boehm-gc/include/gc_allocator.h

   1 /*
   2  * Copyright (c) 1996-1997
   3  * Silicon Graphics Computer Systems, Inc.
   4  *
   5  * Permission to use, copy, modify, distribute and sell this software
   6  * and its documentation for any purpose is hereby granted without fee,
   7  * provided that the above copyright notice appear in all copies and
   8  * that both that copyright notice and this permission notice appear
   9  * in supporting documentation.  Silicon Graphics makes no
  10  * representations about the suitability of this software for any
  11  * purpose.  It is provided "as is" without express or implied warranty.
  12  *
  13  * Copyright (c) 2002
  14  * Hewlett-Packard Company
  15  *
  16  * Permission to use, copy, modify, distribute and sell this software
  17  * and its documentation for any purpose is hereby granted without fee,
  18  * provided that the above copyright notice appear in all copies and
  19  * that both that copyright notice and this permission notice appear
  20  * in supporting documentation.  Hewlett-Packard Company makes no
  21  * representations about the suitability of this software for any
  22  * purpose.  It is provided "as is" without express or implied warranty.
  23  */
  24
  25 /*
  26  * This implements standard-conforming allocators that interact with
  27  * the garbage collector.  Gc_alloctor<T> allocates garbage-collectable
  28  * objects of type T.  Traceable_allocator<T> allocates objects that
  29  * are not temselves garbage collected, but are scanned by the
  30  * collector for pointers to collectable objects.  Traceable_alloc
  31  * should be used for explicitly managed STL containers that may
  32  * point to collectable objects.
  33  *
  34  * This code was derived from an earlier version of the GNU C++ standard
  35  * library, which itself was derived from the SGI STL implementation.
  36  */
  37
  38 #include "gc.h"         // For size_t
  39
  40 /* First some helpers to allow us to dispatch on whether or not a type
  41  * is known to be pointerfree.
  42  * These are private, except that the client may invoke the
  43  * GC_DECLARE_PTRFREE macro.
  44  */
  45
  46 struct GC_true_type {};
  47 struct GC_false_type {};
  48
  49 template <class GC_tp>
  50 struct GC_type_traits {
  51   GC_false_type GC_is_ptr_free;
  52 };
  53
  54 # define GC_DECLARE_PTRFREE(T) \
  55 template<> struct GC_type_traits<T> { GC_true_type GC_is_ptr_free; }
  56
  57 GC_DECLARE_PTRFREE(signed char);
  58 GC_DECLARE_PTRFREE(unsigned char);
  59 GC_DECLARE_PTRFREE(signed short);
  60 GC_DECLARE_PTRFREE(unsigned short);
  61 GC_DECLARE_PTRFREE(signed int);
  62 GC_DECLARE_PTRFREE(unsigned int);
  63 GC_DECLARE_PTRFREE(signed long);
  64 GC_DECLARE_PTRFREE(unsigned long);
  65 GC_DECLARE_PTRFREE(float);
  66 GC_DECLARE_PTRFREE(double);
  67 /* The client may want to add others.   */
  68
  69 // In the following GC_Tp is GC_true_type iff we are allocating a
  70 // pointerfree object.
  71 template <class GC_Tp>
  72 inline void * GC_selective_alloc(size_t n, GC_Tp) {
  73     return GC_MALLOC(n);
  74 }
  75
  76 template <>
  77 inline void * GC_selective_alloc<GC_true_type>(size_t n, GC_true_type) {
  78     return GC_MALLOC_ATOMIC(n);
  79 }
  80
  81 /* Now the public gc_allocator<T> class:
  82  */
  83 template <class GC_Tp>
  84 class gc_allocator {
  85 public:
  86   typedef size_t     size_type;
  87   typedef ptrdiff_t  difference_type;
  88   typedef GC_Tp*       pointer;
  89   typedef const GC_Tp* const_pointer;
  90   typedef GC_Tp&       reference;
  91   typedef const GC_Tp& const_reference;
  92   typedef GC_Tp        value_type;
  93
  94   template <class GC_Tp1> struct rebind {
  95     typedef gc_allocator<GC_Tp1> other;
  96   };
  97
  98   gc_allocator()  {}
  99 # ifndef _MSC_VER
 100     // I'm not sure why this is needed here in addition to the following.
 101     // The standard specifies it for the standard allocator, but VC++ rejects
 102     // it.      -HB
 103     gc_allocator(const gc_allocator&) throw() {}
 104 # endif
 105   template <class GC_Tp1> gc_allocator(const gc_allocator<GC_Tp1>&) throw() {}
 106   ~gc_allocator() throw() {}
 107
 108   pointer address(reference GC_x) const { return &GC_x; }
 109   const_pointer address(const_reference GC_x) const { return &GC_x; }
 110
 111   // GC_n is permitted to be 0.  The C++ standard says nothing about what
 112   // the return value is when GC_n == 0.
 113   GC_Tp* allocate(size_type GC_n, const void* = 0) {
 114     GC_type_traits<GC_Tp> traits;
 115     return static_cast<GC_Tp *>
 116             (GC_selective_alloc(GC_n * sizeof(GC_Tp),
 117                                 traits.GC_is_ptr_free));
 118   }
 119
 120   // __p is not permitted to be a null pointer.
 121   void deallocate(pointer __p, size_type GC_n)
 122     { GC_FREE(__p); }
 123
 124   size_type max_size() const throw()
 125     { return size_t(-1) / sizeof(GC_Tp); }
 126
 127   void construct(pointer __p, const GC_Tp& __val) { new(__p) GC_Tp(__val); }
 128   void destroy(pointer __p) { __p->~GC_Tp(); }
 129 };
 130
 131 template<>
 132 class gc_allocator<void> {
 133   typedef size_t      size_type;
 134   typedef ptrdiff_t   difference_type;
 135   typedef void*       pointer;
 136   typedef const void* const_pointer;
 137   typedef void        value_type;
 138
 139   template <class GC_Tp1> struct rebind {
 140     typedef gc_allocator<GC_Tp1> other;
 141   };
 142 };
 143
 144
 145 template <class GC_T1, class GC_T2>
 146 inline bool operator==(const gc_allocator<GC_T1>&, const gc_allocator<GC_T2>&)
 147 {
 148   return true;
 149 }
 150
 151 template <class GC_T1, class GC_T2>
 152 inline bool operator!=(const gc_allocator<GC_T1>&, const gc_allocator<GC_T2>&)
 153 {
 154   return false;
 155 }
 156
 157 /*
 158  * And the public traceable_allocator class.
 159  */
 160
 161 // Note that we currently don't specialize the pointer-free case, since a
 162 // pointer-free traceable container doesn't make that much sense,
 163 // though it could become an issue due to abstraction boundaries.
 164 template <class GC_Tp>
 165 class traceable_allocator {
 166 public:
 167   typedef size_t     size_type;
 168   typedef ptrdiff_t  difference_type;
 169   typedef GC_Tp*       pointer;
 170   typedef const GC_Tp* const_pointer;
 171   typedef GC_Tp&       reference;
 172   typedef const GC_Tp& const_reference;
 173   typedef GC_Tp        value_type;
 174
 175   template <class GC_Tp1> struct rebind {
 176     typedef traceable_allocator<GC_Tp1> other;
 177   };
 178
 179   traceable_allocator() throw() {}
 180 # ifndef _MSC_VER
 181     traceable_allocator(const traceable_allocator&) throw() {}
 182 # endif
 183   template <class GC_Tp1> traceable_allocator
 184           (const traceable_allocator<GC_Tp1>&) throw() {}
 185   ~traceable_allocator() throw() {}
 186
 187   pointer address(reference GC_x) const { return &GC_x; }
 188   const_pointer address(const_reference GC_x) const { return &GC_x; }
 189
 190   // GC_n is permitted to be 0.  The C++ standard says nothing about what
 191   // the return value is when GC_n == 0.
 192   GC_Tp* allocate(size_type GC_n, const void* = 0) {
 193     return static_cast<GC_Tp*>(GC_MALLOC_UNCOLLECTABLE(GC_n * sizeof(GC_Tp)));
 194   }
 195
 196   // __p is not permitted to be a null pointer.
 197   void deallocate(pointer __p, size_type GC_n)
 198     { GC_FREE(__p); }
 199
 200   size_type max_size() const throw()
 201     { return size_t(-1) / sizeof(GC_Tp); }
 202
 203   void construct(pointer __p, const GC_Tp& __val) { new(__p) GC_Tp(__val); }
 204   void destroy(pointer __p) { __p->~GC_Tp(); }
 205 };
 206
 207 template<>
 208 class traceable_allocator<void> {
 209   typedef size_t      size_type;
 210   typedef ptrdiff_t   difference_type;
 211   typedef void*       pointer;
 212   typedef const void* const_pointer;
 213   typedef void        value_type;
 214
 215   template <class GC_Tp1> struct rebind {
 216     typedef traceable_allocator<GC_Tp1> other;
 217   };
 218 };
 219
 220
 221 template <class GC_T1, class GC_T2>
 222 inline bool operator==(const traceable_allocator<GC_T1>&, const traceable_allocator<GC_T2>&)
 223 {
 224   return true;
 225 }
 226
 227 template <class GC_T1, class GC_T2>
 228 inline bool operator!=(const traceable_allocator<GC_T1>&, const traceable_allocator<GC_T2>&)
 229 {
 230   return false;
 231 }
 232