move Pak.cs to the correct directory

case-sensitive OS require it to compile using MonoDevelop

OpenRA.FileFormats/FileSystem/Pak.cs

@@ -0,0 +1,97 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2013 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 COPYING.
+ */
+#endregion
+
+using System;
+using System.Collections.Generic;
+using System.IO;
+
+namespace OpenRA.FileFormats
+{
+	struct Entry
+	{
+		public uint Offset;
+		public uint Length;
+		public string Filename;
+	}
+
+	public class PakFile : IFolder
+	{
+		string filename;
+		int priority;
+		Dictionary<string, Entry> index;
+		Stream stream;
+
+		public PakFile(string filename, int priority)
+		{
+			this.filename = filename;
+			this.priority = priority;
+			index = new Dictionary<string, Entry>();
+			stream = FileSystem.Open(filename);
+
+			index = new Dictionary<string, Entry>();
+			var offset = stream.ReadUInt32();
+			while (offset != 0)
+			{
+				var file = stream.ReadASCIIZ();
+				var next = stream.ReadUInt32();
+				var length = (next == 0 ? (uint)stream.Length : next) - offset;
+
+				// Ignore duplicate files
+				if (index.ContainsKey(file))
+					continue;
+
+				index.Add(file, new Entry { Offset = offset, Length = length, Filename = file });
+				offset = next;
+			}
+		}
+
+		public Stream GetContent(string filename)
+		{
+			Entry entry;
+			if (!index.TryGetValue(filename, out entry))
+				return null;
+
+			stream.Seek(entry.Offset, SeekOrigin.Begin);
+			var data = new byte[entry.Length];
+			stream.Read(data, 0, (int)entry.Length);
+			return new MemoryStream(data);
+		}
+
+		public IEnumerable<uint> ClassicHashes()
+		{
+			foreach (var filename in index.Keys)
+				yield return PackageEntry.HashFilename(filename, PackageHashType.Classic);
+		}
+
+		public IEnumerable<uint> CrcHashes()
+		{
+			yield break;
+		}
+
+		public IEnumerable<string> AllFileNames()
+		{
+			foreach (var filename in index.Keys)
+				yield return filename;
+		}
+
+		public bool Exists(string filename)
+		{
+			return index.ContainsKey(filename);
+		}
+
+		public void Write(Dictionary<string, byte[]> contents)
+		{
+			throw new NotImplementedException("Cannot save Pak archives.");
+		}
+
+		public int Priority { get { return 1000 + priority; } }
+		public string Name { get { return filename; } }
+	}
+}