copy_with_maping.cpp

template<class HostIterator, class DeviceIterator>
inline DeviceIterator copy(HostIterator first,
                           HostIterator last,
                           DeviceIterator result,
                           boost::compute::command_queue &queue)
{
...
    // map result buffer to host
    value_type *pointer = static_cast<value_type*>(
        queue.enqueue_map_buffer(
            result.get_buffer(),
            CL_MAP_WRITE,
            offset * sizeof(value_type),
            count * sizeof(value_type)
        )
    );

    // copy [first; last) to result buffer
    std::copy(first, last, pointer);

    // unmap result buffer
    boost::compute::event unmapEvent = queue.enqueue_unmap_buffer(
        result.get_buffer(),
        static_cast<void*>(pointer)
    );
    unmapEvent.wait();
...
}