"use strict";
var Promise = require("./promise");A promise queue is an asynchronous linked list, representing a sequence of values over time. Consuming and producing that sequence are temporaly independent. For each respective promise and resolution, the promise may be gotten first and put later, or put first and gotten later.
This implementation comes from Mark Miller’s Concurrency Strawman for ECMAScript.
"use strict";
var Promise = require("./promise");The promise queue constructor returns an entangled get and put pair.
These methods may be passed as functions, granting either the capability to
give or take but not necessarily both.
Internally, a promise queue is an asynchronous linked list of deferreds.
The ends variable is a promise and resolver pair.
The promise is a promise for the next ends pair after this promise is
taken.
The resolver advances the ends pair after a resolution is given.
The promise and resolver are independent properties, not necessarily
corresponding to the same deferred.
module.exports = PromiseQueue;
function PromiseQueue(values) {
if (!(this instanceof PromiseQueue)) {
return new PromiseQueue();
}
var self = this;
var ends = Promise.defer();The resolver side of a promise queue adds a {head, tail} node to the
asynchronous linked list.
The put method creates a new link to the resolver side with the given
head value, and advances the resolver side of the list.
this.put = function (value) {
var next = Promise.defer();
ends.resolver.return({
head: value,
tail: next.promise
});
ends.resolver = next.resolver;
};The promise end of a promise queue is a promise for a {head, tail}
pair.
The head will be the next value, and the tail will be a promise for
the remaining nodes of the list.
The get method obtains and returns a promise for the head value and
advances the promise to become the tail.
this.get = function () {
var result = ends.promise.get("head");
ends.promise = ends.promise.get("tail");
return result;
};The promise queue constructor allows the queue to be initialized with a given population of values.
if (values) {
values.forEach(this.put, this);
}
}