co-semaphore
v0.1.1
Published
Counted semaphore primitive for generator flow-control.
Downloads
6
Readme
co-semaphore
Counted semaphore primitive for generator flow-control.
Installation
Node.js
co-semaphore
is available through npm:
npm install co-semaphore
Example
"use strict";
var co = require('co');
var Semaphore = require('co-semaphore').Semaphore;
function rand() {
return Math.floor(Math.random() * 10) * 100;
}
function *read(i, lock) {
yield lock.acquire();
console.log('start:', i);
yield wait(rand());
lock.release();
console.log('end:', i);
return i * 10;
}
co(function *main() {
var lock = new Semaphore(3);
var res = [];
for (let i = 1; i < 11; i++) {
res.push(read(i, lock));
}
console.log('res', yield res);
})();
Usage
A low-level counted semaphore lock.
- @param {Number} workers
.length
Get length of waiting queue.
- @return {Number} length
.acquired
Get the current number of workers; threads which have acquired the lock but not yet released it.
- @return {Number} acquisitions
.available
Get the current number of unassigned workers; count of threads which can immediately acquire access without being put in the waiting queue.
- @return {Number} available
.count
Get count of semaphore state.
- @return {Number} count
.acquire()
Acquire permission to access shared resources.
yield sem.acquire();
.release()
Notify release of access to shared resources
to a single waiting .acquire()
.
- @return {Boolean} release signalled acquire
var hadListener = sem.release();
.flush()
Notify release of access to shared resources
to all waiting .acquire()
s.
- @return {Boolean} release signalled acquire
var hadListeners = sem.flush();
.lock()
Acquire access to shared resources with closure. Access will be acquired prior to invoking the closure and unlocked as the closure unwinds.
- @param {Generator} closure
var res = yield sem.lock(function*() {
// do async work with lock owned
yield wait(100);
return { hello: 'universe' };
});
License
(The MIT License)
Copyright (c) 2014 Jake Luer [email protected]
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.