please dont rip this site Prev Next

CreateSemaphore info  Overview  Group

The CreateSemaphore function creates a named or unnamed semaphore object.

HANDLE CreateSemaphore(

    LPSECURITY_ATTRIBUTES lpSemaphoreAttributes,

// pointer to security attributes

    LONG lInitialCount,

// initial count

    LONG lMaximumCount,

// maximum count

    LPCTSTR lpName 

// pointer to semaphore-object name

   );

Parameters

lpSemaphoreAttributes
Pointer to a SECURITY_ATTRIBUTES structure that determines whether the returned handle can be inherited by child processes. If lpSemaphoreAttributes is NULL, the handle cannot be inherited.

Windows NT: The lpSecurityDescriptor member of the structure specifies a security descriptor for the new semaphore. If lpSemaphoreAttributes is NULL, the semaphore gets a default security descriptor.

Windows 95: The lpSecurityDescriptor member of the structure is ignored.

lInitialCount
Specifies an initial count for the semaphore object. This value must be greater than or equal to zero and less than or equal to lMaximumCount. The state of a semaphore is signaled when its count is greater than zero and nonsignaled when it is zero. The count is decreased by one whenever a wait function releases a thread that was waiting for the semaphore. The count is increased by a specified amount by calling the ReleaseSemaphore function.
lMaximumCount
Specifies the maximum count for the semaphore object. This value must be greater than zero.
lpName
Points to a null-terminated string specifying the name of the semaphore object. The name is limited to MAX_PATH characters, and can contain any character except the backslash path-separator character (\). Name comparison is case sensitive.

If lpName matches the name of an existing named semaphore object, this function requests SEMAPHORE_ALL_ACCESS access to the existing object. In this case, the lInitialCount and lMaximumCount parameters are ignored because they have already been set by the creating process. If the lpSemaphoreAttributes parameter is not NULL, it determines whether the handle can be inherited, but its security-descriptor member is ignored.

If lpName is NULL, the semaphore object is created without a name.

If lpName matches the name of an existing event, mutex, or file-mapping object, the function fails and the GetLastError function returns ERROR_INVALID_HANDLE. This occurs because event, mutex, semaphore, and file-mapping objects share the same name space.

Return Values

If the function succeeds, the return value is a handle to the semaphore object. If the named semaphore object existed before the function call, the GetLastError function returns ERROR_ALREADY_EXISTS. Otherwise, GetLastError returns zero.

If the function fails, the return value is NULL. To get extended error information, call GetLastError.

Remarks

The handle returned by CreateSemaphore has SEMAPHORE_ALL_ACCESS access to the new semaphore object and can be used in any function that requires a handle to a semaphore object.

Any thread of the calling process can specify the semaphore-object handle in a call to one of the wait functions. The single-object wait functions return when the state of the specified object is signaled. The multiple-object wait functions can be instructed to return either when any one or when all of the specified objects are signaled. When a wait function returns, the waiting thread is released to continue its execution.

The state of a semaphore object is signaled when its count is greater than zero, and nonsignaled when its count is equal to zero. The lInitialCount parameter specifies the initial count. Each time a waiting thread is released because of the semaphore’s signaled state, the count of the semaphore is decreased by one. Use the ReleaseSemaphore function to increment a semaphore’s count by a specified amount. The count can never be less than zero or greater than the value specified in the lMaximumCount parameter.

Multiple processes can have handles of the same semaphore object, enabling use of the object for interprocess synchronization. The following object-sharing mechanisms are available:

Use the CloseHandle function to close the handle. The system closes the handle automatically when the process terminates. The semaphore object is destroyed when its last handle has been closed.

See Also

CloseHandle, CreateProcess, DuplicateHandle, OpenSemaphore, ReleaseSemaphore, SECURITY_ATTRIBUTES

See also:


file: /Techref/os/win/api/win32/func/src/f11_5.htm, 7KB, , updated: 2000/4/7 12:19, local time: 2022/5/24 02:55,
TOP NEW HELP FIND: 
3.236.234.223:LOG IN

 ©2022 These pages are served without commercial sponsorship. (No popup ads, etc...).Bandwidth abuse increases hosting cost forcing sponsorship or shutdown. This server aggressively defends against automated copying for any reason including offline viewing, duplication, etc... Please respect this requirement and DO NOT RIP THIS SITE. Questions?
Please DO link to this page! Digg it! / MAKE!

<A HREF="http://www.piclist.com/techref/os/win/api/win32/func/src/f11_5.htm"> CreateSemaphore</A>

After you find an appropriate page, you are invited to your to this massmind site! (posts will be visible only to you before review) Just type a nice message (short messages are blocked as spam) in the box and press the Post button. (HTML welcomed, but not the <A tag: Instead, use the link box to link to another page. A tutorial is available Members can login to post directly, become page editors, and be credited for their posts.


Link? Put it here: 
if you want a response, please enter your email address: 
Attn spammers: All posts are reviewed before being made visible to anyone other than the poster.
Did you find what you needed?

  PICList 2022 contributors:
o List host: MIT, Site host massmind.org, Top posters @20220524
* Page Editors: James Newton, David Cary, and YOU!
* Roman Black of Black Robotics donates from sales of Linistep stepper controller kits.
* Ashley Roll of Digital Nemesis donates from sales of RCL-1 RS232 to TTL converters.
* Monthly Subscribers: Gregg Rew. on-going support is MOST appreciated!
* Contributors: Richard Seriani, Sr.
 

Welcome to www.piclist.com!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  .