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content / test / data / result_queue.js [blame]
// Copyright 2017 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
// Queue storing asynchronous results. Results are available via `pop` when
// requested.
function ResultQueue() {
// Invariant: this.queue.length == 0 || this.pendingGets.length == 0
this.queue = [];
this.pendingGets = [];
}
// Adds a data item to the queue or sends it to the earliest pending `pop`
// operation.
ResultQueue.prototype.push = function(data) {
if (this.pendingGets.length > 0) {
const resolve = this.pendingGets.pop();
resolve(data);
} else {
this.queue.unshift(data);
}
};
// Returns a promise that resolves with the next data item, when available.
ResultQueue.prototype.pop = function() {
return new Promise((resolve) => {
if (this.queue.length) {
resolve(this.queue.pop());
} else {
this.pendingGets.unshift(resolve);
}
});
};
// Immediately returns the next data item if it is available, otherwise returns
// null.
ResultQueue.prototype.popImmediately = function() {
return this.queue.length ? this.queue.pop() : null;
};