#ifndef BOOST_WIN32_ONCE_HPP
#define BOOST_WIN32_ONCE_HPP

//  once.hpp
//
//  (C) Copyright 2005 Anthony Williams 
//
//  Distributed under 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)

#include <windows.h>
#include <string>
#include <sstream>
#include <limits.h>

namespace boost
{
    struct once_flag
    {
        HANDLE semaphore_handle;
        ~once_flag()
        {
            ::CloseHandle(semaphore_handle);
        }
    };

#define BOOST_ONCE_INIT {0}

    namespace detail
    {
        std::string create_unique_name(void* p,const char* tag)
        {
            std::ostringstream res;
            res<<"unique-"<<tag<<"-name-{C15730E2-145C-4c5e-B005-3BC753F42475}-"
               <<p<<"-"
               <<::GetCurrentProcessId();
            return res.str();
        }

        class semaphore_releaser
        {
            HANDLE semaphore;
            unsigned count_to_release;

        public:
            semaphore_releaser(HANDLE semaphore_,unsigned count_to_release_):
                semaphore(semaphore_),count_to_release(count_to_release_)
            {}
            ~semaphore_releaser()
            {
                ::ReleaseSemaphore(semaphore,count_to_release,NULL);
            }
        };
        
    }
    

    template<typename Function>
    void call_once(Function f,once_flag& flag)
    {
        std::string const once_semaphore_name=detail::create_unique_name(&flag,"once_init");

        LONG const max_semaphore_value=LONG_MAX;
        HANDLE const semaphore_handle(::CreateSemaphore(NULL,0,max_semaphore_value,once_semaphore_name.c_str()));
        if(!semaphore_handle)
        {
            abort();
        }
        if(::GetLastError()==ERROR_ALREADY_EXISTS)
        {
            ::WaitForSingleObject(semaphore_handle,INFINITE);
            detail::semaphore_releaser releaser(semaphore_handle,1);
            ::CloseHandle(semaphore_handle);
        }
        else
        {
            flag.semaphore_handle=semaphore_handle; // leave handle to be cleaned up when flag destroyed
            detail::semaphore_releaser releaser(semaphore_handle,max_semaphore_value);
            f();
        }
    }
}

#endif