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![Peter von der Ahé](/assets/img/avatar_default.png)
Change-Id: Ie436375c78496366accf0ba82938e54cbe30b143 Reviewed-on: https://dart-review.googlesource.com/3001 Commit-Queue: Peter von der Ahé <ahe@google.com> Reviewed-by: Lasse R.H. Nielsen <lrn@google.com> Reviewed-by: Vyacheslav Egorov <vegorov@google.com> Reviewed-by: Johnni Winther <johnniwinther@google.com>
152 lines
3.8 KiB
Dart
152 lines
3.8 KiB
Dart
// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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// part of "core_patch.dart";
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@patch
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class Expando<T> {
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@patch
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Expando([String name])
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: name = name,
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_data = new List(_minSize),
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_used = 0;
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static const _minSize = 8;
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static final _deletedEntry = new _WeakProperty(null, null);
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@patch
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T operator [](Object object) {
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_checkType(object);
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var mask = _size - 1;
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var idx = object._identityHashCode & mask;
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var wp = _data[idx];
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while (wp != null) {
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if (identical(wp.key, object)) {
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return wp.value;
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} else if (wp.key == null) {
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// This entry has been cleared by the GC.
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_data[idx] = _deletedEntry;
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}
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idx = (idx + 1) & mask;
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wp = _data[idx];
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}
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return null;
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}
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@patch
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void operator []=(Object object, T value) {
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_checkType(object);
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var mask = _size - 1;
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var idx = object._identityHashCode & mask;
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var empty_idx = -1;
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var wp = _data[idx];
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while (wp != null) {
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if (identical(wp.key, object)) {
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if (value != null) {
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// Update the associated value.
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wp.value = value;
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} else {
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// Mark the entry as deleted.
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_data[idx] = _deletedEntry;
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}
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return;
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} else if ((empty_idx < 0) && identical(wp, _deletedEntry)) {
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empty_idx = idx; // Insert at this location if not found.
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} else if (wp.key == null) {
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// This entry has been cleared by the GC.
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_data[idx] = _deletedEntry;
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if (empty_idx < 0) {
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empty_idx = idx; // Insert at this location if not found.
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}
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}
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idx = (idx + 1) & mask;
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wp = _data[idx];
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}
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if (value == null) {
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// Not entering a null value. We just needed to make sure to clear an
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// existing value if it existed.
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return;
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}
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if (empty_idx >= 0) {
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// We will be reusing the empty slot below.
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_used--;
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idx = empty_idx;
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}
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if (_used < _limit) {
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_data[idx] = new _WeakProperty(object, value);
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_used++;
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return;
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}
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// Grow/reallocate if too many slots have been used.
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_rehash();
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this[object] = value; // Recursively add the value.
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}
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_rehash() {
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// Determine the population count of the map to allocate an appropriately
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// sized map below.
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var count = 0;
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var old_data = _data;
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var len = old_data.length;
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for (var i = 0; i < len; i++) {
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var entry = old_data[i];
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if ((entry != null) && (entry.key != null)) {
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// Only count non-cleared entries.
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count++;
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}
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}
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var new_size = _size;
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if (count <= (new_size >> 2)) {
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new_size = new_size >> 1;
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} else if (count > (new_size >> 1)) {
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new_size = new_size << 1;
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}
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new_size = (new_size < _minSize) ? _minSize : new_size;
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// Reset the mappings to empty so that we can just add the existing
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// valid entries.
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_data = new List(new_size);
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_used = 0;
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for (var i = 0; i < old_data.length; i++) {
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var entry = old_data[i];
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if (entry != null) {
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// Ensure that the entry.key is not cleared between checking for it and
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// inserting it into the new table.
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var val = entry.value;
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var key = entry.key;
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if (key != null) {
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this[key] = val;
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}
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}
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}
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}
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static _checkType(object) {
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if ((object == null) ||
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(object is bool) ||
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(object is num) ||
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(object is String)) {
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throw new ArgumentError.value(object,
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"Expandos are not allowed on strings, numbers, booleans or null");
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}
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}
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get _size => _data.length;
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get _limit => (3 * (_size ~/ 4));
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List _data;
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int _used; // Number of used (active and deleted) slots.
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}
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