boost/signals/detail/slot_call_iterator.hpp
// Boost.Signals library
// Copyright Douglas Gregor 2001-2004. Use, modification and
// distribution is subject to the Boost Software License, Version
// 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
// For more information, see http://www.boost.org
#ifndef BOOST_SIGNALS_SLOT_CALL_ITERATOR
#define BOOST_SIGNALS_SLOT_CALL_ITERATOR
#include <functional>
#include <boost/iterator/iterator_facade.hpp>
#include <boost/smart_ptr.hpp>
#include <boost/signals/detail/config.hpp>
#include <boost/signals/connection.hpp>
#ifdef BOOST_HAS_ABI_HEADERS
# include BOOST_ABI_PREFIX
#endif
namespace boost {
namespace BOOST_SIGNALS_NAMESPACE {
namespace detail {
// A cached return value from a slot
template<typename T>
struct cached_return_value {
cached_return_value(const T& t) : value(t) {}
T value;
};
// Generates a slot call iterator. Essentially, this is an iterator that:
// - skips over disconnected slots in the underlying list
// - calls the connected slots when dereferenced
// - caches the result of calling the slots
template<typename Function, typename Iterator>
class slot_call_iterator
: public iterator_facade<slot_call_iterator<Function, Iterator>,
typename Function::result_type,
single_pass_traversal_tag,
typename Function::result_type const&>
{
typedef iterator_facade<slot_call_iterator<Function, Iterator>,
typename Function::result_type,
single_pass_traversal_tag,
typename Function::result_type const&>
inherited;
typedef typename Function::result_type result_type;
friend class iterator_core_access;
public:
slot_call_iterator() {}
slot_call_iterator(Iterator iter_in, Iterator end_in, Function f)
: iter(iter_in), end(end_in), f(f), cache()
{
iter = std::find_if(iter, end, std::not1(is_disconnected()));
}
typename inherited::reference
dereference() const
{
if (!cache.get()) {
cache.reset(new cached_return_value<result_type>(f(*iter)));
}
return cache->value;
}
void increment()
{
iter = std::find_if(++iter, end, std::not1(is_disconnected()));
cache.reset();
}
bool equal(const slot_call_iterator& other) const
{
iter = std::find_if(iter, end, std::not1(is_disconnected()));
other.iter = std::find_if(other.iter, other.end,
std::not1(is_disconnected()));
return iter == other.iter;
}
private:
mutable Iterator iter;
Iterator end;
Function f;
mutable shared_ptr< cached_return_value<result_type> > cache;
};
} // end namespace detail
} // end namespace BOOST_SIGNALS_NAMESPACE
} // end namespace boost
#ifdef BOOST_HAS_ABI_HEADERS
# include BOOST_ABI_SUFFIX
#endif
#endif // BOOST_SIGNALS_SLOT_CALL_ITERATOR