00001 // -*- C++ -*- 00002 #ifndef WIBBLE_SINGLETON_H 00003 #define WIBBLE_SINGLETON_H 00004 00005 /* 00006 * Degenerated container to hold a single value 00007 * 00008 * Copyright (C) 2006 Enrico Zini <enrico@debian.org> 00009 * 00010 * This library is free software; you can redistribute it and/or 00011 * modify it under the terms of the GNU Lesser General Public 00012 * License as published by the Free Software Foundation; either 00013 * version 2.1 of the License, or (at your option) any later version. 00014 * 00015 * This library is distributed in the hope that it will be useful, 00016 * but WITHOUT ANY WARRANTY; without even the implied warranty of 00017 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 00018 * Lesser General Public License for more details. 00019 * 00020 * You should have received a copy of the GNU Lesser General Public 00021 * License along with this library; if not, write to the Free Software 00022 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 00023 */ 00024 00025 #include <cstddef> 00026 #include <iterator> 00027 00028 namespace wibble { 00029 00030 template<typename T> 00031 class Singleton 00032 { 00033 protected: 00034 T value; 00035 00036 public: 00037 typedef T value_type; 00038 00039 class const_iterator : public std::iterator<std::forward_iterator_tag, const T, void, const T*, const T&> 00040 { 00041 const T* value; 00042 00043 protected: 00044 const_iterator(const T* value) : value(value) {} 00045 00046 public: 00047 const_iterator() : value(0) {} 00048 00049 const T& operator*() const { return *value; } 00050 const T* operator->() const { return value; } 00051 const_iterator& operator++() { value = 0; return *this; } 00052 bool operator==(const const_iterator& iter) const { return value == iter.value; } 00053 bool operator!=(const const_iterator& iter) const { return value != iter.value; } 00054 00055 friend class Singleton<T>; 00056 }; 00057 00058 class iterator : public std::iterator<std::forward_iterator_tag, T, void, T*, T&> 00059 { 00060 T* value; 00061 00062 protected: 00063 iterator(T* value) : value(value) {} 00064 00065 public: 00066 iterator() : value(0) {} 00067 00068 T& operator*() { return *value; } 00069 T* operator->() { return value; } 00070 iterator& operator++() { value = 0; return *this; } 00071 bool operator==(const iterator& iter) const { return value == iter.value; } 00072 bool operator!=(const iterator& iter) const { return value != iter.value; } 00073 00074 friend class Singleton<T>; 00075 }; 00076 00077 explicit Singleton(const T& value) : value(value) {} 00078 00079 bool empty() const { return false; } 00080 size_t size() const { return 1; } 00081 00082 iterator begin() { return iterator(&value); } 00083 iterator end() { return iterator(); } 00084 const_iterator begin() const { return const_iterator(&value); } 00085 const_iterator end() const { return const_iterator(); } 00086 }; 00087 00088 template<typename T> 00089 Singleton<T> singleton(const T& value) 00090 { 00091 return Singleton<T>(value); 00092 } 00093 00094 } 00095 00096 // vim:set ts=4 sw=4: 00097 #endif