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Diffstat (limited to 'Emby.Server.Implementations/TextEncoding/UniversalDetector/Core/HebrewProber.cs')
| -rw-r--r-- | Emby.Server.Implementations/TextEncoding/UniversalDetector/Core/HebrewProber.cs | 328 |
1 files changed, 0 insertions, 328 deletions
diff --git a/Emby.Server.Implementations/TextEncoding/UniversalDetector/Core/HebrewProber.cs b/Emby.Server.Implementations/TextEncoding/UniversalDetector/Core/HebrewProber.cs deleted file mode 100644 index bd7490ad7..000000000 --- a/Emby.Server.Implementations/TextEncoding/UniversalDetector/Core/HebrewProber.cs +++ /dev/null @@ -1,328 +0,0 @@ -/* ***** 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); - } - } -} |