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