include/salhelper/simplereferenceobject.hxx

   1 /* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
   2 /*
   3  * This file is part of the LibreOffice project.
   4  *
   5  * This Source Code Form is subject to the terms of the Mozilla Public
   6  * License, v. 2.0. If a copy of the MPL was not distributed with this
   7  * file, You can obtain one at http://mozilla.org/MPL/2.0/.
   8  *
   9  * This file incorporates work covered by the following license notice:
  10  *
  11  *   Licensed to the Apache Software Foundation (ASF) under one or more
  12  *   contributor license agreements. See the NOTICE file distributed
  13  *   with this work for additional information regarding copyright
  14  *   ownership. The ASF licenses this file to you under the Apache
  15  *   License, Version 2.0 (the "License"); you may not use this file
  16  *   except in compliance with the License. You may obtain a copy of
  17  *   the License at http://www.apache.org/licenses/LICENSE-2.0 .
  18  */
  19
  20 /*
  21  * This file is part of LibreOffice published API.
  22  */
  23
  24 #ifndef INCLUDED_SALHELPER_SIMPLEREFERENCEOBJECT_HXX
  25 #define INCLUDED_SALHELPER_SIMPLEREFERENCEOBJECT_HXX
  26
  27 #include "osl/interlck.h"
  28 #include "salhelper/salhelperdllapi.h"
  29
  30 #include <cstddef>
  31 #include <new>
  32
  33 namespace salhelper {
  34
  35 /** A simple base implementation for reference-counted objects.
  36
  37     Classes that want to implement a reference-counting mechanism based on the
  38     acquire()/release() interface should derive from this class.
  39
  40     The reason to have class local operators new and delete here is technical.
  41     Imagine a class D derived from SimpleReferenceObject, but implemented in
  42     another shared library that happens to use different global operators new
  43     and delete from those used in this shared library (which, sadly, seems to
  44     be possible with shared libraries).  Now, without the class local
  45     operators new and delete here, a code sequence like "new D" would use the
  46     global operator new as found in the other shared library, while the code
  47     sequence "delete this" in release() would use the global operator delete
  48     as found in this shared library---and these two operators would not be
  49     guaranteed to match.
  50
  51     There are no overloaded operators new and delete for placement new here,
  52     because it is felt that the concept of placement new does not work well
  53     with the concept of reference-counted objects; so it seems best to simply
  54     leave those operators out.
  55
  56     The same problem as with operators new and delete would also be there with
  57     operators new[] and delete[].  But since arrays of reference-counted
  58     objects are of no use, anyway, it seems best to simply
  59     define operators new[] and delete[] as deleted.
  60  */
  61 class SALHELPER_DLLPUBLIC SimpleReferenceObject
  62 {
  63 public:
  64     SimpleReferenceObject(): m_nCount(0) {}
  65
  66     /** @attention
  67         The results are undefined if, for any individual instance of
  68         SimpleReferenceObject, the total number of calls to acquire() exceeds
  69         the total number of calls to release() by a platform dependent amount
  70         (which, hopefully, is quite large).
  71      */
  72     void acquire()
  73     { osl_atomic_increment(&m_nCount); }
  74
  75     void release()
  76     { if (osl_atomic_decrement(&m_nCount) == 0) delete this; }
  77
  78     /** see general class documentation
  79      */
  80     static void * operator new(std::size_t nSize);
  81
  82     /** see general class documentation
  83      */
  84     static void * operator new(std::size_t nSize,
  85                                std::nothrow_t const & rNothrow);
  86
  87     /** see general class documentation
  88      */
  89     static void operator delete(void * pPtr);
  90
  91     /** see general class documentation
  92      */
  93     static void operator delete(void * pPtr, std::nothrow_t const & rNothrow);
  94
  95 protected:
  96     virtual ~SimpleReferenceObject() COVERITY_NOEXCEPT_FALSE;
  97
  98     oslInterlockedCount m_nCount;
  99
 100 private:
 101     /** not implemented
 102      */
 103     SimpleReferenceObject(SimpleReferenceObject &) SAL_DELETED_FUNCTION;
 104
 105     /** not implemented
 106      */
 107     void operator =(SimpleReferenceObject) SAL_DELETED_FUNCTION;
 108
 109     /** see general class documentation
 110      */
 111     static void * operator new[](std::size_t) SAL_DELETED_FUNCTION;
 112
 113     /** see general class documentation
 114      */
 115     static void operator delete[](void * pPtr) SAL_DELETED_FUNCTION;
 116 };
 117
 118 }
 119
 120 #endif // INCLUDED_SALHELPER_SIMPLEREFERENCEOBJECT_HXX
 121
 122 /* vim:set shiftwidth=4 softtabstop=4 expandtab: */