nulib.memory.weak_ptr source code

1 /**
2     Weak pointers
3 
4     Copyright:
5         Copyright © 2023-2025, Kitsunebi Games
6         Copyright © 2023-2025, Inochi2D Project
7     
8     License:   $(LINK2 http://www.boost.org/LICENSE_1_0.txt, Boost License 1.0)
9     Authors:   Luna Nielsen
10 */
11 module nulib.memory.weak_ptr;
12 import nulib.memory.internal;
13 import numem.core.traits;
14 import numem;
15 
16 /**
17     A weak pointer.
18 
19     Weak pointers point to memory owned by shared_ptr or unique_ptr.
20     They do not own the memory allocation and said allocation may
21     become $(D null) at any point.
22 
23     Make sure to check the validity of the underlying value using
24     $(D isValid)!
25 
26     See_Also:
27         $(D nulib.memory.shared_ptr.shared_ptr)
28         $(D nulib.memory.unique_ptr.unique_ptr)
29 */
30 struct weak_ptr(T) {
31 @nogc:
32 private:
33     __refcount_t!(T)* ptr = null;
34 
35 package(nulib.memory):
36 
37     /**
38         Constructs a weak pointer from an internal refcount object.
39     */
40     this(__refcount_t!T* ptr) @system {
41         this.ptr = ptr;
42         ptr.retain!false;
43     }
44 
45 public:
46     alias value this;
47 
48     /**
49         The value stored within the smart pointer.
50     */
51     @property ref T value() @trusted nothrow {
52         return ptr.get();
53     }
54 
55     /**
56         Whether the smart pointer value is still valid.
57     */
58     @property bool isValid() @trusted nothrow {
59         return ptr && ptr.strongrefs > 0 && ptr.ptr !is null;
60     }
61 
62     /// Destructor.
63     ~this() @trusted { 
64         if (ptr) {
65             ptr.release!false;
66             ptr = null;
67         }
68     }
69 
70     /**
71         Copy Constructor.
72     */
73     this(ref inout(typeof(this)) src) {
74         auto srcobj = cast(Unqual!(typeof(this)))src;
75 
76         this.ptr = srcobj.ptr;
77         this.ptr.retain!false;
78     }
79 }