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Revert "Use values iterator and update in map equality/hash (#718)" #858

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Merged
merged 1 commit into from
Feb 11, 2025
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Revert "Use values iterator and update in map equality/hash (#718)" #858

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3 changes: 1 addition & 2 deletions pkgs/collection/CHANGELOG.md
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Original file line number Diff line number Diff line change
@@ -1,9 +1,8 @@

## 1.20.0-wip

- Add `IterableMapEntryExtension` for working on `Map` as a list of pairs, using
`Map.entries`.
- Optimize equality and hash code for maps by using `update` and a `values`
iterator to avoid extra lookups.
- Address diagnostics from `strict_top_level_inference`.

## 1.19.1
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26 changes: 8 additions & 18 deletions pkgs/collection/lib/src/equality.dart
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Expand Up @@ -325,19 +325,16 @@ class MapEquality<K, V> implements Equality<Map<K, V>> {
var length = map1.length;
if (length != map2.length) return false;
Map<_MapEntry, int> equalElementCounts = HashMap();
var values1 = map1.values.iterator;
for (var key in map1.keys) {
var value = (values1..moveNext()).current;
var entry = _MapEntry(this, key, value);
equalElementCounts.update(entry, _addOne, ifAbsent: _one);
var entry = _MapEntry(this, key, map1[key]);
var count = equalElementCounts[entry] ?? 0;
equalElementCounts[entry] = count + 1;
}
final values2 = map2.values.iterator;
for (var key in map2.keys) {
var value = (values2..moveNext()).current;
var entry = _MapEntry(this, key, value);
var count = equalElementCounts.update(entry, _subtractOne,
ifAbsent: _negativeOne);
if (count < 0) return false;
var entry = _MapEntry(this, key, map2[key]);
var count = equalElementCounts[entry];
if (count == null || count == 0) return false;
equalElementCounts[entry] = count - 1;
}
return true;
}
Expand All @@ -346,11 +343,9 @@ class MapEquality<K, V> implements Equality<Map<K, V>> {
int hash(Map<K, V>? map) {
if (map == null) return null.hashCode;
var hash = 0;
var values = map.values.iterator;
for (var key in map.keys) {
var value = (values..moveNext()).current;
var keyHash = _keyEquality.hash(key);
var valueHash = _valueEquality.hash(value);
var valueHash = _valueEquality.hash(map[key] as V);
hash = (hash + 3 * keyHash + 7 * valueHash) & _hashMask;
}
hash = (hash + (hash << 3)) & _hashMask;
Expand Down Expand Up @@ -494,8 +489,3 @@ class CaseInsensitiveEquality implements Equality<String> {
@override
bool isValidKey(Object? object) => object is String;
}

int _addOne(int i) => i + 1;
int _subtractOne(int i) => i - 1;
int _one() => 1;
int _negativeOne() => -1;
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