1 files changed, 69 insertions, 0 deletions
diff --git a/src/common/allocate_unique.h b/src/common/allocate_unique.h
new file mode 100644
index 000000000..4c5cc1c6e
--- /dev/null
+++ b/src/common/allocate_unique.h
@@ -0,0 +1,69 @@
+// -*- 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