LockCookie LockCookie LockCookie LockCookie Struct

Definizione

Definisce il blocco che implementa la semantica writer singolo/visualizzatori multipli.Defines the lock that implements single-writer/multiple-reader semantics. Si tratta di un tipo di valore.This is a value type.

public value class LockCookie
[System.Runtime.InteropServices.ComVisible(true)]
[System.Serializable]
public struct LockCookie
type LockCookie = struct
Public Structure LockCookie
Ereditarietà
LockCookieLockCookieLockCookieLockCookie
Attributi

Esempi

Nell'esempio seguente viene illustrato come richiedere un blocco del lettore, aggiornare il blocco del lettore a un blocco in scrittura e salvare il LockCookie.The following example shows how to request a reader lock, upgrade the reader lock to a writer lock, and save the LockCookie. Usa quindi il LockCookie per effettuare il downgrade a un blocco del lettore.It then uses the LockCookie to downgrade to a reader lock again.

Questo codice è parte di un esempio più esaustivo disponibile per il ReaderWriterLock classe.This code is part of a larger example provided for the ReaderWriterLock class.

// The complete code is located in the ReaderWriterLock
// class topic.
using namespace System;
using namespace System::Threading;
public ref class Test
{
public:

   // Declaring the ReaderWriterLock at the class level
   // makes it visible to all threads.
   static ReaderWriterLock^ rwl = gcnew ReaderWriterLock;

   // For this example, the shared resource protected by the
   // ReaderWriterLock is just an integer.
   static int resource = 0;

// The complete code is located in the ReaderWriterLock class topic.
using System;
using System.Threading;

public class Example
{
   static ReaderWriterLock rwl = new ReaderWriterLock();
   // Define the shared resource protected by the ReaderWriterLock.
   static int resource = 0;
' The complete code is located in the ReaderWriterLock class topic.
Imports System.Threading

Public Module Example
   Private rwl As New ReaderWriterLock()
   ' Define the shared resource protected by the ReaderWriterLock.
   Private resource As Integer = 0
// Shows how to request a reader lock, upgrade the
// reader lock to the writer lock, and downgrade to a
// reader lock again.
static void UpgradeDowngrade( int timeOut )
{
   try
   {
      rwl->AcquireReaderLock( timeOut );
      try
      {
         
         // It is safe for this thread to read from
         // the shared resource.
         Display( String::Format( "reads resource value {0}", resource ) );
         Interlocked::Increment( reads );
         
         // If it is necessary to write to the resource,
         // you must either release the reader lock and 
         // then request the writer lock, or upgrade the
         // reader lock. Note that upgrading the reader lock
         // puts the thread in the write queue, behind any
         // other threads that might be waiting for the 
         // writer lock.
         try
         {
            LockCookie lc = rwl->UpgradeToWriterLock( timeOut );
            try
            {
               
               // It is safe for this thread to read or write
               // from the shared resource.
               resource = rnd->Next( 500 );
               Display( String::Format( "writes resource value {0}", resource ) );
               Interlocked::Increment( writes );
            }
            finally
            {
               
               // Ensure that the lock is released.
               rwl->DowngradeFromWriterLock( lc );
            }

         }
         catch ( ApplicationException^ ) 
         {
            
            // The upgrade request timed out.
            Interlocked::Increment( writerTimeouts );
         }

         
         // When the lock has been downgraded, it is 
         // still safe to read from the resource.
         Display( String::Format( "reads resource value {0}", resource ) );
         Interlocked::Increment( reads );
      }
      finally
      {
         
         // Ensure that the lock is released.
         rwl->ReleaseReaderLock();
      }

   }
   catch ( ApplicationException^ ) 
   {
      
      // The reader lock request timed out.
      Interlocked::Increment( readerTimeouts );
   }

}


// Requests a reader lock, upgrades the reader lock to the writer
// lock, and downgrades it to a reader lock again.
static void UpgradeDowngrade(int timeOut)
{
   try {
      rwl.AcquireReaderLock(timeOut);
      try {
         // It's safe for this thread to read from the shared resource.
         Display("reads resource value " + resource);
         Interlocked.Increment(ref reads);

         // To write to the resource, either release the reader lock and
         // request the writer lock, or upgrade the reader lock. Upgrading
         // the reader lock puts the thread in the write queue, behind any
         // other threads that might be waiting for the writer lock.
         try {
            LockCookie lc = rwl.UpgradeToWriterLock(timeOut);
            try {
               // It's safe for this thread to read or write from the shared resource.
               resource = rnd.Next(500);
               Display("writes resource value " + resource);
               Interlocked.Increment(ref writes);
            }
            finally {
               // Ensure that the lock is released.
               rwl.DowngradeFromWriterLock(ref lc);
            }
         }
         catch (ApplicationException) {
            // The upgrade request timed out.
            Interlocked.Increment(ref writerTimeouts);
         }

         // If the lock was downgraded, it's still safe to read from the resource.
         Display("reads resource value " + resource);
         Interlocked.Increment(ref reads);
      }
      finally {
         // Ensure that the lock is released.
         rwl.ReleaseReaderLock();
      }
   }
   catch (ApplicationException) {
      // The reader lock request timed out.
      Interlocked.Increment(ref readerTimeouts);
   }
}
' Requests a reader lock, upgrades the reader lock to the writer
' lock, and downgrades it to a reader lock again.
Sub UpgradeDowngrade(timeOut As Integer)
   Try
      rwl.AcquireReaderLock(timeOut)
      Try
         ' It's safe for this thread to read from the shared resource.
         Display("reads resource value " & resource)
         Interlocked.Increment(reads)
         
         ' To write to the resource, either release the reader lock and
         ' request the writer lock, or upgrade the reader lock. Upgrading
         ' the reader lock puts the thread in the write queue, behind any
         ' other threads that might be waiting for the writer lock.
         Try
            Dim lc As LockCookie = rwl.UpgradeToWriterLock(timeOut)
            Try
               ' It's safe for this thread to read or write from the shared resource.
               resource = rnd.Next(500)
               Display("writes resource value " & resource)
               Interlocked.Increment(writes)
            Finally
               ' Ensure that the lock is released.
               rwl.DowngradeFromWriterLock(lc)
            End Try
         Catch ex As ApplicationException
            ' The upgrade request timed out.
            Interlocked.Increment(writerTimeouts)
         End Try
         
         ' If the lock was downgraded, it's still safe to read from the resource.
         Display("reads resource value " & resource)
         Interlocked.Increment(reads)
      Finally
         ' Ensure that the lock is released.
         rwl.ReleaseReaderLock()
      End Try
   Catch ex As ApplicationException
      ' The reader lock request timed out.
      Interlocked.Increment(readerTimeouts)
   End Try
End Sub
};


}
End Module

Metodi

Equals(Object) Equals(Object) Equals(Object) Equals(Object)

Indica se un oggetto specificato è una struttura LockCookie ed è uguale all'istanza corrente.Indicates whether a specified object is a LockCookie and is equal to the current instance.

Equals(LockCookie) Equals(LockCookie) Equals(LockCookie) Equals(LockCookie)

Indica se l'istanza corrente è uguale all'oggetto LockCookie specificato.Indicates whether the current instance is equal to the specified LockCookie.

GetHashCode() GetHashCode() GetHashCode() GetHashCode()

Restituisce il codice hash per l'istanza.Returns the hash code for this instance.

Operatori

Equality(LockCookie, LockCookie) Equality(LockCookie, LockCookie) Equality(LockCookie, LockCookie) Equality(LockCookie, LockCookie)

Indica se due strutture LockCookie sono uguali.Indicates whether two LockCookie structures are equal.

Inequality(LockCookie, LockCookie) Inequality(LockCookie, LockCookie) Inequality(LockCookie, LockCookie) Inequality(LockCookie, LockCookie)

Indica se due strutture LockCookie non sono uguali.Indicates whether two LockCookie structures are not equal.

Si applica a

Thread safety

Questo tipo è thread-safe.This type is thread safe.

Vedi anche