|
Using Mutex Objects
You can use a mutex object to protect a shared resource from simultaneous
access by multiple threads or processes. Each thread must wait for ownership of the
mutex before it can execute the code that accesses the shared resource. For
example, if several threads share access to a database, the threads can use a
mutex object to permit only one thread at a time to write to the database.
In the following example, a process uses the CreateMutex function to create a named mutex object or open a handle of an existing mutex
object.
HANDLE hMutex;
// Create a mutex with no initial owner.
hMutex = CreateMutex(
NULL, // no security attributes
FALSE, // initially not owned
"MutexToProtectDatabase"); // name of mutex
if (hMutex == NULL)
{
// Check for error.
}
When a thread of this process writes to the database, as in the next example,
it first requests ownership of the mutex. If it gets ownership, the thread
writes to the database and then releases its ownership.
The example uses the try-finally structured exception-handling syntax to ensure that the thread properly
releases the mutex object. The finally block of code is executed no matter how the try block terminates (unless the try block includes a call to the TerminateThread function). This prevents the mutex object from being abandoned inadvertently.
BOOL FunctionToWriteToDatabase(HANDLE hMutex)
{
DWORD dwWaitResult;
// Request ownership of mutex.
dwWaitResult = WaitForSingleObject(
hMutex, // handle of mutex
5000L); // five-second time-out interval
switch (dwWaitResult)
{
// The thread got mutex ownership.
case WAIT_OBJECT_0:
try {
// Write to the database.
}
finally {
// Release ownership of the mutex object.
if (! ReleaseMutex(hMutex)) {
// Deal with error.
}
break;
}
// Cannot get mutex ownership due to time-out.
case WAIT_TIMEOUT:
return FALSE;
// Got ownership of the abandoned mutex object.
case WAIT_ABANDONED:
return FALSE;
}
return TRUE;
}
| Last news from Greatis Software |
 |
|
Nostalgia .Net |
|
.Net is powerful, but not all-powerful, so sometimes we need to use Win32 API for our .Net applications. It's simple enough with Platform Invoke if you have Win32 skill, but we do not always have time to dig the ancient documentation, declare the special types that are compatible with Win32, find the values of the Win32's constants and so on. Nostalgia .Net offers several simple-to-use classes, and components that will allow you to forget about the headache of Win32 and just use the power of Win32 in your application the same way as you use the native. Net classes. More » |
| Recommended software for developers |
 |
|
Ultimate Pack |
|
Component pack for Delphi and C++ Builder that contains runtime form designer, runtime object inspector, print suite and much more for the very special price. More » |
 |
|
Form Designer .Net |
|
Unique runtime form design solution that allows to edit any form in .Net WinForms application at runtime with full source codes for only 300 euro! More » |
 |
|
Print Suite .Net |
|
Print Suite .Net is a set of components for easy printing texts, images and grids from your WinForms applications. Full C# source codes are available More » |
 |
|
Gradient Controls .Net |
|
Gradient Controls .Net offers controls with gradient background feature. Labels, panels and so on... Full C# source codes are available More » |
 |
|
Greatis iGrid |
|
iGrid plots drawing grid right over your desktop, so you can use it everywhere, with any drawing application without any special plugins for different graphic editors. More » |
All the contacts and projectsDmitry Vasiliev (just.dmitry)
Related LinksSoftware for Visual Studio .NET developers
Software for Delphi and C++ Builder developers
Software for Visual Basic 6 developers
Delphi Tips&Tricks
MegaDetailed.NET More Online Helps Win32 Programmer's Reference
Win32 Multimedia Programmer's Reference
OLE Programmer's Reference
Microsoft Windows Pen API Programmer's Reference
Microsoft Windows Sockets 2 Reference
Microsoft Windows Telephony API (TAPI) Programmer's Reference
Unix Manual Pages
|
