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159 lines
4.4 KiB
159 lines
4.4 KiB
'use strict';
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const unicode = require('../common/unicode');
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const ERR = require('../common/error-codes');
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//Aliases
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const $ = unicode.CODE_POINTS;
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//Const
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const DEFAULT_BUFFER_WATERLINE = 1 << 16;
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//Preprocessor
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//NOTE: HTML input preprocessing
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//(see: http://www.whatwg.org/specs/web-apps/current-work/multipage/parsing.html#preprocessing-the-input-stream)
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class Preprocessor {
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constructor() {
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this.html = null;
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this.pos = -1;
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this.lastGapPos = -1;
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this.lastCharPos = -1;
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this.gapStack = [];
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this.skipNextNewLine = false;
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this.lastChunkWritten = false;
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this.endOfChunkHit = false;
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this.bufferWaterline = DEFAULT_BUFFER_WATERLINE;
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}
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_err() {
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// NOTE: err reporting is noop by default. Enabled by mixin.
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}
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_addGap() {
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this.gapStack.push(this.lastGapPos);
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this.lastGapPos = this.pos;
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}
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_processSurrogate(cp) {
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//NOTE: try to peek a surrogate pair
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if (this.pos !== this.lastCharPos) {
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const nextCp = this.html.charCodeAt(this.pos + 1);
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if (unicode.isSurrogatePair(nextCp)) {
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//NOTE: we have a surrogate pair. Peek pair character and recalculate code point.
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this.pos++;
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//NOTE: add gap that should be avoided during retreat
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this._addGap();
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return unicode.getSurrogatePairCodePoint(cp, nextCp);
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}
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}
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//NOTE: we are at the end of a chunk, therefore we can't infer surrogate pair yet.
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else if (!this.lastChunkWritten) {
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this.endOfChunkHit = true;
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return $.EOF;
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}
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//NOTE: isolated surrogate
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this._err(ERR.surrogateInInputStream);
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return cp;
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}
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dropParsedChunk() {
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if (this.pos > this.bufferWaterline) {
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this.lastCharPos -= this.pos;
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this.html = this.html.substring(this.pos);
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this.pos = 0;
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this.lastGapPos = -1;
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this.gapStack = [];
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}
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}
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write(chunk, isLastChunk) {
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if (this.html) {
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this.html += chunk;
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} else {
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this.html = chunk;
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}
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this.lastCharPos = this.html.length - 1;
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this.endOfChunkHit = false;
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this.lastChunkWritten = isLastChunk;
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}
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insertHtmlAtCurrentPos(chunk) {
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this.html = this.html.substring(0, this.pos + 1) + chunk + this.html.substring(this.pos + 1, this.html.length);
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this.lastCharPos = this.html.length - 1;
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this.endOfChunkHit = false;
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}
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advance() {
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this.pos++;
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if (this.pos > this.lastCharPos) {
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this.endOfChunkHit = !this.lastChunkWritten;
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return $.EOF;
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}
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let cp = this.html.charCodeAt(this.pos);
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//NOTE: any U+000A LINE FEED (LF) characters that immediately follow a U+000D CARRIAGE RETURN (CR) character
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//must be ignored.
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if (this.skipNextNewLine && cp === $.LINE_FEED) {
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this.skipNextNewLine = false;
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this._addGap();
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return this.advance();
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}
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//NOTE: all U+000D CARRIAGE RETURN (CR) characters must be converted to U+000A LINE FEED (LF) characters
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if (cp === $.CARRIAGE_RETURN) {
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this.skipNextNewLine = true;
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return $.LINE_FEED;
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}
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this.skipNextNewLine = false;
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if (unicode.isSurrogate(cp)) {
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cp = this._processSurrogate(cp);
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}
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//OPTIMIZATION: first check if code point is in the common allowed
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//range (ASCII alphanumeric, whitespaces, big chunk of BMP)
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//before going into detailed performance cost validation.
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const isCommonValidRange =
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(cp > 0x1f && cp < 0x7f) || cp === $.LINE_FEED || cp === $.CARRIAGE_RETURN || (cp > 0x9f && cp < 0xfdd0);
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if (!isCommonValidRange) {
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this._checkForProblematicCharacters(cp);
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}
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return cp;
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}
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_checkForProblematicCharacters(cp) {
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if (unicode.isControlCodePoint(cp)) {
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this._err(ERR.controlCharacterInInputStream);
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} else if (unicode.isUndefinedCodePoint(cp)) {
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this._err(ERR.noncharacterInInputStream);
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}
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}
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retreat() {
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if (this.pos === this.lastGapPos) {
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this.lastGapPos = this.gapStack.pop();
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this.pos--;
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}
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this.pos--;
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}
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}
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module.exports = Preprocessor;
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