sbcharsetprober.js
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/*
* The Original Code is Mozilla Universal charset detector code.
*
* The Initial Developer of the Original Code is
* Netscape Communications Corporation.
* Portions created by the Initial Developer are Copyright (C) 2001
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* António Afonso (antonio.afonso gmail.com) - port to JavaScript
* Mark Pilgrim - port to Python
* Shy Shalom - original C code
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
* 02110-1301 USA
*/
!function(jschardet) {
jschardet.SingleByteCharSetProber = function(model, reversed, nameProber) {
jschardet.CharSetProber.apply(this);
var SAMPLE_SIZE = 64;
var SB_ENOUGH_REL_THRESHOLD = 1024;
var POSITIVE_SHORTCUT_THRESHOLD = 0.95;
var NEGATIVE_SHORTCUT_THRESHOLD = 0.05;
var SYMBOL_CAT_ORDER = 250;
var NUMBER_OF_SEQ_CAT = 4;
var POSITIVE_CAT = NUMBER_OF_SEQ_CAT - 1;
//var NEGATIVE_CAT = 0;
var self = this;
function init(model, reversed, nameProber) {
self._mModel = model;
self._mReversed = reversed; // "true" if we need to reverse every pair in the model lookup
self._mNameProber = nameProber; // Optional auxiliary prober for name decision
self.reset();
}
this.reset = function() {
jschardet.SingleByteCharSetProber.prototype.reset.apply(this);
this._mLastOrder = 255; // char order of last character
this._mSeqCounters = [];
for( var i = 0; i < NUMBER_OF_SEQ_CAT; this._mSeqCounters[i++] = 0 );
this._mTotalSeqs = 0;
this._mTotalChar = 0;
this._mFreqChar = 0; // characters that fall in our sampling range
}
this.getCharsetName = function() {
if( this._mNameProber ) {
return this._mNameProber.getCharsetName();
} else {
return this._mModel.charsetName;
}
}
this.feed = function(aBuf) {
if( ! this._mModel.keepEnglishLetter ) {
aBuf = this.filterWithoutEnglishLetters(aBuf);
}
var aLen = aBuf.length;
if( !aLen ) {
return this.getState();
}
for( var i = 0, c; i < aLen; i++ )
{
c = aBuf.charCodeAt(i);
var order = this._mModel.charToOrderMap[c];
if( order < SYMBOL_CAT_ORDER ) {
this._mTotalChar++;
}
if( order < SAMPLE_SIZE ) {
this._mFreqChar++;
if( this._mLastOrder < SAMPLE_SIZE ) {
this._mTotalSeqs++;
if( !this._mReversed ) {
this._mSeqCounters[this._mModel.precedenceMatrix[(this._mLastOrder * SAMPLE_SIZE) + order]]++;
} else { // reverse the order of the letters in the lookup
this._mSeqCounters[this._mModel.precedenceMatrix[(order * SAMPLE_SIZE) + this._mLastOrder]]++;
}
}
}
this._mLastOrder = order;
}
if( this.getState() == jschardet.Constants.detecting ) {
if( self._mTotalSeqs > SB_ENOUGH_REL_THRESHOLD ) {
var cf = this.getConfidence();
if( cf > POSITIVE_SHORTCUT_THRESHOLD ) {
if( jschardet.Constants._debug ) {
jschardet.log(this._mModel.charsetName + " confidence = " + cf + ", we have a winner\n");
}
} else if( cf < NEGATIVE_SHORTCUT_THRESHOLD ) {
if( jschardet.Constants._debug ) {
jschardet.log(this._mModel.charsetName + " confidence = " + cf + ", below negative shortcut threshhold " + NEGATIVE_SHORTCUT_THRESHOLD + "\n");
}
this._mState = jschardet.Constants.notMe;
}
}
}
return this.getState();
}
this.getConfidence = function() {
var r = 0.01;
if( this._mTotalSeqs > 0 ) {
//jschardet.log(this._mSeqCounters[POSITIVE_CAT] + " " + this._mTotalSeqs + " " + this._mModel.mTypicalPositiveRatio);
r = (1.0 * this._mSeqCounters[POSITIVE_CAT]) / this._mTotalSeqs / this._mModel.mTypicalPositiveRatio;
//jschardet.log(r + " " + this._mFreqChar + " " + this._mTotalChar);
r *= this._mFreqChar / this._mTotalChar;
if( r >= 1.0 ) {
r = 0.99;
}
}
return r;
}
reversed = reversed !== undefined ? reversed : false;
nameProber = nameProber !== undefined ? nameProber : null;
init(model, reversed, nameProber);
}
jschardet.SingleByteCharSetProber.prototype = new jschardet.CharSetProber();
}(require('./init'));