Semaphore Construtores

Definição

Inicializa uma nova instância da classe Semaphore.Initializes a new instance of the Semaphore class.

Sobrecargas

Semaphore(Int32, Int32)

Inicializa uma nova instância da classe Semaphore, especificando o número inicial de entradas e o número máximo de entradas simultâneas.Initializes a new instance of the Semaphore class, specifying the initial number of entries and the maximum number of concurrent entries.

Semaphore(Int32, Int32, String)

Inicializa uma nova instância da classe Semaphore, especificando o número inicial de entradas e o número máximo de entradas simultâneas e, opcionalmente, especificando o nome de um objeto de sinal de sistema.Initializes a new instance of the Semaphore class, specifying the initial number of entries and the maximum number of concurrent entries, and optionally specifying the name of a system semaphore object.

Semaphore(Int32, Int32, String, Boolean)

Inicializa uma nova instância da classe Semaphore, especificando o número inicial de entradas e o número máximo de entradas simultâneas, opcionalmente especificando o nome de um objeto de semáforo de sistema e especificando uma variável que recebe um valor que indica se um novo semáforo do sistema foi criado.Initializes a new instance of the Semaphore class, specifying the initial number of entries and the maximum number of concurrent entries, optionally specifying the name of a system semaphore object, and specifying a variable that receives a value indicating whether a new system semaphore was created.

Semaphore(Int32, Int32, String, Boolean, SemaphoreSecurity)

Inicializa uma nova instância da classe Semaphore, especificando o número inicial de entradas e o número máximo de entradas simultâneas, opcionalmente especificando o nome de um objeto de semáforo de sistema, especificando uma variável que recebe um valor que indica se um novo semáforo do sistema foi criado e especificando o controle de acesso de segurança para o semáforo do sistema.Initializes a new instance of the Semaphore class, specifying the initial number of entries and the maximum number of concurrent entries, optionally specifying the name of a system semaphore object, specifying a variable that receives a value indicating whether a new system semaphore was created, and specifying security access control for the system semaphore.

Semaphore(Int32, Int32)

Inicializa uma nova instância da classe Semaphore, especificando o número inicial de entradas e o número máximo de entradas simultâneas.Initializes a new instance of the Semaphore class, specifying the initial number of entries and the maximum number of concurrent entries.

public:
 Semaphore(int initialCount, int maximumCount);
public Semaphore (int initialCount, int maximumCount);
new System.Threading.Semaphore : int * int -> System.Threading.Semaphore
Public Sub New (initialCount As Integer, maximumCount As Integer)

Parâmetros

initialCount
Int32

O número inicial de solicitações para o semáforo que podem ser concedidas ao mesmo tempo.The initial number of requests for the semaphore that can be granted concurrently.

maximumCount
Int32

O número máximo de solicitações para o semáforo que podem ser concedidas ao mesmo tempo.The maximum number of requests for the semaphore that can be granted concurrently.

Exceções

initialCount é maior que maximumCount.initialCount is greater than maximumCount.

maximumCount é menor que 1.maximumCount is less than 1.

- ou --or- initialCount é menor que 0.initialCount is less than 0.

Exemplos

O exemplo a seguir cria um semáforo com uma contagem máxima de três e uma contagem inicial de zero.The following example creates a semaphore with a maximum count of three and an initial count of zero. O exemplo inicia cinco threads, que bloqueia a espera pelo semáforo.The example starts five threads, which block waiting for the semaphore. O thread principal usa a Release(Int32) sobrecarga do método para aumentar a contagem de semáforos para seu máximo, permitindo que três threads insiram o semáforo.The main thread uses the Release(Int32) method overload to increase the semaphore count to its maximum, allowing three threads to enter the semaphore. Cada thread usa o Thread.Sleep método para aguardar um segundo, para simular o trabalho e, em seguida, chama a Release() sobrecarga do método para liberar o semáforo.Each thread uses the Thread.Sleep method to wait for one second, to simulate work, and then calls the Release() method overload to release the semaphore. Cada vez que o semáforo é liberado, a contagem de semáforo anterior é exibida.Each time the semaphore is released, the previous semaphore count is displayed. Mensagens do console acompanham o uso de semáforo.Console messages track semaphore use. O intervalo de trabalho simulado aumenta um pouco para cada thread, para facilitar a leitura da saída.The simulated work interval is increased slightly for each thread, to make the output easier to read.

#using <System.dll>
using namespace System;
using namespace System::Threading;

public ref class Example
{
private:
   // A semaphore that simulates a limited resource pool.
   //
   static Semaphore^ _pool;

   // A padding interval to make the output more orderly.
   static int _padding;

public:
   static void Main()
   {
      // Create a semaphore that can satisfy up to three
      // concurrent requests. Use an initial count of zero,
      // so that the entire semaphore count is initially
      // owned by the main program thread.
      //
      _pool = gcnew Semaphore( 0,3 );
      
      // Create and start five numbered threads.
      //
      for ( int i = 1; i <= 5; i++ )
      {
         Thread^ t = gcnew Thread(
            gcnew ParameterizedThreadStart( Worker ) );
         
         // Start the thread, passing the number.
         //
         t->Start( i );
      }
      
      // Wait for half a second, to allow all the
      // threads to start and to block on the semaphore.
      //
      Thread::Sleep( 500 );
      
      // The main thread starts out holding the entire
      // semaphore count. Calling Release(3) brings the
      // semaphore count back to its maximum value, and
      // allows the waiting threads to enter the semaphore,
      // up to three at a time.
      //
      Console::WriteLine( L"Main thread calls Release(3)." );
      _pool->Release( 3 );

      Console::WriteLine( L"Main thread exits." );
   }

private:
   static void Worker( Object^ num )
   {
      // Each worker thread begins by requesting the
      // semaphore.
      Console::WriteLine( L"Thread {0} begins and waits for the semaphore.", num );
      _pool->WaitOne();
      
      // A padding interval to make the output more orderly.
      int padding = Interlocked::Add( _padding, 100 );

      Console::WriteLine( L"Thread {0} enters the semaphore.", num );
      
      // The thread's "work" consists of sleeping for
      // about a second. Each thread "works" a little
      // longer, just to make the output more orderly.
      //
      Thread::Sleep( 1000 + padding );

      Console::WriteLine( L"Thread {0} releases the semaphore.", num );
      Console::WriteLine( L"Thread {0} previous semaphore count: {1}",
         num, _pool->Release() );
   }
};
using System;
using System.Threading;

public class Example
{
    // A semaphore that simulates a limited resource pool.
    //
    private static Semaphore _pool;

    // A padding interval to make the output more orderly.
    private static int _padding;

    public static void Main()
    {
        // Create a semaphore that can satisfy up to three
        // concurrent requests. Use an initial count of zero,
        // so that the entire semaphore count is initially
        // owned by the main program thread.
        //
        _pool = new Semaphore(0, 3);

        // Create and start five numbered threads. 
        //
        for(int i = 1; i <= 5; i++)
        {
            Thread t = new Thread(new ParameterizedThreadStart(Worker));

            // Start the thread, passing the number.
            //
            t.Start(i);
        }

        // Wait for half a second, to allow all the
        // threads to start and to block on the semaphore.
        //
        Thread.Sleep(500);

        // The main thread starts out holding the entire
        // semaphore count. Calling Release(3) brings the 
        // semaphore count back to its maximum value, and
        // allows the waiting threads to enter the semaphore,
        // up to three at a time.
        //
        Console.WriteLine("Main thread calls Release(3).");
        _pool.Release(3);

        Console.WriteLine("Main thread exits.");
    }

    private static void Worker(object num)
    {
        // Each worker thread begins by requesting the
        // semaphore.
        Console.WriteLine("Thread {0} begins " +
            "and waits for the semaphore.", num);
        _pool.WaitOne();

        // A padding interval to make the output more orderly.
        int padding = Interlocked.Add(ref _padding, 100);

        Console.WriteLine("Thread {0} enters the semaphore.", num);
        
        // The thread's "work" consists of sleeping for 
        // about a second. Each thread "works" a little 
        // longer, just to make the output more orderly.
        //
        Thread.Sleep(1000 + padding);

        Console.WriteLine("Thread {0} releases the semaphore.", num);
        Console.WriteLine("Thread {0} previous semaphore count: {1}",
            num, _pool.Release());
    }
}
Imports System.Threading

Public Class Example

    ' A semaphore that simulates a limited resource pool.
    '
    Private Shared _pool As Semaphore

    ' A padding interval to make the output more orderly.
    Private Shared _padding As Integer

    <MTAThread> _
    Public Shared Sub Main()
        ' Create a semaphore that can satisfy up to three
        ' concurrent requests. Use an initial count of zero,
        ' so that the entire semaphore count is initially
        ' owned by the main program thread.
        '
        _pool = New Semaphore(0, 3)

        ' Create and start five numbered threads. 
        '
        For i As Integer = 1 To 5
            Dim t As New Thread(New ParameterizedThreadStart(AddressOf Worker))
            'Dim t As New Thread(AddressOf Worker)

            ' Start the thread, passing the number.
            '
            t.Start(i)
        Next i

        ' Wait for half a second, to allow all the
        ' threads to start and to block on the semaphore.
        '
        Thread.Sleep(500)

        ' The main thread starts out holding the entire
        ' semaphore count. Calling Release(3) brings the 
        ' semaphore count back to its maximum value, and
        ' allows the waiting threads to enter the semaphore,
        ' up to three at a time.
        '
        Console.WriteLine("Main thread calls Release(3).")
        _pool.Release(3)

        Console.WriteLine("Main thread exits.")
    End Sub

    Private Shared Sub Worker(ByVal num As Object)
        ' Each worker thread begins by requesting the
        ' semaphore.
        Console.WriteLine("Thread {0} begins " _
            & "and waits for the semaphore.", num)
        _pool.WaitOne()

        ' A padding interval to make the output more orderly.
        Dim padding As Integer = Interlocked.Add(_padding, 100)

        Console.WriteLine("Thread {0} enters the semaphore.", num)
        
        ' The thread's "work" consists of sleeping for 
        ' about a second. Each thread "works" a little 
        ' longer, just to make the output more orderly.
        '
        Thread.Sleep(1000 + padding)

        Console.WriteLine("Thread {0} releases the semaphore.", num)
        Console.WriteLine("Thread {0} previous semaphore count: {1}", _
            num, _
            _pool.Release())
    End Sub
End Class

Comentários

Esse construtor inicializa um semáforo sem nome.This constructor initializes an unnamed semaphore. Todos os threads que usam uma instância de tal semáforo devem ter referências à instância.All threads that use an instance of such a semaphore must have references to the instance.

Se initialCount for menor que maximumCount , o efeito será o mesmo que se o thread atual tivesse chamado WaitOne ( maximumCount menos initialCount ) vezes.If initialCount is less than maximumCount, the effect is the same as if the current thread had called WaitOne (maximumCount minus initialCount) times. Se você não quiser reservar nenhuma entrada para o thread que cria o semáforo, use o mesmo número para maximumCount e initialCount .If you do not want to reserve any entries for the thread that creates the semaphore, use the same number for maximumCount and initialCount.

Veja também

Aplica-se a

Semaphore(Int32, Int32, String)

Inicializa uma nova instância da classe Semaphore, especificando o número inicial de entradas e o número máximo de entradas simultâneas e, opcionalmente, especificando o nome de um objeto de sinal de sistema.Initializes a new instance of the Semaphore class, specifying the initial number of entries and the maximum number of concurrent entries, and optionally specifying the name of a system semaphore object.

public:
 Semaphore(int initialCount, int maximumCount, System::String ^ name);
public Semaphore (int initialCount, int maximumCount, string name);
new System.Threading.Semaphore : int * int * string -> System.Threading.Semaphore
Public Sub New (initialCount As Integer, maximumCount As Integer, name As String)

Parâmetros

initialCount
Int32

O número inicial de solicitações para o semáforo que podem ser concedidas ao mesmo tempo.The initial number of requests for the semaphore that can be granted concurrently.

maximumCount
Int32

O número máximo de solicitações para o semáforo que podem ser concedidas ao mesmo tempo.The maximum number of requests for the semaphore that can be granted concurrently.

name
String

O nome, se o objeto de sincronização for ser compartilhado com outros processos; caso contrário, null ou uma cadeia de caracteres vazia.The name, if the synchronization object is to be shared with other processes; otherwise, null or an empty string. O nome diferencia maiúsculas de minúsculas.The name is case-sensitive.

Exceções

initialCount é maior que maximumCount.initialCount is greater than maximumCount.

- ou --or-

Somente .NET Framework: name é maior que MAX_PATH (260 caracteres)..NET Framework only: name is longer than MAX_PATH (260 characters).

maximumCount é menor que 1.maximumCount is less than 1.

- ou --or- initialCount é menor que 0.initialCount is less than 0.

name é inválido.name is invalid. Isso pode ser por vários motivos, incluindo algumas restrições impostas pelo sistema operacional, como um prefixo desconhecido ou caracteres inválidos.This can be for various reasons, including some restrictions that may be placed by the operating system, such as an unknown prefix or invalid characters. Observe que o nome e os prefixos comuns "Global" e "Local" diferenciam maiúsculas de minúsculas.Note that the name and common prefixes "Global" and "Local" are case-sensitive.

- ou --or-

Ocorreu outro erro.There was some other error. A propriedade HResult pode fornecer mais informações.The HResult property may provide more information.

Somente Windows: name especificou um namespace desconhecido.Windows only: name specified an unknown namespace. Confira mais informações em Nomes do objeto.See Object Names for more information.

O name é muito longo.The name is too long. As restrições de comprimento podem depender do sistema operacional ou da configuração.Length restrictions may depend on the operating system or configuration.

O sinal nomeado existe e tem segurança de controle de acesso e o usuário não tem FullControl.The named semaphore exists and has access control security, and the user does not have FullControl.

Não é possível criar um objeto de sincronização com o name fornecido.A synchronization object with the provided name cannot be created. Um objeto de sincronização de um tipo diferente pode ter o mesmo nome.A synchronization object of a different type might have the same name.

Exemplos

O exemplo de código a seguir demonstra o comportamento de processo cruzado de um semáforo nomeado.The following code example demonstrates the cross-process behavior of a named semaphore. O exemplo cria um semáforo nomeado com uma contagem máxima de cinco e uma contagem inicial de cinco.The example creates a named semaphore with a maximum count of five and an initial count of five. O programa faz três chamadas para o WaitOne método.The program makes three calls to the WaitOne method. Portanto, se você executar o exemplo compilado de duas janelas de comando, a segunda cópia será bloqueada na terceira chamada para WaitOne .Thus, if you run the compiled example from two command windows, the second copy will block on the third call to WaitOne. Libere uma ou mais entradas na primeira cópia do programa para desbloquear a segunda.Release one or more entries in the first copy of the program to unblock the second.

#using <System.dll>
using namespace System;
using namespace System::Threading;

public ref class Example
{
public:
   static void main()
   {
      // Create a Semaphore object that represents the named
      // system semaphore "SemaphoreExample3". The semaphore has a
      // maximum count of five. The initial count is also five.
      // There is no point in using a smaller initial count,
      // because the initial count is not used if this program
      // doesn't create the named system semaphore, and with
      // this method overload there is no way to tell. Thus, this
      // program assumes that it is competing with other
      // programs for the semaphore.
      //
      Semaphore^ sem = gcnew Semaphore( 5,5,L"SemaphoreExample3" );
      
      // Attempt to enter the semaphore three times. If another
      // copy of this program is already running, only the first
      // two requests can be satisfied. The third blocks. Note
      // that in a real application, timeouts should be used
      // on the WaitOne calls, to avoid deadlocks.
      //
      sem->WaitOne();
      Console::WriteLine( L"Entered the semaphore once." );
      sem->WaitOne();
      Console::WriteLine( L"Entered the semaphore twice." );
      sem->WaitOne();
      Console::WriteLine( L"Entered the semaphore three times." );
      
      // The thread executing this program has entered the
      // semaphore three times. If a second copy of the program
      // is run, it will block until this program releases the
      // semaphore at least once.
      //
      Console::WriteLine( L"Enter the number of times to call Release." );
      int n;
      if ( Int32::TryParse( Console::ReadLine(),n ) )
      {
         sem->Release( n );
      }

      int remaining = 3 - n;
      if ( remaining > 0 )
      {
         Console::WriteLine( L"Press Enter to release the remaining "
         L"count ({0}) and exit the program.", remaining );
         Console::ReadLine();
         sem->Release( remaining );
      }
   }
};
using System;
using System.Threading;

public class Example
{
    public static void Main()
    {
        // Create a Semaphore object that represents the named 
        // system semaphore "SemaphoreExample3". The semaphore has a
        // maximum count of five. The initial count is also five. 
        // There is no point in using a smaller initial count,
        // because the initial count is not used if this program
        // doesn't create the named system semaphore, and with 
        // this method overload there is no way to tell. Thus, this
        // program assumes that it is competing with other
        // programs for the semaphore.
        //
        Semaphore sem = new Semaphore(5, 5, "SemaphoreExample3");

        // Attempt to enter the semaphore three times. If another 
        // copy of this program is already running, only the first
        // two requests can be satisfied. The third blocks. Note 
        // that in a real application, timeouts should be used
        // on the WaitOne calls, to avoid deadlocks.
        //
        sem.WaitOne();
        Console.WriteLine("Entered the semaphore once.");
        sem.WaitOne();
        Console.WriteLine("Entered the semaphore twice.");
        sem.WaitOne();
        Console.WriteLine("Entered the semaphore three times.");

        // The thread executing this program has entered the 
        // semaphore three times. If a second copy of the program
        // is run, it will block until this program releases the 
        // semaphore at least once.
        //
        Console.WriteLine("Enter the number of times to call Release.");
        int n;
        if (int.TryParse(Console.ReadLine(), out n))
        {
            sem.Release(n);
        }

        int remaining = 3 - n;
        if (remaining > 0)
        {
            Console.WriteLine("Press Enter to release the remaining " +
                "count ({0}) and exit the program.", remaining);
            Console.ReadLine();
            sem.Release(remaining);
        }
    }
}
Imports System.Threading

Public Class Example

    <MTAThread> _
    Public Shared Sub Main()
        ' Create a Semaphore object that represents the named 
        ' system semaphore "SemaphoreExample3". The semaphore has a
        ' maximum count of five. The initial count is also five. 
        ' There is no point in using a smaller initial count,
        ' because the initial count is not used if this program
        ' doesn't create the named system semaphore, and with 
        ' this method overload there is no way to tell. Thus, this
        ' program assumes that it is competing with other
        ' programs for the semaphore.
        '
        Dim sem As New Semaphore(5, 5, "SemaphoreExample3")

        ' Attempt to enter the semaphore three times. If another 
        ' copy of this program is already running, only the first
        ' two requests can be satisfied. The third blocks. Note 
        ' that in a real application, timeouts should be used
        ' on the WaitOne calls, to avoid deadlocks.
        '
        sem.WaitOne()
        Console.WriteLine("Entered the semaphore once.")
        sem.WaitOne()
        Console.WriteLine("Entered the semaphore twice.")
        sem.WaitOne()
        Console.WriteLine("Entered the semaphore three times.")

        ' The thread executing this program has entered the 
        ' semaphore three times. If a second copy of the program
        ' is run, it will block until this program releases the 
        ' semaphore at least once.
        '
        Console.WriteLine("Enter the number of times to call Release.")
        Dim n As Integer
        If Integer.TryParse(Console.ReadLine(), n) Then
            sem.Release(n)
        End If

        Dim remaining As Integer = 3 - n
        If (remaining) > 0 Then
            Console.WriteLine("Press Enter to release the remaining " _
                & "count ({0}) and exit the program.", remaining)
            Console.ReadLine()
            sem.Release(remaining)
        End If

    End Sub 
End Class 

Comentários

Esse construtor inicializa um Semaphore objeto que representa um semáforo de sistema nomeado.This constructor initializes a Semaphore object that represents a named system semaphore. Você pode criar vários Semaphore objetos que representam o mesmo semáforo nomeado do sistema.You can create multiple Semaphore objects that represent the same named system semaphore.

O name pode ser prefixado com Global\ or Local\ para especificar um namespace.The name may be prefixed with Global\ or Local\ to specify a namespace. Quando o Global namespace é especificado, o objeto de sincronização pode ser compartilhado com qualquer processo no sistema.When the Global namespace is specified, the synchronization object may be shared with any processes on the system. Quando o Local namespace é especificado, que também é o padrão quando nenhum namespace é especificado, o objeto de sincronização pode ser compartilhado com processos na mesma sessão.When the Local namespace is specified, which is also the default when no namespace is specified, the synchronization object may be shared with processes in the same session. No Windows, uma sessão é uma sessão de logon e os serviços normalmente são executados em uma sessão não interativa diferente.On Windows, a session is a login session, and services typically run in a different non-interactive session. Em sistemas operacionais semelhantes ao Unix, cada shell tem sua própria sessão.On Unix-like operating systems, each shell has its own session. Os objetos de sincronização de sessão local podem ser apropriados para sincronizar entre processos com uma relação pai/filho em que todos eles são executados na mesma sessão.Session-local synchronization objects may be appropriate for synchronizing between processes with a parent/child relationship where they all run in the same session. Para obter mais informações sobre nomes de objetos Synchornization no Windows, consulte nomes de objetos.For more information about synchornization object names on Windows, see Object Names.

Se um name for fornecido e um objeto de sincronização do tipo solicitado já existir no namespace, o objeto de sincronização existente será usado.If a name is provided and a synchronization object of the requested type already exists in the namespace, the existing synchronization object is used. Se um objeto de sincronização de um tipo diferente já existir no namespace, um WaitHandleCannotBeOpenedException será gerado.If a synchronization object of a different type already exists in the namespace, a WaitHandleCannotBeOpenedException is thrown. Caso contrário, um novo objeto de sincronização será criado.Otherwise, a new synchronization object is created.

Se o semáforo do sistema nomeado não existir, ele será criado com a contagem inicial e a contagem máxima especificada por initialCount e maximumCount .If the named system semaphore does not exist, it is created with the initial count and maximum count specified by initialCount and maximumCount. Se o semáforo do sistema nomeado já existir initialCount e maximumCount não for usado, embora os valores inválidos ainda causem exceções.If the named system semaphore already exists, initialCount and maximumCount are not used, although invalid values still cause exceptions. Se você precisar determinar se um semáforo de sistema nomeado foi criado, use a sobrecarga do Semaphore(Int32, Int32, String, Boolean) Construtor em vez disso.If you need to determine whether or not a named system semaphore was created, use the Semaphore(Int32, Int32, String, Boolean) constructor overload instead.

Importante

Quando você usa essa sobrecarga de construtor, a prática recomendada é especificar o mesmo número para initialCount e maximumCount .When you use this constructor overload, the recommended practice is to specify the same number for initialCount and maximumCount. Se initialCount for menor que maximumCount e um semáforo de sistema nomeado for criado, o efeito será o mesmo que se o thread atual tivesse chamado WaitOne ( maximumCount menos initialCount ) vezes.If initialCount is less than maximumCount, and a named system semaphore is created, the effect is the same as if the current thread had called WaitOne (maximumCount minus initialCount) times. No entanto, com essa sobrecarga de construtor, não há como determinar se um semáforo de sistema nomeado foi criado.However, with this constructor overload there is no way to determine whether a named system semaphore was created.

Se você especificar null ou uma cadeia de caracteres vazia para name , um semáforo local será criado, como se você tivesse chamado Semaphore(Int32, Int32) sobrecarga de construtor.If you specify null or an empty string for name, a local semaphore is created, as if you had called the Semaphore(Int32, Int32) constructor overload.

Como os semáforos nomeados são visíveis em todo o sistema operacional, eles podem ser usados para coordenar o uso de recursos entre limites de processo.Because named semaphores are visible throughout the operating system, they can be used to coordinate resource use across process boundaries.

Se você quiser descobrir se existe um semáforo de sistema nomeado, use o OpenExisting método.If you want to find out whether a named system semaphore exists, use the OpenExisting method. O OpenExisting método tenta abrir um semáforo nomeado existente e gera uma exceção se o semáforo do sistema não existir.The OpenExisting method attempts to open an existing named semaphore, and throws an exception if the system semaphore does not exist.

Veja também

Aplica-se a

Semaphore(Int32, Int32, String, Boolean)

Inicializa uma nova instância da classe Semaphore, especificando o número inicial de entradas e o número máximo de entradas simultâneas, opcionalmente especificando o nome de um objeto de semáforo de sistema e especificando uma variável que recebe um valor que indica se um novo semáforo do sistema foi criado.Initializes a new instance of the Semaphore class, specifying the initial number of entries and the maximum number of concurrent entries, optionally specifying the name of a system semaphore object, and specifying a variable that receives a value indicating whether a new system semaphore was created.

public:
 Semaphore(int initialCount, int maximumCount, System::String ^ name, [Runtime::InteropServices::Out] bool % createdNew);
public Semaphore (int initialCount, int maximumCount, string name, out bool createdNew);
new System.Threading.Semaphore : int * int * string * bool -> System.Threading.Semaphore
Public Sub New (initialCount As Integer, maximumCount As Integer, name As String, ByRef createdNew As Boolean)

Parâmetros

initialCount
Int32

O número inicial de solicitações para o semáforo que podem ser atendidas simultaneamente.The initial number of requests for the semaphore that can be satisfied concurrently.

maximumCount
Int32

O número máximo de solicitações para o semáforo que podem ser atendidas simultaneamente.The maximum number of requests for the semaphore that can be satisfied concurrently.

name
String

O nome, se o objeto de sincronização for ser compartilhado com outros processos; caso contrário, null ou uma cadeia de caracteres vazia.The name, if the synchronization object is to be shared with other processes; otherwise, null or an empty string. O nome diferencia maiúsculas de minúsculas.The name is case-sensitive.

createdNew
Boolean

Quando este método retorna, ele conterá true, se um semáforo local tiver sido criado (isto é, se name for null ou uma cadeia de caracteres vazia) ou se o semáforo de sistema nomeado especificado tiver sido criado, false se o semáforo de sistema nomeado especificado já existia.When this method returns, contains true if a local semaphore was created (that is, if name is null or an empty string) or if the specified named system semaphore was created; false if the specified named system semaphore already existed. Este parâmetro é passado não inicializado.This parameter is passed uninitialized.

Exceções

initialCount é maior que maximumCount.initialCount is greater than maximumCount.

- ou --or-

Somente .NET Framework: name é maior que MAX_PATH (260 caracteres)..NET Framework only: name is longer than MAX_PATH (260 characters).

maximumCount é menor que 1.maximumCount is less than 1.

- ou --or- initialCount é menor que 0.initialCount is less than 0.

name é inválido.name is invalid. Isso pode ser por vários motivos, incluindo algumas restrições impostas pelo sistema operacional, como um prefixo desconhecido ou caracteres inválidos.This can be for various reasons, including some restrictions that may be placed by the operating system, such as an unknown prefix or invalid characters. Observe que o nome e os prefixos comuns "Global" e "Local" diferenciam maiúsculas de minúsculas.Note that the name and common prefixes "Global" and "Local" are case-sensitive.

- ou --or-

Ocorreu outro erro.There was some other error. A propriedade HResult pode fornecer mais informações.The HResult property may provide more information.

Somente Windows: name especificou um namespace desconhecido.Windows only: name specified an unknown namespace. Confira mais informações em Nomes do objeto.See Object Names for more information.

O name é muito longo.The name is too long. As restrições de comprimento podem depender do sistema operacional ou da configuração.Length restrictions may depend on the operating system or configuration.

O sinal nomeado existe e tem segurança de controle de acesso e o usuário não tem FullControl.The named semaphore exists and has access control security, and the user does not have FullControl.

Não é possível criar um objeto de sincronização com o name fornecido.A synchronization object with the provided name cannot be created. Um objeto de sincronização de um tipo diferente pode ter o mesmo nome.A synchronization object of a different type might have the same name.

Exemplos

O exemplo de código a seguir demonstra o comportamento de processo cruzado de um semáforo nomeado.The following code example demonstrates the cross-process behavior of a named semaphore. O exemplo cria um semáforo nomeado com uma contagem máxima de cinco e uma contagem inicial de dois.The example creates a named semaphore with a maximum count of five and an initial count of two. Ou seja, ele reserva três entradas para o thread que chama o construtor.That is, it reserves three entries for the thread that calls the constructor. Se createNew for false , o programa fará três chamadas para o WaitOne método.If createNew is false, the program makes three calls to the WaitOne method. Portanto, se você executar o exemplo compilado de duas janelas de comando, a segunda cópia será bloqueada na terceira chamada para WaitOne .Thus, if you run the compiled example from two command windows, the second copy will block on the third call to WaitOne. Libere uma ou mais entradas na primeira cópia do programa para desbloquear a segunda.Release one or more entries in the first copy of the program to unblock the second.

#using <System.dll>
using namespace System;
using namespace System::Threading;

public ref class Example
{
public:
   static void main()
   {
      // The value of this variable is set by the semaphore
      // constructor. It is true if the named system semaphore was
      // created, and false if the named semaphore already existed.
      //
      bool semaphoreWasCreated;
      
      // Create a Semaphore object that represents the named
      // system semaphore "SemaphoreExample". The semaphore has a
      // maximum count of five, and an initial count of two. The
      // Boolean value that indicates creation of the underlying
      // system object is placed in semaphoreWasCreated.
      //
      Semaphore^ sem = gcnew Semaphore( 2,5,L"SemaphoreExample",
         semaphoreWasCreated );
      if ( semaphoreWasCreated )
      {
         // If the named system semaphore was created, its count is
         // set to the initial count requested in the constructor.
         // In effect, the current thread has entered the semaphore
         // three times.
         //
         Console::WriteLine( L"Entered the semaphore three times." );
      }
      else
      {
         // If the named system semaphore was not created,
         // attempt to enter it three times. If another copy of
         // this program is already running, only the first two
         // requests can be satisfied. The third blocks.
         //
         sem->WaitOne();
         Console::WriteLine( L"Entered the semaphore once." );
         sem->WaitOne();
         Console::WriteLine( L"Entered the semaphore twice." );
         sem->WaitOne();
         Console::WriteLine( L"Entered the semaphore three times." );
      }
      
      // The thread executing this program has entered the
      // semaphore three times. If a second copy of the program
      // is run, it will block until this program releases the
      // semaphore at least once.
      //
      Console::WriteLine( L"Enter the number of times to call Release." );
      int n;
      if ( Int32::TryParse( Console::ReadLine(), n ) )
      {
         sem->Release( n );
      }

      int remaining = 3 - n;
      if ( remaining > 0 )
      {
         Console::WriteLine( L"Press Enter to release the remaining "
         L"count ({0}) and exit the program.", remaining );
         Console::ReadLine();
         sem->Release( remaining );
      }
   }
};
using System;
using System.Threading;

public class Example
{
    public static void Main()
    {
        // The value of this variable is set by the semaphore
        // constructor. It is true if the named system semaphore was
        // created, and false if the named semaphore already existed.
        //
        bool semaphoreWasCreated;

        // Create a Semaphore object that represents the named 
        // system semaphore "SemaphoreExample". The semaphore has a
        // maximum count of five, and an initial count of two. The
        // Boolean value that indicates creation of the underlying 
        // system object is placed in semaphoreWasCreated.
        //
        Semaphore sem = new Semaphore(2, 5, "SemaphoreExample", 
            out semaphoreWasCreated);

        if (semaphoreWasCreated)
        {
            // If the named system semaphore was created, its count is
            // set to the initial count requested in the constructor.
            // In effect, the current thread has entered the semaphore
            // three times.
            // 
            Console.WriteLine("Entered the semaphore three times.");
        }
        else
        {      
            // If the named system semaphore was not created,  
            // attempt to enter it three times. If another copy of
            // this program is already running, only the first two
            // requests can be satisfied. The third blocks.
            //
            sem.WaitOne();
            Console.WriteLine("Entered the semaphore once.");
            sem.WaitOne();
            Console.WriteLine("Entered the semaphore twice.");
            sem.WaitOne();
            Console.WriteLine("Entered the semaphore three times.");
        }

        // The thread executing this program has entered the 
        // semaphore three times. If a second copy of the program
        // is run, it will block until this program releases the 
        // semaphore at least once.
        //
        Console.WriteLine("Enter the number of times to call Release.");
        int n;
        if (int.TryParse(Console.ReadLine(), out n))
        {
            sem.Release(n);
        }

        int remaining = 3 - n;
        if (remaining > 0)
        {
            Console.WriteLine("Press Enter to release the remaining " +
                "count ({0}) and exit the program.", remaining);
            Console.ReadLine();
            sem.Release(remaining);
        }
    } 
} 
Imports System.Threading

Public Class Example

    <MTAThread> _
    Public Shared Sub Main()
        ' The value of this variable is set by the semaphore
        ' constructor. It is True if the named system semaphore was
        ' created, and False if the named semaphore already existed.
        '
        Dim semaphoreWasCreated As Boolean

        ' Create a Semaphore object that represents the named 
        ' system semaphore "SemaphoreExample". The semaphore has a
        ' maximum count of five, and an initial count of two. The
        ' Boolean value that indicates creation of the underlying 
        ' system object is placed in semaphoreWasCreated.
        '
        Dim sem As New Semaphore(2, 5, "SemaphoreExample", _
            semaphoreWasCreated)

        If semaphoreWasCreated Then
            ' If the named system semaphore was created, its count is
            ' set to the initial count requested in the constructor.
            ' In effect, the current thread has entered the semaphore
            ' three times.
            ' 
            Console.WriteLine("Entered the semaphore three times.")
        Else
            ' If the named system semaphore was not created,  
            ' attempt to enter it three times. If another copy of
            ' this program is already running, only the first two
            ' requests can be satisfied. The third blocks.
            '
            sem.WaitOne()
            Console.WriteLine("Entered the semaphore once.")
            sem.WaitOne()
            Console.WriteLine("Entered the semaphore twice.")
            sem.WaitOne()
            Console.WriteLine("Entered the semaphore three times.")
        End If

        ' The thread executing this program has entered the 
        ' semaphore three times. If a second copy of the program
        ' is run, it will block until this program releases the 
        ' semaphore at least once.
        '
        Console.WriteLine("Enter the number of times to call Release.")
        Dim n As Integer
        If Integer.TryParse(Console.ReadLine(), n) Then
            sem.Release(n)
        End If

        Dim remaining As Integer = 3 - n
        If (remaining) > 0 Then
            Console.WriteLine("Press Enter to release the remaining " _
                & "count ({0}) and exit the program.", remaining)
            Console.ReadLine()
            sem.Release(remaining)
        End If

    End Sub 
End Class 

Comentários

O name pode ser prefixado com Global\ or Local\ para especificar um namespace.The name may be prefixed with Global\ or Local\ to specify a namespace. Quando o Global namespace é especificado, o objeto de sincronização pode ser compartilhado com qualquer processo no sistema.When the Global namespace is specified, the synchronization object may be shared with any processes on the system. Quando o Local namespace é especificado, que também é o padrão quando nenhum namespace é especificado, o objeto de sincronização pode ser compartilhado com processos na mesma sessão.When the Local namespace is specified, which is also the default when no namespace is specified, the synchronization object may be shared with processes in the same session. No Windows, uma sessão é uma sessão de logon e os serviços normalmente são executados em uma sessão não interativa diferente.On Windows, a session is a login session, and services typically run in a different non-interactive session. Em sistemas operacionais semelhantes ao Unix, cada shell tem sua própria sessão.On Unix-like operating systems, each shell has its own session. Os objetos de sincronização de sessão local podem ser apropriados para sincronizar entre processos com uma relação pai/filho em que todos eles são executados na mesma sessão.Session-local synchronization objects may be appropriate for synchronizing between processes with a parent/child relationship where they all run in the same session. Para obter mais informações sobre nomes de objetos Synchornization no Windows, consulte nomes de objetos.For more information about synchornization object names on Windows, see Object Names.

Se um name for fornecido e um objeto de sincronização do tipo solicitado já existir no namespace, o objeto de sincronização existente será usado.If a name is provided and a synchronization object of the requested type already exists in the namespace, the existing synchronization object is used. Se um objeto de sincronização de um tipo diferente já existir no namespace, um WaitHandleCannotBeOpenedException será gerado.If a synchronization object of a different type already exists in the namespace, a WaitHandleCannotBeOpenedException is thrown. Caso contrário, um novo objeto de sincronização será criado.Otherwise, a new synchronization object is created.

Esse construtor inicializa um Semaphore objeto que representa um semáforo de sistema nomeado.This constructor initializes a Semaphore object that represents a named system semaphore. Você pode criar vários Semaphore objetos que representam o mesmo semáforo nomeado do sistema.You can create multiple Semaphore objects that represent the same named system semaphore.

Se o semáforo do sistema nomeado não existir, ele será criado com a contagem inicial e a contagem máxima especificada por initialCount e maximumCount .If the named system semaphore does not exist, it is created with the initial count and maximum count specified by initialCount and maximumCount. Se o semáforo do sistema nomeado já existir initialCount e maximumCount não for usado, embora os valores inválidos ainda causem exceções.If the named system semaphore already exists, initialCount and maximumCount are not used, although invalid values still cause exceptions. Use createdNew para determinar se o semáforo do sistema foi criado.Use createdNew to determine whether the system semaphore was created.

Se initialCount for menor que maximumCount e createdNew for true , o efeito será o mesmo que se o thread atual tivesse chamado WaitOne ( maximumCount menos initialCount ) vezes.If initialCount is less than maximumCount, and createdNew is true, the effect is the same as if the current thread had called WaitOne (maximumCount minus initialCount) times.

Se você especificar null ou uma cadeia de caracteres vazia para name , um semáforo local será criado, como se você tivesse chamado Semaphore(Int32, Int32) sobrecarga de construtor.If you specify null or an empty string for name, a local semaphore is created, as if you had called the Semaphore(Int32, Int32) constructor overload. Nesse caso, createdNew é sempre true .In this case, createdNew is always true.

Como os semáforos nomeados são visíveis em todo o sistema operacional, eles podem ser usados para coordenar o uso de recursos entre limites de processo.Because named semaphores are visible throughout the operating system, they can be used to coordinate resource use across process boundaries.

Veja também

Aplica-se a

Semaphore(Int32, Int32, String, Boolean, SemaphoreSecurity)

Inicializa uma nova instância da classe Semaphore, especificando o número inicial de entradas e o número máximo de entradas simultâneas, opcionalmente especificando o nome de um objeto de semáforo de sistema, especificando uma variável que recebe um valor que indica se um novo semáforo do sistema foi criado e especificando o controle de acesso de segurança para o semáforo do sistema.Initializes a new instance of the Semaphore class, specifying the initial number of entries and the maximum number of concurrent entries, optionally specifying the name of a system semaphore object, specifying a variable that receives a value indicating whether a new system semaphore was created, and specifying security access control for the system semaphore.

public:
 Semaphore(int initialCount, int maximumCount, System::String ^ name, [Runtime::InteropServices::Out] bool % createdNew, System::Security::AccessControl::SemaphoreSecurity ^ semaphoreSecurity);
public Semaphore (int initialCount, int maximumCount, string name, out bool createdNew, System.Security.AccessControl.SemaphoreSecurity semaphoreSecurity);
new System.Threading.Semaphore : int * int * string * bool * System.Security.AccessControl.SemaphoreSecurity -> System.Threading.Semaphore
Public Sub New (initialCount As Integer, maximumCount As Integer, name As String, ByRef createdNew As Boolean, semaphoreSecurity As SemaphoreSecurity)

Parâmetros

initialCount
Int32

O número inicial de solicitações para o semáforo que podem ser atendidas simultaneamente.The initial number of requests for the semaphore that can be satisfied concurrently.

maximumCount
Int32

O número máximo de solicitações para o semáforo que podem ser atendidas simultaneamente.The maximum number of requests for the semaphore that can be satisfied concurrently.

name
String

O nome, se o objeto de sincronização for ser compartilhado com outros processos; caso contrário, null ou uma cadeia de caracteres vazia.The name, if the synchronization object is to be shared with other processes; otherwise, null or an empty string. O nome diferencia maiúsculas de minúsculas.The name is case-sensitive.

createdNew
Boolean

Quando este método retorna, ele conterá true, se um semáforo local tiver sido criado (isto é, se name for null ou uma cadeia de caracteres vazia) ou se o semáforo de sistema nomeado especificado tiver sido criado, false se o semáforo de sistema nomeado especificado já existia.When this method returns, contains true if a local semaphore was created (that is, if name is null or an empty string) or if the specified named system semaphore was created; false if the specified named system semaphore already existed. Este parâmetro é passado não inicializado.This parameter is passed uninitialized.

semaphoreSecurity
SemaphoreSecurity

Um objeto SemaphoreSecurity que representa a segurança de controle de acesso a ser aplicada ao semáforo de sistema nomeado.A SemaphoreSecurity object that represents the access control security to be applied to the named system semaphore.

Exceções

initialCount é maior que maximumCount.initialCount is greater than maximumCount.

- ou --or-

Somente .NET Framework: name é maior que MAX_PATH (260 caracteres)..NET Framework only: name is longer than MAX_PATH (260 characters).

maximumCount é menor que 1.maximumCount is less than 1.

- ou --or- initialCount é menor que 0.initialCount is less than 0.

O sinal nomeado existe e tem segurança de controle de acesso e o usuário não tem FullControl.The named semaphore exists and has access control security, and the user does not have FullControl.

name é inválido.name is invalid. Isso pode ser por vários motivos, incluindo algumas restrições impostas pelo sistema operacional, como um prefixo desconhecido ou caracteres inválidos.This can be for various reasons, including some restrictions that may be placed by the operating system, such as an unknown prefix or invalid characters. Observe que o nome e os prefixos comuns "Global" e "Local" diferenciam maiúsculas de minúsculas.Note that the name and common prefixes "Global" and "Local" are case-sensitive.

- ou --or-

Ocorreu outro erro.There was some other error. A propriedade HResult pode fornecer mais informações.The HResult property may provide more information.

Somente Windows: name especificou um namespace desconhecido.Windows only: name specified an unknown namespace. Confira mais informações em Nomes do objeto.See Object Names for more information.

O name é muito longo.The name is too long. As restrições de comprimento podem depender do sistema operacional ou da configuração.Length restrictions may depend on the operating system or configuration.

Não é possível criar um objeto de sincronização com o name fornecido.A synchronization object with the provided name cannot be created. Um objeto de sincronização de um tipo diferente pode ter o mesmo nome.A synchronization object of a different type might have the same name.

Exemplos

O exemplo de código a seguir demonstra o comportamento de processo cruzado de um semáforo nomeado com segurança de controle de acesso.The following code example demonstrates the cross-process behavior of a named semaphore with access control security. O exemplo usa a OpenExisting(String) sobrecarga do método para testar a existência de um semáforo nomeado.The example uses the OpenExisting(String) method overload to test for the existence of a named semaphore. Se o semáforo não existir, ele será criado com uma contagem máxima de dois e com segurança de controle de acesso que nega ao usuário atual o direito de usar o semáforo, mas concede o direito de ler e alterar permissões no semáforo.If the semaphore does not exist, it is created with a maximum count of two and with access control security that denies the current user the right to use the semaphore but grants the right to read and change permissions on the semaphore. Se você executar o exemplo compilado de duas janelas de comando, a segunda cópia gerará uma exceção de violação de acesso na chamada para o OpenExisting(String) método.If you run the compiled example from two command windows, the second copy will throw an access violation exception on the call to the OpenExisting(String) method. A exceção é capturada e o exemplo usa a OpenExisting(String, SemaphoreRights) sobrecarga do método para abrir o semáforo com os direitos necessários para ler e alterar as permissões.The exception is caught, and the example uses the OpenExisting(String, SemaphoreRights) method overload to open the semaphore with the rights needed to read and change the permissions.

Depois que as permissões forem alteradas, o semáforo será aberto com os direitos necessários para entrar e liberar.After the permissions are changed, the semaphore is opened with the rights required to enter and release. Se você executar o exemplo compilado de uma terceira janela de comando, ele será executado usando as novas permissões.If you run the compiled example from a third command window, it runs using the new permissions.

#using <System.dll>
using namespace System;
using namespace System::Threading;
using namespace System::Security::AccessControl;
using namespace System::Security::Permissions;

public ref class Example
{
public:
   [SecurityPermissionAttribute(SecurityAction::Demand, Flags = SecurityPermissionFlag::UnmanagedCode)]
   static void main()
   {
      String^ semaphoreName = L"SemaphoreExample5";

      Semaphore^ sem = nullptr;
      bool doesNotExist = false;
      bool unauthorized = false;
      
      // Attempt to open the named semaphore.
      try
      {
         // Open the semaphore with (SemaphoreRights.Synchronize
         // | SemaphoreRights.Modify), to enter and release the
         // named semaphore.
         //
         sem = Semaphore::OpenExisting( semaphoreName );
      }
      catch ( WaitHandleCannotBeOpenedException^ ex ) 
      {
         Console::WriteLine( L"Semaphore does not exist." );
         doesNotExist = true;
      }
      catch ( UnauthorizedAccessException^ ex ) 
      {
         Console::WriteLine( L"Unauthorized access: {0}", ex->Message );
         unauthorized = true;
      }

      // There are three cases: (1) The semaphore does not exist.
      // (2) The semaphore exists, but the current user doesn't
      // have access. (3) The semaphore exists and the user has
      // access.
      //
      if ( doesNotExist )
      {
         // The semaphore does not exist, so create it.
         //
         // The value of this variable is set by the semaphore
         // constructor. It is true if the named system semaphore was
         // created, and false if the named semaphore already existed.
         //
         bool semaphoreWasCreated;
         
         // Create an access control list (ACL) that denies the
         // current user the right to enter or release the
         // semaphore, but allows the right to read and change
         // security information for the semaphore.
         //
         String^ user = String::Concat( Environment::UserDomainName,
            L"\\", Environment::UserName );
         SemaphoreSecurity^ semSec = gcnew SemaphoreSecurity;

         SemaphoreAccessRule^ rule = gcnew SemaphoreAccessRule( user,
            static_cast<SemaphoreRights>(
               SemaphoreRights::Synchronize |
               SemaphoreRights::Modify ),
            AccessControlType::Deny );
         semSec->AddAccessRule( rule );

         rule = gcnew SemaphoreAccessRule( user,
            static_cast<SemaphoreRights>(
               SemaphoreRights::ReadPermissions |
               SemaphoreRights::ChangePermissions ),
            AccessControlType::Allow );
         semSec->AddAccessRule( rule );
         
         // Create a Semaphore object that represents the system
         // semaphore named by the constant 'semaphoreName', with
         // maximum count three, initial count three, and the
         // specified security access. The Boolean value that
         // indicates creation of the underlying system object is
         // placed in semaphoreWasCreated.
         //
         sem = gcnew Semaphore( 3,3,semaphoreName,semaphoreWasCreated,semSec );
         
         // If the named system semaphore was created, it can be
         // used by the current instance of this program, even
         // though the current user is denied access. The current
         // program enters the semaphore. Otherwise, exit the
         // program.
         //
         if ( semaphoreWasCreated )
         {
            Console::WriteLine( L"Created the semaphore." );
         }
         else
         {
            Console::WriteLine( L"Unable to create the semaphore." );
            return;
         }

      }
      else if ( unauthorized )
      {
         // Open the semaphore to read and change the access
         // control security. The access control security defined
         // above allows the current user to do this.
         //
         try
         {
            sem = Semaphore::OpenExisting( semaphoreName,
               static_cast<SemaphoreRights>(
                  SemaphoreRights::ReadPermissions |
                  SemaphoreRights::ChangePermissions ));
            
            // Get the current ACL. This requires
            // SemaphoreRights.ReadPermissions.
            SemaphoreSecurity^ semSec = sem->GetAccessControl();

            String^ user = String::Concat( Environment::UserDomainName,
               L"\\", Environment::UserName );
            
            // First, the rule that denied the current user
            // the right to enter and release the semaphore must
            // be removed.
            SemaphoreAccessRule^ rule = gcnew SemaphoreAccessRule( user,
               static_cast<SemaphoreRights>(
                  SemaphoreRights::Synchronize |
                  SemaphoreRights::Modify ),
               AccessControlType::Deny );
            semSec->RemoveAccessRule( rule );
            
            // Now grant the user the correct rights.
            //
            rule = gcnew SemaphoreAccessRule( user,
               static_cast<SemaphoreRights>(
                  SemaphoreRights::Synchronize |
                  SemaphoreRights::Modify ),
               AccessControlType::Allow );
            semSec->AddAccessRule( rule );
            
            // Update the ACL. This requires
            // SemaphoreRights.ChangePermissions.
            sem->SetAccessControl( semSec );

            Console::WriteLine( L"Updated semaphore security." );
            
            // Open the semaphore with (SemaphoreRights.Synchronize
            // | SemaphoreRights.Modify), the rights required to
            // enter and release the semaphore.
            //
            sem = Semaphore::OpenExisting( semaphoreName );

         }
         catch ( UnauthorizedAccessException^ ex ) 
         {
            Console::WriteLine( L"Unable to change permissions: {0}", ex->Message );
            return;
         }
      }
      
      // Enter the semaphore, and hold it until the program
      // exits.
      //
      try
      {
         sem->WaitOne();
         Console::WriteLine( L"Entered the semaphore." );
         Console::WriteLine( L"Press the Enter key to exit." );
         Console::ReadLine();
         sem->Release();
      }
      catch ( UnauthorizedAccessException^ ex ) 
      {
         Console::WriteLine( L"Unauthorized access: {0}", ex->Message );
      }
   }
};
using System;
using System.Threading;
using System.Security.AccessControl;

internal class Example
{
    internal static void Main()
    {
        const string semaphoreName = "SemaphoreExample5";

        Semaphore sem = null;
        bool doesNotExist = false;
        bool unauthorized = false;

        // Attempt to open the named semaphore.
        try
        {
            // Open the semaphore with (SemaphoreRights.Synchronize
            // | SemaphoreRights.Modify), to enter and release the
            // named semaphore.
            //
            sem = Semaphore.OpenExisting(semaphoreName);
        }
        catch(WaitHandleCannotBeOpenedException)
        {
            Console.WriteLine("Semaphore does not exist.");
            doesNotExist = true;
        }
        catch(UnauthorizedAccessException ex)
        {
            Console.WriteLine("Unauthorized access: {0}", ex.Message);
            unauthorized = true;
        }

        // There are three cases: (1) The semaphore does not exist.
        // (2) The semaphore exists, but the current user doesn't 
        // have access. (3) The semaphore exists and the user has
        // access.
        //
        if (doesNotExist)
        {
            // The semaphore does not exist, so create it.
            //
            // The value of this variable is set by the semaphore
            // constructor. It is true if the named system semaphore was
            // created, and false if the named semaphore already existed.
            //
            bool semaphoreWasCreated;

            // Create an access control list (ACL) that denies the
            // current user the right to enter or release the 
            // semaphore, but allows the right to read and change
            // security information for the semaphore.
            //
            string user = Environment.UserDomainName + "\\" 
                + Environment.UserName;
            SemaphoreSecurity semSec = new SemaphoreSecurity();

            SemaphoreAccessRule rule = new SemaphoreAccessRule(
                user, 
                SemaphoreRights.Synchronize | SemaphoreRights.Modify, 
                AccessControlType.Deny);
            semSec.AddAccessRule(rule);

            rule = new SemaphoreAccessRule(
                user, 
                SemaphoreRights.ReadPermissions | SemaphoreRights.ChangePermissions,
                AccessControlType.Allow);
            semSec.AddAccessRule(rule);

            // Create a Semaphore object that represents the system
            // semaphore named by the constant 'semaphoreName', with
            // maximum count three, initial count three, and the
            // specified security access. The Boolean value that 
            // indicates creation of the underlying system object is
            // placed in semaphoreWasCreated.
            //
            sem = new Semaphore(3, 3, semaphoreName, 
                out semaphoreWasCreated, semSec);

            // If the named system semaphore was created, it can be
            // used by the current instance of this program, even 
            // though the current user is denied access. The current
            // program enters the semaphore. Otherwise, exit the
            // program.
            // 
            if (semaphoreWasCreated)
            {
                Console.WriteLine("Created the semaphore.");
            }
            else
            {
                Console.WriteLine("Unable to create the semaphore.");
                return;
            }
        }
        else if (unauthorized)
        {
            // Open the semaphore to read and change the access
            // control security. The access control security defined
            // above allows the current user to do this.
            //
            try
            {
                sem = Semaphore.OpenExisting(
                    semaphoreName, 
                    SemaphoreRights.ReadPermissions 
                        | SemaphoreRights.ChangePermissions);

                // Get the current ACL. This requires 
                // SemaphoreRights.ReadPermissions.
                SemaphoreSecurity semSec = sem.GetAccessControl();
                
                string user = Environment.UserDomainName + "\\" 
                    + Environment.UserName;

                // First, the rule that denied the current user 
                // the right to enter and release the semaphore must
                // be removed.
                SemaphoreAccessRule rule = new SemaphoreAccessRule(
                    user, 
                    SemaphoreRights.Synchronize | SemaphoreRights.Modify, 
                    AccessControlType.Deny);
                semSec.RemoveAccessRule(rule);

                // Now grant the user the correct rights.
                // 
                rule = new SemaphoreAccessRule(user, 
                     SemaphoreRights.Synchronize | SemaphoreRights.Modify, 
                     AccessControlType.Allow);
                semSec.AddAccessRule(rule);

                // Update the ACL. This requires
                // SemaphoreRights.ChangePermissions.
                sem.SetAccessControl(semSec);

                Console.WriteLine("Updated semaphore security.");

                // Open the semaphore with (SemaphoreRights.Synchronize 
                // | SemaphoreRights.Modify), the rights required to
                // enter and release the semaphore.
                //
                sem = Semaphore.OpenExisting(semaphoreName);
            }
            catch(UnauthorizedAccessException ex)
            {
                Console.WriteLine("Unable to change permissions: {0}", ex.Message);
                return;
            }
        }

        // Enter the semaphore, and hold it until the program
        // exits.
        //
        try
        {
            sem.WaitOne();
            Console.WriteLine("Entered the semaphore.");
            Console.WriteLine("Press the Enter key to exit.");
            Console.ReadLine();
            sem.Release();
        }
        catch(UnauthorizedAccessException ex)
        {
            Console.WriteLine("Unauthorized access: {0}", ex.Message);
        }
    }
}
Imports System.Threading
Imports System.Security.AccessControl

Friend Class Example

    <MTAThread> _
    Friend Shared Sub Main()
        Const semaphoreName As String = "SemaphoreExample5"

        Dim sem As Semaphore = Nothing
        Dim doesNotExist as Boolean = False
        Dim unauthorized As Boolean = False

        ' Attempt to open the named semaphore.
        Try
            ' Open the semaphore with (SemaphoreRights.Synchronize
            ' Or SemaphoreRights.Modify), to enter and release the
            ' named semaphore.
            '
            sem = Semaphore.OpenExisting(semaphoreName)
        Catch ex As WaitHandleCannotBeOpenedException
            Console.WriteLine("Semaphore does not exist.")
            doesNotExist = True
        Catch ex As UnauthorizedAccessException
            Console.WriteLine("Unauthorized access: {0}", ex.Message)
            unauthorized = True
        End Try

        ' There are three cases: (1) The semaphore does not exist.
        ' (2) The semaphore exists, but the current user doesn't 
        ' have access. (3) The semaphore exists and the user has
        ' access.
        '
        If doesNotExist Then
            ' The semaphore does not exist, so create it.
            '
            ' The value of this variable is set by the semaphore
            ' constructor. It is True if the named system semaphore was
            ' created, and False if the named semaphore already existed.
            '
            Dim semaphoreWasCreated As Boolean

            ' Create an access control list (ACL) that denies the
            ' current user the right to enter or release the 
            ' semaphore, but allows the right to read and change
            ' security information for the semaphore.
            '
            Dim user As String = Environment.UserDomainName _ 
                & "\" & Environment.UserName
            Dim semSec As New SemaphoreSecurity()

            Dim rule As New SemaphoreAccessRule(user, _
                SemaphoreRights.Synchronize Or SemaphoreRights.Modify, _
                AccessControlType.Deny)
            semSec.AddAccessRule(rule)

            rule = New SemaphoreAccessRule(user, _
                SemaphoreRights.ReadPermissions Or _
                SemaphoreRights.ChangePermissions, _
                AccessControlType.Allow)
            semSec.AddAccessRule(rule)

            ' Create a Semaphore object that represents the system
            ' semaphore named by the constant 'semaphoreName', with
            ' maximum count three, initial count three, and the
            ' specified security access. The Boolean value that 
            ' indicates creation of the underlying system object is
            ' placed in semaphoreWasCreated.
            '
            sem = New Semaphore(3, 3, semaphoreName, _
                semaphoreWasCreated, semSec)

            ' If the named system semaphore was created, it can be
            ' used by the current instance of this program, even 
            ' though the current user is denied access. The current
            ' program enters the semaphore. Otherwise, exit the
            ' program.
            ' 
            If semaphoreWasCreated Then
                Console.WriteLine("Created the semaphore.")
            Else
                Console.WriteLine("Unable to create the semaphore.")
                Return
            End If

        ElseIf unauthorized Then

            ' Open the semaphore to read and change the access
            ' control security. The access control security defined
            ' above allows the current user to do this.
            '
            Try
                sem = Semaphore.OpenExisting(semaphoreName, _
                    SemaphoreRights.ReadPermissions Or _
                    SemaphoreRights.ChangePermissions)

                ' Get the current ACL. This requires 
                ' SemaphoreRights.ReadPermissions.
                Dim semSec As SemaphoreSecurity = sem.GetAccessControl()
                
                Dim user As String = Environment.UserDomainName _ 
                    & "\" & Environment.UserName

                ' First, the rule that denied the current user 
                ' the right to enter and release the semaphore must
                ' be removed.
                Dim rule As New SemaphoreAccessRule(user, _
                    SemaphoreRights.Synchronize Or SemaphoreRights.Modify, _
                    AccessControlType.Deny)
                semSec.RemoveAccessRule(rule)

                ' Now grant the user the correct rights.
                ' 
                rule = New SemaphoreAccessRule(user, _
                    SemaphoreRights.Synchronize Or SemaphoreRights.Modify, _
                    AccessControlType.Allow)
                semSec.AddAccessRule(rule)

                ' Update the ACL. This requires
                ' SemaphoreRights.ChangePermissions.
                sem.SetAccessControl(semSec)

                Console.WriteLine("Updated semaphore security.")

                ' Open the semaphore with (SemaphoreRights.Synchronize 
                ' Or SemaphoreRights.Modify), the rights required to
                ' enter and release the semaphore.
                '
                sem = Semaphore.OpenExisting(semaphoreName)

            Catch ex As UnauthorizedAccessException
                Console.WriteLine("Unable to change permissions: {0}", _
                    ex.Message)
                Return
            End Try

        End If

        ' Enter the semaphore, and hold it until the program
        ' exits.
        '
        Try
            sem.WaitOne()
            Console.WriteLine("Entered the semaphore.")
            Console.WriteLine("Press the Enter key to exit.")
            Console.ReadLine()
            sem.Release()
        Catch ex As UnauthorizedAccessException
            Console.WriteLine("Unauthorized access: {0}", _
                ex.Message)
        End Try
    End Sub 
End Class 

Comentários

Use este construtor para aplicar a segurança de controle de acesso a um semáforo do sistema nomeado quando ele é criado, impedindo que outro código controle o semáforo.Use this constructor to apply access control security to a named system semaphore when it is created, preventing other code from taking control of the semaphore.

O name pode ser prefixado com Global\ or Local\ para especificar um namespace.The name may be prefixed with Global\ or Local\ to specify a namespace. Quando o Global namespace é especificado, o objeto de sincronização pode ser compartilhado com qualquer processo no sistema.When the Global namespace is specified, the synchronization object may be shared with any processes on the system. Quando o Local namespace é especificado, que também é o padrão quando nenhum namespace é especificado, o objeto de sincronização pode ser compartilhado com processos na mesma sessão.When the Local namespace is specified, which is also the default when no namespace is specified, the synchronization object may be shared with processes in the same session. No Windows, uma sessão é uma sessão de logon e os serviços normalmente são executados em uma sessão não interativa diferente.On Windows, a session is a login session, and services typically run in a different non-interactive session. Em sistemas operacionais semelhantes ao Unix, cada shell tem sua própria sessão.On Unix-like operating systems, each shell has its own session. Os objetos de sincronização de sessão local podem ser apropriados para sincronizar entre processos com uma relação pai/filho em que todos eles são executados na mesma sessão.Session-local synchronization objects may be appropriate for synchronizing between processes with a parent/child relationship where they all run in the same session. Para obter mais informações sobre nomes de objetos Synchornization no Windows, consulte nomes de objetos.For more information about synchornization object names on Windows, see Object Names.

Se um name for fornecido e um objeto de sincronização do tipo solicitado já existir no namespace, o objeto de sincronização existente será usado.If a name is provided and a synchronization object of the requested type already exists in the namespace, the existing synchronization object is used. Se um objeto de sincronização de um tipo diferente já existir no namespace, um WaitHandleCannotBeOpenedException será gerado.If a synchronization object of a different type already exists in the namespace, a WaitHandleCannotBeOpenedException is thrown. Caso contrário, um novo objeto de sincronização será criado.Otherwise, a new synchronization object is created.

Esse construtor inicializa um Semaphore objeto que representa um semáforo de sistema nomeado.This constructor initializes a Semaphore object that represents a named system semaphore. Você pode criar vários Semaphore objetos que representam o mesmo semáforo nomeado do sistema.You can create multiple Semaphore objects that represent the same named system semaphore.

Se o semáforo do sistema nomeado não existir, ele será criado com a segurança de controle de acesso especificada.If the named system semaphore does not exist, it is created with the specified access control security. Se o semáforo nomeado existir, a segurança de controle de acesso especificada será ignorada.If the named semaphore exists, the specified access control security is ignored.

Observação

O chamador tem controle total sobre o objeto recém-criado Semaphore , mesmo que semaphoreSecurity negue ou não conceda alguns direitos de acesso ao usuário atual.The caller has full control over the newly created Semaphore object even if semaphoreSecurity denies or fails to grant some access rights to the current user. No entanto, se o usuário atual tentar obter outro Semaphore objeto para representar o mesmo semáforo nomeado, usando um construtor ou o OpenExisting método, a segurança do controle de acesso do Windows será aplicada.However, if the current user attempts to get another Semaphore object to represent the same named semaphore, using either a constructor or the OpenExisting method, Windows access control security is applied.

Se o semáforo do sistema nomeado não existir, ele será criado com a contagem inicial e a contagem máxima especificada por initialCount e maximumCount .If the named system semaphore does not exist, it is created with the initial count and maximum count specified by initialCount and maximumCount. Se o semáforo do sistema nomeado já existir initialCount e maximumCount não for usado, embora os valores inválidos ainda causem exceções.If the named system semaphore already exists, initialCount and maximumCount are not used, although invalid values still cause exceptions. Use o createdNew parâmetro para determinar se o semáforo do sistema foi criado por esse construtor.Use the createdNew parameter to determine whether the system semaphore was created by this constructor.

Se initialCount for menor que maximumCount e createdNew for true , o efeito será o mesmo que se o thread atual tivesse chamado WaitOne ( maximumCount menos initialCount ) vezes.If initialCount is less than maximumCount, and createdNew is true, the effect is the same as if the current thread had called WaitOne (maximumCount minus initialCount) times.

Se você especificar null ou uma cadeia de caracteres vazia para name , um semáforo local será criado, como se você tivesse chamado Semaphore(Int32, Int32) sobrecarga de construtor.If you specify null or an empty string for name, a local semaphore is created, as if you had called the Semaphore(Int32, Int32) constructor overload. Nesse caso, createdNew é sempre true .In this case, createdNew is always true.

Como os semáforos nomeados são visíveis em todo o sistema operacional, eles podem ser usados para coordenar o uso de recursos entre limites de processo.Because named semaphores are visible throughout the operating system, they can be used to coordinate resource use across process boundaries.

Veja também

Aplica-se a