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// Copyright 2011 The Closure Library Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS-IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
/**
* @fileoverview Utility class to manage the mathematics behind computing an
* exponential backoff model. Given an initial backoff value and a maximum
* backoff value, every call to backoff() will double the value until maximum
* backoff value is reached.
*
*/
goog.provide('goog.math.ExponentialBackoff');
goog.require('goog.asserts');
/**
* @constructor
*
* @param {number} initialValue The initial backoff value.
* @param {number} maxValue The maximum backoff value.
*/
goog.math.ExponentialBackoff = function(initialValue, maxValue) {
goog.asserts.assert(initialValue > 0,
'Initial value must be greater than zero.');
goog.asserts.assert(maxValue >= initialValue,
'Max value should be at least as large as initial value.');
/**
* @type {number}
* @private
*/
this.initialValue_ = initialValue;
/**
* @type {number}
* @private
*/
this.maxValue_ = maxValue;
/**
* The current backoff value.
* @type {number}
* @private
*/
this.currValue_ = initialValue;
};
/**
* The number of backoffs that have happened.
* @type {number}
* @private
*/
goog.math.ExponentialBackoff.prototype.currCount_ = 0;
/**
* Resets the backoff value to its initial value.
*/
goog.math.ExponentialBackoff.prototype.reset = function() {
this.currValue_ = this.initialValue_;
this.currCount_ = 0;
};
/**
* @return {number} The current backoff value.
*/
goog.math.ExponentialBackoff.prototype.getValue = function() {
return this.currValue_;
};
/**
* @return {number} The number of times this class has backed off.
*/
goog.math.ExponentialBackoff.prototype.getBackoffCount = function() {
return this.currCount_;
};
/**
* Initiates a backoff.
*/
goog.math.ExponentialBackoff.prototype.backoff = function() {
this.currValue_ = Math.min(this.maxValue_, this.currValue_ * 2);
this.currCount_++;
};
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