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Unified Diff: sdk/lib/internal/lru.dart

Issue 375043003: Revert r37059 and dependent r37589. This effectively reduced the size of the getter and setter cach… (Closed) Base URL: https://dart.googlecode.com/svn/branches/bleeding_edge/dart
Patch Set: Created 6 years, 5 months ago
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Index: sdk/lib/internal/lru.dart
diff --git a/sdk/lib/internal/lru.dart b/sdk/lib/internal/lru.dart
deleted file mode 100644
index 8f8a64a5fe6b7473707271041da221e87e101851..0000000000000000000000000000000000000000
--- a/sdk/lib/internal/lru.dart
+++ /dev/null
@@ -1,125 +0,0 @@
-// Copyright (c) 2014, 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.
-
-part of dart._internal;
-
-class LRUAssociation<K,V> {
- K key;
- V value;
- LRUAssociation previous;
- LRUAssociation next;
-
- void insertBetween(before, after) {
- after.previous = this;
- before.next = this;
- this.next = after;
- this.previous = before;
- }
-
- void remove() {
- var after = next;
- var before = previous;
- after.previous = before;
- before.next = after;
- }
-}
-
-/**
- * A map with a fixed capacity that evicts associations when capacity is reached
- * on a least-recently-used basis. Implemented as an open addressing hash table
- * with doubly-linked entries forming the LRU queue.
- */
-class LRUMap<K,V> {
- final LRUAssociation<K,V> _head;
- final List _table;
- final int _mask;
- final int _capacity; // Max number of associations before we start evicting.
- int _size = 0; // Current number of associations.
-
- /**
- * Create an LRUMap whose capacity is 75% of 2^shift.
- */
- LRUMap.withShift(int shift)
- : this._mask = (1 << shift) - 1
- , this._capacity = (1 << shift) * 3 ~/ 4
- , this._table = new List(1 << shift)
- , this._head = new LRUAssociation() {
- // The scheme used here for handling collisions relies on there always
- // being at least one empty slot.
- if (shift < 1) throw new Exception("LRUMap requires a shift >= 1");
- assert(_table.length > _capacity);
- _head.insertBetween(_head, _head);
- }
-
- int _scanFor(K key) {
- var start = key.hashCode & _mask;
- var index = start;
- do {
- var assoc = _table[index];
- if (null == assoc || assoc.key == key) {
- return index;
- }
- index = (index + 1) & _mask;
- } while (index != start);
- // Should never happen because we start evicting associations before the
- // table is full.
- throw new Exception("Internal error: LRUMap table full");
- }
-
- void _fixCollisionsAfter(start) {
- var assoc;
- var index = (start + 1) & _mask;
- while (null != (assoc = _table[index])) {
- var newIndex = _scanFor(assoc.key);
- if (newIndex != index) {
- assert(_table[newIndex] == null);
- _table[newIndex] = assoc;
- _table[index] = null;
- }
- index = (index + 1) & _mask;
- }
- }
-
- operator []=(K key, V value) {
- int index = _scanFor(key);
- var assoc = _table[index];
- if (null != assoc) {
- // Existing key, replace value.
- assert(assoc.key == key);
- assoc.value = value;
- assoc.remove();
- assoc.insertBetween(_head, _head.next);
- } else {
- // New key.
- var newAssoc;
- if (_size == _capacity) {
- // Knock out the oldest association.
- var lru = _head.previous;
- lru.remove();
- index = _scanFor(lru.key);
- _table[index] = null;
- _fixCollisionsAfter(index);
- index = _scanFor(key);
- newAssoc = lru; // Recycle the association.
- } else {
- newAssoc = new LRUAssociation();
- _size++;
- }
- newAssoc.key = key;
- newAssoc.value = value;
- newAssoc.insertBetween(_head, _head.next);
- _table[index] = newAssoc;
- }
- }
-
- V operator [](K key) {
- var index = _scanFor(key);
- var assoc = _table[index];
- if (null == assoc) return null;
- // Move to front of LRU queue.
- assoc.remove();
- assoc.insertBetween(_head, _head.next);
- return assoc.value;
- }
-}
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