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# shared_ptr.h

    00001 /*
    00002  *             Copyright (C) 2005 Maarten Keijzer
    00003  *
    00004  *          This program is free software; you can redistribute it and/or modify
    00005  *          it under the terms of version 2 of the GNU General Public License as
    00006  *          published by the Free Software Foundation.
    00007  *
    00008  *          This program is distributed in the hope that it will be useful,
    00009  *          but WITHOUT ANY WARRANTY; without even the implied warranty of
    00010  *          MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    00011  *          GNU General Public License for more details.
    00012  *
    00013  *          You should have received a copy of the GNU General Public License
    00014  *          along with this program; if not, write to the Free Software
    00015  *          Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
    00016  */
    00017
    00018 #ifndef _SHARED_PTR_H
    00019 #define _SHARED_PTR_H
    00020
    00021
    00022 template <class T> class weak_ptr;
    00023
    00024 template <class T>
    00025 class shared_ptr {
    00026     private:
    00027         T* ptr;
    00028         unsigned* count; //
    00029
    00030         /* special case, null pointer (nil-code) */
    00031         static unsigned* nil() { static unsigned nil_counter(1); return &nil_counter; }
    00032
    00033         void decref() { if (--(*count) == 0) { delete ptr; delete count; }}
    00034         void incref() { ++(*count); }
    00035
    00036         friend class weak_ptr<T>;
    00037
    00038     public:
    00039
    00040         shared_ptr() : ptr(0), count(nil()) { incref(); }
    00041         ~shared_ptr() { decref(); }
    00042
    00043         shared_ptr(const shared_ptr<T>& o) : ptr(o.ptr), count(o.count) { incref(); }
    00044         shared_ptr(T* p) : ptr(p), count(new unsigned(1)) {}
    00045         explicit shared_ptr(const weak_ptr<T>& w) : ptr(w.ptr), count(w.count) { incref(); }
    00046
    00047         shared_ptr<T>& operator=(const shared_ptr<T>& o) {
    00048             if (ptr == o.ptr) return *this;
    00049             decref();
    00050             ptr = o.ptr;
    00051             count = o.count;
    00052             incref();
    00053             return *this;
    00054         }
    00055
    00056         T* get() { return ptr; }
    00057         T* operator->() { return ptr; }
    00058         T& operator*()  { return *ptr; }
    00059
    00060         const T* get() const { return ptr; }
    00061         const T* operator->() const { return ptr; }
    00062         const T& operator*() const { return *ptr; }
    00063
    00064         bool operator==(const shared_ptr<T>& o) const { return ptr == o.ptr; }
    00065         bool operator!=(const shared_ptr<T>& o) const { return ptr != o.ptr; }
    00066         bool operator<(const shared_ptr<T>& o) const { return ptr < o.ptr; }
    00067
    00068         unsigned refcount() const { return *count; }
    00069 };
    00070
    00071 template <class T>
    00072 class weak_ptr {
    00073         T* ptr;
    00074         unsigned* count;
    00075
    00076         friend class shared_ptr<T>;
    00077
    00078     public:
    00079
    00080         weak_ptr() : ptr(0), count(shared_ptr<T>::nil()) {}
    00081         explicit weak_ptr( const shared_ptr<T>& s) : ptr(s.ptr), count(s.count) {}
    00082
    00083         shared_ptr<T> lock() const { return shared_ptr<T>(*this); }
    00084
    00085
    00086         T* get() { return ptr; }
    00087         T* operator->() { return ptr; }
    00088         T& operator*()  { return *ptr; }
    00089
    00090         const T* get() const { return ptr; }
    00091         const T* operator->() const { return ptr; }
    00092         const T& operator*() const { return *ptr; }
    00093
    00094         bool operator==(const shared_ptr<T>& o) const { return ptr == o.ptr; }
    00095         bool operator!=(const shared_ptr<T>& o) const { return ptr != o.ptr; }
    00096         bool operator<(const shared_ptr<T>& o) const { return ptr < o.ptr; }
    00097
    00098         unsigned refcount() const { return *count; }
    00099
    00100 };
    00101
    00102 #endif