mirror of
https://github.com/mozilla/gecko-dev.git
synced 2024-11-05 08:35:26 +00:00
fda6cabeb6
--HG-- extra : commitid : JVZx97WUQxy extra : rebase_source : 5cef069fd3071ad305a3e3f04e0addff577b1093
136 lines
3.4 KiB
C++
136 lines
3.4 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
|
|
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
|
|
/* This Source Code Form is subject to the terms of the Mozilla Public
|
|
* License, v. 2.0. If a copy of the MPL was not distributed with this
|
|
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
|
|
|
|
/* RAII class for executing arbitrary actions at scope end. */
|
|
|
|
#ifndef mozilla_ScopeExit_h
|
|
#define mozilla_ScopeExit_h
|
|
|
|
/*
|
|
* See http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2014/n4189.pdf for a
|
|
* standards-track version of this.
|
|
*
|
|
* Error handling can be complex when various actions need to be performed that
|
|
* need to be undone if an error occurs midway. This can be handled with a
|
|
* collection of boolean state variables and gotos, which can get clunky and
|
|
* error-prone:
|
|
*
|
|
* {
|
|
* if (!a.setup())
|
|
* goto fail;
|
|
* isASetup = true;
|
|
*
|
|
* if (!b.setup())
|
|
* goto fail;
|
|
* isBSetup = true;
|
|
*
|
|
* ...
|
|
* return true;
|
|
*
|
|
* fail:
|
|
* if (isASetup)
|
|
* a.teardown();
|
|
* if (isBSetup)
|
|
* b.teardown();
|
|
* return false;
|
|
* }
|
|
*
|
|
* ScopeExit is a mechanism to simplify this pattern by keeping an RAII guard
|
|
* class that will perform the teardown on destruction, unless released. So the
|
|
* above would become:
|
|
*
|
|
* {
|
|
* if (!a.setup()) {
|
|
* return false;
|
|
* }
|
|
* auto guardA = MakeScopeExit([&] {
|
|
* a.teardown();
|
|
* });
|
|
*
|
|
* if (!b.setup()) {
|
|
* return false;
|
|
* }
|
|
* auto guardB = MakeScopeExit([&] {
|
|
* b.teardown();
|
|
* });
|
|
*
|
|
* ...
|
|
* guardA.release();
|
|
* guardB.release();
|
|
* return true;
|
|
* }
|
|
*
|
|
* This header provides:
|
|
*
|
|
* - |ScopeExit| - a container for a cleanup call, automically called at the
|
|
* end of the scope;
|
|
* - |MakeScopeExit| - a convenience function for constructing a |ScopeExit|
|
|
* with a given cleanup routine, commonly used with a lambda function.
|
|
*
|
|
* Note that the RAII classes defined in this header do _not_ perform any form
|
|
* of reference-counting or garbage-collection. These classes have exactly two
|
|
* behaviors:
|
|
*
|
|
* - if |release()| has not been called, the cleanup is always performed at
|
|
* the end of the scope;
|
|
* - if |release()| has been called, nothing will happen at the end of the
|
|
* scope.
|
|
*/
|
|
|
|
#include "mozilla/GuardObjects.h"
|
|
#include "mozilla/Move.h"
|
|
|
|
namespace mozilla {
|
|
|
|
template <typename ExitFunction>
|
|
class ScopeExit {
|
|
ExitFunction mExitFunction;
|
|
bool mExecuteOnDestruction;
|
|
MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
|
|
|
|
public:
|
|
explicit ScopeExit(ExitFunction&& cleanup
|
|
MOZ_GUARD_OBJECT_NOTIFIER_PARAM)
|
|
: mExitFunction(cleanup)
|
|
, mExecuteOnDestruction(true)
|
|
{
|
|
MOZ_GUARD_OBJECT_NOTIFIER_INIT;
|
|
}
|
|
|
|
ScopeExit(ScopeExit&& rhs)
|
|
: mExitFunction(mozilla::Move(rhs.mExitFunction))
|
|
, mExecuteOnDestruction(rhs.mExecuteOnDestruction)
|
|
{
|
|
rhs.release();
|
|
}
|
|
|
|
~ScopeExit() {
|
|
if (mExecuteOnDestruction) {
|
|
mExitFunction();
|
|
}
|
|
}
|
|
|
|
void release() {
|
|
mExecuteOnDestruction = false;
|
|
}
|
|
|
|
private:
|
|
explicit ScopeExit(const ScopeExit&) = delete;
|
|
ScopeExit& operator=(const ScopeExit&) = delete;
|
|
ScopeExit& operator=(ScopeExit&&) = delete;
|
|
};
|
|
|
|
template <typename ExitFunction>
|
|
ScopeExit<ExitFunction>
|
|
MakeScopeExit(ExitFunction&& exitFunction)
|
|
{
|
|
return ScopeExit<ExitFunction>(mozilla::Move(exitFunction));
|
|
}
|
|
|
|
} /* namespace mozilla */
|
|
|
|
#endif /* mozilla_ScopeExit_h */
|