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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using System.IO;
using Microsoft.Win32;
using Microsoft.Win32.SafeHandles;
using System.Runtime.InteropServices;
using System.Threading;
using System.Runtime.Versioning;
namespace System.Threading
{
public sealed partial class Semaphore : WaitHandle
{
// creates a nameless semaphore object
// Win32 only takes maximum count of Int32.MaxValue
public Semaphore(int initialCount, int maximumCount)
{
VerifyCounts(initialCount, maximumCount);
bool createdNew;
CreateSemaphoreCore(initialCount, maximumCount, null, out createdNew);
}
public Semaphore(int initialCount, int maximumCount, string name)
{
VerifyCounts(initialCount, maximumCount);
VerifyNameForCreate(name);
bool createdNew;
CreateSemaphoreCore(initialCount, maximumCount, name, out createdNew);
}
public Semaphore(int initialCount, int maximumCount, string name, out bool createdNew)
{
VerifyCounts(initialCount, maximumCount);
VerifyNameForCreate(name);
CreateSemaphoreCore(initialCount, maximumCount, name, out createdNew);
}
private static void VerifyCounts(int initialCount, int maximumCount)
{
if (initialCount < 0)
{
throw new ArgumentOutOfRangeException(nameof(initialCount), SR.ArgumentOutOfRange_NeedNonNegNumRequired);
}
if (maximumCount < 1)
{
throw new ArgumentOutOfRangeException(nameof(maximumCount), SR.ArgumentOutOfRange_NeedNonNegNumRequired);
}
if (initialCount > maximumCount)
{
throw new ArgumentException(SR.Argument_SemaphoreInitialMaximum);
}
}
public static Semaphore OpenExisting(string name)
{
Semaphore result;
switch (OpenExistingWorker(name, out result))
{
case OpenExistingResult.NameNotFound:
throw new WaitHandleCannotBeOpenedException();
case OpenExistingResult.NameInvalid:
throw new WaitHandleCannotBeOpenedException(SR.Format(SR.Threading_WaitHandleCannotBeOpenedException_InvalidHandle, name));
case OpenExistingResult.PathNotFound:
throw new IOException(SR.Format(SR.IO_PathNotFound_Path, name));
default:
return result;
}
}
public static bool TryOpenExisting(string name, out Semaphore result) =>
OpenExistingWorker(name, out result) == OpenExistingResult.Success;
// increase the count on a semaphore, returns previous count
public int Release() => ReleaseCore(1);
// increase the count on a semaphore, returns previous count
public int Release(int releaseCount)
{
if (releaseCount < 1)
{
throw new ArgumentOutOfRangeException(nameof(releaseCount), SR.ArgumentOutOfRange_NeedNonNegNumRequired);
}
return ReleaseCore(releaseCount);
}
private int ReleaseCore(int releaseCount)
{
// The field value is modifiable via the public <see cref="WaitHandle.SafeWaitHandle"/> property, save it locally
// to ensure that one instance is used in all places in this method
SafeWaitHandle waitHandle = _waitHandle;
if (waitHandle == null)
{
ThrowInvalidHandleException();
}
waitHandle.DangerousAddRef();
try
{
return ReleaseCore(waitHandle.DangerousGetHandle(), releaseCount);
}
finally
{
waitHandle.DangerousRelease();
}
}
}
}
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