src/base/RefCount.h

   1 /*
   2  * Copyright (C) 1996-2016 The Squid Software Foundation and contributors
   3  *
   4  * Squid software is distributed under GPLv2+ license and includes
   5  * contributions from numerous individuals and organizations.
   6  * Please see the COPYING and CONTRIBUTORS files for details.
   7  */
   8
   9 /* DEBUG: section --    Refcount allocator */
  10
  11 #ifndef SQUID_REFCOUNT_H_
  12 #define SQUID_REFCOUNT_H_
  13
  14 // reference counting requires the Lock API on base classes
  15 #include "base/Lock.h"
  16
  17 #include <iostream>
  18
  19 /**
  20  * Template for Reference Counting pointers.
  21  *
  22  * Objects of type 'C' must inherit from 'RefCountable' in base/Lock.h
  23  * which provides the locking interface used by reference counting.
  24  */
  25 template <class C>
  26 class RefCount
  27 {
  28
  29 public:
  30     RefCount () : p_ (NULL) {}
  31
  32     RefCount (C const *p) : p_(p) { reference (*this); }
  33
  34     ~RefCount() {
  35         dereference();
  36     }
  37
  38     RefCount (const RefCount &p) : p_(p.p_) {
  39         reference (p);
  40     }
  41
  42 #if __cplusplus >= 201103L
  43     RefCount (RefCount &&p) : p_(std::move(p.p_)) {
  44         p.p_=NULL;
  45     }
  46 #endif
  47
  48     RefCount& operator = (const RefCount& p) {
  49         // DO NOT CHANGE THE ORDER HERE!!!
  50         // This preserves semantics on self assignment
  51         C const *newP_ = p.p_;
  52         reference(p);
  53         dereference(newP_);
  54         return *this;
  55     }
  56
  57 #if __cplusplus >= 201103L
  58     RefCount& operator = (RefCount&& p) {
  59         if (this != &p) {
  60             dereference(p.p_);
  61             p.p_ = NULL;
  62         }
  63         return *this;
  64     }
  65 #endif
  66
  67     explicit operator bool() const { return p_; }
  68
  69     bool operator !() const { return !p_; }
  70
  71     C * operator-> () const {return const_cast<C *>(p_); }
  72
  73     C & operator * () const {return *const_cast<C *>(p_); }
  74
  75     C const * getRaw() const {return p_; }
  76
  77     C * getRaw() {return const_cast<C *>(p_); }
  78
  79     bool operator == (const RefCount& p) const {
  80         return p.p_ == p_;
  81     }
  82
  83     bool operator != (const RefCount &p) const {
  84         return p.p_ != p_;
  85     }
  86
  87 private:
  88     void dereference(C const *newP = NULL) {
  89         /* Setting p_ first is important:
  90         * we may be freed ourselves as a result of
  91         * delete p_;
  92         */
  93         C const (*tempP_) (p_);
  94         p_ = newP;
  95
  96         if (tempP_ && tempP_->unlock() == 0)
  97             delete tempP_;
  98     }
  99
 100     void reference (const RefCount& p) {
 101         if (p.p_)
 102             p.p_->lock();
 103     }
 104
 105     C const *p_;
 106
 107 };
 108
 109 template <class C>
 110 inline std::ostream &operator <<(std::ostream &os, const RefCount<C> &p)
 111 {
 112     if (p != NULL)
 113         return os << p.getRaw() << '*' << p->LockCount();
 114     else
 115         return os << "NULL";
 116 }
 117
 118 #endif /* SQUID_REFCOUNT_H_ */
 119