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- /* -*- 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 <shooshX@gmail.com>
- * 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__ */
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