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// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef COMPONENTS_SERVICES_STORAGE_INDEXED_DB_LOCKS_PARTITIONED_LOCK_H_
#define COMPONENTS_SERVICES_STORAGE_INDEXED_DB_LOCKS_PARTITIONED_LOCK_H_
#include <iosfwd>
#include "base/functional/callback.h"
#include "components/services/storage/indexed_db/locks/partitioned_lock_id.h"
namespace content::indexed_db {
// Represents a granted lock by the PartitionedLockManager. When this object is
// destroyed, the lock is released. Since default construction is supported,
// |is_locked()| can be used to inquire locked status. Also, |Release()| can
// be called to manually release the lock, which appropriately updates the
// |is_locked()| result.
class PartitionedLock {
public:
using LockReleasedCallback =
base::OnceCallback<void(PartitionedLockId lock_id)>;
PartitionedLock();
PartitionedLock(const PartitionedLock&) = delete;
PartitionedLock& operator=(const PartitionedLock&) = delete;
~PartitionedLock();
PartitionedLock(PartitionedLock&&) noexcept;
// |lock_released_callback| is called when the lock is released, either by
// destruction of this object or by the |Released()| call. It will be called
// synchronously on the sequence runner this lock is released on.
PartitionedLock(PartitionedLockId lock_id,
LockReleasedCallback lock_released_callback);
// The lock in |other| is not released, and |this| must not be holding a lock.
PartitionedLock& operator=(PartitionedLock&& other) noexcept;
// Returns true if this object is holding a lock.
bool is_locked() const { return !lock_released_callback_.is_null(); }
// Explicitly releases the granted lock.
//
// The lock is also released implicitly when this instance is destroyed.
// This method is idempotent, i.e. it's valid to call Release() on an
// instance that does not hold a granted lock.
void Release();
const PartitionedLockId& lock_id() const { return lock_id_; }
private:
PartitionedLockId lock_id_;
// Closure to run when the lock is released. The lock is held when this is
// non-null.
LockReleasedCallback lock_released_callback_;
};
// Logging support.
std::ostream& operator<<(std::ostream& out, const PartitionedLock& lock_id);
// Equality doesn't take into account whether the lock 'is_locked()' or not,
// only the partition and the lock_id.
bool operator==(const PartitionedLock& x, const PartitionedLock& y);
// Comparison operator to allow sorting for locking / unlocking order.
bool operator<(const PartitionedLock& x, const PartitionedLock& y);
} // namespace content::indexed_db
#endif // COMPONENTS_SERVICES_STORAGE_INDEXED_DB_LOCKS_PARTITIONED_LOCK_H_
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