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//-----------------------------------------------------------------------------
// Copyright (c) Microsoft Corporation. All rights reserved.
//-----------------------------------------------------------------------------
namespace System.Runtime
{
using System;
using System.Threading;
sealed class BackoffTimeoutHelper
{
readonly static int maxSkewMilliseconds = (int)(IOThreadTimer.SystemTimeResolutionTicks / TimeSpan.TicksPerMillisecond);
readonly static long maxDriftTicks = IOThreadTimer.SystemTimeResolutionTicks * 2;
readonly static TimeSpan defaultInitialWaitTime = TimeSpan.FromMilliseconds(1);
readonly static TimeSpan defaultMaxWaitTime = TimeSpan.FromMinutes(1);
DateTime deadline;
TimeSpan maxWaitTime;
TimeSpan waitTime;
IOThreadTimer backoffTimer;
Action<object> backoffCallback;
object backoffState;
Random random;
TimeSpan originalTimeout;
internal BackoffTimeoutHelper(TimeSpan timeout)
: this(timeout, BackoffTimeoutHelper.defaultMaxWaitTime)
{
}
internal BackoffTimeoutHelper(TimeSpan timeout, TimeSpan maxWaitTime)
: this(timeout, maxWaitTime, BackoffTimeoutHelper.defaultInitialWaitTime)
{
}
internal BackoffTimeoutHelper(TimeSpan timeout, TimeSpan maxWaitTime, TimeSpan initialWaitTime)
{
this.random = new Random(GetHashCode());
this.maxWaitTime = maxWaitTime;
this.originalTimeout = timeout;
Reset(timeout, initialWaitTime);
}
public TimeSpan OriginalTimeout
{
get
{
return this.originalTimeout;
}
}
void Reset(TimeSpan timeout, TimeSpan initialWaitTime)
{
if (timeout == TimeSpan.MaxValue)
{
this.deadline = DateTime.MaxValue;
}
else
{
this.deadline = DateTime.UtcNow + timeout;
}
this.waitTime = initialWaitTime;
}
public bool IsExpired()
{
if (this.deadline == DateTime.MaxValue)
{
return false;
}
else
{
return (DateTime.UtcNow >= this.deadline);
}
}
public void WaitAndBackoff(Action<object> callback, object state)
{
if (this.backoffCallback != callback || this.backoffState != state)
{
if (this.backoffTimer != null)
{
this.backoffTimer.Cancel();
}
this.backoffCallback = callback;
this.backoffState = state;
this.backoffTimer = new IOThreadTimer(callback, state, false, BackoffTimeoutHelper.maxSkewMilliseconds);
}
TimeSpan backoffTime = WaitTimeWithDrift();
Backoff();
this.backoffTimer.Set(backoffTime);
}
public void WaitAndBackoff()
{
Thread.Sleep(WaitTimeWithDrift());
Backoff();
}
TimeSpan WaitTimeWithDrift()
{
return Ticks.ToTimeSpan(Math.Max(
Ticks.FromTimeSpan(BackoffTimeoutHelper.defaultInitialWaitTime),
Ticks.Add(Ticks.FromTimeSpan(this.waitTime),
(long)(uint)this.random.Next() % (2 * BackoffTimeoutHelper.maxDriftTicks + 1) - BackoffTimeoutHelper.maxDriftTicks)));
}
void Backoff()
{
if (waitTime.Ticks >= (maxWaitTime.Ticks / 2))
{
waitTime = maxWaitTime;
}
else
{
waitTime = TimeSpan.FromTicks(waitTime.Ticks * 2);
}
if (this.deadline != DateTime.MaxValue)
{
TimeSpan remainingTime = this.deadline - DateTime.UtcNow;
if (this.waitTime > remainingTime)
{
this.waitTime = remainingTime;
if (this.waitTime < TimeSpan.Zero)
{
this.waitTime = TimeSpan.Zero;
}
}
}
}
}
}
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