'use strict';
|
|
const unicode = require('../common/unicode');
|
const ERR = require('../common/error-codes');
|
|
//Aliases
|
const $ = unicode.CODE_POINTS;
|
|
//Const
|
const 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)
|
class Preprocessor {
|
constructor() {
|
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;
|
}
|
|
_err() {
|
// NOTE: err reporting is noop by default. Enabled by mixin.
|
}
|
|
_addGap() {
|
this.gapStack.push(this.lastGapPos);
|
this.lastGapPos = this.pos;
|
}
|
|
_processSurrogate(cp) {
|
//NOTE: try to peek a surrogate pair
|
if (this.pos !== this.lastCharPos) {
|
const nextCp = this.html.charCodeAt(this.pos + 1);
|
|
if (unicode.isSurrogatePair(nextCp)) {
|
//NOTE: we have a surrogate pair. Peek pair character and recalculate code point.
|
this.pos++;
|
|
//NOTE: add gap that should be avoided during retreat
|
this._addGap();
|
|
return unicode.getSurrogatePairCodePoint(cp, nextCp);
|
}
|
}
|
|
//NOTE: we are at the end of a chunk, therefore we can't infer surrogate pair yet.
|
else if (!this.lastChunkWritten) {
|
this.endOfChunkHit = true;
|
return $.EOF;
|
}
|
|
//NOTE: isolated surrogate
|
this._err(ERR.surrogateInInputStream);
|
|
return cp;
|
}
|
|
dropParsedChunk() {
|
if (this.pos > this.bufferWaterline) {
|
this.lastCharPos -= this.pos;
|
this.html = this.html.substring(this.pos);
|
this.pos = 0;
|
this.lastGapPos = -1;
|
this.gapStack = [];
|
}
|
}
|
|
write(chunk, isLastChunk) {
|
if (this.html) {
|
this.html += chunk;
|
} else {
|
this.html = chunk;
|
}
|
|
this.lastCharPos = this.html.length - 1;
|
this.endOfChunkHit = false;
|
this.lastChunkWritten = isLastChunk;
|
}
|
|
insertHtmlAtCurrentPos(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;
|
}
|
|
advance() {
|
this.pos++;
|
|
if (this.pos > this.lastCharPos) {
|
this.endOfChunkHit = !this.lastChunkWritten;
|
return $.EOF;
|
}
|
|
let 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;
|
|
if (unicode.isSurrogate(cp)) {
|
cp = this._processSurrogate(cp);
|
}
|
|
//OPTIMIZATION: first check if code point is in the common allowed
|
//range (ASCII alphanumeric, whitespaces, big chunk of BMP)
|
//before going into detailed performance cost validation.
|
const isCommonValidRange =
|
(cp > 0x1f && cp < 0x7f) || cp === $.LINE_FEED || cp === $.CARRIAGE_RETURN || (cp > 0x9f && cp < 0xfdd0);
|
|
if (!isCommonValidRange) {
|
this._checkForProblematicCharacters(cp);
|
}
|
|
return cp;
|
}
|
|
_checkForProblematicCharacters(cp) {
|
if (unicode.isControlCodePoint(cp)) {
|
this._err(ERR.controlCharacterInInputStream);
|
} else if (unicode.isUndefinedCodePoint(cp)) {
|
this._err(ERR.noncharacterInInputStream);
|
}
|
}
|
|
retreat() {
|
if (this.pos === this.lastGapPos) {
|
this.lastGapPos = this.gapStack.pop();
|
this.pos--;
|
}
|
|
this.pos--;
|
}
|
}
|
|
module.exports = Preprocessor;
|
