mirror of
https://github.com/clementine-player/Clementine
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177 lines
8.2 KiB
C++
177 lines
8.2 KiB
C++
/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* ***** BEGIN LICENSE BLOCK *****
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* Version: MPL 1.1/GPL 2.0/LGPL 2.1
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*
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* The contents of this file are subject to the Mozilla Public License Version
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* 1.1 (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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* http://www.mozilla.org/MPL/
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*
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* Software distributed under the License is distributed on an "AS IS" basis,
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* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
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* for the specific language governing rights and limitations under the
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* License.
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*
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* The Original Code is Mozilla Universal charset detector code.
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*
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* The Initial Developer of the Original Code is
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* Shy Shalom <shooshX@gmail.com>
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* Portions created by the Initial Developer are Copyright (C) 2005
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* the Initial Developer: All Rights Reserved.
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*
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* Contributor(s):
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*
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* Alternatively, the contents of this file may be used under the terms of
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* either the GNU General Public License Version 2 or later (the "GPL"), or
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* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
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* in which case the provisions of the GPL or the LGPL are applicable instead
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* of those above. If you wish to allow use of your version of this file only
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* under the terms of either the GPL or the LGPL, and not to allow others to
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* use your version of this file under the terms of the MPL, indicate your
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* decision by deleting the provisions above and replace them with the notice
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* and other provisions required by the GPL or the LGPL. If you do not delete
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* the provisions above, a recipient may use your version of this file under
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* the terms of any one of the MPL, the GPL or the LGPL.
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*
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* ***** END LICENSE BLOCK ***** */
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#ifndef nsHebrewProber_h__
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#define nsHebrewProber_h__
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#include "nsSBCharSetProber.h"
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// This prober doesn't actually recognize a language or a charset.
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// It is a helper prober for the use of the Hebrew model probers
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class nsHebrewProber: public nsCharSetProber
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{
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public:
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nsHebrewProber(void) :mLogicalProb(0), mVisualProb(0) { Reset(); }
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virtual ~nsHebrewProber(void) {}
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virtual nsProbingState HandleData(const char* aBuf, uint32_t aLen);
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virtual const char* GetCharSetName();
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virtual void Reset(void);
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virtual nsProbingState GetState(void);
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virtual float GetConfidence(void) { return (float)0.0; }
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virtual void SetOpion() {}
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void SetModelProbers(nsCharSetProber *logicalPrb, nsCharSetProber *visualPrb)
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{ mLogicalProb = logicalPrb; mVisualProb = visualPrb; }
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#ifdef DEBUG_chardet
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virtual void DumpStatus();
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#endif
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protected:
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static bool isFinal(char c);
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static bool isNonFinal(char c);
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int32_t mFinalCharLogicalScore, mFinalCharVisualScore;
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// The two last characters seen in the previous buffer.
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char mPrev, mBeforePrev;
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// These probers are owned by the group prober.
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nsCharSetProber *mLogicalProb, *mVisualProb;
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};
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/**
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* ** General ideas of the Hebrew charset recognition **
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*
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* Four main charsets exist in Hebrew:
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* "ISO-8859-8" - Visual Hebrew
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* "windows-1255" - Logical Hebrew
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* "ISO-8859-8-I" - Logical Hebrew
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* "x-mac-hebrew" - ?? Logical Hebrew ??
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*
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* Both "ISO" charsets use a completely identical set of code points, whereas
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* "windows-1255" and "x-mac-hebrew" are two different proper supersets of
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* these code points. windows-1255 defines additional characters in the range
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* 0x80-0x9F as some misc punctuation marks as well as some Hebrew-specific
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* diacritics and additional 'Yiddish' ligature letters in the range 0xc0-0xd6.
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* x-mac-hebrew defines similar additional code points but with a different
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* mapping.
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*
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* As far as an average Hebrew text with no diacritics is concerned, all four
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* charsets are identical with respect to code points. Meaning that for the
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* main Hebrew alphabet, all four map the same values to all 27 Hebrew letters
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* (including final letters).
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*
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* The dominant difference between these charsets is their directionality.
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* "Visual" directionality means that the text is ordered as if the renderer is
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* not aware of a BIDI rendering algorithm. The renderer sees the text and
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* draws it from left to right. The text itself when ordered naturally is read
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* backwards. A buffer of Visual Hebrew generally looks like so:
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* "[last word of first line spelled backwards] [whole line ordered backwards
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* and spelled backwards] [first word of first line spelled backwards]
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* [end of line] [last word of second line] ... etc' "
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* adding punctuation marks, numbers and English text to visual text is
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* naturally also "visual" and from left to right.
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*
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* "Logical" directionality means the text is ordered "naturally" according to
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* the order it is read. It is the responsibility of the renderer to display
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* the text from right to left. A BIDI algorithm is used to place general
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* punctuation marks, numbers and English text in the text.
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*
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* Texts in x-mac-hebrew are almost impossible to find on the Internet. From
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* what little evidence I could find, it seems that its general directionality
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* is Logical.
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*
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* To sum up all of the above, the Hebrew probing mechanism knows about two
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* charsets:
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* Visual Hebrew - "ISO-8859-8" - backwards text - Words and sentences are
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* backwards while line order is natural. For charset recognition purposes
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* the line order is unimportant (In fact, for this implementation, even
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* word order is unimportant).
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* Logical Hebrew - "windows-1255" - normal, naturally ordered text.
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*
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* "ISO-8859-8-I" is a subset of windows-1255 and doesn't need to be
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* specifically identified.
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* "x-mac-hebrew" is also identified as windows-1255. A text in x-mac-hebrew
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* that contain special punctuation marks or diacritics is displayed with
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* some unconverted characters showing as question marks. This problem might
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* be corrected using another model prober for x-mac-hebrew. Due to the fact
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* that x-mac-hebrew texts are so rare, writing another model prober isn't
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* worth the effort and performance hit.
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*
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* *** The Prober ***
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*
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* The prober is divided between two nsSBCharSetProbers and an nsHebrewProber,
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* all of which are managed, created, fed data, inquired and deleted by the
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* nsSBCSGroupProber. The two nsSBCharSetProbers identify that the text is in
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* fact some kind of Hebrew, Logical or Visual. The final decision about which
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* one is it is made by the nsHebrewProber by combining final-letter scores
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* with the scores of the two nsSBCharSetProbers to produce a final answer.
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*
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* The nsSBCSGroupProber is responsible for stripping the original text of HTML
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* tags, English characters, numbers, low-ASCII punctuation characters, spaces
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* and new lines. It reduces any sequence of such characters to a single space.
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* The buffer fed to each prober in the SBCS group prober is pure text in
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* high-ASCII.
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* The two nsSBCharSetProbers (model probers) share the same language model:
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* Win1255Model.
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* The first nsSBCharSetProber uses the model normally as any other
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* nsSBCharSetProber does, to recognize windows-1255, upon which this model was
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* built. The second nsSBCharSetProber is told to make the pair-of-letter
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* lookup in the language model backwards. This in practice exactly simulates
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* a visual Hebrew model using the windows-1255 logical Hebrew model.
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*
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* The nsHebrewProber is not using any language model. All it does is look for
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* final-letter evidence suggesting the text is either logical Hebrew or visual
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* Hebrew. Disjointed from the model probers, the results of the nsHebrewProber
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* alone are meaningless. nsHebrewProber always returns 0.00 as confidence
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* since it never identifies a charset by itself. Instead, the pointer to the
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* nsHebrewProber is passed to the model probers as a helper "Name Prober".
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* When the Group prober receives a positive identification from any prober,
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* it asks for the name of the charset identified. If the prober queried is a
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* Hebrew model prober, the model prober forwards the call to the
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* nsHebrewProber to make the final decision. In the nsHebrewProber, the
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* decision is made according to the final-letters scores maintained and Both
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* model probers scores. The answer is returned in the form of the name of the
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* charset identified, either "windows-1255" or "ISO-8859-8".
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*
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*/
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#endif /* nsHebrewProber_h__ */
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