|
|
|
1 |
|
/*** |
2 |
|
*gcroot.h |
3 |
|
* |
4 |
|
* Copyright (c) Microsoft Corporation. All rights reserved. |
5 |
|
* |
6 |
|
*Purpose: Template class that wraps GCHandle from mscorlib.dll. |
7 |
|
* |
8 |
|
* Use this class to declare gc "pointers" that live in the C++ heap. |
9 |
|
* |
10 |
|
* Example: |
11 |
|
* struct StringList { |
12 |
|
* msclr::gcroot<String^> str; |
13 |
|
* StringList *next; |
14 |
|
* StringList(); // should have ctors and dtors |
15 |
|
* ~StringList(); |
16 |
|
* }; |
17 |
|
* |
18 |
|
* By convention, we maintain a 1-to-1 relationship between C++ objects |
19 |
|
* and the handle slots they "point" to. Thus, two distinct C++ objects |
20 |
|
* always refer to two distinct handles, even if they "point" to the same |
21 |
|
* object. Therefore, when the C++ object is destroyed, its handle can |
22 |
|
* be freed without error. |
23 |
|
* |
24 |
|
* Note that we cannot currently embed a GCHandle directly in an unmanaged C++ |
25 |
|
* class. We therefore store a void*, and use the conversion methods of |
26 |
|
* GCHandle to reconstitute a GCHandle from the void* on demand. |
27 |
|
* |
28 |
|
* [Public] |
29 |
|
* |
30 |
|
****/ |
31 |
|
|
32 |
|
#pragma once |
33 |
|
|
34 |
|
#if !defined(_INC_MSCLR_GCROOT) |
35 |
|
#define _INC_MSCLR_GCROOT |
36 |
|
#ifndef RC_INVOKED |
37 |
|
|
38 |
|
#include <stddef.h> |
39 |
|
|
40 |
|
|
41 |
|
#ifdef __cplusplus_cli |
42 |
|
#define __GCHANDLE_TO_VOIDPTR(x) ((GCHandle::operator System::IntPtr(x)).ToPointer()) |
43 |
|
#define __VOIDPTR_TO_GCHANDLE(x) (GCHandle::operator GCHandle(System::IntPtr(x))) |
44 |
|
#define __NULLPTR nullptr |
45 |
|
#else |
46 |
|
#define __GCHANDLE_TO_VOIDPTR(x) ((GCHandle::op_Explicit(x)).ToPointer()) |
47 |
|
#define __VOIDPTR_TO_GCHANDLE(x) (GCHandle::op_Explicit(x)) |
48 |
|
#define __NULLPTR 0 |
49 |
|
#endif |
50 |
|
|
51 |
|
#ifndef __DEFINE_GCROOT_IN_GLOBAL_NAMESPACE |
52 |
|
namespace msclr |
53 |
|
{ |
54 |
|
#endif |
55 |
|
|
56 |
|
template <class T> struct gcroot { |
57 |
|
|
58 |
|
typedef System::Runtime::InteropServices::GCHandle GCHandle; |
59 |
|
|
60 |
|
// always allocate a new handle during construction (see above) |
61 |
|
// |
62 |
|
[System::Diagnostics::DebuggerStepThroughAttribute] |
63 |
|
gcroot() { |
64 |
|
_handle = __GCHANDLE_TO_VOIDPTR(GCHandle::Alloc(__NULLPTR)); |
65 |
|
} |
66 |
|
|
67 |
|
// this can't be T& here because & does not yet work on managed types |
68 |
|
// (T should be a pointer anyway). |
69 |
|
// |
70 |
|
gcroot(T t) { |
71 |
|
_handle = __GCHANDLE_TO_VOIDPTR(GCHandle::Alloc(t)); |
72 |
|
} |
73 |
|
|
74 |
|
gcroot(const gcroot& r) { |
75 |
|
// don't copy a handle, copy what it points to (see above) |
76 |
|
_handle = __GCHANDLE_TO_VOIDPTR( |
77 |
|
GCHandle::Alloc( |
78 |
|
__VOIDPTR_TO_GCHANDLE(r._handle).Target )); |
79 |
|
} |
80 |
|
|
81 |
|
// Since C++ objects and handles are allocated 1-to-1, we can |
82 |
|
// free the handle when the object is destroyed |
83 |
|
// |
84 |
|
[System::Diagnostics::DebuggerStepThroughAttribute] |
85 |
|
~gcroot() { |
86 |
|
GCHandle g = __VOIDPTR_TO_GCHANDLE(_handle); |
87 |
|
g.Free(); |
88 |
|
_handle = 0; // should fail if reconstituted |
89 |
|
} |
90 |
|
|
101 |
|
__VOIDPTR_TO_GCHANDLE(_handle).Target = t; |
102 |
|
return *this; |
103 |
|
} |
104 |
|
|
105 |
|
void swap( gcroot<T> & _right ) |
106 |
|
{ |
107 |
|
using std::swap; |
108 |
|
swap( _handle, _right._handle ); |
109 |
|
} |
110 |
|
|
111 |
|
operator T () const { |
112 |
|
// gcroot is typesafe, so use static_cast |
113 |
|
return static_cast<T>( __VOIDPTR_TO_GCHANDLE(_handle).Target ); |
114 |
|
} |
115 |
|
|
116 |
|
// don't return T& here because & to gc pointer not yet implemented |
117 |
|
// (T should be a pointer anyway). |
118 |
|
T operator->() const { |
119 |
|
// gcroot is typesafe, so use static_cast |
120 |
|
return static_cast<T>(__VOIDPTR_TO_GCHANDLE(_handle).Target); |
121 |
|
} |
122 |
|
|
123 |
|
private: |
124 |
|
// Don't let anyone copy the handle value directly, or make a copy |
125 |
|
// by taking the address of this object and pointing to it from |
126 |
|
// somewhere else. The root will be freed when the dtor of this |
127 |
|
// object gets called, and anyone pointing to it still will |
128 |
|
// cause serious harm to the Garbage Collector. |
129 |
|
// |
130 |
|
void* _handle; |
131 |
|
T* operator& (); |
132 |
|
}; |
133 |
|
|
134 |
|
template<typename T> |
135 |
|
void swap( gcroot<T> & _left, |
136 |
|
gcroot<T> & _right ) |
137 |
|
{ |
138 |
|
_left.swap( _right ); |
139 |
|
} |
140 |
|
|
141 |
|
#ifndef __DEFINE_GCROOT_IN_GLOBAL_NAMESPACE |
142 |
|
} // namespace msclr |
143 |
|
#endif |
144 |
|
|
145 |
|
#undef __GCHANDLE_TO_VOIDPTR |
146 |
|
#undef __VOIDPTR_TO_GCHANDLE |
147 |
|
#undef __NULLPTR |
148 |
|
|
149 |
|
#endif /* RC_INVOKED */ |
150 |
|
#endif // _INC_MSCLR_GCROOT |
151 |
|
|
|
|
|