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chore: do not send repeated snapshots (#126)
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| // Copyright (c) 2013, the Dart project authors. Please see the AUTHORS file | ||
| // for details. All rights reserved. Use of this source code is governed by a | ||
| // BSD-style license that can be found in the LICENSE file. | ||
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| // Adapted from https://github.com/dart-lang/core/blob/7f9f597e64fa52faebd3c0a2214f61a7b081174d/pkgs/collection/lib/src/equality.dart#L164 | ||
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| // ignore_for_file: library_private_types_in_public_api | ||
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| const int _hashMask = 0x7fffffff; | ||
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| /// A generic equality relation on objects. | ||
| abstract class _Equality<E> { | ||
| const factory _Equality() = _DefaultEquality<E>; | ||
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| /// Compare two elements for being equal. | ||
| /// | ||
| /// This should be a proper equality relation. | ||
| bool equals(E e1, E e2); | ||
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| /// Get a hashcode of an element. | ||
| /// | ||
| /// The hashcode should be compatible with [equals], so that if | ||
| /// `equals(a, b)` then `hash(a) == hash(b)`. | ||
| int hash(E e); | ||
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| /// Test whether an object is a valid argument to [equals] and [hash]. | ||
| /// | ||
| /// Some implementations may be restricted to only work on specific types | ||
| /// of objects. | ||
| bool isValidKey(Object? o); | ||
| } | ||
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| /// Equality of objects that compares only the natural equality of the objects. | ||
| /// | ||
| /// This equality uses the objects' own [Object.==] and [Object.hashCode] for | ||
| /// the equality. | ||
| /// | ||
| /// Note that [equals] and [hash] take `Object`s rather than `E`s. This allows | ||
| /// `E` to be inferred as `Null` in const contexts where `E` wouldn't be a | ||
| /// compile-time constant, while still allowing the class to be used at runtime. | ||
| class _DefaultEquality<E> implements _Equality<E> { | ||
| const _DefaultEquality(); | ||
| @override | ||
| bool equals(Object? e1, Object? e2) => e1 == e2; | ||
| @override | ||
| int hash(Object? e) => e.hashCode; | ||
| @override | ||
| bool isValidKey(Object? o) => true; | ||
| } | ||
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| /// Equality on lists. | ||
| /// | ||
| /// Two lists are equal if they have the same length and their elements | ||
| /// at each index are equal. | ||
| /// | ||
| /// This is effectively the same as [IterableEquality] except that it | ||
| /// accesses elements by index instead of through iteration. | ||
| /// | ||
| /// The [equals] and [hash] methods accepts `null` values, | ||
| /// even if the [isValidKey] returns `false` for `null`. | ||
| /// The [hash] of `null` is `null.hashCode`. | ||
| class PHListEquality<E> implements _Equality<List<E>> { | ||
| final _Equality<E> _elementEquality; | ||
| const PHListEquality( | ||
| [_Equality<E> elementEquality = const _DefaultEquality<Never>()]) | ||
| : _elementEquality = elementEquality; | ||
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| @override | ||
| bool equals(List<E>? list1, List<E>? list2) { | ||
| if (identical(list1, list2)) return true; | ||
| if (list1 == null || list2 == null) return false; | ||
| var length = list1.length; | ||
| if (length != list2.length) return false; | ||
| for (var i = 0; i < length; i++) { | ||
| if (!_elementEquality.equals(list1[i], list2[i])) return false; | ||
| } | ||
| return true; | ||
| } | ||
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| @override | ||
| int hash(List<E>? list) { | ||
| if (list == null) return null.hashCode; | ||
| // Jenkins's one-at-a-time hash function. | ||
| // This code is almost identical to the one in IterableEquality, except | ||
| // that it uses indexing instead of iterating to get the elements. | ||
| var hash = 0; | ||
| for (var i = 0; i < list.length; i++) { | ||
| var c = _elementEquality.hash(list[i]); | ||
| hash = (hash + c) & _hashMask; | ||
| hash = (hash + (hash << 10)) & _hashMask; | ||
| hash ^= hash >> 6; | ||
| } | ||
| hash = (hash + (hash << 3)) & _hashMask; | ||
| hash ^= hash >> 11; | ||
| hash = (hash + (hash << 15)) & _hashMask; | ||
| return hash; | ||
| } | ||
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| @override | ||
| bool isValidKey(Object? o) => o is List<E>; | ||
| } |