third_party/WebKit/Source/wtf/CurrentTime.h

/*
 * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
 * Copyright (C) 2008 Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
 * copyright notice, this list of conditions and the following disclaimer
 * in the documentation and/or other materials provided with the
 * distribution.
 *     * Neither the name of Google Inc. nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#ifndef CurrentTime_h
#define CurrentTime_h

#include "wtf/WTFExport.h"

namespace WTF {

// Returns the current UTC time in seconds, counted from January 1, 1970.
// Precision varies depending on platform but is usually as good or better
// than a millisecond.
WTF_EXPORT double currentTime();

// Same thing, in milliseconds.
inline double currentTimeMS() {
  return currentTime() * 1000.0;
}

// Provides a monotonically increasing time in seconds since an arbitrary point
// in the past.  On unsupported platforms, this function only guarantees the
// result will be non-decreasing.
WTF_EXPORT double monotonicallyIncreasingTime();

// Same thing, in milliseconds.
inline double monotonicallyIncreasingTimeMS() {
  return monotonicallyIncreasingTime() * 1000.0;
}

using TimeFunction = double (*)();

// Make all the time functions (currentTime(), monotonicallyIncreasingTime(),
// systemTraceTime()) return the result of the supplied function. Returns the
// pointer to the old time function. For both setting and getting, nullptr
// means using the default timing function returning the actual time.
WTF_EXPORT TimeFunction setTimeFunctionsForTesting(TimeFunction);

}  // namespace WTF

using WTF::currentTime;
using WTF::currentTimeMS;
using WTF::monotonicallyIncreasingTime;
using WTF::monotonicallyIncreasingTimeMS;
using WTF::TimeFunction;
using WTF::setTimeFunctionsForTesting;

#endif  // CurrentTime_h