Wire up the rest of saving. Save-as will now properly overwrite existing contents.

OpenRA.FileFormats/Filesystem/FileSystem.cs

@@ -41,6 +41,20 @@ namespace OpenRA.FileFormats
             return OpenPackage(filename, order++);
 		}
 
+		public static IFolder CreatePackage(string filename, int order, Dictionary<string, byte[]> content)
+        {
+			if (filename.EndsWith(".mix", StringComparison.InvariantCultureIgnoreCase))
+                return new MixFile(filename, order, content);
+            else if (filename.EndsWith(".zip", StringComparison.InvariantCultureIgnoreCase))
+                return new ZipFile(filename, order, content);
+            else if (filename.EndsWith(".oramap", StringComparison.InvariantCultureIgnoreCase))
+                return new ZipFile(filename, order, content);
+            else if (filename.EndsWith(".Z", StringComparison.InvariantCultureIgnoreCase))
+                throw new NotImplementedException("Creating .Z archives is unsupported");
+            else
+                return new Folder(filename, order, content);
+        }
+		
         public static IFolder OpenPackage(string filename, int order)
         {
             if (filename.EndsWith(".mix", StringComparison.InvariantCultureIgnoreCase))

OpenRA.FileFormats/Filesystem/Folder.cs

@@ -20,7 +20,22 @@ namespace OpenRA.FileFormats
 
 		int priority;
 
-		public Folder(string path, int priority) { this.path = path; this.priority = priority; }
+		// Create a new folder package
+		public Folder(string path, int priority, Dictionary<string, byte[]> contents)
+		{
+			this.path = path;
+			this.priority = priority;
+			if (Directory.Exists(path))
+				Directory.Delete(path);
+			
+			Write(contents);
+		}
+		
+		public Folder(string path, int priority)
+		{
+			this.path = path;
+			this.priority = priority;
+		}
 
 		public Stream GetContent(string filename)
 		{

OpenRA.FileFormats/Filesystem/MixFile.cs

@@ -31,6 +31,17 @@ namespace OpenRA.FileFormats
 		readonly long dataStart;
 		readonly Stream s;
 		int priority;
+		
+		// Create a new MixFile
+		public MixFile(string filename, int priority, Dictionary<string, byte[]> contents)
+		{
+			this.priority = priority;
+			if (File.Exists(filename))
+				File.Delete(filename);
+			
+			s = File.Create(filename);
+			Write(contents);
+		}
 
 		public MixFile(string filename, int priority)
 		{
@@ -162,6 +173,14 @@ namespace OpenRA.FileFormats
 		
 		public void Write(Dictionary<string, byte[]> contents)
 		{
+			// Cannot modify existing mixfile - rename existing file and
+			// create a new one with original content plus modifications
+			FileSystem.Unmount(this);
+			
+			// TODO: Add existing data to the contents list
+			if (index.Count > 0)
+				throw new NotImplementedException("Updating mix files unfinished");
+		
 			// Construct a list of entries for the file header
 			uint dataSize = 0;
 			var items = new List<PackageEntry>();
@@ -173,6 +192,8 @@ namespace OpenRA.FileFormats
 				dataSize += length;
 			}
 
+			// Write the new file
+			s.Seek(0,SeekOrigin.Begin);
 			using (var writer = new BinaryWriter(s))
 			{
 				// Write file header

OpenRA.FileFormats/Filesystem/ZipFile.cs

@@ -23,19 +23,25 @@ namespace OpenRA.FileFormats
 		public ZipFile(string filename, int priority)
 		{
 			this.priority = priority;
-			if (File.Exists(filename))
+			try
 			{
-				try
-				{
-					pkg = new SZipFile(File.OpenRead(filename));
-				}
-				catch (ZipException e)
-				{
-					Log.Write("debug", "Couldn't load zip file: {0}", e.Message);
-				}
+				pkg = new SZipFile(File.OpenRead(filename));
 			}
-			else
-				pkg = SZipFile.Create(filename);
+			catch (ZipException e)
+			{
+				Log.Write("debug", "Couldn't load zip file: {0}", e.Message);
+			}
+		}
+
+		// Create a new zip with the specified contents
+		public ZipFile(string filename, int priority, Dictionary<string, byte[]> contents)
+		{
+			this.priority = priority;
+			if (File.Exists(filename))
+				File.Delete(filename);
+			
+			pkg = SZipFile.Create(filename);
+			Write(contents);
 		}
 
 		public Stream GetContent(string filename)