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universaldetector.py
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Sun, Jul 6, 22:44

universaldetector.py
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######################## BEGIN LICENSE BLOCK ########################
# 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):
# Mark Pilgrim - port to Python
# Shy Shalom - original C code
#
# 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 #########################
import codecs
import re
import sys
from . import constants
from .escprober import EscCharSetProber # ISO-2122, etc.
from .latin1prober import Latin1Prober # windows-1252
from .mbcsgroupprober import MBCSGroupProber # multi-byte character sets
from .sbcsgroupprober import SBCSGroupProber # single-byte character sets
MINIMUM_THRESHOLD = 0.20
ePureAscii = 0
eEscAscii = 1
eHighbyte = 2
class UniversalDetector:
def __init__(self):
self._highBitDetector = re.compile(b'[\x80-\xFF]')
self._escDetector = re.compile(b'(\033|~{)')
self._mEscCharSetProber = None
self._mCharSetProbers = []
self.reset()
def reset(self):
self.result = {'encoding': None, 'confidence': 0.0}
self.done = False
self._mStart = True
self._mGotData = False
self._mInputState = ePureAscii
self._mLastChar = b''
if self._mEscCharSetProber:
self._mEscCharSetProber.reset()
for prober in self._mCharSetProbers:
prober.reset()
def feed(self, aBuf):
if self.done:
return
aLen = len(aBuf)
if not aLen:
return
if not self._mGotData:
# If the data starts with BOM, we know it is UTF
if aBuf[:3] == codecs.BOM_UTF8:
# EF BB BF UTF-8 with BOM
self.result = {'encoding': "UTF-8-SIG", 'confidence': 1.0}
elif aBuf[:4] == codecs.BOM_UTF32_LE:
# FF FE 00 00 UTF-32, little-endian BOM
self.result = {'encoding': "UTF-32LE", 'confidence': 1.0}
elif aBuf[:4] == codecs.BOM_UTF32_BE:
# 00 00 FE FF UTF-32, big-endian BOM
self.result = {'encoding': "UTF-32BE", 'confidence': 1.0}
elif aBuf[:4] == b'\xFE\xFF\x00\x00':
# FE FF 00 00 UCS-4, unusual octet order BOM (3412)
self.result = {
'encoding': "X-ISO-10646-UCS-4-3412",
'confidence': 1.0
}
elif aBuf[:4] == b'\x00\x00\xFF\xFE':
# 00 00 FF FE UCS-4, unusual octet order BOM (2143)
self.result = {
'encoding': "X-ISO-10646-UCS-4-2143",
'confidence': 1.0
}
elif aBuf[:2] == codecs.BOM_LE:
# FF FE UTF-16, little endian BOM
self.result = {'encoding': "UTF-16LE", 'confidence': 1.0}
elif aBuf[:2] == codecs.BOM_BE:
# FE FF UTF-16, big endian BOM
self.result = {'encoding': "UTF-16BE", 'confidence': 1.0}
self._mGotData = True
if self.result['encoding'] and (self.result['confidence'] > 0.0):
self.done = True
return
if self._mInputState == ePureAscii:
if self._highBitDetector.search(aBuf):
self._mInputState = eHighbyte
elif ((self._mInputState == ePureAscii) and
self._escDetector.search(self._mLastChar + aBuf)):
self._mInputState = eEscAscii
self._mLastChar = aBuf[-1:]
if self._mInputState == eEscAscii:
if not self._mEscCharSetProber:
self._mEscCharSetProber = EscCharSetProber()
if self._mEscCharSetProber.feed(aBuf) == constants.eFoundIt:
self.result = {'encoding': self._mEscCharSetProber.get_charset_name(),
'confidence': self._mEscCharSetProber.get_confidence()}
self.done = True
elif self._mInputState == eHighbyte:
if not self._mCharSetProbers:
self._mCharSetProbers = [MBCSGroupProber(), SBCSGroupProber(),
Latin1Prober()]
for prober in self._mCharSetProbers:
if prober.feed(aBuf) == constants.eFoundIt:
self.result = {'encoding': prober.get_charset_name(),
'confidence': prober.get_confidence()}
self.done = True
break
def close(self):
if self.done:
return
if not self._mGotData:
if constants._debug:
sys.stderr.write('no data received!\n')
return
self.done = True
if self._mInputState == ePureAscii:
self.result = {'encoding': 'ascii', 'confidence': 1.0}
return self.result
if self._mInputState == eHighbyte:
proberConfidence = None
maxProberConfidence = 0.0
maxProber = None
for prober in self._mCharSetProbers:
if not prober:
continue
proberConfidence = prober.get_confidence()
if proberConfidence > maxProberConfidence:
maxProberConfidence = proberConfidence
maxProber = prober
if maxProber and (maxProberConfidence > MINIMUM_THRESHOLD):
self.result = {'encoding': maxProber.get_charset_name(),
'confidence': maxProber.get_confidence()}
return self.result
if constants._debug:
sys.stderr.write('no probers hit minimum threshhold\n')
for prober in self._mCharSetProbers[0].mProbers:
if not prober:
continue
sys.stderr.write('%s confidence = %s\n' %
(prober.get_charset_name(),
prober.get_confidence()))

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