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55 lines
1.9 KiB
55 lines
1.9 KiB
5 years ago
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'use strict';
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module.exports = class SymbolTreeNode {
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constructor() {
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this.parent = null;
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this.previousSibling = null;
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this.nextSibling = null;
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this.firstChild = null;
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this.lastChild = null;
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/** This value is incremented anytime a children is added or removed */
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this.childrenVersion = 0;
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/** The last child object which has a cached index */
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this.childIndexCachedUpTo = null;
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/** This value represents the cached node index, as long as
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* cachedIndexVersion matches with the childrenVersion of the parent */
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this.cachedIndex = -1;
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this.cachedIndexVersion = NaN; // NaN is never equal to anything
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}
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get isAttached() {
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return Boolean(this.parent || this.previousSibling || this.nextSibling);
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}
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get hasChildren() {
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return Boolean(this.firstChild);
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}
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childrenChanged() {
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/* jshint -W016 */
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// integer wrap around
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this.childrenVersion = (this.childrenVersion + 1) & 0xFFFFFFFF;
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this.childIndexCachedUpTo = null;
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}
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getCachedIndex(parentNode) {
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// (assumes parentNode is actually the parent)
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if (this.cachedIndexVersion !== parentNode.childrenVersion) {
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this.cachedIndexVersion = NaN;
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// cachedIndex is no longer valid
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return -1;
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}
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return this.cachedIndex; // -1 if not cached
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}
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setCachedIndex(parentNode, index) {
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// (assumes parentNode is actually the parent)
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this.cachedIndexVersion = parentNode.childrenVersion;
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this.cachedIndex = index;
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}
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};
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