python/lib/requests/requests/packages/charade/sbcharsetprober.py

   1 ######################## BEGIN LICENSE BLOCK ########################
   2 # The Original Code is Mozilla Universal charset detector code.
   3 #
   4 # The Initial Developer of the Original Code is
   5 # Netscape Communications Corporation.
   6 # Portions created by the Initial Developer are Copyright (C) 2001
   7 # the Initial Developer. All Rights Reserved.
   8 #
   9 # Contributor(s):
  10 #   Mark Pilgrim - port to Python
  11 #   Shy Shalom - original C code
  12 #
  13 # This library is free software; you can redistribute it and/or
  14 # modify it under the terms of the GNU Lesser General Public
  15 # License as published by the Free Software Foundation; either
  16 # version 2.1 of the License, or (at your option) any later version.
  17 #
  18 # This library is distributed in the hope that it will be useful,
  19 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  20 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  21 # Lesser General Public License for more details.
  22 #
  23 # You should have received a copy of the GNU Lesser General Public
  24 # License along with this library; if not, write to the Free Software
  25 # Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
  26 # 02110-1301  USA
  27 ######################### END LICENSE BLOCK #########################
  28
  29 import sys
  30 from . import constants
  31 from .charsetprober import CharSetProber
  32 from .compat import wrap_ord
  33
  34 SAMPLE_SIZE = 64
  35 SB_ENOUGH_REL_THRESHOLD = 1024
  36 POSITIVE_SHORTCUT_THRESHOLD = 0.95
  37 NEGATIVE_SHORTCUT_THRESHOLD = 0.05
  38 SYMBOL_CAT_ORDER = 250
  39 NUMBER_OF_SEQ_CAT = 4
  40 POSITIVE_CAT = NUMBER_OF_SEQ_CAT - 1
  41 #NEGATIVE_CAT = 0
  42
  43
  44 class SingleByteCharSetProber(CharSetProber):
  45     def __init__(self, model, reversed=False, nameProber=None):
  46         CharSetProber.__init__(self)
  47         self._mModel = model
  48         # TRUE if we need to reverse every pair in the model lookup
  49         self._mReversed = reversed
  50         # Optional auxiliary prober for name decision
  51         self._mNameProber = nameProber
  52         self.reset()
  53
  54     def reset(self):
  55         CharSetProber.reset(self)
  56         # char order of last character
  57         self._mLastOrder = 255
  58         self._mSeqCounters = [0] * NUMBER_OF_SEQ_CAT
  59         self._mTotalSeqs = 0
  60         self._mTotalChar = 0
  61         # characters that fall in our sampling range
  62         self._mFreqChar = 0
  63
  64     def get_charset_name(self):
  65         if self._mNameProber:
  66             return self._mNameProber.get_charset_name()
  67         else:
  68             return self._mModel['charsetName']
  69
  70     def feed(self, aBuf):
  71         if not self._mModel['keepEnglishLetter']:
  72             aBuf = self.filter_without_english_letters(aBuf)
  73         aLen = len(aBuf)
  74         if not aLen:
  75             return self.get_state()
  76         for c in aBuf:
  77             order = self._mModel['charToOrderMap'][wrap_ord(c)]
  78             if order < SYMBOL_CAT_ORDER:
  79                 self._mTotalChar += 1
  80             if order < SAMPLE_SIZE:
  81                 self._mFreqChar += 1
  82                 if self._mLastOrder < SAMPLE_SIZE:
  83                     self._mTotalSeqs += 1
  84                     if not self._mReversed:
  85                         i = (self._mLastOrder * SAMPLE_SIZE) + order
  86                         model = self._mModel['precedenceMatrix'][i]
  87                     else:  # reverse the order of the letters in the lookup
  88                         i = (order * SAMPLE_SIZE) + self._mLastOrder
  89                         model = self._mModel['precedenceMatrix'][i]
  90                     self._mSeqCounters[model] += 1
  91             self._mLastOrder = order
  92
  93         if self.get_state() == constants.eDetecting:
  94             if self._mTotalSeqs > SB_ENOUGH_REL_THRESHOLD:
  95                 cf = self.get_confidence()
  96                 if cf > POSITIVE_SHORTCUT_THRESHOLD:
  97                     if constants._debug:
  98                         sys.stderr.write('%s confidence = %s, we have a'
  99                                          'winner\n' %
 100                                          (self._mModel['charsetName'], cf))
 101                     self._mState = constants.eFoundIt
 102                 elif cf < NEGATIVE_SHORTCUT_THRESHOLD:
 103                     if constants._debug:
 104                         sys.stderr.write('%s confidence = %s, below negative'
 105                                          'shortcut threshhold %s\n' %
 106                                          (self._mModel['charsetName'], cf,
 107                                           NEGATIVE_SHORTCUT_THRESHOLD))
 108                     self._mState = constants.eNotMe
 109
 110         return self.get_state()
 111
 112     def get_confidence(self):
 113         r = 0.01
 114         if self._mTotalSeqs > 0:
 115             r = ((1.0 * self._mSeqCounters[POSITIVE_CAT]) / self._mTotalSeqs
 116                  / self._mModel['mTypicalPositiveRatio'])
 117             r = r * self._mFreqChar / self._mTotalChar
 118             if r >= 1.0:
 119                 r = 0.99
 120         return r