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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.
//
/*=============================================================================
**
**
**
** Purpose: Synchronizes access to a shared resource or region of code in a multi-threaded
** program.
**
**
=============================================================================*/
using System.Diagnostics;
using System.Diagnostics.CodeAnalysis;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Runtime.Versioning;
namespace System.Threading
{
public static partial class Monitor
{
/*=========================================================================
** Obtain the monitor lock of obj. Will block if another thread holds the lock
** Will not block if the current thread holds the lock,
** however the caller must ensure that the same number of Exit
** calls are made as there were Enter calls.
**
** Exceptions: ArgumentNullException if object is null.
=========================================================================*/
[MethodImpl(MethodImplOptions.InternalCall)]
public static extern void Enter(object obj);
// Use a ref bool instead of out to ensure that unverifiable code must
// initialize this value to something. If we used out, the value
// could be uninitialized if we threw an exception in our prolog.
// The JIT should inline this method to allow check of lockTaken argument to be optimized out
// in the typical case. Note that the method has to be transparent for inlining to be allowed by the VM.
public static void Enter(object obj, ref bool lockTaken)
{
if (lockTaken)
ThrowLockTakenException();
ReliableEnter(obj, ref lockTaken);
Debug.Assert(lockTaken);
}
[DoesNotReturn]
private static void ThrowLockTakenException()
{
throw new ArgumentException(SR.Argument_MustBeFalse, "lockTaken");
}
[MethodImpl(MethodImplOptions.InternalCall)]
private static extern void ReliableEnter(object obj, ref bool lockTaken);
/*=========================================================================
** Release the monitor lock. If one or more threads are waiting to acquire the
** lock, and the current thread has executed as many Exits as
** Enters, one of the threads will be unblocked and allowed to proceed.
**
** Exceptions: ArgumentNullException if object is null.
** SynchronizationLockException if the current thread does not
** own the lock.
=========================================================================*/
[MethodImpl(MethodImplOptions.InternalCall)]
public static extern void Exit(object obj);
/*=========================================================================
** Similar to Enter, but will never block. That is, if the current thread can
** acquire the monitor lock without blocking, it will do so and TRUE will
** be returned. Otherwise FALSE will be returned.
**
** Exceptions: ArgumentNullException if object is null.
=========================================================================*/
public static bool TryEnter(object obj)
{
bool lockTaken = false;
TryEnter(obj, 0, ref lockTaken);
return lockTaken;
}
// The JIT should inline this method to allow check of lockTaken argument to be optimized out
// in the typical case. Note that the method has to be transparent for inlining to be allowed by the VM.
public static void TryEnter(object obj, ref bool lockTaken)
{
if (lockTaken)
ThrowLockTakenException();
ReliableEnterTimeout(obj, 0, ref lockTaken);
}
/*=========================================================================
** Version of TryEnter that will block, but only up to a timeout period
** expressed in milliseconds. If timeout == Timeout.Infinite the method
** becomes equivalent to Enter.
**
** Exceptions: ArgumentNullException if object is null.
** ArgumentException if timeout < -1 (Timeout.Infinite).
=========================================================================*/
// The JIT should inline this method to allow check of lockTaken argument to be optimized out
// in the typical case. Note that the method has to be transparent for inlining to be allowed by the VM.
public static bool TryEnter(object obj, int millisecondsTimeout)
{
bool lockTaken = false;
TryEnter(obj, millisecondsTimeout, ref lockTaken);
return lockTaken;
}
// The JIT should inline this method to allow check of lockTaken argument to be optimized out
// in the typical case. Note that the method has to be transparent for inlining to be allowed by the VM.
public static void TryEnter(object obj, int millisecondsTimeout, ref bool lockTaken)
{
if (lockTaken)
ThrowLockTakenException();
ReliableEnterTimeout(obj, millisecondsTimeout, ref lockTaken);
}
[MethodImpl(MethodImplOptions.InternalCall)]
private static extern void ReliableEnterTimeout(object obj, int timeout, ref bool lockTaken);
public static bool IsEntered(object obj)
{
ArgumentNullException.ThrowIfNull(obj);
return IsEnteredNative(obj);
}
[MethodImpl(MethodImplOptions.InternalCall)]
private static extern bool IsEnteredNative(object obj);
/*========================================================================
** Waits for notification from the object (via a Pulse/PulseAll).
** timeout indicates how long to wait before the method returns.
** This method acquires the monitor waithandle for the object
** If this thread holds the monitor lock for the object, it releases it.
** On exit from the method, it obtains the monitor lock back.
**
** Exceptions: ArgumentNullException if object is null.
========================================================================*/
[LibraryImport(RuntimeHelpers.QCall, EntryPoint = "Monitor_Wait")]
[return: MarshalAs(UnmanagedType.Bool)]
private static partial bool Wait(ObjectHandleOnStack obj, int millisecondsTimeout);
[UnsupportedOSPlatform("browser")]
public static bool Wait(object obj, int millisecondsTimeout)
{
ArgumentNullException.ThrowIfNull(obj);
ArgumentOutOfRangeException.ThrowIfLessThan(millisecondsTimeout, -1);
return Wait(ObjectHandleOnStack.Create(ref obj), millisecondsTimeout);
}
/*========================================================================
** Sends a notification to a single waiting object.
* Exceptions: SynchronizationLockException if this method is not called inside
* a synchronized block of code.
========================================================================*/
[LibraryImport(RuntimeHelpers.QCall, EntryPoint = "Monitor_Pulse")]
private static partial void Pulse(ObjectHandleOnStack obj);
public static void Pulse(object obj)
{
ArgumentNullException.ThrowIfNull(obj);
Pulse(ObjectHandleOnStack.Create(ref obj));
}
/*========================================================================
** Sends a notification to all waiting objects.
========================================================================*/
[LibraryImport(RuntimeHelpers.QCall, EntryPoint = "Monitor_PulseAll")]
private static partial void PulseAll(ObjectHandleOnStack obj);
public static void PulseAll(object obj)
{
ArgumentNullException.ThrowIfNull(obj);
PulseAll(ObjectHandleOnStack.Create(ref obj));
}
/// <summary>
/// Gets the number of times there was contention upon trying to take a <see cref="Monitor"/>'s lock so far.
/// </summary>
public static long LockContentionCount => GetLockContentionCount() + Lock.ContentionCount;
[LibraryImport(RuntimeHelpers.QCall, EntryPoint = "Monitor_GetLockContentionCount")]
private static partial long GetLockContentionCount();
}
}
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