webrtc/system_wrappers/interface/event_wrapper.h

/*
 *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#ifndef WEBRTC_SYSTEM_WRAPPERS_INTERFACE_EVENT_WRAPPER_H_
#define WEBRTC_SYSTEM_WRAPPERS_INTERFACE_EVENT_WRAPPER_H_

namespace webrtc {
enum EventTypeWrapper
{
    kEventSignaled = 1,
    kEventError = 2,
    kEventTimeout = 3
};

#define WEBRTC_EVENT_10_SEC   10000
#define WEBRTC_EVENT_INFINITE 0xffffffff

class EventWrapper
{
public:
    // Factory method. Constructor disabled.
    static EventWrapper* Create();
    virtual ~EventWrapper() {}

    // Releases threads who are calling Wait() and has started waiting. Please
    // note that a thread calling Wait() will not start waiting immediately.
    // assumptions to the contrary is a very common source of issues in
    // multithreaded programming.
    // Set is sticky in the sense that it will release at least one thread
    // either immediately or some time in the future.
    virtual bool Set() = 0;

    // Prevents future Wait() calls from finishing without a new Set() call.
    virtual bool Reset() = 0;

    // Puts the calling thread into a wait state. The thread may be released
    // by a Set() call depending on if other threads are waiting and if so on
    // timing. The thread that was released will call Reset() before leaving
    // preventing more threads from being released. If multiple threads
    // are waiting for the same Set(), only one (random) thread is guaranteed to
    // be released. It is possible that multiple (random) threads are released
    // Depending on timing.
    virtual EventTypeWrapper Wait(unsigned long maxTime) = 0;

    // Starts a timer that will call a non-sticky version of Set() either once
    // or periodically. If the timer is periodic it ensures that there is no
    // drift over time relative to the system clock.
    virtual bool StartTimer(bool periodic, unsigned long time) = 0;

    virtual bool StopTimer() = 0;

    // Only implemented on Windows
    // Returns 1 if a key has been pressed since last call to this function.
    // -1 indicates failure
    // 0 indicates no key has been pressed since last call
    // TODO(hellner) this function does not seem to belong here
    static int KeyPressed();
};
} // namespace webrtc

#endif // WEBRTC_SYSTEM_WRAPPERS_INTERFACE_EVENT_WRAPPER_H_