Make our IFolder zip support actually work.

OpenRA.FileFormats/Filesystem/ZipFile.cs

@@ -0,0 +1,52 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2010 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made 
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation. For more information,
+ * see LICENSE.
+ */
+#endregion
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+using ICSharpCode.SharpZipLib.Zip;
+using SZipFile = ICSharpCode.SharpZipLib.Zip.ZipFile;
+using System.Linq;
+
+namespace OpenRA.FileFormats
+{
+	public class ZipFile : IFolder
+	{
+		readonly SZipFile pkg;
+		int priority;
+
+		public ZipFile(string filename, int priority)
+		{
+			this.priority = priority;
+			pkg = new SZipFile(File.OpenRead(filename));
+		}
+
+		public Stream GetContent(string filename)
+		{
+			return pkg.GetInputStream(pkg.GetEntry(filename));
+		}
+
+		public IEnumerable<uint> AllFileHashes()
+		{
+			foreach(ZipEntry entry in pkg)
+				yield return PackageEntry.HashFilename(entry.Name);
+		}
+		
+		public bool Exists(string filename)
+		{
+			return pkg.GetEntry(filename) != null;
+		}
+
+		public int Priority
+		{
+			get { return 500 + priority; }
+		}
+	}
+}