src/base/RefCount.h

   1 /*
   2  * DEBUG: section --    Refcount allocator
   3  * AUTHOR:  Robert Collins
   4  *
   5  * SQUID Web Proxy Cache          http://www.squid-cache.org/
   6  * ----------------------------------------------------------
   7  *
   8  *  Squid is the result of efforts by numerous individuals from
   9  *  the Internet community; see the CONTRIBUTORS file for full
  10  *  details.   Many organizations have provided support for Squid's
  11  *  development; see the SPONSORS file for full details.  Squid is
  12  *  Copyrighted (C) 2001 by the Regents of the University of
  13  *  California; see the COPYRIGHT file for full details.  Squid
  14  *  incorporates software developed and/or copyrighted by other
  15  *  sources; see the CREDITS file for full details.
  16  *
  17  *  This program is free software; you can redistribute it and/or modify
  18  *  it under the terms of the GNU General Public License as published by
  19  *  the Free Software Foundation; either version 2 of the License, or
  20  *  (at your option) any later version.
  21  *
  22  *  This program is distributed in the hope that it will be useful,
  23  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  24  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  25  *  GNU General Public License for more details.
  26  *
  27  *  You should have received a copy of the GNU General Public License
  28  *  along with this program; if not, write to the Free Software
  29  *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111, USA.
  30  *
  31  */
  32
  33 #ifndef SQUID_REFCOUNT_H_
  34 #define SQUID_REFCOUNT_H_
  35
  36 // reference counting requires the Lock API on base classes
  37 #include "base/Lock.h"
  38
  39 #include <iostream>
  40
  41 /**
  42  * Template for Reference Counting pointers.
  43  *
  44  * Objects of type 'C' must inherit from 'RefCountable' in base/Lock.h
  45  * which provides the locking interface used by reference counting.
  46  */
  47 template <class C>
  48 class RefCount
  49 {
  50
  51 public:
  52     RefCount () : p_ (NULL) {}
  53
  54     RefCount (C const *p) : p_(p) { reference (*this); }
  55
  56     ~RefCount() {
  57         dereference();
  58     }
  59
  60     RefCount (const RefCount &p) : p_(p.p_) {
  61         reference (p);
  62     }
  63
  64     RefCount& operator = (const RefCount& p) {
  65         // DO NOT CHANGE THE ORDER HERE!!!
  66         // This preserves semantics on self assignment
  67         C const *newP_ = p.p_;
  68         reference(p);
  69         dereference(newP_);
  70         return *this;
  71     }
  72
  73     bool operator !() const { return !p_; }
  74
  75     C * operator-> () const {return const_cast<C *>(p_); }
  76
  77     C & operator * () const {return *const_cast<C *>(p_); }
  78
  79     C const * getRaw() const {return p_; }
  80
  81     C * getRaw() {return const_cast<C *>(p_); }
  82
  83     bool operator == (const RefCount& p) const {
  84         return p.p_ == p_;
  85     }
  86
  87     bool operator != (const RefCount &p) const {
  88         return p.p_ != p_;
  89     }
  90
  91 private:
  92     void dereference(C const *newP = NULL) {
  93         /* Setting p_ first is important:
  94         * we may be freed ourselves as a result of
  95         * delete p_;
  96         */
  97         C const (*tempP_) (p_);
  98         p_ = newP;
  99
 100         if (tempP_ && tempP_->unlock() == 0)
 101             delete tempP_;
 102     }
 103
 104     void reference (const RefCount& p) {
 105         if (p.p_)
 106             p.p_->lock();
 107     }
 108
 109     C const *p_;
 110
 111 };
 112
 113 template <class C>
 114 inline std::ostream &operator <<(std::ostream &os, const RefCount<C> &p)
 115 {
 116     if (p != NULL)
 117         return os << p.getRaw() << '*' << p->LockCount();
 118     else
 119         return os << "NULL";
 120 }
 121
 122 #endif /* SQUID_REFCOUNT_H_ */