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eventobject.cs
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// ==========================================================================
// This software is subject to the provisions of the Zope Public License,
// Version 2.0 (ZPL). A copy of the ZPL should accompany this distribution.
// THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
// WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
// WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
// FOR A PARTICULAR PURPOSE.
// ==========================================================================
using System;
using System.Collections;
using System.Reflection;
namespace Python.Runtime {
//========================================================================
// Implements a Python descriptor type that provides access to CLR events.
//========================================================================
internal class EventObject : ExtensionType {
internal string name;
internal EventBinding unbound;
internal EventInfo info;
internal Hashtable reg;
public EventObject(EventInfo info) : base() {
this.name = info.Name;
this.info = info;
}
//====================================================================
// Register a new Python object event handler with the event.
//====================================================================
internal bool AddEventHandler(IntPtr target, IntPtr handler) {
Object obj = null;
if (target != IntPtr.Zero) {
CLRObject co = (CLRObject)ManagedType.GetManagedObject(target);
obj = co.inst;
}
// Create a true delegate instance of the appropriate type to
// wrap the Python handler. Note that wrapper delegate creation
// always succeeds, though calling the wrapper may fail.
Type type = this.info.EventHandlerType;
Delegate d = PythonEngine.DelegateManager.GetDelegate(type, handler);
// Now register the handler in a mapping from instance to pairs
// of (handler hash, delegate) so we can lookup to remove later.
// All this is done lazily to avoid overhead until an event is
// actually subscribed to by a Python event handler.
if (reg == null) {
reg = new Hashtable();
}
object key = (obj != null) ? obj : this.info.ReflectedType;
ArrayList list = reg[key] as ArrayList;
if (list == null) {
list = new ArrayList();
reg[key] = list;
}
list.Add(new Handler(Runtime.PyObject_Hash(handler), d));
// Note that AddEventHandler helper only works for public events,
// so we have to get the underlying add method explicitly.
object[] args = { d };
MethodInfo mi = this.info.GetAddMethod(true);
mi.Invoke(obj, BindingFlags.Default, null, args, null);
return true;
}
//====================================================================
// Remove the given Python object event handler.
//====================================================================
internal bool RemoveEventHandler(IntPtr target, IntPtr handler) {
Object obj = null;
if (target != IntPtr.Zero) {
CLRObject co = (CLRObject)ManagedType.GetManagedObject(target);
obj = co.inst;
}
IntPtr hash = Runtime.PyObject_Hash(handler);
if (Exceptions.ErrorOccurred() || (reg == null)) {
Exceptions.SetError(Exceptions.ValueError,
"unknown event handler"
);
return false;
}
object key = (obj != null) ? obj : this.info.ReflectedType;
ArrayList list = reg[key] as ArrayList;
if (list == null) {
Exceptions.SetError(Exceptions.ValueError,
"unknown event handler"
);
return false;
}
object[] args = { null };
MethodInfo mi = this.info.GetRemoveMethod(true);
for (int i = 0; i < list.Count; i++) {
Handler item = (Handler)list[i];
if (item.hash != hash) {
continue;
}
args[0] = item.del;
try {
mi.Invoke(obj, BindingFlags.Default, null, args, null);
}
catch {
continue;
}
list.RemoveAt(i);
return true;
}
Exceptions.SetError(Exceptions.ValueError,
"unknown event handler"
);
return false;
}
//====================================================================
// Descriptor __get__ implementation. A getattr on an event returns
// a "bound" event that keeps a reference to the object instance.
//====================================================================
public static IntPtr tp_descr_get(IntPtr ds, IntPtr ob, IntPtr tp) {
EventObject self = GetManagedObject(ds) as EventObject;
EventBinding binding;
if (self == null) {
return Exceptions.RaiseTypeError("invalid argument");
}
// If the event is accessed through its type (rather than via
// an instance) we return an 'unbound' EventBinding that will
// be cached for future accesses through the type.
if (ob == IntPtr.Zero) {
if (self.unbound == null) {
self.unbound = new EventBinding(self, IntPtr.Zero);
}
binding = self.unbound;
Runtime.Incref(binding.pyHandle);
return binding.pyHandle;
}
if (Runtime.PyObject_IsInstance(ob, tp) < 1) {
return Exceptions.RaiseTypeError("invalid argument");
}
binding = new EventBinding(self, ob);
return binding.pyHandle;
}
//====================================================================
// Descriptor __set__ implementation. This actually never allows you
// to set anything; it exists solely to support the '+=' spelling of
// event handler registration. The reason is that given code like:
// 'ob.SomeEvent += method', Python will attempt to set the attribute
// SomeEvent on ob to the result of the '+=' operation.
//====================================================================
public static new int tp_descr_set(IntPtr ds, IntPtr ob, IntPtr val) {
EventBinding e = GetManagedObject(val) as EventBinding;
if (e != null) {
return 0;
}
string message = "cannot set event attributes";
Exceptions.RaiseTypeError(message);
return -1;
}
//====================================================================
// Descriptor __repr__ implementation.
//====================================================================
public static IntPtr tp_repr(IntPtr ob) {
EventObject self = (EventObject)GetManagedObject(ob);
string s = String.Format("<event '{0}'>", self.name);
return Runtime.PyString_FromString(s);
}
//====================================================================
// Descriptor dealloc implementation.
//====================================================================
public static new void tp_dealloc(IntPtr ob) {
EventObject self = (EventObject)GetManagedObject(ob);
if (self.unbound != null) {
Runtime.Decref(self.unbound.pyHandle);
}
ExtensionType.FinalizeObject(self);
}
}
internal class Handler {
public IntPtr hash;
public Delegate del;
public Handler(IntPtr hash, Delegate d) {
this.hash = hash;
this.del = d;
}
}
}