fix detection of UTF-32 and add Unit Tests

src/Main/Base/Project/Src/Services/MimeTypeDetection.cs

@@ -29,7 +29,9 @@ namespace ICSharpCode.SharpDevelop
 				// UTF-16 Big Endian
 				(buffer.Length >= 2 && buffer[0] == 0xFE && buffer[1] == 0xFF) ||
 				// UTF-16 Little Endian
-				(buffer.Length >= 2 && buffer[0] == 0xFF && buffer[1] == 0xFE))
+				(buffer.Length >= 2 && buffer[0] == 0xFF && buffer[1] == 0xFE) ||
+				// UTF-32 Big Endian
+				(buffer.Length >= 4 && buffer[0] == 0x00 && buffer[1] == 0x00 && buffer[2] == 0xFE && buffer[3] == 0xFF))
 				return "text/plain";
 			
 			fixed (byte *b = &buffer[offset]) {
@@ -60,15 +62,5 @@ namespace ICSharpCode.SharpDevelop
 			stream.Position = 0;
 			return FindMimeType(buffer, 0, stream.Read(buffer, 0, buffer.Length));
 		}
-		
-		public static string FindMimeType(ITextBuffer buffer)
-		{
-			if (buffer == null)
-				throw new ArgumentNullException("buffer");
-			// TODO USE PROPER ENCODING!
-			// Maybe use Encoding detection from AvalonEdit?
-			byte[] bytes = Encoding.Default.GetBytes(buffer.TextLength > BUFFER_SIZE ? buffer.GetText(0, BUFFER_SIZE) : buffer.Text);
-			return FindMimeType(bytes, 0, bytes.Length);
-		}
 	}
 }

src/Main/Base/Test/ICSharpCode.SharpDevelop.Tests.csproj

@@ -81,6 +81,7 @@
     <Compile Include="GetElementByReflectionNameTests.cs" />
     <Compile Include="Highlighting\AddInHighlightingResourceTests.cs" />
     <Compile Include="Highlighting\SyntaxDoozerAddsHighlightingToHighlightingManagerTestFixture.cs" />
+    <Compile Include="MimeDetectionTests.cs" />
     <Compile Include="NRefactoryResolverTests.cs" />
     <Compile Include="CollectionClassOverridesTestFixture.cs" />
     <Compile Include="OutputTextLineParserTests.cs" />

src/Main/Base/Test/MimeDetectionTests.cs

@@ -0,0 +1,34 @@
+// Copyright (c) AlphaSierraPapa for the SharpDevelop Team (for details please see \doc\copyright.txt)
+// This code is distributed under the GNU LGPL (for details please see \doc\license.txt)
+
+using System;
+using NUnit.Framework;
+
+namespace ICSharpCode.SharpDevelop.Tests
+{
+	[TestFixture]
+	public class MimeTypeDetectionTests
+	{
+		[Test]
+		public void TextPlain()
+		{
+			// always open empty files with text editor
+			TestMime(new byte[] {}, "text/plain");
+			// UTF-8
+			TestMime(new byte[] { 0xEF, 0xBB, 0xBF }, "text/plain");
+			// UTF-16 Big Endian
+			TestMime(new byte[] { 0xFE, 0xFF }, "text/plain");
+			// UTF-16 Little Endian
+			TestMime(new byte[] { 0xFF, 0xFE }, "text/plain");
+			// UTF-32 Big Endian
+			TestMime(new byte[] { 0x00, 0x00, 0xFE, 0xFF }, "text/plain");
+			// UTF-32 Little Endian
+			TestMime(new byte[] { 0xFF, 0xFE, 0x00, 0x00 }, "text/plain");
+		}
+		
+		void TestMime(byte[] bytes, string expectedMime)
+		{
+			Assert.AreEqual(expectedMime, MimeTypeDetection.FindMimeType(bytes));
+		}
+	}
+}