--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/ThirdParty/CharDet/chardet/hebrewprober.py Mon Dec 28 16:03:33 2009 +0000
@@ -0,0 +1,269 @@
+######################## BEGIN LICENSE BLOCK ########################
+# The Original Code is Mozilla Universal charset detector code.
+#
+# The Initial Developer of the Original Code is
+# Shy Shalom
+# Portions created by the Initial Developer are Copyright (C) 2005
+# the Initial Developer. All Rights Reserved.
+#
+# Contributor(s):
+# Mark Pilgrim - port to Python
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
+# 02110-1301 USA
+######################### END LICENSE BLOCK #########################
+
+from charsetprober import CharSetProber
+import constants
+
+# This prober doesn't actually recognize a language or a charset.
+# It is a helper prober for the use of the Hebrew model probers
+
+### 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 SBCharSetProbers and a HebrewProber,
+# all of which are managed, created, fed data, inquired and deleted by the
+# SBCSGroupProber. The two SBCharSetProbers 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 HebrewProber by combining final-letter scores
+# with the scores of the two SBCharSetProbers to produce a final answer.
+#
+# The SBCSGroupProber 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 SBCharSetProbers (model probers) share the same language model:
+# Win1255Model.
+# The first SBCharSetProber uses the model normally as any other
+# SBCharSetProber does, to recognize windows-1255, upon which this model was
+# built. The second SBCharSetProber 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 HebrewProber 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 HebrewProber
+# alone are meaningless. HebrewProber always returns 0.00 as confidence
+# since it never identifies a charset by itself. Instead, the pointer to the
+# HebrewProber 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
+# HebrewProber to make the final decision. In the HebrewProber, 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".
+
+# windows-1255 / ISO-8859-8 code points of interest
+FINAL_KAF = '\xea'
+NORMAL_KAF = '\xeb'
+FINAL_MEM = '\xed'
+NORMAL_MEM = '\xee'
+FINAL_NUN = '\xef'
+NORMAL_NUN = '\xf0'
+FINAL_PE = '\xf3'
+NORMAL_PE = '\xf4'
+FINAL_TSADI = '\xf5'
+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.
+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.
+MIN_MODEL_DISTANCE = 0.01
+
+VISUAL_HEBREW_NAME = "ISO-8859-8"
+LOGICAL_HEBREW_NAME = "windows-1255"
+
+class HebrewProber(CharSetProber):
+ def __init__(self):
+ CharSetProber.__init__(self)
+ self._mLogicalProber = None
+ self._mVisualProber = None
+ self.reset()
+
+ def reset(self):
+ self._mFinalCharLogicalScore = 0
+ self._mFinalCharVisualScore = 0
+ # The two last characters seen in the previous buffer,
+ # mPrev and mBeforePrev are initialized to space in order to simulate a word
+ # delimiter at the beginning of the data
+ self._mPrev = ' '
+ self._mBeforePrev = ' '
+ # These probers are owned by the group prober.
+
+ def set_model_probers(self, logicalProber, visualProber):
+ self._mLogicalProber = logicalProber
+ self._mVisualProber = visualProber
+
+ def is_final(self, c):
+ return c in [FINAL_KAF, FINAL_MEM, FINAL_NUN, FINAL_PE, FINAL_TSADI]
+
+ def is_non_final(self, c):
+ # 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 c in [NORMAL_KAF, NORMAL_MEM, NORMAL_NUN, NORMAL_PE]
+
+ def feed(self, aBuf):
+ # 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.
+ #
+ # We automatically filter out all 7-bit characters (replace them with spaces)
+ # so the word boundary detection works properly. [MAP]
+
+ if self.get_state() == constants.eNotMe:
+ # Both model probers say it's not them. No reason to continue.
+ return constants.eNotMe
+
+ aBuf = self.filter_high_bit_only(aBuf)
+
+ for cur in aBuf:
+ if cur == ' ':
+ # We stand on a space - a word just ended
+ if self._mBeforePrev != ' ':
+ # next-to-last char was not a space so self._mPrev is not a 1 letter word
+ if self.is_final(self._mPrev):
+ # case (1) [-2:not space][-1:final letter][cur:space]
+ self._mFinalCharLogicalScore += 1
+ elif self.is_non_final(self._mPrev):
+ # case (2) [-2:not space][-1:Non-Final letter][cur:space]
+ self._mFinalCharVisualScore += 1
+ else:
+ # Not standing on a space
+ if (self._mBeforePrev == ' ') and (self.is_final(self._mPrev)) and (cur != ' '):
+ # case (3) [-2:space][-1:final letter][cur:not space]
+ self._mFinalCharVisualScore += 1
+ self._mBeforePrev = self._mPrev
+ self._mPrev = cur
+
+ # Forever detecting, till the end or until both model probers return eNotMe (handled above)
+ return constants.eDetecting
+
+ def get_charset_name(self):
+ # Make the decision: is it Logical or Visual?
+ # If the final letter score distance is dominant enough, rely on it.
+ finalsub = self._mFinalCharLogicalScore - self._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.
+ modelsub = self._mLogicalProber.get_confidence() - self._mVisualProber.get_confidence()
+ 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 < 0.0:
+ return VISUAL_HEBREW_NAME
+
+ # (finalsub > 0 - Logical) or (don't know what to do) default to Logical.
+ return LOGICAL_HEBREW_NAME
+
+ def get_state(self):
+ # Remain active as long as any of the model probers are active.
+ if (self._mLogicalProber.get_state() == constants.eNotMe) and \
+ (self._mVisualProber.get_state() == constants.eNotMe):
+ return constants.eNotMe
+ return constants.eDetecting
