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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) 2020 Red Hat
*
* 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.
*
*/
#pragma once
#include <memory>
namespace ceph {
/// An allocator-aware 'Deleter' for std::unique_ptr<T, Deleter>. The
/// allocator's traits must have a value_type of T.
template <typename Alloc>
class deallocator {
using allocator_type = Alloc;
using allocator_traits = std::allocator_traits<allocator_type>;
using pointer = typename allocator_traits::pointer;
allocator_type alloc;
public:
explicit deallocator(const allocator_type& alloc) noexcept : alloc(alloc) {}
void operator()(pointer p) {
allocator_traits::destroy(alloc, p);
allocator_traits::deallocate(alloc, p, 1);
}
};
/// deallocator alias that rebinds Alloc's value_type to T
template <typename T, typename Alloc>
using deallocator_t = deallocator<typename std::allocator_traits<Alloc>
::template rebind_alloc<T>>;
/// std::unique_ptr alias that rebinds Alloc if necessary, and avoids repetition
/// of the template parameter T.
template <typename T, typename Alloc>
using allocated_unique_ptr = std::unique_ptr<T, deallocator_t<T, Alloc>>;
/// Returns a std::unique_ptr whose memory is managed by the given allocator.
template <typename T, typename Alloc, typename... Args>
static auto allocate_unique(Alloc& alloc, Args&&... args)
-> allocated_unique_ptr<T, Alloc>
{
static_assert(!std::is_array_v<T>, "allocate_unique() does not support T[]");
using allocator_type = typename std::allocator_traits<Alloc>
::template rebind_alloc<T>;
using allocator_traits = std::allocator_traits<allocator_type>;
auto a = allocator_type{alloc};
auto p = allocator_traits::allocate(a, 1);
try {
allocator_traits::construct(a, p, std::forward<Args>(args)...);
return {p, deallocator<allocator_type>{a}};
} catch (...) {
allocator_traits::deallocate(a, p, 1);
throw;
}
}
} // namespace ceph
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