src/gallium/state_trackers/clover/util/pointer.hpp

   1 //
   2 // Copyright 2013 Francisco Jerez
   3 //
   4 // Permission is hereby granted, free of charge, to any person obtaining a
   5 // copy of this software and associated documentation files (the "Software"),
   6 // to deal in the Software without restriction, including without limitation
   7 // the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8 // and/or sell copies of the Software, and to permit persons to whom the
   9 // Software is furnished to do so, subject to the following conditions:
  10 //
  11 // The above copyright notice and this permission notice shall be included in
  12 // all copies or substantial portions of the Software.
  13 //
  14 // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  15 // IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  16 // FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  17 // THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
  18 // OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
  19 // ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
  20 // OTHER DEALINGS IN THE SOFTWARE.
  21 //
  22
  23 #ifndef CLOVER_UTIL_POINTER_HPP
  24 #define CLOVER_UTIL_POINTER_HPP
  25
  26 #include <atomic>
  27
  28 namespace clover {
  29    ///
  30    /// Base class for objects that support reference counting.
  31    ///
  32    class ref_counter {
  33    public:
  34       ref_counter() : _ref_count(1) {}
  35
  36       unsigned
  37       ref_count() {
  38          return _ref_count;
  39       }
  40
  41       void
  42       retain() {
  43          _ref_count++;
  44       }
  45
  46       bool
  47       release() {
  48          return (--_ref_count) == 0;
  49       }
  50
  51    private:
  52       std::atomic<unsigned> _ref_count;
  53    };
  54
  55    ///
  56    /// Intrusive smart pointer for objects that implement the
  57    /// clover::ref_counter interface.
  58    ///
  59    template<typename T>
  60    class ref_ptr {
  61    public:
  62       ref_ptr(T *q = NULL) : p(NULL) {
  63          reset(q);
  64       }
  65
  66       ref_ptr(const ref_ptr<T> &ref) : p(NULL) {
  67          reset(ref.p);
  68       }
  69
  70       ~ref_ptr() {
  71          reset(NULL);
  72       }
  73
  74       void
  75       reset(T *q = NULL) {
  76          if (q)
  77             q->retain();
  78          if (p && p->release())
  79             delete p;
  80          p = q;
  81       }
  82
  83       ref_ptr &
  84       operator=(const ref_ptr &ref) {
  85          reset(ref.p);
  86          return *this;
  87       }
  88
  89       T &
  90       operator*() const {
  91          return *p;
  92       }
  93
  94       T *
  95       operator->() const {
  96          return p;
  97       }
  98
  99       explicit operator bool() const {
 100          return p;
 101       }
 102
 103    private:
 104       T *p;
 105    };
 106
 107    ///
 108    /// Transfer the caller's ownership of a reference-counted object
 109    /// to a clover::ref_ptr smart pointer.
 110    ///
 111    template<typename T>
 112    inline ref_ptr<T>
 113    transfer(T *p) {
 114       ref_ptr<T> ref { p };
 115       p->release();
 116       return ref;
 117    }
 118
 119    ///
 120    /// Class that implements the usual pointer interface but in fact
 121    /// contains the object it seems to be pointing to.
 122    ///
 123    template<typename T>
 124    class pseudo_ptr {
 125    public:
 126       pseudo_ptr(T x) : x(x) {
 127       }
 128
 129       pseudo_ptr(const pseudo_ptr &p) : x(p.x) {
 130       }
 131
 132       pseudo_ptr &
 133       operator=(const pseudo_ptr &p) {
 134          x = p.x;
 135          return *this;
 136       }
 137
 138       T &
 139       operator*() {
 140          return x;
 141       }
 142
 143       T *
 144       operator->() {
 145          return &x;
 146       }
 147
 148       explicit operator bool() const {
 149          return true;
 150       }
 151
 152    private:
 153       T x;
 154    };
 155 }
 156
 157 #endif