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// cachedIndex is no longer valid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