只允许应用程序有 3 个使用信号量的实例

发布于 2024-12-05 07:37:46 字数 316 浏览 1 评论 0原文

我正在尝试使用信号量实现一个简单的例程，该例程允许我仅运行该应用程序的 3 个实例。我可以使用 3 个互斥体，但这不是一个好方法，到目前为止我已经尝试过，

var
  hSem:THandle;
begin
  hSem := CreateSemaphore(nil,3,3,'MySemp3');
  if hSem = 0 then
  begin
    ShowMessage('Application can be run only 3 times at once');
    Halt(1);
  end;

我怎样才能正确地做到这一点？

原文

I am trying to implement a simple routine using semaphores that will allow me to run only 3 instances of the application. I could use 3 mutexes but that is not a nice approach i tried this so far

var
  hSem:THandle;
begin
  hSem := CreateSemaphore(nil,3,3,'MySemp3');
  if hSem = 0 then
  begin
    ShowMessage('Application can be run only 3 times at once');
    Halt(1);
  end;

How can i do this properly ?

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浅蓝的眸勾画不出的柔情 2024-12-12 07:37:46

始终确保释放信号量，因为如果应用程序终止，这不会自动完成。

program Project72;

{$APPTYPE CONSOLE}

uses
  Windows,
  SysUtils;

var
  hSem: THandle;

begin
  try
    hSem := CreateSemaphore(nil, 3, 3, 'C15F8F92-2620-4F3C-B8EA-A27285F870DC/myApp');
    Win32Check(hSem <> 0);
    try
      if WaitForSingleObject(hSem, 0) <> WAIT_OBJECT_0 then
        Writeln('Cannot execute, 3 instances already running')
      else begin
        try
          // place your code here
          Writeln('Running, press Enter to stop ...');
          Readln;
        finally ReleaseSemaphore(hSem, 1, nil); end;
      end;
    finally CloseHandle(hSem); end;
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
end.

Always make sure that you release a semaphore because this is not done automatically if your application dies.

program Project72;

{$APPTYPE CONSOLE}

uses
  Windows,
  SysUtils;

var
  hSem: THandle;

begin
  try
    hSem := CreateSemaphore(nil, 3, 3, 'C15F8F92-2620-4F3C-B8EA-A27285F870DC/myApp');
    Win32Check(hSem <> 0);
    try
      if WaitForSingleObject(hSem, 0) <> WAIT_OBJECT_0 then
        Writeln('Cannot execute, 3 instances already running')
      else begin
        try
          // place your code here
          Writeln('Running, press Enter to stop ...');
          Readln;
        finally ReleaseSemaphore(hSem, 1, nil); end;
      end;
    finally CloseHandle(hSem); end;
  except
    on E: Exception do
      Writeln(E.ClassName, ': ', E.Message);
  end;
end.

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初见终念 2024-12-12 07:37:46

您可以使用 JCL。

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音盲 2024-12-12 07:37:46

你必须尝试看看它是否被创建
你必须使用其中一个等待函数来看看你是否可以得到一个计数
最后你必须释放锁并释放它。处理，以便下次用户关闭和打开您的应用程序时它可以工作

干杯

var
  hSem: THandle;
begin
  hSem := OpenSemaphore(nil, SEMAPHORE_ALL_ACCESS, True, 'MySemp3');
  if hSem = 0 then
    hSem := CreateSemaphore(nil, 3, 3,'MySemp3');

  if hSem = 0 then
  begin
    ShowMessage('... show the error');
    Halt(1);
    Exit;     
  end;

  if WaitForSingleObject(hSem, 0) <> WAIT_OBJECT_0 then
  begin
    CloseHandle(hSem);
    ShowMessage('Application can be runed only 3 times at once');
    Halt(1);
    Exit; 
  end;

  try   
    your application.run codes..

  finally
    ReleaseSemaphore(hSem, 1, nil);
    CloseHandle(hSem);
  end;

You must try to see if it was created
You must use one of the wait function to see if you can get a count
At the end, you must release the lock & handle so that it can work the next time user close and open your app

Cheers

var
  hSem: THandle;
begin
  hSem := OpenSemaphore(nil, SEMAPHORE_ALL_ACCESS, True, 'MySemp3');
  if hSem = 0 then
    hSem := CreateSemaphore(nil, 3, 3,'MySemp3');

  if hSem = 0 then
  begin
    ShowMessage('... show the error');
    Halt(1);
    Exit;     
  end;

  if WaitForSingleObject(hSem, 0) <> WAIT_OBJECT_0 then
  begin
    CloseHandle(hSem);
    ShowMessage('Application can be runed only 3 times at once');
    Halt(1);
    Exit; 
  end;

  try   
    your application.run codes..

  finally
    ReleaseSemaphore(hSem, 1, nil);
    CloseHandle(hSem);
  end;

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