mirror of https://github.com/facebook/rocksdb.git
53 lines
1.4 KiB
C++
53 lines
1.4 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
|
|
// This source code is licensed under both the GPLv2 (found in the
|
|
// COPYING file in the root directory) and Apache 2.0 License
|
|
// (found in the LICENSE.Apache file in the root directory).
|
|
|
|
#pragma once
|
|
|
|
#include <functional>
|
|
|
|
namespace ROCKSDB_NAMESPACE {
|
|
|
|
// Defers the execution of the provided function until the Defer
|
|
// object goes out of scope.
|
|
//
|
|
// Usage example:
|
|
//
|
|
// Status DeferTest() {
|
|
// Status s;
|
|
// Defer defer([&s]() {
|
|
// if (!s.ok()) {
|
|
// // do cleanups ...
|
|
// }
|
|
// });
|
|
// // do something ...
|
|
// if (!s.ok()) return;
|
|
// // do some other things ...
|
|
// return s;
|
|
// }
|
|
//
|
|
// The above code ensures that cleanups will always happen on returning.
|
|
//
|
|
// Without the help of Defer, you can
|
|
// 1. every time when !s.ok(), do the cleanup;
|
|
// 2. instead of returning when !s.ok(), continue the work only when s.ok(),
|
|
// but sometimes, this might lead to nested blocks of "if (s.ok()) {...}".
|
|
//
|
|
// With the help of Defer, you can centralize the cleanup logic inside the
|
|
// lambda passed to Defer, and you can return immediately on failure when necessary.
|
|
class Defer final {
|
|
public:
|
|
Defer(std::function<void()>&& fn) : fn_(std::move(fn)) {}
|
|
~Defer() { fn_(); }
|
|
|
|
// Disallow copy.
|
|
Defer(const Defer&) = delete;
|
|
Defer& operator=(const Defer&) = delete;
|
|
|
|
private:
|
|
std::function<void()> fn_;
|
|
};
|
|
|
|
} // namespace ROCKSDB_NAMESPACE
|