#if NET_4_0 || BOOTSTRAP_NET_4_0
// SpinWait.cs
//
// Copyright (c) 2008 Jrmie "Garuma" Laval
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//
//
using System;
namespace System.Threading{
public struct SpinWait
{
// The number of step until SpinOnce yield on multicore machine
const int step = 5;
static readonly bool isSingleCpu = (Environment.ProcessorCount == 1);
int ntime;
public void SpinOnce ()
{
// On a single-CPU system, spinning does no good
if (isSingleCpu) {
Yield ();
} else {
if (Interlocked.Increment (ref ntime) % step == 0) {
Yield ();
} else {
// Multi-CPU system might be hyper-threaded, let other thread run
Thread.SpinWait (2 * (ntime + 1));
}
}
}
public static void SpinUntil (Func<bool> predicate)
{
SpinWait sw = new SpinWait ();
while (!predicate ())
sw.SpinOnce ();
}
public static bool SpinUntil (Func<bool> predicate, TimeSpan ts)
{
return SpinUntil (predicate, (int)ts.TotalMilliseconds);
}
public static bool SpinUntil (Func<bool> predicate, int milliseconds)
{
SpinWait sw = new SpinWait ();
Watch watch = Watch.StartNew ();
while (!predicate ()) {
if (watch.ElapsedMilliseconds > milliseconds)
return false;
sw.SpinOnce ();
}
return true;
}
void Yield ()
{
// Replace sched_yield by Thread.Sleep(0) which does almost the same thing
// (going back in kernel mode and yielding) but avoid the branching and unmanaged bridge
Thread.Sleep (0);
}
public void Reset ()
{
ntime = 0;
}
public bool NextSpinWillYield {
get {
return isSingleCpu ? true : ntime % step == 0;
}
}
public int Count {
get {
return ntime;
}
}
}
}
#endif
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