alloc.h

// Copyright (c) Microsoft. All rights reserved.
// Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
#pragma once
 
#include <bond/core/config.h>
 
#include <boost/utility/enable_if.hpp>
 
#include <type_traits>
 
 
namespace bond
{
namespace detail
{
 
template <typename Alloc, typename Enable = void>
class allocator_holder;
 
template <typename Alloc>
using empty_base_eligible = std::integral_constant<bool,
    true
    #if __cplusplus >= 201402L
    && !std::is_final<Alloc>::value
    #endif
    && std::is_empty<Alloc>::value
    && std::is_copy_constructible<Alloc>::value>;
 
template <typename Alloc>
class allocator_holder<Alloc, typename boost::enable_if<empty_base_eligible<Alloc>>::type>
    : private Alloc
{
public:
    allocator_holder() = default;
 
    explicit allocator_holder(const Alloc& alloc) BOND_NOEXCEPT_IF(
        std::is_nothrow_copy_constructible<Alloc>::value)
        : Alloc{ alloc }
    {}
 
    const Alloc& get() const BOND_NOEXCEPT
    {
        return *this;
    }
 
    Alloc& get() BOND_NOEXCEPT
    {
        return *this;
    }
};
 
template <typename Alloc>
class allocator_holder<Alloc, typename boost::disable_if<empty_base_eligible<Alloc>>::type>
{
public:
    allocator_holder() = default;
 
    explicit allocator_holder(const Alloc& alloc) BOND_NOEXCEPT_IF(
        std::is_nothrow_copy_constructible<Alloc>::value)
        : _alloc{ alloc }
    {}
 
    const Alloc& get() const BOND_NOEXCEPT
    {
        return _alloc;
    }
 
    Alloc& get() BOND_NOEXCEPT
    {
        return _alloc;
    }
 
private:
    Alloc _alloc;
};
} // namespace detail
} // namespace bond