Module ringo/concurrent
Utilities for working with multiple concurrently running threads.
Semaphore (permits)
A counting semaphore that can be used to coordinate and synchronize cooperation between synchronous threads. A semaphore keeps a number of permits.
Note that Worker events are usually run in the single thread of the local
event loop and thus don't require synchronization provided by semaphores.
The only case when you may want to use a semaphore with workers is when
setting the syncCallbacks flag as second argument to Worker.postMessage()
since this will cause callbacks from the worker to be run in their own
thread instead of the event loop.
To synchronize threads using a semaphore, a threads may ask for one or more permits using the wait and tryWait methods. If the requested number of permits is available, they are subtracted from the number of permits in the semaphore and the method returns immediately.
If the number of requested permits is not available, the wait and tryWait
methods block until another thread adds the required permits using the
signal method or, in the case of tryWait,
the specified timeout expires.
Parameters
| Number | permits | the number of initial permits, defaults to 0 |
Semaphore.prototype. signal (permits)
Add one or more permits to the semaphore.
Parameters
| Number | permits | the number of permits to give, defaults to 1 |
Semaphore.prototype. tryWait (timeout, permits)
Wait for one or more permits for the given span of time. Returns true if the requested permits could be acquired before the timeout elapsed.
Parameters
| Number | timeout | The span of time to wait, in milliseconds |
| Number | permits | the number of permits to wait for, defaults to 1 |
Returns
true if the requested permits could be acquired, false if the timeout elapsed |
Semaphore.prototype. wait (permits)
Wait for one or more permits.
Parameters
| Number | permits | the number of permits to wait for, defaults to 1 |