gstreamer/subprojects/gstreamer-sharp/sources/custom/DynamicSignal.cs

// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.
//
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

//
//
// Copyright (C) 2006 Novell Inc.
// Copyright (C) 2009 Sebastian Dröge <sebastian.droege@collabora.co.uk>
// Copyright (C) 2013 Stephan Sundermann <stephansundermann@gmail.com>
//
// This class implements functions to bind callbacks to GObject signals
// dynamically and to emit signals dynamically.
//
//

using GLib;
using System;
using System.Collections;
using System.Reflection;
using System.Runtime.InteropServices;

namespace Gst {

	[UnmanagedFunctionPointer(CallingConvention.Cdecl)]
	delegate void GClosureMarshal(IntPtr closure, ref GLib.Value retval, uint argc, IntPtr argsPtr,
								 IntPtr invocation_hint, IntPtr data);

	public delegate void SignalHandler(object o, SignalArgs args);

	public static class DynamicSignal {

		private static readonly int gvalue_struct_size = Marshal.SizeOf(typeof(GLib.Value));

		class ObjectSignalKey {
			object o;
			string signal_name;

			public ObjectSignalKey(object o, string name) {
				this.o = o;
				signal_name = name;
			}

			public override bool Equals(object o) {
				if (o is ObjectSignalKey) {
					ObjectSignalKey k = (ObjectSignalKey)o;
					return k.o.Equals(this.o) && signal_name.Equals(k.signal_name);
				}
				return base.Equals(o);
			}

			public override int GetHashCode() {
				return o.GetHashCode() ^ signal_name.GetHashCode();
			}
		}

		class SignalInfo : IDisposable {
			uint handlerId;
			IntPtr closure;
			Delegate registeredHandler;
			Type argsType;
			GCHandle gch;

			public IntPtr Closure {
				get {
					return closure;
				}
				set {
					closure = value;
				}
			}

			public uint HandlerId {
				get {
					return handlerId;
				}
				set {
					handlerId = value;
				}
			}

			public Delegate RegisteredHandler {
				get {
					return registeredHandler;
				}
				set {
					registeredHandler = value;
				}
			}

			public Type ArgsType {
				get {
					return argsType;
				}
				set {
					argsType = value;
				}
			}

			public SignalInfo(uint handlerId, IntPtr closure, Delegate registeredHandler, GCHandle gch) {
				this.handlerId = handlerId;
				this.closure = closure;
				this.registeredHandler = registeredHandler;
				this.gch = gch;

				if (!IsValidDelegate(registeredHandler))
					throw new Exception("Invalid delegate");

				MethodInfo mi = registeredHandler.Method;
				ParameterInfo[] parms = mi.GetParameters();
				this.argsType = parms[1].ParameterType;
			}

			public void UpdateArgsType(Delegate d) {
				if (!IsCompatibleDelegate(d))
					throw new Exception("Incompatible delegate");

				MethodInfo mi = d.Method;
				ParameterInfo[] parms = mi.GetParameters();

				Type t1 = parms[1].ParameterType;
				Type t2 = argsType;

				if (t1 == t2)
					return;

				if (t1.IsSubclassOf(t2))
					argsType = t1;
				else if (t2.IsSubclassOf(t1))
					argsType = t2;
				else
					throw new Exception("Incompatible delegate");
			}

			public bool IsCompatibleDelegate(Delegate d) {
				if (!IsValidDelegate(d))
					return false;

				MethodInfo mi = d.Method;
				ParameterInfo[] parms = mi.GetParameters();

				if (parms[1].ParameterType != this.argsType &&
						!parms[1].ParameterType.IsSubclassOf(this.argsType) &&
						!this.argsType.IsSubclassOf(parms[1].ParameterType))
					return false;

				return true;
			}

			public void Dispose() {
				registeredHandler = null;
				gch.Free();
				GC.SuppressFinalize(this);
			}

			public static bool IsValidDelegate(Delegate d) {
				MethodInfo mi = d.Method;

				if (mi.ReturnType != typeof(void))
					return false;

				ParameterInfo[] parms = mi.GetParameters();
				if (parms.Length != 2)
					return false;

				if (parms[1].ParameterType != typeof(GLib.SignalArgs) &&
						!parms[1].ParameterType.IsSubclassOf(typeof(GLib.SignalArgs)))
					return false;

				return true;
			}
		}

		static Hashtable SignalHandlers = new Hashtable();

		static GClosureMarshal marshalHandler = new GClosureMarshal(OnMarshal);

		public static void Connect(GLib.Object o, string name, SignalHandler handler) {
			Connect(o, name, false, (Delegate)handler);
		}

		public static void Connect(GLib.Object o, string name,
									  bool after, SignalHandler handler) {
			Connect(o, name, after, (Delegate)handler);
		}

		public static void Connect(GLib.Object o, string name, Delegate handler) {
			Connect(o, name, false, handler);
		}

		public static void Connect(GLib.Object o, string name,
									  bool after, Delegate handler) {
			Delegate newHandler;

			ObjectSignalKey k = new ObjectSignalKey(o, name);

			if (!SignalInfo.IsValidDelegate(handler))
				throw new Exception("Invalid delegate");

			if (SignalHandlers[k] != null) {
				SignalInfo si = (SignalInfo)SignalHandlers[k];
				if (!si.IsCompatibleDelegate(handler))
					throw new Exception("Incompatible delegate");

				newHandler = Delegate.Combine(si.RegisteredHandler, handler);
				si.UpdateArgsType(handler);
				si.RegisteredHandler = newHandler;
			}
			else {
				if (!SignalInfo.IsValidDelegate(handler))
					throw new Exception("Invalid delegate");

				// Let's allocate 64bytes for the GClosure, it should be more than necessary.
				IntPtr closure = g_closure_new_simple(64, IntPtr.Zero);
				GCHandle gch = GCHandle.Alloc(k);
				g_closure_set_meta_marshal(closure, (IntPtr)gch, marshalHandler);
				uint signalId = g_signal_connect_closure(o.Handle, name, closure, after);
				SignalHandlers.Add(k, new SignalInfo(signalId, closure, handler, gch));
			}
		}

		public static void Disconnect(GLib.Object o, string name, Delegate handler) {
			ObjectSignalKey k = new ObjectSignalKey(o, name);
			if (SignalHandlers[k] != null) {
				SignalInfo si = (SignalInfo)SignalHandlers[k];
				Delegate newHandler = Delegate.Remove(si.RegisteredHandler, handler);
				if (newHandler == null || handler == null) {
					g_signal_handler_disconnect(o.Handle, si.HandlerId);
					SignalHandlers.Remove(k);
					si.Dispose();
				}
				else {
					si.RegisteredHandler = newHandler;
				}
			}
		}

		static void OnMarshal(IntPtr closure, ref GLib.Value retval, uint argc, IntPtr argsPtr,
								 IntPtr ihint, IntPtr data) {
			object[] args = new object[argc - 1];
			object o = ((GLib.Value)Marshal.PtrToStructure(argsPtr, typeof(GLib.Value))).Val;

			for (int i = 1; i < argc; i++) {
				IntPtr struct_ptr = (IntPtr)((long)argsPtr + (i * gvalue_struct_size));
				GLib.Value argument = (GLib.Value)Marshal.PtrToStructure(struct_ptr, typeof(GLib.Value));
				args[i - 1] = argument.Val;
			}

			if (data == IntPtr.Zero) {
				Console.Error.WriteLine("No available data");
				return;
			}

			ObjectSignalKey k = (ObjectSignalKey)((GCHandle)data).Target;
			if (k != null) {
				SignalInfo si = (SignalInfo)SignalHandlers[k];
				GLib.SignalArgs arg = (GLib.SignalArgs)Activator.CreateInstance(si.ArgsType);
				arg.Args = args;
				si.RegisteredHandler.DynamicInvoke(new object[] { o, arg });
				if (arg.RetVal != null) {
					retval.Val = arg.RetVal;
				}
			}
		}


		[DllImport("gobject-2.0-0.dll", CallingConvention = CallingConvention.Cdecl)]
		static extern IntPtr g_closure_new_simple(int size, IntPtr data);

		[DllImport("gobject-2.0-0.dll", CallingConvention = CallingConvention.Cdecl)]
		static extern uint g_signal_connect_closure(IntPtr instance,
													   string name, IntPtr closure, bool after);

		[DllImport("gobject-2.0-0.dll", CallingConvention = CallingConvention.Cdecl)]
		static extern void g_closure_set_meta_marshal(IntPtr closure, IntPtr data, GClosureMarshal marshal);

		class GTypeSignalKey {
			GType type;
			string signal_name;

			public GTypeSignalKey(GType type, string name) {
				this.type = type;
				signal_name = name;
			}

			public override bool Equals(object o) {
				if (o is GTypeSignalKey) {
					GTypeSignalKey k = (GTypeSignalKey)o;
					return k.type.Equals(this.type) && signal_name.Equals(k.signal_name);
				}
				return base.Equals(o);
			}

			public override int GetHashCode() {
				return type.GetHashCode() ^ signal_name.GetHashCode();
			}
		}

		struct SignalQuery {
			public uint signal_id;
			public string signal_name;
			public GType itype;
			public uint signal_flags;
			public GType return_type;
			public uint n_params;
			public Type[] param_types;
		}

		static Hashtable SignalEmitInfo = new Hashtable();

		public static object Emit(GLib.Object o, string name, params object[] parameters) {
			SignalQuery query;
			GType gtype = o.NativeType;
			IntPtr type = gtype.Val;
			string signal_name, signal_detail;
			uint signal_detail_quark = 0;
			int colon;

			colon = name.LastIndexOf("::");

			if (colon == -1) {
				signal_name = name;
				signal_detail = String.Empty;
			}
			else {
				signal_name = name.Substring(0, colon);
				signal_detail = name.Substring(colon + 2);
			}

			GTypeSignalKey key = new GTypeSignalKey(gtype, signal_name);

			if (SignalEmitInfo[key] == null) {
				IntPtr native_string = GLib.Marshaller.StringToPtrGStrdup(signal_name);
				uint signal_id = g_signal_lookup(native_string, type);
				GLib.Marshaller.Free(native_string);

				if (signal_id == 0)
					throw new NotSupportedException(String.Format("{0} has no signal of name {1}", o, name));
				GSignalQuery q = new GSignalQuery();
				g_signal_query(signal_id, ref q);

				if (q.signal_id == 0)
					throw new NotSupportedException(String.Format("{0} couldn't be queried for signal with name {1}", o, name));

				query = new SignalQuery();

				query.signal_id = signal_id;
				query.signal_name = GLib.Marshaller.Utf8PtrToString(q.signal_name);
				query.itype = new GType(q.itype);
				query.signal_flags = q.signal_flags;
				query.return_type = new GType(q.return_type);
				query.n_params = q.n_params;
				query.param_types = new Type[q.n_params];

				for (int i = 0; i < query.n_params; i++) {
					IntPtr t = Marshal.ReadIntPtr(q.param_types, i * IntPtr.Size);
					GType g = new GType(t);

					query.param_types[i] = (Type)g;
				}

				SignalEmitInfo.Add(key, query);
			}

			query = (SignalQuery)SignalEmitInfo[key];
			GLib.Value[] signal_parameters = new GLib.Value[query.n_params + 1];
			signal_parameters[0] = new GLib.Value(o);

			if (parameters.Length != query.n_params)
				throw new ApplicationException(String.Format("Invalid number of parameters: expected {0}, got {1}", query.n_params, parameters.Length));

			for (int i = 0; i < query.n_params; i++) {
				Type expected_type = (Type)query.param_types[i];
				Type given_type = parameters[i].GetType();

				if (expected_type != given_type && !given_type.IsSubclassOf(given_type))
					throw new ApplicationException(String.Format("Invalid parameter type: expected {0}, got {1}", expected_type, given_type));

				signal_parameters[i + 1] = new GLib.Value(parameters[i]);
			}

			GLib.Value return_value = new GLib.Value();
			if (query.return_type != GType.Invalid && query.return_type != GType.None)
				return_value.Init(query.return_type);

			if (signal_detail != String.Empty) {
				IntPtr native_string = GLib.Marshaller.StringToPtrGStrdup(signal_detail);
				signal_detail_quark = g_quark_from_string(native_string);
				GLib.Marshaller.Free(native_string);
			}

			g_signal_emitv(signal_parameters, query.signal_id, signal_detail_quark, ref return_value);

			foreach (GLib.Value v in signal_parameters)
				v.Dispose();

			object ret = (query.return_type != GType.Invalid && query.return_type != GType.None) ? return_value.Val : null;

			if (ret != null)
				return_value.Dispose();

			return ret;
		}

		[DllImport("gobject-2.0-0.dll", CallingConvention = CallingConvention.Cdecl)]
		static extern int g_signal_handler_disconnect(IntPtr o, uint handler_id);

		[DllImport("gobject-2.0-0.dll", CallingConvention = CallingConvention.Cdecl)]
		static extern uint g_signal_lookup(IntPtr name, IntPtr itype);

		[DllImport("glib-2.0-0.dll", CallingConvention = CallingConvention.Cdecl)]
		static extern uint g_quark_from_string(IntPtr str);

		[DllImport("gobject-2.0-0.dll", CallingConvention = CallingConvention.Cdecl)]
		static extern void g_signal_emitv(GLib.Value[] parameters, uint signal_id, uint detail, ref GLib.Value return_value);

		[StructLayout(LayoutKind.Sequential)]
		struct GSignalQuery {
			public uint signal_id;
			public IntPtr signal_name;
			public IntPtr itype;
			public uint signal_flags;
			public IntPtr return_type;
			public uint n_params;
			public IntPtr param_types;
		}

		[DllImport("gobject-2.0-0.dll", CallingConvention = CallingConvention.Cdecl)]
		static extern void g_signal_query(uint signal_id, ref GSignalQuery query);
	}
}