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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__ */