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// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
// vim: ts=8 sw=2 smarttab
#pragma once
// Based on bind_executor.h from Boost.Asio which is Copyright (c)
// 2003-2019 Christopher M. Kohlhoff (chris at kohlhoff dot com)
//
// 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 <boost/asio/associated_executor.hpp>
#include <boost/asio/associated_allocator.hpp>
#include <boost/asio/async_result.hpp>
#include <boost/asio/execution_context.hpp>
#include "include/uses_allocator.h"
namespace ceph::async {
namespace detail {
template<typename T>
struct allocator_binder_check
{
typedef void type;
};
// Helper to:
// - Apply the empty base optimization to the allocator.
// - Perform uses_allocator construction of the target type, if required.
template<typename T, typename Allocator, bool UsesAllocator>
class allocator_binder_base;
template<typename T, typename Allocator>
class allocator_binder_base<T, Allocator, true>
: protected Allocator
{
protected:
template<typename A, typename U>
allocator_binder_base(A&& a, U&& u)
: Allocator(std::forward<A>(a),
target(ceph::make_obj_using_allocator(*this,
std::forward<U>(u)))) {}
T target;
};
template <typename T, typename Allocator>
class allocator_binder_base<T, Allocator, false>
: protected Allocator
{
protected:
template<typename A, typename U>
allocator_binder_base(A&& a, U&& u)
: Allocator(std::forward<A>(a)),
target(std::forward<U>(u)) {}
T target;
};
// Helper to enable SFINAE on zero-argument operator() below.
template<typename T, typename = void>
struct allocator_binder_result_of0
{
using type = void;
};
template<typename T>
struct allocator_binder_result_of0<
T, typename allocator_binder_check<std::result_of_t<T()>>::type>
{
using type = typename std::result_of_t<T()>;
};
} // namespace detail
/// A call wrapper type to bind an allocator of type @c Allocator to
/// an object of type @c T.
template<typename T, typename Allocator>
class allocator_binder
: private detail::allocator_binder_base<T, Allocator,
std::uses_allocator<T, Allocator>
::value>
{
public:
/// The type of the target object.
using target_type = T;
/// The type of the associated allocator.
using allocator_type = Allocator;
/// Construct an allocator wrapper for the specified object.
/**
* This constructor is only valid if the type @c T is constructible from type
* @c U.
*/
template<typename U>
allocator_binder(std::allocator_arg_t, const allocator_type& a,
U&& u)
: base_type(a, std::forward<U>(u)) {}
/// Copy constructor.
allocator_binder(const allocator_binder& other)
: base_type(other.get_allocator(), other.get()) {}
/// Construct a copy, but specify a different allocator.
allocator_binder(std::allocator_arg_t, const allocator_type& e,
const allocator_binder& other)
: base_type(e, other.get()) {}
/// Construct a copy of a different allocator wrapper type.
/**
* This constructor is only valid if the @c Allocator type is
* constructible from type @c OtherAllocator, and the type @c T is
* constructible from type @c U.
*/
template<typename U, typename OtherAllocator>
allocator_binder(const allocator_binder<U, OtherAllocator>& other)
: base_type(other.get_allocator(), other.get()) {}
/// Construct a copy of a different allocator wrapper type, but specify a
/// different allocator.
/**
* This constructor is only valid if the type @c T is constructible from type
* @c U.
*/
template<typename U, typename OtherAllocator>
allocator_binder(std::allocator_arg_t, const allocator_type& a,
const allocator_binder<U, OtherAllocator>& other)
: base_type(a, other.get()) {}
/// Move constructor.
allocator_binder(allocator_binder&& other)
: base_type(std::move(other.get_allocator()),
std::move(other.get())) {}
/// Move construct the target object, but specify a different allocator.
allocator_binder(std::allocator_arg_t, const allocator_type& e,
allocator_binder&& other)
: base_type(e, std::move(other.get())) {}
/// Move construct from a different allocator wrapper type.
template<typename U, typename OtherAllocator>
allocator_binder(allocator_binder<U, OtherAllocator>&& other)
: base_type(std::move(other.get_allocator()), std::move(other.get())) {}
/// Move construct from a different allocator wrapper type, but specify a
/// different allocator.
template<typename U, typename OtherAllocator>
allocator_binder(std::allocator_arg_t, const allocator_type& a,
allocator_binder<U, OtherAllocator>&& other)
: base_type(a, std::move(other.get())) {}
/// Destructor.
~allocator_binder() = default;
/// Obtain a reference to the target object.
target_type& get() noexcept
{
return this->target;
}
/// Obtain a reference to the target object.
const target_type& get() const noexcept
{
return this->target;
}
/// Obtain the associated allocator.
allocator_type get_allocator() const noexcept {
return static_cast<const Allocator&>(*this);
}
/// Forwarding function call operator.
template<typename... Args>
decltype(auto) operator()(Args&&... args) {
return this->target(std::forward<Args>(args)...);
}
/// Forwarding function call operator.
template<typename... Args>
decltype(auto) operator()(Args&&... args) const {
return this->target(std::forward<Args>(args)...);
}
private:
using base_type =
detail::allocator_binder_base<T, Allocator,
std::uses_allocator_v<T, Allocator>>;
};
/// Associate an object of type @c T with an allocator of type @c Allocator.
template<typename Allocator, typename T>
inline allocator_binder<typename std::decay_t<T>, Allocator>
bind_allocator(const Allocator& a, T&& t)
{
return allocator_binder<std::decay_t<T>, Allocator>(std::allocator_arg_t(),
a, std::forward<T>(t));
}
} // namespace ceph::async
// Since we have an allocator_type member we shouldn't need a
// uses_allocator specialization.
namespace boost::asio {
template<typename T, typename Allocator, typename Signature>
class async_result<ceph::async::allocator_binder<T, Allocator>, Signature>
{
public:
using completion_handler_type =
ceph::async::allocator_binder<
typename async_result<T, Signature>::completion_handler_type, Allocator>;
using return_type = typename async_result<T, Signature>::return_type;
explicit async_result(ceph::async::allocator_binder<T, Allocator>& b)
: target(b.get()) {}
return_type get() {
return target.get();
}
private:
async_result(const async_result&) = delete;
async_result& operator=(const async_result&) = delete;
async_result<T, Signature> target;
};
template<typename T, typename Allocator, typename Executor>
struct associated_executor<ceph::async::allocator_binder<T, Allocator>,
Executor>
{
using type = typename associated_executor<T, Executor>::type;
static type get(const ceph::async::allocator_binder<T, Allocator>& b,
Executor ex = {}) noexcept {
return get_associated_executor(b.get(), ex);
}
};
} // namespace boost::asio
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