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sjisprober.py
######################## BEGIN LICENSE BLOCK ########################
# The Original Code is mozilla.org code.
#
# The Initial Developer of the Original Code is
# Netscape Communications Corporation.
# Portions created by the Initial Developer are Copyright (C) 1998
# 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 mbcharsetprober import MultiByteCharSetProber
from codingstatemachine import CodingStateMachine
from chardistribution import SJISDistributionAnalysis
from jpcntx import SJISContextAnalysis
from mbcssm import SJISSMModel
import constants, sys
from constants import eStart, eError, eItsMe

00036 class SJISProber(MultiByteCharSetProber):
    def __init__(self):
        MultiByteCharSetProber.__init__(self)
        self._mCodingSM = CodingStateMachine(SJISSMModel)
        self._mDistributionAnalyzer = SJISDistributionAnalysis()
        self._mContextAnalyzer = SJISContextAnalysis()
        self.reset()

    def reset(self):
        MultiByteCharSetProber.reset(self)
        self._mContextAnalyzer.reset()
        
    def get_charset_name(self):
        return "SHIFT_JIS"

    def feed(self, aBuf):
        aLen = len(aBuf)
        for i in range(0, aLen):
            codingState = self._mCodingSM.next_state(aBuf[i])
            if codingState == eError:
                if constants._debug:
                    sys.stderr.write(self.get_charset_name() + ' prober hit error at byte ' + str(i) + '\n')
                self._mState = constants.eNotMe
                break
            elif codingState == eItsMe:
                self._mState = constants.eFoundIt
                break
            elif codingState == eStart:
                charLen = self._mCodingSM.get_current_charlen()
                if i == 0:
                    self._mLastChar[1] = aBuf[0]
                    self._mContextAnalyzer.feed(self._mLastChar[2 - charLen :], charLen)
                    self._mDistributionAnalyzer.feed(self._mLastChar, charLen)
                else:
                    self._mContextAnalyzer.feed(aBuf[i + 1 - charLen : i + 3 - charLen], charLen)
                    self._mDistributionAnalyzer.feed(aBuf[i - 1 : i + 1], charLen)
                    
        self._mLastChar[0] = aBuf[aLen - 1]
        
        if self.get_state() == constants.eDetecting:
            if self._mContextAnalyzer.got_enough_data() and \
                   (self.get_confidence() > constants.SHORTCUT_THRESHOLD):
                self._mState = constants.eFoundIt

        return self.get_state()

    def get_confidence(self):
        contxtCf = self._mContextAnalyzer.get_confidence()
        distribCf = self._mDistributionAnalyzer.get_confidence()
        return max(contxtCf, distribCf)

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