Re: Using semaphores in PHP.

Jim Winstead <jimw@php.net> writes: > On Nov 16, Tom May wrote: > > Any input on whether adding semaphore wrappers would be a reasonable > > thing to do, and how to deal with the time limit problem (other than > > not using a time limit)? > > Semaphores would be cool, especially if they were cross-platform. I would > recommend looking at the resource-list management in PHP as a means of > registering and cleaning up these semaphores. (Check out php3_list.h, > list.c, and a module like db.c to see how these functions are used.) The resource list stuff works great. I've implemented System V semaphore wrappers with the following interface: $sem = sem_get(int key, [int max_acquire]); Gets or creates a System V semaphore and returns an id you can use to access it, or false on failure The number of processes that can acquire the semaphore simultaneously is set to max_acquire (defaults to 1). Actually this value is set only if the process finds it is the only process currently attached to the semaphore. The semaphore is created with permissions = 666. sem_acquire($sem); Blocks (if necessary) until the semaphore can be acquired. Attempting to acquire a semaphore that is currently acquired will block forever. This behavior can easily be changed to allows calls to sem_acquire and sem_release to nest. Returns true on success, false on failure. sem_release($sem); Releases the semaphore if it is currently acquired, otherwise logs an error and returns false. Returns true on success, false on failure. Semaphores are automatically released (if necessary) when a request is finished. I've done rudimentary testing on Solaris 2.6 and Linux 2.1.122. Note that System V semaphores are required. I'll leave the cross-platform stuff for someone else or until I need it on another platform myself :-) It won't be easy to make it truly cross-platform. It may even be impossible. If you want it, cool, I can commit it along with the necessary changes to configure.in, Makefile.in, config.h.in, and internal_functions.c. I'll even attempt to do the documentation. If you don't want it, fine, I can just dl() it and use it myself. Tom. -- PHP Development Mailing List http://www.php.net/ To unsubscribe send an empty message to php-dev-unsubscribe@lists.php.net For help: php-dev-help@lists.php.net