1 /**
2 * Implementation of array assignment support routines.
3 *
4 * Copyright: Copyright Digital Mars 2004 - 2010.
5 * License: $(HTTP www.boost.org/LICENSE_1_0.txt, Boost License 1.0).
6 * Authors: Walter Bright, Sean Kelly
7 * Source: $(DRUNTIMESRC rt/_cast_.d)
8 */
9
10 /* Copyright Digital Mars 2004 - 2010.
11 * Distributed under the Boost Software License, Version 1.0.
12 * (See accompanying file LICENSE or copy at
13 * http://www.boost.org/LICENSE_1_0.txt)
14 */
15 module rt.cast_;
16
17 extern (C):
18 @nogc:
19 nothrow:
20 pure:
21
22 // Needed because ClassInfo.opEquals(Object) does a dynamic cast,
23 // but we are trying to implement dynamic cast.
areClassInfosEqual(scope const ClassInfo a,scope const ClassInfo b)24 extern (D) private bool areClassInfosEqual(scope const ClassInfo a, scope const ClassInfo b) @safe
25 {
26 if (a is b)
27 return true;
28 // take care of potential duplicates across binaries
29 return a.name == b.name;
30 }
31
32 /******************************************
33 * Given a pointer:
34 * If it is an Object, return that Object.
35 * If it is an interface, return the Object implementing the interface.
36 * If it is null, return null.
37 * Else, undefined crash
38 */
_d_toObject(return scope void * p)39 Object _d_toObject(return scope void* p)
40 {
41 if (!p)
42 return null;
43
44 Object o = cast(Object) p;
45 ClassInfo oc = typeid(o);
46 Interface* pi = **cast(Interface***) p;
47
48 /* Interface.offset lines up with ClassInfo.name.ptr,
49 * so we rely on pointers never being less than 64K,
50 * and Objects never being greater.
51 */
52 if (pi.offset < 0x10000)
53 {
54 debug(cast_) printf("\tpi.offset = %d\n", pi.offset);
55 return cast(Object)(p - pi.offset);
56 }
57 return o;
58 }
59
60 /*************************************
61 * Attempts to cast Object o to class c.
62 * Returns o if successful, null if not.
63 */
_d_interface_cast(void * p,ClassInfo c)64 void* _d_interface_cast(void* p, ClassInfo c)
65 {
66 debug(cast_) printf("_d_interface_cast(p = %p, c = '%.*s')\n", p, c.name);
67 if (!p)
68 return null;
69
70 Interface* pi = **cast(Interface***) p;
71
72 debug(cast_) printf("\tpi.offset = %d\n", pi.offset);
73 return _d_dynamic_cast(cast(Object)(p - pi.offset), c);
74 }
75
_d_dynamic_cast(Object o,ClassInfo c)76 void* _d_dynamic_cast(Object o, ClassInfo c)
77 {
78 debug(cast_) printf("_d_dynamic_cast(o = %p, c = '%.*s')\n", o, c.name);
79
80 void* res = null;
81 size_t offset = 0;
82 if (o && _d_isbaseof2(typeid(o), c, offset))
83 {
84 debug(cast_) printf("\toffset = %d\n", offset);
85 res = cast(void*) o + offset;
86 }
87 debug(cast_) printf("\tresult = %p\n", res);
88 return res;
89 }
90
_d_isbaseof2(scope ClassInfo oc,scope const ClassInfo c,scope ref size_t offset)91 int _d_isbaseof2(scope ClassInfo oc, scope const ClassInfo c, scope ref size_t offset) @safe
92 {
93 if (areClassInfosEqual(oc, c))
94 return true;
95
96 do
97 {
98 if (oc.base && areClassInfosEqual(oc.base, c))
99 return true;
100
101 // Bugzilla 2013: Use depth-first search to calculate offset
102 // from the derived (oc) to the base (c).
103 foreach (iface; oc.interfaces)
104 {
105 if (areClassInfosEqual(iface.classinfo, c) || _d_isbaseof2(iface.classinfo, c, offset))
106 {
107 offset += iface.offset;
108 return true;
109 }
110 }
111
112 oc = oc.base;
113 } while (oc);
114
115 return false;
116 }
117
_d_isbaseof(scope ClassInfo oc,scope const ClassInfo c)118 int _d_isbaseof(scope ClassInfo oc, scope const ClassInfo c) @safe
119 {
120 if (areClassInfosEqual(oc, c))
121 return true;
122
123 do
124 {
125 if (oc.base && areClassInfosEqual(oc.base, c))
126 return true;
127
128 foreach (iface; oc.interfaces)
129 {
130 if (areClassInfosEqual(iface.classinfo, c) || _d_isbaseof(iface.classinfo, c))
131 return true;
132 }
133
134 oc = oc.base;
135 } while (oc);
136
137 return false;
138 }
139