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comparison dwt/dwthelper/WeakRef.d @ 198:be4ce760802a

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Add: missing files
author Frank Benoit <benoit@tionex.de>
date Thu, 10 Apr 2008 11:20:26 +0200
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1 /*==========================================================================
2 * weakref.d
3 * Written in the D Programming Language (http://www.digitalmars.com/d)
4 */
5 /***************************************************************************
6 * Creates a weak reference to a class instance.
7 *
8 * A weak reference lets you hold onto a pointer to an object without
9 * preventing the garbage collector from collecting it.
10 * If the garbage collector collects the object then the weak pointer will
11 * become 'null'. Thus one should always check a weak pointer for null
12 * before doing anything that depends upon it having a value.
13 *
14 * Tested with:
15 * DMD 1.025 / Phobos 1.025
16 * DMD 1.025 / Tango 0.99.4
17 *
18 * Usage example:
19 ---
20 class Something {}
21
22 auto a = new Something();
23 auto wa = new WeakRef!(Something)(a);
24 std.gc.fullCollect();
25
26 // Reference 'a' prevents collection so wa.ptr is non-null
27 assert(wa.ptr is a);
28
29 delete a;
30
31 // 'a' is gone now, so wa.ptr magically becomes null
32 assert(wa.ptr is null);
33 ---
34 *
35 *
36 * Author: William V. Baxter III
37 * Contributors:
38 * Date: 21 Jan 2008
39 * Copyright: (C) 2008 William Baxter
40 * License: Public Domain where allowed by law, ZLIB/PNG otherwise.
41 */
42 //===========================================================================
43
44 module dwt.dwthelper.WeakRef;
45
46 private {
47 alias void delegate(Object) DisposeEvt;
48 extern (C) void rt_attachDisposeEvent( Object obj, DisposeEvt evt );
49 extern (C) void rt_detachDisposeEvent( Object obj, DisposeEvt evt );
50 }
51
52 class WeakRef(T : Object) {
53 private:
54 size_t cast_ptr_;
55 void unhook(Object o) {
56 if (cast(size_t)cast(void*)o == cast_ptr_) {
57 rt_detachDisposeEvent(o, &unhook);
58 cast_ptr_ = 0;
59 }
60 }
61 public:
62
63 this(T tptr) {
64 cast_ptr_ = cast(size_t)cast(void*)tptr;
65 rt_attachDisposeEvent(tptr, &unhook);
66 }
67 ~this() {
68 T p = ptr();
69 if (p) {
70 rt_detachDisposeEvent(p, &unhook);
71 }
72 }
73 T ptr() {
74 return cast(T)cast(void*)cast_ptr_;
75 }
76 WeakRef dup() {
77 return new WeakRef(ptr());
78 }
79 int opEquals( Object o ){
80 if( auto other = cast( WeakRef!(T) )o ){
81 return other.cast_ptr_ is cast_ptr_;
82 }
83 return false;
84 }
85 hash_t toHash(){
86 return cast_ptr_;
87 }
88 }