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// -*- C++ -*-
#ifndef WIBBLE_SINGLETON_H
#define WIBBLE_SINGLETON_H
/*
* Degenerated container to hold a single value
*
* Copyright (C) 2006 Enrico Zini <enrico@debian.org>
* (C) 2013 Petr Rockai <me@mornfall.net>
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <cstddef>
#include <iterator>
namespace wibble {
template<typename T>
class Singleton
{
protected:
T value;
public:
typedef T value_type;
class const_iterator : public std::iterator<std::forward_iterator_tag, const T, void, const T*, const T&>
{
const T* value;
protected:
const_iterator(const T* value) : value(value) {}
public:
const_iterator() : value(0) {}
const T& operator*() const { return *value; }
const T* operator->() const { return value; }
const_iterator& operator++() { value = 0; return *this; }
bool operator==(const const_iterator& iter) const { return value == iter.value; }
bool operator!=(const const_iterator& iter) const { return value != iter.value; }
friend class Singleton<T>;
};
class iterator : public std::iterator<std::forward_iterator_tag, T, void, T*, T&>
{
T* value;
protected:
iterator(T* value) : value(value) {}
public:
iterator() : value(0) {}
T& operator*() { return *value; }
T* operator->() { return value; }
iterator& operator++() { value = 0; return *this; }
bool operator==(const iterator& iter) const { return value == iter.value; }
bool operator!=(const iterator& iter) const { return value != iter.value; }
friend class Singleton<T>;
};
explicit Singleton(const T& value) : value(value) {}
Singleton() : value() {}
bool empty() const { return false; }
size_t size() const { return 1; }
iterator begin() { return iterator(&value); }
iterator end() { return iterator(); }
const_iterator begin() const { return const_iterator(&value); }
const_iterator end() const { return const_iterator(); }
iterator insert( iterator /* position */, const value_type &v )
{
value = v;
return begin();
}
iterator insert( const value_type &v ) {
value = v;
return begin();
}
};
template<typename T>
Singleton<T> singleton(const T& value)
{
return Singleton<T>(value);
}
}
// vim:set ts=4 sw=4:
#endif
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