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232 lines
9.7 KiB
Python
232 lines
9.7 KiB
Python
######################## BEGIN LICENSE BLOCK ########################
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# The Original Code is Mozilla Universal charset detector code.
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#
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# The Initial Developer of the Original Code is
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# Netscape Communications Corporation.
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# Portions created by the Initial Developer are Copyright (C) 2001
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# the Initial Developer. All Rights Reserved.
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#
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# Contributor(s):
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# Mark Pilgrim - port to Python
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# Shy Shalom - original C code
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#
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# This library is free software; you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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# License as published by the Free Software Foundation; either
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# version 2.1 of the License, or (at your option) any later version.
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#
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# This library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public
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# License along with this library; if not, write to the Free Software
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# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
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# 02110-1301 USA
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######################### END LICENSE BLOCK #########################
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"""
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Module containing the UniversalDetector detector class, which is the primary
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class a user of ``chardet`` should use.
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:author: Mark Pilgrim (initial port to Python)
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:author: Shy Shalom (original C code)
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:author: Dan Blanchard (major refactoring for 3.0)
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:author: Ian Cordasco
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"""
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import codecs
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import logging
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import re
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from .enums import InputState, LanguageFilter, ProbingState
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from .escprober import EscCharSetProber
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from .latin1prober import Latin1Prober
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from .mbcsgroupprober import MBCSGroupProber
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from .sbcsgroupprober import SBCSGroupProber
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class UniversalDetector(object):
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"""
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The ``UniversalDetector`` class underlies the ``chardet.detect`` function
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and coordinates all of the different charset probers.
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To get a ``dict`` containing an encoding and its confidence, you can simply
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run:
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.. code::
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u = UniversalDetector()
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u.feed(some_bytes)
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u.close()
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detected = u.result
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"""
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MINIMUM_THRESHOLD = 0.20
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HIGH_BYTE_DETECTOR = re.compile(b'[\x80-\xFF]')
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ESC_DETECTOR = re.compile(b'(\033|~{)')
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def __init__(self, lang_filter=LanguageFilter.all):
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self._esc_charset_prober = None
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self._charset_probers = []
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self.result = None
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self.done = None
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self._got_data = None
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self._input_state = None
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self._last_char = None
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self.lang_filter = lang_filter
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self.logger = logging.getLogger(__name__)
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self.reset()
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def reset(self):
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"""
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Reset the UniversalDetector and all of its probers back to their
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initial states. This is called by ``__init__``, so you only need to
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call this directly in between analyses of different documents.
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"""
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self.result = {'encoding': None, 'confidence': 0.0}
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self.done = False
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self._got_data = False
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self._input_state = InputState.pure_ascii
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self._last_char = b''
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if self._esc_charset_prober:
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self._esc_charset_prober.reset()
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for prober in self._charset_probers:
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prober.reset()
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def feed(self, byte_str):
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"""
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Takes a chunk of a document and feeds it through all of the relevant
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charset probers.
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After calling ``feed``, you can check the value of the ``done``
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attribute to see if you need to continue feeding the
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``UniversalDetector`` more data, or if it has made a prediction
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(in the ``result`` attribute).
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.. note::
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You should always call ``close`` when you're done feeding in your
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document if ``done`` is not already ``True``.
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"""
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if self.done:
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return
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if not len(byte_str):
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return
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# First check for known BOMs, since these are guaranteed to be correct
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if not self._got_data:
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# If the data starts with BOM, we know it is UTF
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if byte_str.startswith(codecs.BOM_UTF8):
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# EF BB BF UTF-8 with BOM
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self.result = {'encoding': "UTF-8-SIG", 'confidence': 1.0}
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elif byte_str.startswith(codecs.BOM_UTF32_LE) or byte_str.startswith(codecs.BOM_UTF32_BE):
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# FF FE 00 00 UTF-32, little-endian BOM
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# 00 00 FE FF UTF-32, big-endian BOM
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self.result = {'encoding': "UTF-32", 'confidence': 1.0}
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elif byte_str.startswith(b'\xFE\xFF\x00\x00'):
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# FE FF 00 00 UCS-4, unusual octet order BOM (3412)
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self.result = {'encoding': "X-ISO-10646-UCS-4-3412",
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'confidence': 1.0}
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elif byte_str.startswith(b'\x00\x00\xFF\xFE'):
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# 00 00 FF FE UCS-4, unusual octet order BOM (2143)
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self.result = {'encoding': "X-ISO-10646-UCS-4-2143",
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'confidence': 1.0}
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elif byte_str.startswith(codecs.BOM_LE) or byte_str.startswith(codecs.BOM_BE):
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# FF FE UTF-16, little endian BOM
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# FE FF UTF-16, big endian BOM
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self.result = {'encoding': "UTF-16", 'confidence': 1.0}
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self._got_data = True
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if self.result['encoding'] is not None:
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self.done = True
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return
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# If none of those matched and we've only see ASCII so far, check
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# for high bytes and escape sequences
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if self._input_state == InputState.pure_ascii:
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if self.HIGH_BYTE_DETECTOR.search(byte_str):
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self._input_state = InputState.high_byte
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elif self._input_state == InputState.pure_ascii and \
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self.ESC_DETECTOR.search(self._last_char + byte_str):
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self._input_state = InputState.esc_ascii
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self._last_char = byte_str[-1:]
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# If we've seen escape sequences, use the EscCharSetProber, which
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# uses a simple state machine to check for known escape sequences in
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# HZ and ISO-2022 encodings, since those are the only encodings that
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# use such sequences.
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if self._input_state == InputState.esc_ascii:
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if not self._esc_charset_prober:
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self._esc_charset_prober = EscCharSetProber(self.lang_filter)
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if self._esc_charset_prober.feed(byte_str) == ProbingState.found_it:
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self.result = {'encoding':
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self._esc_charset_prober.charset_name,
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'confidence':
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self._esc_charset_prober.get_confidence()}
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self.done = True
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# If we've seen high bytes (i.e., those with values greater than 127),
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# we need to do more complicated checks using all our multi-byte and
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# single-byte probers that are left. The single-byte probers
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# use character bigram distributions to determine the encoding, whereas
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# the multi-byte probers use a combination of character unigram and
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# bigram distributions.
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elif self._input_state == InputState.high_byte:
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if not self._charset_probers:
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self._charset_probers = [MBCSGroupProber(self.lang_filter)]
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# If we're checking non-CJK encodings, use single-byte prober
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if self.lang_filter & LanguageFilter.non_cjk:
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self._charset_probers.append(SBCSGroupProber())
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self._charset_probers.append(Latin1Prober())
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for prober in self._charset_probers:
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if prober.feed(byte_str) == ProbingState.found_it:
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self.result = {'encoding': prober.charset_name,
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'confidence': prober.get_confidence()}
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self.done = True
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break
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def close(self):
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"""
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Stop analyzing the current document and come up with a final
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prediction.
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:returns: The ``result`` attribute if a prediction was made, otherwise
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``None``.
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"""
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if self.done:
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return self.result
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if not self._got_data:
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self.logger.debug('no data received!')
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return
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self.done = True
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if self._input_state in (InputState.pure_ascii, InputState.esc_ascii):
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self.result = {'encoding': 'ascii', 'confidence': 1.0}
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return self.result
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if self._input_state == InputState.high_byte:
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proberConfidence = None
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max_prober_confidence = 0.0
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max_prober = None
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for prober in self._charset_probers:
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if not prober:
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continue
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proberConfidence = prober.get_confidence()
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if proberConfidence > max_prober_confidence:
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max_prober_confidence = proberConfidence
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max_prober = prober
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if max_prober and (max_prober_confidence > self.MINIMUM_THRESHOLD):
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self.result = {'encoding': max_prober.charset_name,
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'confidence': max_prober.get_confidence()}
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return self.result
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if self.logger.getEffectiveLevel() == logging.DEBUG:
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self.logger.debug('no probers hit minimum threshold')
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for prober in self._charset_probers[0].probers:
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if not prober:
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continue
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self.logger.debug('%s confidence = %s', prober.charset_name,
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prober.get_confidence())
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