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 #if HAVE_IOSTREAM
  40 #include <iostream>
  41 #endif
  42
  43 /**
  44  * Template for Reference Counting pointers.
  45  *
  46  * Objects of type 'C' must inherit from 'RefCountable' in base/Lock.h
  47  * which provides the locking interface used by reference counting.
  48  */
  49 template <class C>
  50 class RefCount
  51 {
  52
  53 public:
  54     RefCount () : p_ (NULL) {}
  55
  56     RefCount (C const *p) : p_(p) { reference (*this); }
  57
  58     ~RefCount() {
  59         dereference();
  60     }
  61
  62     RefCount (const RefCount &p) : p_(p.p_) {
  63         reference (p);
  64     }
  65
  66     RefCount& operator = (const RefCount& p) {
  67         // DO NOT CHANGE THE ORDER HERE!!!
  68         // This preserves semantics on self assignment
  69         C const *newP_ = p.p_;
  70         reference(p);
  71         dereference(newP_);
  72         return *this;
  73     }
  74
  75     bool operator !() const { return !p_; }
  76
  77     C * operator-> () const {return const_cast<C *>(p_); }
  78
  79     C & operator * () const {return *const_cast<C *>(p_); }
  80
  81     C const * getRaw() const {return p_; }
  82
  83     C * getRaw() {return const_cast<C *>(p_); }
  84
  85     bool operator == (const RefCount& p) const {
  86         return p.p_ == p_;
  87     }
  88
  89     bool operator != (const RefCount &p) const {
  90         return p.p_ != p_;
  91     }
  92
  93 private:
  94     void dereference(C const *newP = NULL) {
  95         /* Setting p_ first is important:
  96         * we may be freed ourselves as a result of
  97         * delete p_;
  98         */
  99         C const (*tempP_) (p_);
 100         p_ = newP;
 101
 102         if (tempP_ && tempP_->unlock() == 0)
 103             delete tempP_;
 104     }
 105
 106     void reference (const RefCount& p) {
 107         if (p.p_)
 108             p.p_->lock();
 109     }
 110
 111     C const *p_;
 112
 113 };
 114
 115 template <class C>
 116 inline std::ostream &operator <<(std::ostream &os, const RefCount<C> &p)
 117 {
 118     if (p != NULL)
 119         return os << p.getRaw() << '*' << p->LockCount();
 120     else
 121         return os << "NULL";
 122 }
 123
 124 #endif /* SQUID_REFCOUNT_H_ */