/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ /* ***** BEGIN LICENSE BLOCK ***** * Version: MPL 1.1/GPL 2.0/LGPL 2.1 * * The contents of this file are subject to the Mozilla Public License Version * 1.1 (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * http://www.mozilla.org/MPL/ * * Software distributed under the License is distributed on an "AS IS" basis, * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License * for the specific language governing rights and limitations under the * License. * * The Original Code is Mozilla Universal charset detector code. * * The Initial Developer of the Original Code is * Shy Shalom * Portions created by the Initial Developer are Copyright (C) 2005 * the Initial Developer: All Rights Reserved. * * Contributor(s): * * Alternatively, the contents of this file may be used under the terms of * either the GNU General Public License Version 2 or later (the "GPL"), or * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"), * in which case the provisions of the GPL or the LGPL are applicable instead * of those above. If you wish to allow use of your version of this file only * under the terms of either the GPL or the LGPL, and not to allow others to * use your version of this file under the terms of the MPL, indicate your * decision by deleting the provisions above and replace them with the notice * and other provisions required by the GPL or the LGPL. If you do not delete * the provisions above, a recipient may use your version of this file under * the terms of any one of the MPL, the GPL or the LGPL. * * ***** END LICENSE BLOCK ***** */ #ifndef nsHebrewProber_h__ #define nsHebrewProber_h__ #include "nsSBCharSetProber.h" // This prober doesn't actually recognize a language or a charset. // It is a helper prober for the use of the Hebrew model probers class nsHebrewProber: public nsCharSetProber { public: nsHebrewProber(void) :mLogicalProb(0), mVisualProb(0) { Reset(); } virtual ~nsHebrewProber(void) {} virtual nsProbingState HandleData(const char* aBuf, PRUint32 aLen); virtual const char* GetCharSetName(); virtual void Reset(void); virtual nsProbingState GetState(void); virtual float GetConfidence(void) { return (float)0.0; } virtual void SetOpion() {} void SetModelProbers(nsCharSetProber *logicalPrb, nsCharSetProber *visualPrb) { mLogicalProb = logicalPrb; mVisualProb = visualPrb; } #ifdef DEBUG_chardet virtual void DumpStatus(); #endif protected: static PRBool isFinal(char c); static PRBool isNonFinal(char c); PRInt32 mFinalCharLogicalScore, mFinalCharVisualScore; // The two last characters seen in the previous buffer. char mPrev, mBeforePrev; // These probers are owned by the group prober. nsCharSetProber *mLogicalProb, *mVisualProb; }; /** * ** General ideas of the Hebrew charset recognition ** * * Four main charsets exist in Hebrew: * "ISO-8859-8" - Visual Hebrew * "windows-1255" - Logical Hebrew * "ISO-8859-8-I" - Logical Hebrew * "x-mac-hebrew" - ?? Logical Hebrew ?? * * Both "ISO" charsets use a completely identical set of code points, whereas * "windows-1255" and "x-mac-hebrew" are two different proper supersets of * these code points. windows-1255 defines additional characters in the range * 0x80-0x9F as some misc punctuation marks as well as some Hebrew-specific * diacritics and additional 'Yiddish' ligature letters in the range 0xc0-0xd6. * x-mac-hebrew defines similar additional code points but with a different * mapping. * * As far as an average Hebrew text with no diacritics is concerned, all four * charsets are identical with respect to code points. Meaning that for the * main Hebrew alphabet, all four map the same values to all 27 Hebrew letters * (including final letters). * * The dominant difference between these charsets is their directionality. * "Visual" directionality means that the text is ordered as if the renderer is * not aware of a BIDI rendering algorithm. The renderer sees the text and * draws it from left to right. The text itself when ordered naturally is read * backwards. A buffer of Visual Hebrew generally looks like so: * "[last word of first line spelled backwards] [whole line ordered backwards * and spelled backwards] [first word of first line spelled backwards] * [end of line] [last word of second line] ... etc' " * adding punctuation marks, numbers and English text to visual text is * naturally also "visual" and from left to right. * * "Logical" directionality means the text is ordered "naturally" according to * the order it is read. It is the responsibility of the renderer to display * the text from right to left. A BIDI algorithm is used to place general * punctuation marks, numbers and English text in the text. * * Texts in x-mac-hebrew are almost impossible to find on the Internet. From * what little evidence I could find, it seems that its general directionality * is Logical. * * To sum up all of the above, the Hebrew probing mechanism knows about two * charsets: * Visual Hebrew - "ISO-8859-8" - backwards text - Words and sentences are * backwards while line order is natural. For charset recognition purposes * the line order is unimportant (In fact, for this implementation, even * word order is unimportant). * Logical Hebrew - "windows-1255" - normal, naturally ordered text. * * "ISO-8859-8-I" is a subset of windows-1255 and doesn't need to be * specifically identified. * "x-mac-hebrew" is also identified as windows-1255. A text in x-mac-hebrew * that contain special punctuation marks or diacritics is displayed with * some unconverted characters showing as question marks. This problem might * be corrected using another model prober for x-mac-hebrew. Due to the fact * that x-mac-hebrew texts are so rare, writing another model prober isn't * worth the effort and performance hit. * * *** The Prober *** * * The prober is divided between two nsSBCharSetProbers and an nsHebrewProber, * all of which are managed, created, fed data, inquired and deleted by the * nsSBCSGroupProber. The two nsSBCharSetProbers identify that the text is in * fact some kind of Hebrew, Logical or Visual. The final decision about which * one is it is made by the nsHebrewProber by combining final-letter scores * with the scores of the two nsSBCharSetProbers to produce a final answer. * * The nsSBCSGroupProber is responsible for stripping the original text of HTML * tags, English characters, numbers, low-ASCII punctuation characters, spaces * and new lines. It reduces any sequence of such characters to a single space. * The buffer fed to each prober in the SBCS group prober is pure text in * high-ASCII. * The two nsSBCharSetProbers (model probers) share the same language model: * Win1255Model. * The first nsSBCharSetProber uses the model normally as any other * nsSBCharSetProber does, to recognize windows-1255, upon which this model was * built. The second nsSBCharSetProber is told to make the pair-of-letter * lookup in the language model backwards. This in practice exactly simulates * a visual Hebrew model using the windows-1255 logical Hebrew model. * * The nsHebrewProber is not using any language model. All it does is look for * final-letter evidence suggesting the text is either logical Hebrew or visual * Hebrew. Disjointed from the model probers, the results of the nsHebrewProber * alone are meaningless. nsHebrewProber always returns 0.00 as confidence * since it never identifies a charset by itself. Instead, the pointer to the * nsHebrewProber is passed to the model probers as a helper "Name Prober". * When the Group prober receives a positive identification from any prober, * it asks for the name of the charset identified. If the prober queried is a * Hebrew model prober, the model prober forwards the call to the * nsHebrewProber to make the final decision. In the nsHebrewProber, the * decision is made according to the final-letters scores maintained and Both * model probers scores. The answer is returned in the form of the name of the * charset identified, either "windows-1255" or "ISO-8859-8". * */ #endif /* nsHebrewProber_h__ */