1 /*
2  * Copyright (c) Facebook, Inc. and its affiliates.
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *     http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #pragma once
18 
19 #include <exception>
20 
21 namespace folly {
22 namespace detail {
23 
24 //  thunk
25 //
26 //  A carefully curated collection of generic general-purpose thunk templates:
27 //  * make: operator new with given arguments
28 //  * ruin: operator delete
29 //  * ctor: in-place constructor with given arguments
30 //  * dtor: in-place destructor
31 //  * noop: no-op function with the given arguments
32 //  * fail: terminating function with the given return and arguments
33 struct thunk {
34   template <typename T, typename... A>
makethunk35   static void* make(A... a) {
36     return new T(static_cast<A>(a)...);
37   }
38   template <typename T>
ruinthunk39   static void ruin(void* const ptr) noexcept {
40     delete static_cast<T*>(ptr);
41   }
42 
43   template <typename T, typename... A>
ctorthunk44   static void ctor(void* const ptr, A... a) {
45     ::new (ptr) T(static_cast<A>(a)...);
46   }
47   template <typename T>
dtorthunk48   static void dtor(void* const ptr) noexcept {
49     static_cast<T*>(ptr)->~T();
50   }
51 
52   template <typename... A>
noopthunk53   static void noop(A...) noexcept {}
54 
55   template <typename R, typename... A>
failthunk56   static R fail(A...) noexcept {
57     std::terminate();
58   }
59 };
60 
61 } // namespace detail
62 } // namespace folly
63