104 lines
3.3 KiB
JavaScript
104 lines
3.3 KiB
JavaScript
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'use strict';
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var anchors = require('../doc/anchors.js');
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var visit = require('../visit.js');
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var identity = require('./identity.js');
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var Node = require('./Node.js');
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var toJS = require('./toJS.js');
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class Alias extends Node.NodeBase {
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constructor(source) {
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super(identity.ALIAS);
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this.source = source;
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Object.defineProperty(this, 'tag', {
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set() {
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throw new Error('Alias nodes cannot have tags');
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}
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});
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}
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/**
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* Resolve the value of this alias within `doc`, finding the last
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* instance of the `source` anchor before this node.
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*/
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resolve(doc) {
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let found = undefined;
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visit.visit(doc, {
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Node: (_key, node) => {
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if (node === this)
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return visit.visit.BREAK;
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if (node.anchor === this.source)
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found = node;
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}
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});
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return found;
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}
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toJSON(_arg, ctx) {
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if (!ctx)
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return { source: this.source };
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const { anchors, doc, maxAliasCount } = ctx;
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const source = this.resolve(doc);
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if (!source) {
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const msg = `Unresolved alias (the anchor must be set before the alias): ${this.source}`;
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throw new ReferenceError(msg);
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}
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let data = anchors.get(source);
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if (!data) {
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// Resolve anchors for Node.prototype.toJS()
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toJS.toJS(source, null, ctx);
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data = anchors.get(source);
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}
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/* istanbul ignore if */
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if (!data || data.res === undefined) {
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const msg = 'This should not happen: Alias anchor was not resolved?';
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throw new ReferenceError(msg);
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}
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if (maxAliasCount >= 0) {
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data.count += 1;
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if (data.aliasCount === 0)
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data.aliasCount = getAliasCount(doc, source, anchors);
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if (data.count * data.aliasCount > maxAliasCount) {
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const msg = 'Excessive alias count indicates a resource exhaustion attack';
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throw new ReferenceError(msg);
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}
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}
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return data.res;
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}
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toString(ctx, _onComment, _onChompKeep) {
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const src = `*${this.source}`;
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if (ctx) {
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anchors.anchorIsValid(this.source);
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if (ctx.options.verifyAliasOrder && !ctx.anchors.has(this.source)) {
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const msg = `Unresolved alias (the anchor must be set before the alias): ${this.source}`;
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throw new Error(msg);
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}
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if (ctx.implicitKey)
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return `${src} `;
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}
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return src;
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}
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}
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function getAliasCount(doc, node, anchors) {
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if (identity.isAlias(node)) {
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const source = node.resolve(doc);
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const anchor = anchors && source && anchors.get(source);
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return anchor ? anchor.count * anchor.aliasCount : 0;
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}
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else if (identity.isCollection(node)) {
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let count = 0;
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for (const item of node.items) {
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const c = getAliasCount(doc, item, anchors);
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if (c > count)
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count = c;
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}
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return count;
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}
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else if (identity.isPair(node)) {
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const kc = getAliasCount(doc, node.key, anchors);
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const vc = getAliasCount(doc, node.value, anchors);
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return Math.max(kc, vc);
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}
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return 1;
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}
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exports.Alias = Alias;
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