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// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
// vim: ts=8 sw=2 smarttab
/*
* Ceph - scalable distributed file system
*
* Copyright (C) 2004-2006 Sage Weil <sage@newdream.net>
*
* This is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License version 2.1, as published by the Free Software
* Foundation. See file COPYING.
*
*/
#include <mutex>
#include <memory>
#include <optional>
#include <shared_mutex>
#include <type_traits>
#include <utility>
#include <boost/optional.hpp>
#include "include/ceph_assert.h" // I despise you. Not you the reader, I'm talking
// to the include file.
#ifndef CEPH_COMMON_CONVENIENCE_H
#define CEPH_COMMON_CONVENIENCE_H
namespace ceph {
// boost::optional is wonderful! Unfortunately it lacks a function for
// the thing you would most obviously want to do with it: apply a
// function to its contents.
// There are two obvious candidates. The first is a function that
// takes a function and an optional value and returns an optional
// value, either holding the return value of the function or holding
// nothing.
//
// I'd considered making more overloads for mutable lvalue
// references, but those are going a bit beyond likely use cases.
//
template<typename T, typename F>
auto maybe_do(const boost::optional<T>& t, F&& f) ->
boost::optional<std::result_of_t<F(const std::decay_t<T>)>>
{
if (t)
return { std::forward<F>(f)(*t) };
else
return boost::none;
}
// The other obvious function takes an optional but returns an
// ‘unwrapped’ value, either the result of evaluating the function or
// a provided alternate value.
//
template<typename T, typename F, typename U>
auto maybe_do_or(const boost::optional<T>& t, F&& f, U&& u) ->
std::result_of_t<F(const std::decay_t<T>)>
{
static_assert(std::is_convertible_v<U, std::result_of_t<F(T)>>,
"Alternate value must be convertible to function return type.");
if (t)
return std::forward<F>(f)(*t);
else
return std::forward<U>(u);
}
// Same thing but for std::optional
template<typename T, typename F>
auto maybe_do(const std::optional<T>& t, F&& f) ->
std::optional<std::result_of_t<F(const std::decay_t<T>)>>
{
if (t)
return { std::forward<F>(f)(*t) };
else
return std::nullopt;
}
// The other obvious function takes an optional but returns an
// ‘unwrapped’ value, either the result of evaluating the function or
// a provided alternate value.
//
template<typename T, typename F, typename U>
auto maybe_do_or(const std::optional<T>& t, F&& f, U&& u) ->
std::result_of_t<F(const std::decay_t<T>)>
{
static_assert(std::is_convertible_v<U, std::result_of_t<F(T)>>,
"Alternate value must be convertible to function return type.");
if (t)
return std::forward<F>(f)(*t);
else
return std::forward<U>(u);
}
namespace _convenience {
template<typename... Ts, typename F, std::size_t... Is>
inline void for_each_helper(const std::tuple<Ts...>& t, const F& f,
std::index_sequence<Is...>) {
(f(std::get<Is>(t)), ..., void());
}
template<typename... Ts, typename F, std::size_t... Is>
inline void for_each_helper(std::tuple<Ts...>& t, const F& f,
std::index_sequence<Is...>) {
(f(std::get<Is>(t)), ..., void());
}
template<typename... Ts, typename F, std::size_t... Is>
inline void for_each_helper(const std::tuple<Ts...>& t, F& f,
std::index_sequence<Is...>) {
(f(std::get<Is>(t)), ..., void());
}
template<typename... Ts, typename F, std::size_t... Is>
inline void for_each_helper(std::tuple<Ts...>& t, F& f,
std::index_sequence<Is...>) {
(f(std::get<Is>(t)), ..., void());
}
}
template<typename... Ts, typename F>
inline void for_each(const std::tuple<Ts...>& t, const F& f) {
_convenience::for_each_helper(t, f, std::index_sequence_for<Ts...>{});
}
template<typename... Ts, typename F>
inline void for_each(std::tuple<Ts...>& t, const F& f) {
_convenience::for_each_helper(t, f, std::index_sequence_for<Ts...>{});
}
template<typename... Ts, typename F>
inline void for_each(const std::tuple<Ts...>& t, F& f) {
_convenience::for_each_helper(t, f, std::index_sequence_for<Ts...>{});
}
template<typename... Ts, typename F>
inline void for_each(std::tuple<Ts...>& t, F& f) {
_convenience::for_each_helper(t, f, std::index_sequence_for<Ts...>{});
}
}
#endif // CEPH_COMMON_CONVENIENCE_H
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