/libs/headers/gc/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#ifndef GC_ALLOCATOR_H
 39
 40#define GC_ALLOCATOR_H
 41
 42#include "gc.h"
 43#include <new> // for placement new
 44
 45#if defined(__GNUC__)
 46#  define GC_ATTR_UNUSED __attribute__((unused))
 47#else
 48#  define GC_ATTR_UNUSED
 49#endif
 50
 51/* First some helpers to allow us to dispatch on whether or not a type
 52 * is known to be pointerfree.
 53 * These are private, except that the client may invoke the
 54 * GC_DECLARE_PTRFREE macro.
 55 */
 56
 57struct GC_true_type {};
 58struct GC_false_type {};
 59
 60template <class GC_tp>
 61struct GC_type_traits {
 62  GC_false_type GC_is_ptr_free;
 63};
 64
 65# define GC_DECLARE_PTRFREE(T) \
 66template<> struct GC_type_traits<T> { GC_true_type GC_is_ptr_free; }
 67
 68GC_DECLARE_PTRFREE(char);
 69GC_DECLARE_PTRFREE(signed char);
 70GC_DECLARE_PTRFREE(unsigned char);
 71GC_DECLARE_PTRFREE(signed short);
 72GC_DECLARE_PTRFREE(unsigned short);
 73GC_DECLARE_PTRFREE(signed int);
 74GC_DECLARE_PTRFREE(unsigned int);
 75GC_DECLARE_PTRFREE(signed long);
 76GC_DECLARE_PTRFREE(unsigned long);
 77GC_DECLARE_PTRFREE(float);
 78GC_DECLARE_PTRFREE(double);
 79GC_DECLARE_PTRFREE(long double);
 80/* The client may want to add others.	*/
 81
 82// In the following GC_Tp is GC_true_type iff we are allocating a
 83// pointerfree object.
 84template <class GC_Tp>
 85inline void * GC_selective_alloc(size_t n, GC_Tp) {
 86    return GC_MALLOC(n);
 87}
 88
 89template <>
 90inline void * GC_selective_alloc<GC_true_type>(size_t n, GC_true_type) {
 91    return GC_MALLOC_ATOMIC(n);
 92}
 93
 94/* Now the public gc_allocator<T> class:
 95 */
 96template <class GC_Tp>
 97class gc_allocator {
 98public:
 99  typedef size_t     size_type;
100  typedef ptrdiff_t  difference_type;
101  typedef GC_Tp*       pointer;
102  typedef const GC_Tp* const_pointer;
103  typedef GC_Tp&       reference;
104  typedef const GC_Tp& const_reference;
105  typedef GC_Tp        value_type;
106
107  template <class GC_Tp1> struct rebind {
108    typedef gc_allocator<GC_Tp1> other;
109  };
110
111  gc_allocator()  {}
112    gc_allocator(const gc_allocator&) throw() {}
113# if !(GC_NO_MEMBER_TEMPLATES || 0 < _MSC_VER && _MSC_VER <= 1200)
114  // MSVC++ 6.0 do not support member templates
115  template <class GC_Tp1> gc_allocator(const gc_allocator<GC_Tp1>&) throw() {}
116# endif
117  ~gc_allocator() throw() {}
118
119  pointer address(reference GC_x) const { return &GC_x; }
120  const_pointer address(const_reference GC_x) const { return &GC_x; }
121
122  // GC_n is permitted to be 0.  The C++ standard says nothing about what
123  // the return value is when GC_n == 0.
124  GC_Tp* allocate(size_type GC_n, const void* = 0) {
125    GC_type_traits<GC_Tp> traits;
126    return static_cast<GC_Tp *>
127	    (GC_selective_alloc(GC_n * sizeof(GC_Tp),
128			        traits.GC_is_ptr_free));
129  }
130
131  // __p is not permitted to be a null pointer.
132  void deallocate(pointer __p, size_type GC_ATTR_UNUSED GC_n)
133    { GC_FREE(__p); }
134
135  size_type max_size() const throw()
136    { return size_t(-1) / sizeof(GC_Tp); }
137
138  void construct(pointer __p, const GC_Tp& __val) { new(__p) GC_Tp(__val); }
139  void destroy(pointer __p) { __p->~GC_Tp(); }
140};
141
142template<>
143class gc_allocator<void> {
144  typedef size_t      size_type;
145  typedef ptrdiff_t   difference_type;
146  typedef void*       pointer;
147  typedef const void* const_pointer;
148  typedef void        value_type;
149
150  template <class GC_Tp1> struct rebind {
151    typedef gc_allocator<GC_Tp1> other;
152  };
153};
154
155
156template <class GC_T1, class GC_T2>
157inline bool operator==(const gc_allocator<GC_T1>&, const gc_allocator<GC_T2>&)
158{
159  return true;
160}
161
162template <class GC_T1, class GC_T2>
163inline bool operator!=(const gc_allocator<GC_T1>&, const gc_allocator<GC_T2>&)
164{
165  return false;
166}
167
168/*
169 * And the public traceable_allocator class.
170 */
171
172// Note that we currently don't specialize the pointer-free case, since a
173// pointer-free traceable container doesn't make that much sense,
174// though it could become an issue due to abstraction boundaries.
175template <class GC_Tp>
176class traceable_allocator {
177public:
178  typedef size_t     size_type;
179  typedef ptrdiff_t  difference_type;
180  typedef GC_Tp*       pointer;
181  typedef const GC_Tp* const_pointer;
182  typedef GC_Tp&       reference;
183  typedef const GC_Tp& const_reference;
184  typedef GC_Tp        value_type;
185
186  template <class GC_Tp1> struct rebind {
187    typedef traceable_allocator<GC_Tp1> other;
188  };
189
190  traceable_allocator() throw() {}
191    traceable_allocator(const traceable_allocator&) throw() {}
192# if !(GC_NO_MEMBER_TEMPLATES || 0 < _MSC_VER && _MSC_VER <= 1200)
193  // MSVC++ 6.0 do not support member templates
194  template <class GC_Tp1> traceable_allocator
195	  (const traceable_allocator<GC_Tp1>&) throw() {}
196# endif
197  ~traceable_allocator() throw() {}
198
199  pointer address(reference GC_x) const { return &GC_x; }
200  const_pointer address(const_reference GC_x) const { return &GC_x; }
201
202  // GC_n is permitted to be 0.  The C++ standard says nothing about what
203  // the return value is when GC_n == 0.
204  GC_Tp* allocate(size_type GC_n, const void* = 0) {
205    return static_cast<GC_Tp*>(GC_MALLOC_UNCOLLECTABLE(GC_n * sizeof(GC_Tp)));
206  }
207
208  // __p is not permitted to be a null pointer.
209  void deallocate(pointer __p, size_type GC_ATTR_UNUSED GC_n)
210    { GC_FREE(__p); }
211
212  size_type max_size() const throw()
213    { return size_t(-1) / sizeof(GC_Tp); }
214
215  void construct(pointer __p, const GC_Tp& __val) { new(__p) GC_Tp(__val); }
216  void destroy(pointer __p) { __p->~GC_Tp(); }
217};
218
219template<>
220class traceable_allocator<void> {
221  typedef size_t      size_type;
222  typedef ptrdiff_t   difference_type;
223  typedef void*       pointer;
224  typedef const void* const_pointer;
225  typedef void        value_type;
226
227  template <class GC_Tp1> struct rebind {
228    typedef traceable_allocator<GC_Tp1> other;
229  };
230};
231
232
233template <class GC_T1, class GC_T2>
234inline bool operator==(const traceable_allocator<GC_T1>&, const traceable_allocator<GC_T2>&)
235{
236  return true;
237}
238
239template <class GC_T1, class GC_T2>
240inline bool operator!=(const traceable_allocator<GC_T1>&, const traceable_allocator<GC_T2>&)
241{
242  return false;
243}
244
245#endif /* GC_ALLOCATOR_H */