New XML parser implementation
Custom XML parser implementation in pure JS that's orders of magnitude faster than libxmljs mainly due to the overhead of JS-native calls in libxmljs.
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Zaid Abdulla committed
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@@ -0,0 +1,338 @@
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const CHAR_SINGLE_QUOTE = 39;
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const CHAR_DOUBLE_QUOTE = 34;
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const CHAR_LESS_THAN = 60;
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const CHAR_GREATER_THAN = 62;
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const CHAR_COLON = 58;
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const CHAR_SPACE = 32;
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const CHAR_TAB = 9;
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const CHAR_CR = 13;
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const CHAR_LF = 10;
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const CHAR_SLASH = 47;
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const CHAR_EXMARK = 33;
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const CHAR_QMARK = 63;
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const CHAR_EQUAL = 61;
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const STATE_LESS_THAN = 1;
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const STATE_SINGLE_QUOTE = 2;
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const STATE_DOUBLE_QUOTE = 3;
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export interface Attribute {
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name: string;
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namespace: string;
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localName: string;
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value: string;
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}
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export interface Element {
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name: string;
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namespace: string;
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localName: string;
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attrs: string;
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text: string;
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bodyIndex: number;
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children: Element[];
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}
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export function parseXmlDeclaration(buffer: Buffer): Attribute[] {
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for (const enc of ["utf16le", "utf8", "latin1", "ascii"]) {
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let str = buffer.toString(enc, 0, 150);
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if (str.startsWith("<?xml")) {
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str = str.split("\n")[0].trim();
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try {
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return parseAttrs(str.slice(5, -2));
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} catch (err) {
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// Ignore
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}
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}
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}
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return null;
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}
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export function parseAttrs(string: string): Attribute[] {
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const attrs: Attribute[] = [];
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const len = string.length;
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let state = 0;
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let name = "";
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let namespace = "";
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let localName = "";
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let idx = 0;
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let colonIdx = 0;
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for (let i = 0; i < len; ++i) {
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const c = string.charCodeAt(i);
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switch (c) {
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case CHAR_SINGLE_QUOTE:
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case CHAR_DOUBLE_QUOTE:
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if (state === c) {
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state = 0;
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if (name) {
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const value = string.slice(idx + 1, i);
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const e = {
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name: name,
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namespace: namespace,
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localName: localName,
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value: value
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};
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attrs.push(e);
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name = "";
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idx = i + 1;
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}
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} else {
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state = c;
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idx = i;
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}
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continue;
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case CHAR_COLON:
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if (idx >= colonIdx) colonIdx = i;
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continue;
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case CHAR_EQUAL:
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if (name) throw new Error(`Unexpected character at ${i}`);
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name = string.slice(idx, i).trim();
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// TODO validate name
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if (colonIdx > idx) {
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namespace = string.slice(idx, colonIdx).trim();
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localName = string.slice(colonIdx + 1, i).trim();
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} else {
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namespace = "";
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localName = name;
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}
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}
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}
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if (name) throw new Error(`Attribute must have value at ${idx}`);
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const tail = string.slice(idx);
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if (tail.trim()) throw new Error(`Unexpected string at ${len - tail.length}`);
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return attrs;
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}
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export function decodeEntities(string): string {
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return string.replace(/&[0-9a-z#]+;/gi, match => {
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switch (match) {
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case """:
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return '"';
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case "&":
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return "&";
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case "'":
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return "'";
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case "<":
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return "<";
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case ">":
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return ">";
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default:
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if (match.startsWith("&#x")) {
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const str = match.slice(3, -1).toLowerCase();
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const n = parseInt(str, 16);
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if (str.endsWith(n.toString(16))) return String.fromCharCode(n);
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} else if (match.startsWith("&#")) {
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const str = match.slice(2, -1);
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const n = parseInt(str);
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if (str.endsWith(n.toString())) return String.fromCharCode(n);
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}
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}
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return match;
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});
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}
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export function encodeEntities(string): string {
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const entities = {
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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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return string.replace(/[&"'<>]/g, m => entities[m]);
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}
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export function parseXml(string: string): Element {
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const len = string.length;
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let state1 = 0;
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let state1Index = 0;
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let state2 = 0;
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let state2Index = 0;
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const root: Element = {
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name: "root",
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namespace: "",
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localName: "root",
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attrs: "",
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text: "",
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bodyIndex: 0,
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children: []
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};
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const stack: Element[] = [root];
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for (let i = 0; i < len; ++i) {
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switch (string.charCodeAt(i)) {
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case CHAR_SINGLE_QUOTE:
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switch (state1 & 0xff) {
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case STATE_SINGLE_QUOTE:
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state1 = state2;
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state1Index = state2Index;
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state2 = 0;
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continue;
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case STATE_LESS_THAN:
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state2 = state1;
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state2Index = state1Index;
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state1 = STATE_SINGLE_QUOTE;
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state1Index = i;
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continue;
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}
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continue;
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case CHAR_DOUBLE_QUOTE:
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switch (state1 & 0xff) {
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case STATE_DOUBLE_QUOTE:
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state1 = state2;
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state1Index = state2Index;
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state2 = 0;
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continue;
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case STATE_LESS_THAN:
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state2 = state1;
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state2Index = state1Index;
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state1 = STATE_DOUBLE_QUOTE;
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state1Index = i;
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continue;
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}
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continue;
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case CHAR_LESS_THAN:
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if ((state1 & 0xff) === 0) {
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state2 = state1;
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state2Index = state1Index;
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state1 = STATE_LESS_THAN;
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state1Index = i;
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}
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continue;
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case CHAR_COLON:
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if ((state1 & 0xff) === STATE_LESS_THAN) {
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const colonIndex = (state1 >> 8) & 0xff;
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if (colonIndex === 0) state1 ^= ((i - state1Index) & 0xff) << 8;
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}
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continue;
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case CHAR_SPACE:
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case CHAR_TAB:
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case CHAR_CR:
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case CHAR_LF:
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if ((state1 & 0xff) === STATE_LESS_THAN) {
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const wsIndex = (state1 >> 16) & 0xff;
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if (wsIndex === 0) state1 ^= ((i - state1Index) & 0xff) << 16;
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}
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continue;
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case CHAR_GREATER_THAN:
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if ((state1 & 0xff) === STATE_LESS_THAN) {
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const secondChar = string.charCodeAt(state1Index + 1);
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const wsIndex: number = (state1 >> 16) & 0xff;
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let name: string,
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colonIndex: number,
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e: Element,
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parent: Element,
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selfClosing: number,
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localName: string,
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namespace: string;
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switch (secondChar) {
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case CHAR_SLASH:
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e = stack.pop();
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name =
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wsIndex === 0
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? string.slice(state1Index + 2, i)
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: string.slice(state1Index + 2, state1Index + wsIndex);
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if (e.name !== name)
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throw new Error(`Unmatched closing tag at ${i}`);
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if (!e.children.length)
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e.text = string.slice(e.bodyIndex, state1Index);
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state1 = state2;
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state1Index = state2Index;
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state2 = 0;
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continue;
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case CHAR_EXMARK:
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if (string.startsWith("![CDATA[", state1Index + 1)) {
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if (string.endsWith("]]", i))
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throw new Error(`CDATA nodes are not supported at ${i}`);
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} else if (string.startsWith("!--", state1Index + 1)) {
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// Comment node, ignore
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if (string.endsWith("--", i)) {
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state1 = state2;
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state1Index = state2Index;
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state2 = 0;
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}
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}
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continue;
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case CHAR_QMARK:
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if (string.charCodeAt(i - 1) === CHAR_QMARK) {
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// XML declaration node, ignore
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state1 = state2;
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state1Index = state2Index;
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state2 = 0;
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}
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continue;
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default:
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selfClosing = +(string.charCodeAt(i - 1) === CHAR_SLASH);
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parent = stack[stack.length - 1];
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colonIndex = (state1 >> 8) & 0xff;
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name =
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wsIndex === 0
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? string.slice(state1Index + 1, i - selfClosing)
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: string.slice(state1Index + 1, state1Index + wsIndex);
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if (colonIndex && (!wsIndex || colonIndex < wsIndex)) {
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localName = name.slice(colonIndex);
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namespace = name.slice(0, colonIndex - 1);
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} else {
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localName = name;
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namespace = "";
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}
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e = {
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name: name,
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namespace: namespace,
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localName: localName,
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attrs: wsIndex
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? string.slice(state1Index + wsIndex + 1, i - selfClosing)
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: "",
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text: "",
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bodyIndex: i + 1,
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children: []
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};
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parent.children.push(e);
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if (!selfClosing) stack.push(e);
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state1 = state2;
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state1Index = state2Index;
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state2 = 0;
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continue;
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}
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}
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continue;
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}
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}
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if (state1) throw new Error(`Unclosed token at ${state1Index}`);
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if (stack.length > 1) {
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const e = stack[stack.length - 1];
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throw new Error(`Unclosed XML element at ${e.bodyIndex}`);
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}
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if (!root.children.length) root.text = string;
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return root;
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}
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