The Tor Browser: extensions/universalchardet/src/base/nsHebrewProber.cpp@b8a032363ba2 (annotated)

extensions/universalchardet/src/base/nsHebrewProber.cpp@b8a032363ba2 (annotated)

extensions/universalchardet/src/base/nsHebrewProber.cpp

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 #include "nsHebrewProber.h"
 #include <stdio.h>
 // windows-1255 / ISO-8859-8 code points of interest
 #define FINAL_KAF ('\xea')
 #define NORMAL_KAF ('\xeb')
 #define FINAL_MEM ('\xed')
 #define NORMAL_MEM ('\xee')
 #define FINAL_NUN ('\xef')
 #define NORMAL_NUN ('\xf0')
 #define FINAL_PE ('\xf3')
 #define NORMAL_PE ('\xf4')
 #define FINAL_TSADI ('\xf5')
 #define NORMAL_TSADI ('\xf6')
 // Minimum Visual vs Logical final letter score difference.
 // If the difference is below this, don't rely solely on the final letter score distance.
 #define 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.
 #define MIN_MODEL_DISTANCE (0.01)
 #define VISUAL_HEBREW_NAME ("ISO-8859-8")
 #define LOGICAL_HEBREW_NAME ("windows-1255")
 bool nsHebrewProber::isFinal(char c)
 {
   return ((c == FINAL_KAF) || (c == FINAL_MEM) || (c == FINAL_NUN) || (c == FINAL_PE) || (c == FINAL_TSADI));
 }
 bool nsHebrewProber::isNonFinal(char c)
 {
   return ((c == NORMAL_KAF) || (c == NORMAL_MEM) || (c == NORMAL_NUN) || (c == NORMAL_PE));
   // 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.
 }
 /** HandleData
  * 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.
  */
 nsProbingState nsHebrewProber::HandleData(const char* aBuf, uint32_t aLen)
 {
   // Both model probers say it's not them. No reason to continue.
   if (GetState() == eNotMe)
     return eNotMe;
   const char *curPtr, *endPtr = aBuf+aLen;
   char cur;
   for (curPtr = (char*)aBuf; curPtr < endPtr; ++curPtr)
   {
     cur = *curPtr;
     if (cur == ' ') // We stand on a space - a word just ended
     {
       if (mBeforePrev != ' ') // *(curPtr-2) was not a space so prev is not a 1 letter word
       {
         if (isFinal(mPrev)) // case (1) [-2:not space][-1:final letter][cur:space]
           ++mFinalCharLogicalScore;
         else if (isNonFinal(mPrev)) // case (2) [-2:not space][-1:Non-Final letter][cur:space]
           ++mFinalCharVisualScore;
       }
     }
     else  // Not standing on a space
     {
       if ((mBeforePrev == ' ') && (isFinal(mPrev)) && (cur != ' ')) // case (3) [-2:space][-1:final letter][cur:not space]
         ++mFinalCharVisualScore;
     }
     mBeforePrev = mPrev;
     mPrev = cur;
   }
   // Forever detecting, till the end or until both model probers return eNotMe (handled above).
   return eDetecting;
 }
 // Make the decision: is it Logical or Visual?
 const char* nsHebrewProber::GetCharSetName()
 {
   // If the final letter score distance is dominant enough, rely on it.
   int32_t finalsub = mFinalCharLogicalScore - mFinalCharVisualScore;
   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 = mLogicalProb->GetConfidence() - mVisualProb->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;
 }
 void nsHebrewProber::Reset(void)
 {
   mFinalCharLogicalScore = 0;
   mFinalCharVisualScore = 0;
   // mPrev and mBeforePrev are initialized to space in order to simulate a word
   // delimiter at the beginning of the data
   mPrev = ' ';
   mBeforePrev = ' ';
 }
 nsProbingState nsHebrewProber::GetState(void)
 {
   // Remain active as long as any of the model probers are active.
   if ((mLogicalProb->GetState() == eNotMe) && (mVisualProb->GetState() == eNotMe))
     return eNotMe;
   return eDetecting;
 }
 #ifdef DEBUG_chardet
 void  nsHebrewProber::DumpStatus()
 {
   printf("  HEB: %d - %d [Logical-Visual score]\r\n", mFinalCharLogicalScore, mFinalCharVisualScore);
 }
 #endif

The Tor Browser / annotate

extensions/universalchardet/src/base/nsHebrewProber.cpp@b8a032363ba2 (annotated)

extensions/universalchardet/src/base/nsHebrewProber.cpp