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// Copyright (c) 2012 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.
// This file provides a macro ONLY for use in testing.
// DO NOT USE IN PRODUCTION CODE. There are much better ways to wait.
// This code is very helpful in testing multi-threaded code, without depending
// on almost any primitives. This is especially helpful if you are testing
// those primitive multi-threaded constructs.
// We provide a simple one argument spin wait (for 1 second), and a generic
// spin wait (for longer periods of time).
#ifndef BASE_SYNCHRONIZATION_SPIN_WAIT_H_
#define BASE_SYNCHRONIZATION_SPIN_WAIT_H_
#include "base/threading/platform_thread.h"
#include "base/time/time.h"
// Provide a macro that will wait no longer than 1 second for an asynchronous
// change is the value of an expression.
// A typical use would be:
//
// SPIN_FOR_1_SECOND_OR_UNTIL_TRUE(0 == f(x));
//
// The expression will be evaluated repeatedly until it is true, or until
// the time (1 second) expires.
// Since tests generally have a 5 second watch dog timer, this spin loop is
// typically used to get the padding needed on a given test platform to assure
// that the test passes, even if load varies, and external events vary.
#define SPIN_FOR_1_SECOND_OR_UNTIL_TRUE(expression) \
SPIN_FOR_TIMEDELTA_OR_UNTIL_TRUE(base::TimeDelta::FromSeconds(1), \
(expression))
#define SPIN_FOR_TIMEDELTA_OR_UNTIL_TRUE(delta, expression) do { \
base::TimeTicks start = base::TimeTicks::Now(); \
const base::TimeDelta kTimeout = delta; \
while (!(expression)) { \
if (kTimeout < base::TimeTicks::Now() - start) { \
EXPECT_LE((base::TimeTicks::Now() - start).InMilliseconds(), \
kTimeout.InMilliseconds()) << "Timed out"; \
break; \
} \
base::PlatformThread::Sleep(base::TimeDelta::FromMilliseconds(50)); \
} \
} while (0)
#endif // BASE_SYNCHRONIZATION_SPIN_WAIT_H_
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