMethod]
+	public async Task InvalidHash()
+	{
+		var result = await _fm2Parser.Parse(Embedded("hash-invalid.fm2"), EmbeddedLength("hash-invalid.fm2"));
+		Assert.AreEqual(0, result.Hashes.Count);
+	}
 }

tests/TASVideos.MovieParsers.Tests/Fm2SampleFiles/hash-invalid.fm2

@@ -0,0 +1,2 @@
+romChecksum base64:ThisIsNotBase64
+

tests/TASVideos.MovieParsers.Tests/Fm2SampleFiles/hash.fm2

@@ -0,0 +1 @@
+romChecksum base64:6DgvglcLxhawvMAshDwbeQ==