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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).

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#ifndef BUTIL_SYNCHRONIZATION_SPIN_WAIT_H_
#define BUTIL_SYNCHRONIZATION_SPIN_WAIT_H_
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#include "butil/threading/platform_thread.h"
#include "butil/time/time.h"
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// 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) \
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    SPIN_FOR_TIMEDELTA_OR_UNTIL_TRUE(butil::TimeDelta::FromSeconds(1), \
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                                     (expression))

#define SPIN_FOR_TIMEDELTA_OR_UNTIL_TRUE(delta, expression) do { \
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  butil::TimeTicks start = butil::TimeTicks::Now(); \
  const butil::TimeDelta kTimeout = delta; \
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    while (!(expression)) { \
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      if (kTimeout < butil::TimeTicks::Now() - start) { \
      EXPECT_LE((butil::TimeTicks::Now() - start).InMilliseconds(), \
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                kTimeout.InMilliseconds()) << "Timed out"; \
        break; \
      } \
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      butil::PlatformThread::Sleep(butil::TimeDelta::FromMilliseconds(50)); \
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    } \
  } while (0)

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#endif  // BUTIL_SYNCHRONIZATION_SPIN_WAIT_H_