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// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef MOJO_SYSTEM_WAITER_H_
#define MOJO_SYSTEM_WAITER_H_
#include "base/basictypes.h"
#include "base/synchronization/condition_variable.h"
#include "base/synchronization/lock.h"
#include "mojo/public/c/system/core.h"
#include "mojo/system/system_impl_export.h"
namespace mojo {
namespace system {
// IMPORTANT (all-caps gets your attention, right?): |Waiter| methods are called
// under other locks, in particular, |Dispatcher::lock_|s, so |Waiter| methods
// must never call out to other objects (in particular, |Dispatcher|s). This
// class is thread-safe.
class MOJO_SYSTEM_IMPL_EXPORT Waiter {
public:
Waiter();
~Waiter();
// A |Waiter| can be used multiple times; |Init()| should be called before
// each time it's used.
void Init();
// Waits until a suitable |Awake()| is called.
// Returns:
// - The |wake_result| passed to |Dispatcher::AddWaiter()| if it was woken up
// by that dispatcher for the reason specified by |flags| (in the call to
// |AddWaiter()|).
// - |MOJO_RESULT_CANCELLED| if a handle (on which |MojoWait()| was called)
// was closed; and
// - |MOJO_RESULT_FAILED_PRECONDITION| if the reasons for being awoken given
// by |flags| cannot (or can no longer) be satisfied (e.g., if the other
// end of a pipe is closed).
MojoResult Wait(MojoDeadline deadline);
// Wake the waiter up with the given result (or no-op if it's been woken up
// already).
void Awake(MojoResult wait_result);
private:
base::ConditionVariable cv_; // Associated to |lock_|.
base::Lock lock_; // Protects the following members.
#ifndef NDEBUG
bool initialized_;
#endif
bool awoken_;
MojoResult wait_result_;
DISALLOW_COPY_AND_ASSIGN(Waiter);
};
} // namespace system
} // namespace mojo
#endif // MOJO_SYSTEM_WAITER_H_
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