mirror of
https://github.com/jellyfin/jellyfin.git
synced 2024-09-06 19:37:55 +02:00
328 lines
15 KiB
C#
328 lines
15 KiB
C#
/* ***** 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
|
|
* Netscape Communications Corporation.
|
|
* Portions created by the Initial Developer are Copyright (C) 2001
|
|
* the Initial Developer. All Rights Reserved.
|
|
*
|
|
* Contributor(s):
|
|
* Shy Shalom <shooshX@gmail.com>
|
|
* Rudi Pettazzi <rudi.pettazzi@gmail.com> (C# port)
|
|
*
|
|
* 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 ***** */
|
|
|
|
|
|
/**
|
|
* 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".
|
|
*
|
|
*/
|
|
namespace UniversalDetector.Core
|
|
{
|
|
|
|
/// <summary>
|
|
/// This prober doesn't actually recognize a language or a charset.
|
|
/// It is a helper prober for the use of the Hebrew model probers
|
|
/// </summary>
|
|
public class HebrewProber : CharsetProber
|
|
{
|
|
// windows-1255 / ISO-8859-8 code points of interest
|
|
private const byte FINAL_KAF = 0xEA;
|
|
private const byte NORMAL_KAF = 0xEB;
|
|
private const byte FINAL_MEM = 0xED;
|
|
private const byte NORMAL_MEM = 0xEE;
|
|
private const byte FINAL_NUN = 0xEF;
|
|
private const byte NORMAL_NUN = 0xF0;
|
|
private const byte FINAL_PE = 0xF3;
|
|
private const byte NORMAL_PE = 0xF4;
|
|
private const byte FINAL_TSADI = 0xF5;
|
|
private const byte NORMAL_TSADI = 0xF6;
|
|
|
|
// Minimum Visual vs Logical final letter score difference.
|
|
// If the difference is below this, don't rely solely on the final letter score distance.
|
|
private const int MIN_FINAL_CHAR_DISTANCE = 5;
|
|
|
|
// Minimum Visual vs Logical model score difference.
|
|
// If the difference is below this, don't rely at all on the model score distance.
|
|
private const float MIN_MODEL_DISTANCE = 0.01f;
|
|
|
|
protected const string VISUAL_HEBREW_NAME = "ISO-8859-8";
|
|
protected const string LOGICAL_HEBREW_NAME = "windows-1255";
|
|
|
|
// owned by the group prober.
|
|
protected CharsetProber logicalProber, visualProber;
|
|
protected int finalCharLogicalScore, finalCharVisualScore;
|
|
|
|
// The two last bytes seen in the previous buffer.
|
|
protected byte prev, beforePrev;
|
|
|
|
public HebrewProber()
|
|
{
|
|
Reset();
|
|
}
|
|
|
|
public void SetModelProbers(CharsetProber logical, CharsetProber visual)
|
|
{
|
|
logicalProber = logical;
|
|
visualProber = visual;
|
|
}
|
|
|
|
/**
|
|
* Final letter analysis for logical-visual decision.
|
|
* Look for evidence that the received buffer is either logical Hebrew or
|
|
* visual Hebrew.
|
|
* The following cases are checked:
|
|
* 1) A word longer than 1 letter, ending with a final letter. This is an
|
|
* indication that the text is laid out "naturally" since the final letter
|
|
* really appears at the end. +1 for logical score.
|
|
* 2) A word longer than 1 letter, ending with a Non-Final letter. In normal
|
|
* Hebrew, words ending with Kaf, Mem, Nun, Pe or Tsadi, should not end with
|
|
* the Non-Final form of that letter. Exceptions to this rule are mentioned
|
|
* above in isNonFinal(). This is an indication that the text is laid out
|
|
* backwards. +1 for visual score
|
|
* 3) A word longer than 1 letter, starting with a final letter. Final letters
|
|
* should not appear at the beginning of a word. This is an indication that
|
|
* the text is laid out backwards. +1 for visual score.
|
|
*
|
|
* The visual score and logical score are accumulated throughout the text and
|
|
* are finally checked against each other in GetCharSetName().
|
|
* No checking for final letters in the middle of words is done since that case
|
|
* is not an indication for either Logical or Visual text.
|
|
*
|
|
* The input buffer should not contain any white spaces that are not (' ')
|
|
* or any low-ascii punctuation marks.
|
|
*/
|
|
public override ProbingState HandleData(byte[] buf, int offset, int len)
|
|
{
|
|
// Both model probers say it's not them. No reason to continue.
|
|
if (GetState() == ProbingState.NotMe)
|
|
return ProbingState.NotMe;
|
|
|
|
int max = offset + len;
|
|
|
|
for (int i = offset; i < max; i++)
|
|
{
|
|
|
|
byte b = buf[i];
|
|
|
|
// a word just ended
|
|
if (b == 0x20)
|
|
{
|
|
// *(curPtr-2) was not a space so prev is not a 1 letter word
|
|
if (beforePrev != 0x20)
|
|
{
|
|
// case (1) [-2:not space][-1:final letter][cur:space]
|
|
if (IsFinal(prev))
|
|
finalCharLogicalScore++;
|
|
// case (2) [-2:not space][-1:Non-Final letter][cur:space]
|
|
else if (IsNonFinal(prev))
|
|
finalCharVisualScore++;
|
|
}
|
|
|
|
}
|
|
else
|
|
{
|
|
// case (3) [-2:space][-1:final letter][cur:not space]
|
|
if ((beforePrev == 0x20) && (IsFinal(prev)) && (b != ' '))
|
|
++finalCharVisualScore;
|
|
}
|
|
beforePrev = prev;
|
|
prev = b;
|
|
}
|
|
|
|
// Forever detecting, till the end or until both model probers
|
|
// return NotMe (handled above).
|
|
return ProbingState.Detecting;
|
|
}
|
|
|
|
// Make the decision: is it Logical or Visual?
|
|
public override string GetCharsetName()
|
|
{
|
|
// If the final letter score distance is dominant enough, rely on it.
|
|
int finalsub = finalCharLogicalScore - finalCharVisualScore;
|
|
if (finalsub >= MIN_FINAL_CHAR_DISTANCE)
|
|
return LOGICAL_HEBREW_NAME;
|
|
if (finalsub <= -(MIN_FINAL_CHAR_DISTANCE))
|
|
return VISUAL_HEBREW_NAME;
|
|
|
|
// It's not dominant enough, try to rely on the model scores instead.
|
|
float modelsub = logicalProber.GetConfidence() - visualProber.GetConfidence();
|
|
if (modelsub > MIN_MODEL_DISTANCE)
|
|
return LOGICAL_HEBREW_NAME;
|
|
if (modelsub < -(MIN_MODEL_DISTANCE))
|
|
return VISUAL_HEBREW_NAME;
|
|
|
|
// Still no good, back to final letter distance, maybe it'll save the day.
|
|
if (finalsub < 0)
|
|
return VISUAL_HEBREW_NAME;
|
|
|
|
// (finalsub > 0 - Logical) or (don't know what to do) default to Logical.
|
|
return LOGICAL_HEBREW_NAME;
|
|
}
|
|
|
|
public override void Reset()
|
|
{
|
|
finalCharLogicalScore = 0;
|
|
finalCharVisualScore = 0;
|
|
prev = 0x20;
|
|
beforePrev = 0x20;
|
|
}
|
|
|
|
public override ProbingState GetState()
|
|
{
|
|
// Remain active as long as any of the model probers are active.
|
|
if (logicalProber.GetState() == ProbingState.NotMe &&
|
|
visualProber.GetState() == ProbingState.NotMe)
|
|
return ProbingState.NotMe;
|
|
return ProbingState.Detecting;
|
|
}
|
|
|
|
public override void DumpStatus()
|
|
{
|
|
//Console.WriteLine(" HEB: {0} - {1} [Logical-Visual score]", finalCharLogicalScore, finalCharVisualScore);
|
|
}
|
|
|
|
public override float GetConfidence()
|
|
{
|
|
return 0.0f;
|
|
}
|
|
|
|
protected static bool IsFinal(byte b)
|
|
{
|
|
return (b == FINAL_KAF || b == FINAL_MEM || b == FINAL_NUN
|
|
|| b == FINAL_PE || b == FINAL_TSADI);
|
|
}
|
|
|
|
protected static bool IsNonFinal(byte b)
|
|
{
|
|
// The normal Tsadi is not a good Non-Final letter due to words like
|
|
// 'lechotet' (to chat) containing an apostrophe after the tsadi. This
|
|
// apostrophe is converted to a space in FilterWithoutEnglishLetters causing
|
|
// the Non-Final tsadi to appear at an end of a word even though this is not
|
|
// the case in the original text.
|
|
// The letters Pe and Kaf rarely display a related behavior of not being a
|
|
// good Non-Final letter. Words like 'Pop', 'Winamp' and 'Mubarak' for
|
|
// example legally end with a Non-Final Pe or Kaf. However, the benefit of
|
|
// these letters as Non-Final letters outweighs the damage since these words
|
|
// are quite rare.
|
|
return (b == NORMAL_KAF || b == NORMAL_MEM || b == NORMAL_NUN
|
|
|| b == NORMAL_PE);
|
|
}
|
|
}
|
|
}
|