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node_modules/parse5/lib/tokenizer/preprocessor.js

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+'use strict';
+
+var UNICODE = require('../common/unicode');
+
+//Aliases
+var $ = UNICODE.CODE_POINTS;
+
+//Utils
+
+//OPTIMIZATION: these utility functions should not be moved out of this module. V8 Crankshaft will not inline
+//this functions if they will be situated in another module due to context switch.
+//Always perform inlining check before modifying this functions ('node --trace-inlining').
+function isSurrogatePair(cp1, cp2) {
+    return cp1 >= 0xD800 && cp1 <= 0xDBFF && cp2 >= 0xDC00 && cp2 <= 0xDFFF;
+}
+
+function getSurrogatePairCodePoint(cp1, cp2) {
+    return (cp1 - 0xD800) * 0x400 + 0x2400 + cp2;
+}
+
+
+//Const
+var DEFAULT_BUFFER_WATERLINE = 1 << 16;
+
+
+//Preprocessor
+//NOTE: HTML input preprocessing
+//(see: http://www.whatwg.org/specs/web-apps/current-work/multipage/parsing.html#preprocessing-the-input-stream)
+var Preprocessor = module.exports = function () {
+    this.html = null;
+
+    this.pos = -1;
+    this.lastGapPos = -1;
+    this.lastCharPos = -1;
+
+    this.gapStack = [];
+
+    this.skipNextNewLine = false;
+
+    this.lastChunkWritten = false;
+    this.endOfChunkHit = false;
+    this.bufferWaterline = DEFAULT_BUFFER_WATERLINE;
+};
+
+Preprocessor.prototype.dropParsedChunk = function () {
+    if (this.pos > this.bufferWaterline) {
+        this.lastCharPos -= this.pos;
+        this.html = this.html.substring(this.pos);
+        this.pos = 0;
+        this.lastGapPos = -1;
+        this.gapStack = [];
+    }
+};
+
+Preprocessor.prototype._addGap = function () {
+    this.gapStack.push(this.lastGapPos);
+    this.lastGapPos = this.pos;
+};
+
+Preprocessor.prototype._processHighRangeCodePoint = function (cp) {
+    //NOTE: try to peek a surrogate pair
+    if (this.pos !== this.lastCharPos) {
+        var nextCp = this.html.charCodeAt(this.pos + 1);
+
+        if (isSurrogatePair(cp, nextCp)) {
+            //NOTE: we have a surrogate pair. Peek pair character and recalculate code point.
+            this.pos++;
+            cp = getSurrogatePairCodePoint(cp, nextCp);
+
+            //NOTE: add gap that should be avoided during retreat
+            this._addGap();
+        }
+    }
+
+    // NOTE: we've hit the end of chunk, stop processing at this point
+    else if (!this.lastChunkWritten) {
+        this.endOfChunkHit = true;
+        return $.EOF;
+    }
+
+    return cp;
+};
+
+Preprocessor.prototype.write = function (chunk, isLastChunk) {
+    if (this.html)
+        this.html += chunk;
+
+    else
+        this.html = chunk;
+
+    this.lastCharPos = this.html.length - 1;
+    this.endOfChunkHit = false;
+    this.lastChunkWritten = isLastChunk;
+};
+
+Preprocessor.prototype.insertHtmlAtCurrentPos = function (chunk) {
+    this.html = this.html.substring(0, this.pos + 1) +
+                chunk +
+                this.html.substring(this.pos + 1, this.html.length);
+
+    this.lastCharPos = this.html.length - 1;
+    this.endOfChunkHit = false;
+};
+
+
+Preprocessor.prototype.advance = function () {
+    this.pos++;
+
+    if (this.pos > this.lastCharPos) {
+        if (!this.lastChunkWritten)
+            this.endOfChunkHit = true;
+
+        return $.EOF;
+    }
+
+    var cp = this.html.charCodeAt(this.pos);
+
+    //NOTE: any U+000A LINE FEED (LF) characters that immediately follow a U+000D CARRIAGE RETURN (CR) character
+    //must be ignored.
+    if (this.skipNextNewLine && cp === $.LINE_FEED) {
+        this.skipNextNewLine = false;
+        this._addGap();
+        return this.advance();
+    }
+
+    //NOTE: all U+000D CARRIAGE RETURN (CR) characters must be converted to U+000A LINE FEED (LF) characters
+    if (cp === $.CARRIAGE_RETURN) {
+        this.skipNextNewLine = true;
+        return $.LINE_FEED;
+    }
+
+    this.skipNextNewLine = false;
+
+    //OPTIMIZATION: first perform check if the code point in the allowed range that covers most common
+    //HTML input (e.g. ASCII codes) to avoid performance-cost operations for high-range code points.
+    return cp >= 0xD800 ? this._processHighRangeCodePoint(cp) : cp;
+};
+
+Preprocessor.prototype.retreat = function () {
+    if (this.pos === this.lastGapPos) {
+        this.lastGapPos = this.gapStack.pop();
+        this.pos--;
+    }
+
+    this.pos--;
+};
+