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-rw-r--r--src/common/allocate_unique.h69
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diff --git a/src/common/allocate_unique.h b/src/common/allocate_unique.h
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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