Coro::Semaphore - counting semaphores
use Coro::Semaphore; $sig = new Coro::Semaphore [initial value]; $sig->down; # wait for signal # ... some other "thread" $sig->up;
This module implements counting semaphores. You can initialize a mutex with any level of parallel users, that is, you can intialize a sempahore that can be downed more than once until it blocks. There is no owner associated with semaphores, so one coroutine can down it while another can up it.
down
up
Counting semaphores are typically used to coordinate access to resources, with the semaphore count initialized to the number of free resources. Coroutines then increment the count when resources are added and decrement the count when resources are removed.
Creates a new sempahore object with the given initial lock count. The default lock count is 1, which means it is unlocked by default. Zero (or negative values) are also allowed, in which case the semaphore is locked by default.
Returns the current semaphore count.
Atomically adds the amount given to the current semaphore count. If the count becomes positive, wakes up any waiters. Does not block if the count becomes negative, however.
Decrement the counter, therefore "locking" the semaphore. This method waits until the semaphore is available if the counter is zero.
Similar to down, but does not actually decrement the counter. Instead, when this function returns, a following call to down or try is guaranteed to succeed without blocking, until the next coroutine switch (cede etc.).
try
cede
Note that using wait is much less efficient than using down, so try to prefer down whenever possible.
wait
If you pass a callback argument to wait, it will not wait, but immediately return. The callback will be called as soon as the semaphore becomes available (which might be instantly), and gets passed the semaphore as first argument.
The callback might down the semaphore exactly once, might wake up other coroutines, but is NOT allowed to block (switch to other coroutines).
This is considered a rather experimental interface, and is subject to change.
Unlock the semaphore again.
Try to down the semaphore. Returns true when this was possible, otherwise return false and leave the semaphore unchanged.
In scalar context, returns the number of coroutines waiting for this semaphore.
This method calls down and then creates a guard object. When the guard object is destroyed it automatically calls up.
Marc Lehmann <schmorp@schmorp.de> http://home.schmorp.de/
To install Coro, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Coro
CPAN shell
perl -MCPAN -e shell install Coro
For more information on module installation, please visit the detailed CPAN module installation guide.