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/**
* Copyright (c) 2013-present, Facebook, Inc.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*
* @providesModule equalsIterable
* @flow
*/
'use strict';
const enumerate = require('./enumerate');
/**
* Checks if two iterables are equal. A custom areEqual function may be provided
* as an optional third argument.
*/
function equalsIterable<T>(one: Iterable<T>, two: Iterable<T>, areEqual?: ?(one: T, two: T) => boolean): boolean {
if (one === two) {
return true;
}
// We might be able to short circuit by using the size or length fields.
var oneSize = maybeGetSize(one);
var twoSize = maybeGetSize(two);
if (oneSize != null && twoSize != null && oneSize !== twoSize) {
return false;
}
// Otherwise use the iterators to check equality. Here we cannot use for-of
// because we need to advance the iterators at the same time.
var oneIterator = enumerate(one);
var oneItem = oneIterator.next();
var twoIterator = enumerate(two);
var twoItem = twoIterator.next();
var safeAreEqual = areEqual || referenceEquality;
while (!(oneItem.done || twoItem.done)) {
if (!safeAreEqual(oneItem.value, twoItem.value)) {
return false;
}
oneItem = oneIterator.next();
twoItem = twoIterator.next();
}
return oneItem.done === twoItem.done;
}
function maybeGetSize(o: any): ?number {
if (o == null) {
return null;
}
if (typeof o.size === 'number') {
return o.size;
}
if (typeof o.length === 'number') {
return o.length;
}
return null;
}
function referenceEquality<T>(one: T, two: T): boolean {
return one === two;
}
module.exports = equalsIterable;
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