src/base/RefCount.h

   1 /*
   2  * Copyright (C) 1996-2015 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     RefCount (RefCount &&p) : p_(std::move(p.p_)) {
  43         p.p_=NULL;
  44     }
  45
  46     RefCount& operator = (const RefCount& p) {
  47         // DO NOT CHANGE THE ORDER HERE!!!
  48         // This preserves semantics on self assignment
  49         C const *newP_ = p.p_;
  50         reference(p);
  51         dereference(newP_);
  52         return *this;
  53     }
  54
  55     RefCount& operator = (RefCount&& p) {
  56         if (this != &p) {
  57             dereference(p.p_);
  58             p.p_ = NULL;
  59         }
  60         return *this;
  61     }
  62
  63     bool operator !() const { return !p_; }
  64
  65     C * operator-> () const {return const_cast<C *>(p_); }
  66
  67     C & operator * () const {return *const_cast<C *>(p_); }
  68
  69     C const * getRaw() const {return p_; }
  70
  71     C * getRaw() {return const_cast<C *>(p_); }
  72
  73     bool operator == (const RefCount& p) const {
  74         return p.p_ == p_;
  75     }
  76
  77     bool operator != (const RefCount &p) const {
  78         return p.p_ != p_;
  79     }
  80
  81 private:
  82     void dereference(C const *newP = NULL) {
  83         /* Setting p_ first is important:
  84         * we may be freed ourselves as a result of
  85         * delete p_;
  86         */
  87         C const (*tempP_) (p_);
  88         p_ = newP;
  89
  90         if (tempP_ && tempP_->unlock() == 0)
  91             delete tempP_;
  92     }
  93
  94     void reference (const RefCount& p) {
  95         if (p.p_)
  96             p.p_->lock();
  97     }
  98
  99     C const *p_;
 100
 101 };
 102
 103 template <class C>
 104 inline std::ostream &operator <<(std::ostream &os, const RefCount<C> &p)
 105 {
 106     if (p != NULL)
 107         return os << p.getRaw() << '*' << p->LockCount();
 108     else
 109         return os << "NULL";
 110 }
 111
 112 #endif /* SQUID_REFCOUNT_H_ */
 113