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Diffstat (limited to 'lib/chardet/chardistribution.py')
| -rw-r--r-- | lib/chardet/chardistribution.py | 259 |
1 files changed, 259 insertions, 0 deletions
diff --git a/lib/chardet/chardistribution.py b/lib/chardet/chardistribution.py new file mode 100644 index 0000000..27b4a29 --- /dev/null +++ b/lib/chardet/chardistribution.py @@ -0,0 +1,259 @@ +######################## BEGIN LICENSE BLOCK ######################## +# The Original Code is Mozilla Communicator client 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 .big5freq import ( + BIG5_CHAR_TO_FREQ_ORDER, + BIG5_TABLE_SIZE, + BIG5_TYPICAL_DISTRIBUTION_RATIO, +) +from .euckrfreq import ( + EUCKR_CHAR_TO_FREQ_ORDER, + EUCKR_TABLE_SIZE, + EUCKR_TYPICAL_DISTRIBUTION_RATIO, +) +from .euctwfreq import ( + EUCTW_CHAR_TO_FREQ_ORDER, + EUCTW_TABLE_SIZE, + EUCTW_TYPICAL_DISTRIBUTION_RATIO, +) +from .gb2312freq import ( + GB2312_CHAR_TO_FREQ_ORDER, + GB2312_TABLE_SIZE, + GB2312_TYPICAL_DISTRIBUTION_RATIO, +) +from .jisfreq import ( + JIS_CHAR_TO_FREQ_ORDER, + JIS_TABLE_SIZE, + JIS_TYPICAL_DISTRIBUTION_RATIO, +) +from .johabfreq import JOHAB_TO_EUCKR_ORDER_TABLE + + +class CharDistributionAnalysis: + ENOUGH_DATA_THRESHOLD = 1024 + SURE_YES = 0.99 + SURE_NO = 0.01 + MINIMUM_DATA_THRESHOLD = 3 + + def __init__(self): + # Mapping table to get frequency order from char order (get from + # GetOrder()) + self._char_to_freq_order = tuple() + self._table_size = None # Size of above table + # This is a constant value which varies from language to language, + # used in calculating confidence. See + # http://www.mozilla.org/projects/intl/UniversalCharsetDetection.html + # for further detail. + self.typical_distribution_ratio = None + self._done = None + self._total_chars = None + self._freq_chars = None + self.reset() + + def reset(self): + """reset analyser, clear any state""" + # If this flag is set to True, detection is done and conclusion has + # been made + self._done = False + self._total_chars = 0 # Total characters encountered + # The number of characters whose frequency order is less than 512 + self._freq_chars = 0 + + def feed(self, char, char_len): + """feed a character with known length""" + if char_len == 2: + # we only care about 2-bytes character in our distribution analysis + order = self.get_order(char) + else: + order = -1 + if order >= 0: + self._total_chars += 1 + # order is valid + if order < self._table_size: + if 512 > self._char_to_freq_order[order]: + self._freq_chars += 1 + + def get_confidence(self): + """return confidence based on existing data""" + # if we didn't receive any character in our consideration range, + # return negative answer + if self._total_chars <= 0 or self._freq_chars <= self.MINIMUM_DATA_THRESHOLD: + return self.SURE_NO + + if self._total_chars != self._freq_chars: + r = self._freq_chars / ( + (self._total_chars - self._freq_chars) * self.typical_distribution_ratio + ) + if r < self.SURE_YES: + return r + + # normalize confidence (we don't want to be 100% sure) + return self.SURE_YES + + def got_enough_data(self): + # It is not necessary to receive all data to draw conclusion. + # For charset detection, certain amount of data is enough + return self._total_chars > self.ENOUGH_DATA_THRESHOLD + + def get_order(self, _): + # We do not handle characters based on the original encoding string, + # but convert this encoding string to a number, here called order. + # This allows multiple encodings of a language to share one frequency + # table. + return -1 + + +class EUCTWDistributionAnalysis(CharDistributionAnalysis): + def __init__(self): + super().__init__() + self._char_to_freq_order = EUCTW_CHAR_TO_FREQ_ORDER + self._table_size = EUCTW_TABLE_SIZE + self.typical_distribution_ratio = EUCTW_TYPICAL_DISTRIBUTION_RATIO + + def get_order(self, byte_str): + # for euc-TW encoding, we are interested + # first byte range: 0xc4 -- 0xfe + # second byte range: 0xa1 -- 0xfe + # no validation needed here. State machine has done that + first_char = byte_str[0] + if first_char >= 0xC4: + return 94 * (first_char - 0xC4) + byte_str[1] - 0xA1 + return -1 + + +class EUCKRDistributionAnalysis(CharDistributionAnalysis): + def __init__(self): + super().__init__() + self._char_to_freq_order = EUCKR_CHAR_TO_FREQ_ORDER + self._table_size = EUCKR_TABLE_SIZE + self.typical_distribution_ratio = EUCKR_TYPICAL_DISTRIBUTION_RATIO + + def get_order(self, byte_str): + # for euc-KR encoding, we are interested + # first byte range: 0xb0 -- 0xfe + # second byte range: 0xa1 -- 0xfe + # no validation needed here. State machine has done that + first_char = byte_str[0] + if first_char >= 0xB0: + return 94 * (first_char - 0xB0) + byte_str[1] - 0xA1 + return -1 + + +class JOHABDistributionAnalysis(CharDistributionAnalysis): + def __init__(self): + super().__init__() + self._char_to_freq_order = EUCKR_CHAR_TO_FREQ_ORDER + self._table_size = EUCKR_TABLE_SIZE + self.typical_distribution_ratio = EUCKR_TYPICAL_DISTRIBUTION_RATIO + + def get_order(self, byte_str): + first_char = byte_str[0] + if 0x88 <= first_char < 0xD4: + code = first_char * 256 + byte_str[1] + return JOHAB_TO_EUCKR_ORDER_TABLE.get(code, -1) + return -1 + + +class GB2312DistributionAnalysis(CharDistributionAnalysis): + def __init__(self): + super().__init__() + self._char_to_freq_order = GB2312_CHAR_TO_FREQ_ORDER + self._table_size = GB2312_TABLE_SIZE + self.typical_distribution_ratio = GB2312_TYPICAL_DISTRIBUTION_RATIO + + def get_order(self, byte_str): + # for GB2312 encoding, we are interested + # first byte range: 0xb0 -- 0xfe + # second byte range: 0xa1 -- 0xfe + # no validation needed here. State machine has done that + first_char, second_char = byte_str[0], byte_str[1] + if (first_char >= 0xB0) and (second_char >= 0xA1): + return 94 * (first_char - 0xB0) + second_char - 0xA1 + return -1 + + +class Big5DistributionAnalysis(CharDistributionAnalysis): + def __init__(self): + super().__init__() + self._char_to_freq_order = BIG5_CHAR_TO_FREQ_ORDER + self._table_size = BIG5_TABLE_SIZE + self.typical_distribution_ratio = BIG5_TYPICAL_DISTRIBUTION_RATIO + + def get_order(self, byte_str): + # for big5 encoding, we are interested + # first byte range: 0xa4 -- 0xfe + # second byte range: 0x40 -- 0x7e , 0xa1 -- 0xfe + # no validation needed here. State machine has done that + first_char, second_char = byte_str[0], byte_str[1] + if first_char >= 0xA4: + if second_char >= 0xA1: + return 157 * (first_char - 0xA4) + second_char - 0xA1 + 63 + return 157 * (first_char - 0xA4) + second_char - 0x40 + return -1 + + +class SJISDistributionAnalysis(CharDistributionAnalysis): + def __init__(self): + super().__init__() + self._char_to_freq_order = JIS_CHAR_TO_FREQ_ORDER + self._table_size = JIS_TABLE_SIZE + self.typical_distribution_ratio = JIS_TYPICAL_DISTRIBUTION_RATIO + + def get_order(self, byte_str): + # for sjis encoding, we are interested + # first byte range: 0x81 -- 0x9f , 0xe0 -- 0xfe + # second byte range: 0x40 -- 0x7e, 0x81 -- oxfe + # no validation needed here. State machine has done that + first_char, second_char = byte_str[0], byte_str[1] + if 0x81 <= first_char <= 0x9F: + order = 188 * (first_char - 0x81) + elif 0xE0 <= first_char <= 0xEF: + order = 188 * (first_char - 0xE0 + 31) + else: + return -1 + order = order + second_char - 0x40 + if second_char > 0x7F: + order = -1 + return order + + +class EUCJPDistributionAnalysis(CharDistributionAnalysis): + def __init__(self): + super().__init__() + self._char_to_freq_order = JIS_CHAR_TO_FREQ_ORDER + self._table_size = JIS_TABLE_SIZE + self.typical_distribution_ratio = JIS_TYPICAL_DISTRIBUTION_RATIO + + def get_order(self, byte_str): + # for euc-JP encoding, we are interested + # first byte range: 0xa0 -- 0xfe + # second byte range: 0xa1 -- 0xfe + # no validation needed here. State machine has done that + char = byte_str[0] + if char >= 0xA0: + return 94 * (char - 0xA1) + byte_str[1] - 0xA1 + return -1 |