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74 lines
2.4 KiB
74 lines
2.4 KiB
/**
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* @license
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* Copyright 2016 Google Inc. All Rights Reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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var CircularBuffer = require('./circular-buffer');
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var Task = require('./task');
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exports.inject = function(wait, getTime) {
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return {
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/**
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* Creates a ThrottledQueue. The queue stores tasks, which will be executed
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* asynchronously, at a controlled rate.
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*
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* @param {number} limit The maximum number of tasks that can be executed
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* over one period.
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* @param {number} period The time period (ms) over which limit is
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* enforceable.
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* @return {ThrottledQueue}
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*/
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create: function(limit, period) {
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var me = {};
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var queue = Task.withValue();
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var recentTimes = CircularBuffer.create(limit);
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/**
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* Adds a task to the work queue.
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*
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* @param {function(): Task<T>} doSomething Starts the task. This function
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* will be called when the rate limit allows.
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* @return {Task<T>} The delayed task.
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* @template T
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*/
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me.add = function(doSomething) {
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// Return a separate task from the queue, so that cancelling a task
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// doesn't propagate back and cancel the whole queue.
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var waitForMyTurn = Task
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.start(function(resolve) {
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queue.finally(resolve);
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})
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.thenDo(function() {
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var lastTime = recentTimes.item(limit - 1);
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if (lastTime == undefined) return;
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return wait(Math.max(lastTime + period - getTime(), 0));
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})
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.thenDo(function() {
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recentTimes.insert(getTime());
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});
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queue = queue.thenDo(function() {
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return Task.start(function(resolve) {
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waitForMyTurn.finally(resolve);
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});
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});
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return waitForMyTurn.thenDo(doSomething);
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};
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return me;
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}
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};
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};
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