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/* -*- 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/. */
#ifndef DOM_QUOTA_CLIENTDIRECTORYLOCKHANDLE_H_
#define DOM_QUOTA_CLIENTDIRECTORYLOCKHANDLE_H_
#include "mozilla/RefPtr.h"
#include "mozilla/dom/quota/ConditionalCompilation.h"
#include "nsISupportsImpl.h"
namespace mozilla::dom::quota {
class ClientDirectoryLock;
/**
* @class ClientDirectoryLockHandle
* @brief RAII-style wrapper for managing a ClientDirectoryLock.
*
* ClientDirectoryLockHandle is a RAII-style wrapper that manages a
* ClientDirectoryLock created by QuotaManager::OpenClientDirectory.
*
* This class ensures that the associated directory lock remains acquired
* while the handle is in scope and automatically drops it when destroyed.
*
* ## Usage:
* - See QuotaManager::OpenClientDirectory for details on obtaining a
* ClientDirectoryLockHandle.
* - The handle should be retained for as long as access to the directory is
* needed.
*
* ## Threading:
* - Must be used only on the thread that created it, except that it may be
* safely destroyed from another thread after being moved (see also
* Destruction).
* - `AssertIsOnOwningThread()` is primarily used internally to verify correct
* threading, but clients can use it for additional thread-safety checks if
* needed.
*
* ## Destruction:
* - If the lock has already been dropped (e.g., due to move), the destructor
* does nothing.
* - The destructor automatically drops the lock if it is still held.
* - Thus, it is safe to destroy a handle from any thread as long as the handle
* was moved beforehand on the owning thread.
*
* ## Key Features:
* - Move-only: Prevents accidental copies.
* - Implicit boolean conversion to check if the handle holds a valid
* `ClientDirectoryLock`.
* - Easy access to the underlying ClientDirectoryLock using `operator*` and
* `operator->`.
* - Moved-from handles are placed in a well-defined inert state and can be
* safely inspected using `IsInert()` for diagnostic purposes.
*/
class ClientDirectoryLockHandle final {
public:
ClientDirectoryLockHandle();
explicit ClientDirectoryLockHandle(
RefPtr<ClientDirectoryLock> aClientDirectoryLock);
ClientDirectoryLockHandle(const ClientDirectoryLockHandle&) = delete;
ClientDirectoryLockHandle(ClientDirectoryLockHandle&& aOther) noexcept;
~ClientDirectoryLockHandle();
void AssertIsOnOwningThread() const;
ClientDirectoryLockHandle& operator=(const ClientDirectoryLockHandle&) =
delete;
ClientDirectoryLockHandle& operator=(
ClientDirectoryLockHandle&& aOther) noexcept;
explicit operator bool() const;
ClientDirectoryLock* get() const;
ClientDirectoryLock& operator*() const;
ClientDirectoryLock* operator->() const;
bool IsRegistered() const;
void SetRegistered(bool aRegistered);
/**
* Returns true if this handle is in an inert state — either it was
* default-constructed and never assigned a lock, or it was explicitly
* cleared (via move).
*
* This method is primarily intended for use in destructors of objects that
* own a ClientDirectoryLockHandle, to assert that the lock has been properly
* dropped and cleared before destruction.
*
* It is safe to call this method at any time on the owning thread. It may
* also be called from other threads during destruction, under the assumption
* that no other thread is concurrently accessing or modifying the handle.
*
* This method should not be used for control flow or runtime decision
* making.
*/
DIAGNOSTICONLY(bool IsInert() const);
private:
NS_DECL_OWNINGTHREAD
// If new members are added or existing ones are changed, make sure to update
// the move constructor and move assignment operator accordingly to preserve
// correct state during moves.
RefPtr<ClientDirectoryLock> mClientDirectoryLock;
bool mRegistered = false;
};
} // namespace mozilla::dom::quota
#endif // DOM_QUOTA_CLIENTDIRECTORYLOCKHANDLE_H_
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