libphobos/libdruntime/rt/cast_.d

   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.
  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  */
  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  */
  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
  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
  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
 118 int _d_isbaseof(scope ClassInfo oc, scope const ClassInfo c) @safe
 119 {
 120     size_t offset = 0;
 121     return _d_isbaseof2(oc, c, offset);
 122 }