node_modules

1 files changed, 67 insertions, 0 deletions

diff --git a/node_modules/fbjs/lib/equalsIterable.js.flow b/node_modules/fbjs/lib/equalsIterable.js.flow
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+++ b/node_modules/fbjs/lib/equalsIterable.js.flow
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+/**
+ * Copyright (c) 2013-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ *
+ * @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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