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61 lines
1.8 KiB
61 lines
1.8 KiB
3 years ago
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'use strict';
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exports.type = 'visitor';
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exports.name = 'sortDefsChildren';
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exports.active = true;
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exports.description = 'Sorts children of <defs> to improve compression';
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/**
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* Sorts children of defs in order to improve compression.
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* Sorted first by frequency then by element name length then by element name (to ensure grouping).
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*
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* @author David Leston
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*
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* @type {import('../lib/types').Plugin<void>}
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*/
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exports.fn = () => {
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return {
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element: {
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enter: (node) => {
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if (node.name === 'defs') {
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/**
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* @type {Map<string, number>}
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*/
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const frequencies = new Map();
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for (const child of node.children) {
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if (child.type === 'element') {
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const frequency = frequencies.get(child.name);
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if (frequency == null) {
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frequencies.set(child.name, 1);
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} else {
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frequencies.set(child.name, frequency + 1);
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}
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}
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}
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node.children.sort((a, b) => {
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if (a.type !== 'element' || b.type !== 'element') {
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return 0;
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}
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const aFrequency = frequencies.get(a.name);
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const bFrequency = frequencies.get(b.name);
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if (aFrequency != null && bFrequency != null) {
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const frequencyComparison = bFrequency - aFrequency;
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if (frequencyComparison !== 0) {
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return frequencyComparison;
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}
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}
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const lengthComparison = b.name.length - a.name.length;
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if (lengthComparison !== 0) {
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return lengthComparison;
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}
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if (a.name !== b.name) {
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return a.name > b.name ? -1 : 1;
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}
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return 0;
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});
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}
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},
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},
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};
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};
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