Press n or j to go to the next uncovered block, b, p or k for the previous block.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 | export default class Queue {
constructor(limit) {
this.limit = limit;
this.size = 0;
this.awaiting = null;
}
/**
* Creates a new "proxy" function associated with the current execution queue
* instance. When the returned function is invoked, the queue limit is checked
* to make sure the limit of scheduled tasks is respected (throwing an
* exception when the limit has been reached and before calling the original
* function). The original function is only invoked after all the previously
* scheduled tasks have finished executing (their returned promises have
* resolved/rejected);
*
* @param {function} task The function whose execution will be associated
* with the current Queue instance;
* @returns {function} The "proxy" function bound to the current Queue
* instance;
*/
bind(task) {
return bind(this, task);
}
bindSafe(task, onError) {
const boundTask = bind(this, task);
return async function safeTask(...args) {
try {
return await boundTask(...args);
} catch (e) {
onError(e);
}
};
}
}
/**
* Utils
*/
function bind(queue, task) {
const cleaner = clean.bind(null, queue);
return async function boundTask(...args) {
Iif (queue.size >= queue.limit) {
throw new Error('Queue limit reached');
}
const promise = chain(queue.awaiting, task, args);
queue.awaiting = promise.then(cleaner, cleaner);
queue.size++;
return promise;
};
}
function clean(queue) {
Iif (queue.size > 0 && --queue.size === 0) {
queue.awaiting = null;
}
}
async function chain(prev, task, args) {
await prev;
return task(...args);
}
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