Ticket #9058: with_lock_guard.hpp

// (C) Copyright 2013 Ruslan Baratov
//
// 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)

//  See www.boost.org/libs/thread for documentation.

#ifndef BOOST_THREAD_WITH_LOCK_GUARD_HPP
#define BOOST_THREAD_WITH_LOCK_GUARD_HPP

#include <boost/thread/lock_guard.hpp>
#include <boost/utility/result_of.hpp>

namespace boost {

#if !defined(BOOST_NO_CXX11_VARIADIC_TEMPLATES)

/**
 * Utility to run functions in scope protected by mutex.
 *
 * Examples:
 *
 *     int func(int, int&);
 *     boost::mutex m;
 *     int a;
 *     int result = boost::with_scoped_lock(m, func, 1, boost::ref(a));
 *
 *     // using boost::bind
 *     int result = boost::with_scoped_lock(
 *         m, boost::bind(func, 2, boost::ref(a))
 *     );
 *
 *     // using lambda
 *     int a;
 *     int result = boost::with_scoped_lock(
 *         m,
 *         [&a](int x) {
 *           a = 3;
 *           return x + 4;
 *         },
 *         5
 *     );
 */
template <class Lockable, class Function, class... Args>
auto with_lock_guard(
    Lockable& m,
    BOOST_FWD_REF(Function) f,
    BOOST_FWD_REF(Args)... args
) -> decltype(f(boost::forward<Args>(args)...)) {
  boost::lock_guard<Lockable> lock(m);
  return f(boost::forward<Args>(args)...);
}

#else

// Workaround versions for compilers without c++11 support.
// (function arguments limit: 4, no lambda support)

template <class Lockable, class Func>
typename boost::result_of<Func()>::type with_lock_guard(
    Lockable& m,
    Func func
) {
  boost::lock_guard<Lockable> lock(m);
  return func();
}

template <class Lockable, class Func, class Arg>
typename boost::result_of<Func(Arg)>::type with_lock_guard(
    Lockable& m,
    Func func,
    Arg arg
) {
  boost::lock_guard<Lockable> lock(m);
  return func(arg);
}

template <class Lockable, class Func, class Arg1, class Arg2>
typename boost::result_of<Func(Arg1, Arg2)>::type with_lock_guard(
    Lockable& m,
    Func func,
    Arg1 arg1,
    Arg2 arg2
) {
  boost::lock_guard<Lockable> lock(m);
  return func(arg1, arg2);
}

template <class Lockable, class Func, class Arg1, class Arg2, class Arg3>
typename boost::result_of<Func(Arg1, Arg2, Arg3)>::type with_lock_guard(
    Lockable& m,
    Func func,
    Arg1 arg1,
    Arg2 arg2,
    Arg3 arg3
) {
  boost::lock_guard<Lockable> lock(m);
  return func(arg1, arg2, arg3);
}

template <
    class Lockable, class Func, class Arg1, class Arg2, class Arg3, class Arg4
>
typename boost::result_of<Func(Arg1, Arg2, Arg3, Arg4)>::type with_lock_guard(
    Lockable& m,
    Func func,
    Arg1 arg1,
    Arg2 arg2,
    Arg3 arg3,
    Arg4 arg4
) {
  boost::lock_guard<Lockable> lock(m);
  return func(arg1, arg2, arg3, arg4);
}

#endif // BOOST_NO_CXX11_VARIADIC_TEMPLATES

} // namespace boost

#endif // BOOST_THREAD_WITH_LOCK_GUARD_HPP