148 lines
4.0 KiB
JavaScript
148 lines
4.0 KiB
JavaScript
'use strict';
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var UNICODE = require('../common/unicode');
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//Aliases
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var $ = UNICODE.CODE_POINTS;
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//Utils
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//OPTIMIZATION: these utility functions should not be moved out of this module. V8 Crankshaft will not inline
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//this functions if they will be situated in another module due to context switch.
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//Always perform inlining check before modifying this functions ('node --trace-inlining').
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function isSurrogatePair(cp1, cp2) {
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return cp1 >= 0xD800 && cp1 <= 0xDBFF && cp2 >= 0xDC00 && cp2 <= 0xDFFF;
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}
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function getSurrogatePairCodePoint(cp1, cp2) {
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return (cp1 - 0xD800) * 0x400 + 0x2400 + cp2;
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}
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//Const
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var 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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var Preprocessor = module.exports = function () {
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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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Preprocessor.prototype.dropParsedChunk = function () {
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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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Preprocessor.prototype._addGap = function () {
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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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Preprocessor.prototype._processHighRangeCodePoint = function (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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var nextCp = this.html.charCodeAt(this.pos + 1);
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if (isSurrogatePair(cp, 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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cp = getSurrogatePairCodePoint(cp, nextCp);
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//NOTE: add gap that should be avoided during retreat
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this._addGap();
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}
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}
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// NOTE: we've hit the end of chunk, stop processing at this point
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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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return cp;
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};
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Preprocessor.prototype.write = function (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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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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Preprocessor.prototype.insertHtmlAtCurrentPos = function (chunk) {
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this.html = this.html.substring(0, this.pos + 1) +
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chunk +
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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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Preprocessor.prototype.advance = function () {
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this.pos++;
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if (this.pos > this.lastCharPos) {
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if (!this.lastChunkWritten)
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this.endOfChunkHit = true;
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return $.EOF;
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}
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var 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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//OPTIMIZATION: first perform check if the code point in the allowed range that covers most common
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//HTML input (e.g. ASCII codes) to avoid performance-cost operations for high-range code points.
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return cp >= 0xD800 ? this._processHighRangeCodePoint(cp) : cp;
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};
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Preprocessor.prototype.retreat = function () {
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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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