434 lines
9.6 KiB
JavaScript
434 lines
9.6 KiB
JavaScript
/**
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* @license Apache-2.0
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*
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* Copyright (c) 2018 The Stdlib Authors.
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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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/* eslint-disable no-restricted-syntax, no-invalid-this */
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'use strict';
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// MODULES //
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var isCollection = require( '@stdlib/assert/is-collection' );
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var isPositiveInteger = require( '@stdlib/assert/is-positive-integer' ).isPrimitive;
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var isNonNegativeInteger = require( '@stdlib/assert/is-nonnegative-integer' ).isPrimitive;
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var setReadOnly = require( './../../define-nonenumerable-read-only-property' );
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var setReadOnlyAccessor = require( './../../define-nonenumerable-read-only-accessor' );
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var iteratorSymbol = require( '@stdlib/symbol/iterator' );
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var MAX_ITERATIONS = require( '@stdlib/constants/float64/max' );
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// MAIN //
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/**
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* Circular buffer constructor.
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*
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* @constructor
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* @param {(PositiveInteger|Collection)} buffer - buffer size or an array-like object to use as the underlying buffer
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* @throws {TypeError} must provide either a valid buffer size or an array-like object
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* @returns {CircularBuffer} circular buffer instance
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*
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* @example
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* var b = new CircularBuffer( 3 );
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*
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* // Fill the buffer...
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* var v = b.push( 'foo' );
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* // returns undefined
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*
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* v = b.push( 'bar' );
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* // returns undefined
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*
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* v = b.push( 'beep' );
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* // returns undefined
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*
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* // Add another value to the buffer and return the removed element:
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* v = b.push( 'boop' );
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* // returns 'foo'
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*/
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function CircularBuffer( buffer ) {
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var i;
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if ( !(this instanceof CircularBuffer) ) {
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return new CircularBuffer( buffer );
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}
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if ( isPositiveInteger( buffer ) ) {
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this._buffer = [];
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for ( i = 0; i < buffer; i++ ) {
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this._buffer.push( 0.0 ); // initialize with zeros, but could be any value (we're just ensuring a contiguous block of memory)
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}
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} else if ( isCollection( buffer ) ) {
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this._buffer = buffer;
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} else {
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throw new TypeError( 'invalid argument. Must provide either a valid buffer size (positive integer) or an array-like object which can serve as the underlying buffer. Value: `' + buffer + '`.' );
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}
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this._length = this._buffer.length;
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this._count = 0;
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this._i = -1;
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return this;
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}
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/**
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* Clears the buffer.
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*
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* @name clear
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* @memberof CircularBuffer.prototype
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* @type {Function}
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* @returns {CircularBuffer} circular buffer instance
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*
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* @example
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* var b = new CircularBuffer( 2 );
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*
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* // Add values to the buffer:
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* b.push( 'foo' );
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* b.push( 'bar' );
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* b.push( 'beep' );
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* b.push( 'boop' );
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*
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* // Get the number of elements currently in the buffer:
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* var n = b.count;
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* // returns 2
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*
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* // Clear the buffer:
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* b.clear();
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*
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* // Get the number of buffer values:
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* n = b.count;
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* // returns 0
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*/
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setReadOnly( CircularBuffer.prototype, 'clear', function clear() {
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this._count = 0;
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this._i = -1; // NOTE: this ensures that we always fill the buffer starting at index `0`.
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return this;
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});
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/**
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* Number of elements currently in the buffer.
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*
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* @name count
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* @memberof CircularBuffer.prototype
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* @type {NonNegativeInteger}
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*
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* @example
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* var b = new CircularBuffer( 4 );
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*
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* // Get the value count:
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* var n = b.count;
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* // returns 0
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*
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* // Add values to the buffer:
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* b.push( 'foo' );
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* b.push( 'bar' );
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*
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* // Get the value count:
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* n = b.count;
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* // returns 2
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*/
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setReadOnlyAccessor( CircularBuffer.prototype, 'count', function get() {
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return this._count;
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});
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/**
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* Boolean indicating whether a circular buffer is full.
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*
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* @name full
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* @memberof CircularBuffer.prototype
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* @type {boolean}
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*
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* @example
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* var b = new CircularBuffer( 3 );
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*
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* // Determine if the buffer is full:
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* var bool = b.full;
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* // returns false
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*
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* // Add values to the buffer:
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* b.push( 'foo' );
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* b.push( 'bar' );
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* b.push( 'beep' );
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* b.push( 'boop' );
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*
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* // Determine if the buffer is full:
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* bool = b.full;
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* // returns true
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*/
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setReadOnlyAccessor( CircularBuffer.prototype, 'full', function get() {
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return this._count === this._length;
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});
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/**
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* Returns an iterator for iterating over a circular buffer.
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*
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* ## Notes
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*
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* - An iterator does not iterate over partially full buffers.
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*
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* @name iterator
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* @memberof CircularBuffer.prototype
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* @type {Function}
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* @param {NonNegativeInteger} [niters] - number of iterations
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* @throws {TypeError} must provide a nonnegative integer
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* @returns {Iterator} iterator
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*
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* @example
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* var b = new CircularBuffer( 3 );
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*
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* // Add values to the buffer:
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* b.push( 'foo' );
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* b.push( 'bar' );
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* b.push( 'beep' );
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* b.push( 'boop' );
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*
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* // Create an iterator:
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* var it = b.iterator( b.length );
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*
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* // Iterate over the buffer...
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* var v = it.next().value;
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* // returns 'bar'
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*
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* v = it.next().value;
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* // returns 'beep'
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*
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* v = it.next().value;
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* // returns 'boop'
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*
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* var bool = it.next().done;
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* // returns true
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*/
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setReadOnly( CircularBuffer.prototype, 'iterator', function iterator( niters ) {
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var iter;
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var self;
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var FLG;
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var N;
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var n;
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var i;
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if ( arguments.length ) {
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if ( !isNonNegativeInteger( niters ) ) {
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throw new TypeError( 'invalid argument. Must provide a nonnegative integer. Value: `' + niters + '`.' );
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}
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N = niters;
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} else {
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N = MAX_ITERATIONS;
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}
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self = this;
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// Initialize the iteration index and counter:
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i = this._i;
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n = 0;
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// Create an iterator protocol-compliant object:
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iter = {};
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setReadOnly( iter, 'next', next );
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setReadOnly( iter, 'return', end );
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if ( iteratorSymbol ) {
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setReadOnly( iter, iteratorSymbol, factory );
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}
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return iter;
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/**
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* Returns an iterator protocol-compliant object containing the next iterated value.
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*
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* @private
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* @returns {Object} iterator protocol-compliant object
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*/
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function next() {
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/* eslint-disable no-underscore-dangle */
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n += 1;
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if ( FLG || n > N ) {
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return {
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'done': true
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};
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}
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// If the buffer is only partially full, don't allow iteration over "undefined" elements (this ensures similar behavior with `toArray()`)...
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if ( self._count !== self._length ) {
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FLG = true;
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return {
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'done': true
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};
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}
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i = (i+1) % self._length;
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return {
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'value': self._buffer[ i ],
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'done': false
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};
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/* eslint-enable no-underscore-dangle */
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}
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/**
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* Finishes an iterator.
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*
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* @private
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* @param {*} [value] - value to return
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* @returns {Object} iterator protocol-compliant object
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*/
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function end( value ) {
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FLG = true;
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if ( arguments.length ) {
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return {
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'value': value,
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'done': true
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};
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}
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return {
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'done': true
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};
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}
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/**
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* Returns a new iterator.
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*
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* @private
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* @returns {Iterator} iterator
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*/
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function factory() {
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return self.iterator( N );
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}
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});
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/**
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* Circular buffer length (capacity).
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*
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* @name length
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* @memberof CircularBuffer.prototype
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* @type {NonNegativeInteger}
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*
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* @example
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* var b = new CircularBuffer( 4 );
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*
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* // Get the buffer capacity:
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* var len = b.length;
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* // returns 4
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*/
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setReadOnlyAccessor( CircularBuffer.prototype, 'length', function get() {
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return this._length;
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});
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/**
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* Adds a value to the circular buffer.
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*
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* @name push
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* @memberof CircularBuffer.prototype
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* @type {Function}
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* @returns {(*|void)} removed element or undefined
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*
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* @example
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* var b = new CircularBuffer( 3 );
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*
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* // Fill the buffer:
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* var v = b.push( 'foo' );
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* // returns undefined
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*
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* v = b.push( 'bar' );
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* // returns undefined
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*
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* v = b.push( 'beep' );
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* // returns undefined
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*
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* // Add another value to the buffer and return the removed element:
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* v = b.push( 'boop' );
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* // returns 'foo'
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*/
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setReadOnly( CircularBuffer.prototype, 'push', function push( value ) {
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var v;
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// Compute the next buffer index:
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this._i = (this._i+1) % this._length;
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// Check if we are still filling the buffer...
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if ( this._count < this._length ) {
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this._buffer[ this._i ] = value;
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this._count += 1;
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return;
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}
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// Replace an existing buffer element...
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v = this._buffer[ this._i ];
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this._buffer[ this._i ] = value;
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return v;
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});
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/**
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* Returns an array of circular buffer values.
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*
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* @name toArray
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* @memberof CircularBuffer.prototype
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* @type {Function}
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* @returns {Array} circular buffer values
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*
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* @example
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* var b = new CircularBuffer( 3 );
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*
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* // Add values to the buffer:
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* b.push( 'foo' );
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* b.push( 'bar' );
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* b.push( 'beep' );
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* b.push( 'boop' );
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*
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* // Get an array of buffer values:
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* var vals = b.toArray();
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* // returns [ 'bar', 'beep', 'boop' ]
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*/
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setReadOnly( CircularBuffer.prototype, 'toArray', function toArray() {
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var out;
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var k;
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var i;
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out = [];
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for ( i = 1; i <= this._count; i++ ) {
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// Note: in a full buffer, `count == length`; in a partially full buffer, we need to ensure we always start at index `0`
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k = (this._i+i) % this._count;
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out.push( this._buffer[ k ] );
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}
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return out;
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});
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/**
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* Serializes a circular buffer as JSON.
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*
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* ## Notes
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*
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* - `JSON.stringify()` implicitly calls this method when stringifying a `CircularBuffer` instance.
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*
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* @name toJSON
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* @memberof CircularBuffer.prototype
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* @type {Function}
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* @returns {Object} serialized circular buffer
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*
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* @example
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* var b = new CircularBuffer( 3 );
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*
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* // Add values to the buffer:
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* b.push( 'foo' );
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* b.push( 'bar' );
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* b.push( 'beep' );
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* b.push( 'boop' );
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*
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* // Serialize to JSON:
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* var o = b.toJSON();
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* // returns { 'type': 'circular-buffer', 'length': 3, 'data': [ 'bar', 'beep', 'boop' ] }
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*/
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setReadOnly( CircularBuffer.prototype, 'toJSON', function toJSON() {
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var out = {};
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out.type = 'circular-buffer';
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out.length = this._length;
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out.data = this.toArray();
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return out;
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});
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// EXPORTS //
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module.exports = CircularBuffer;
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