JezK
Edit File: chardistribution.py
######################## 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 typing import Tuple, Union 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) -> None: # Mapping table to get frequency order from char order (get from # GetOrder()) self._char_to_freq_order: Tuple[int, ...] = tuple() self._table_size = 0 # 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 = 0.0 self._done = False self._total_chars = 0 self._freq_chars = 0 self.reset() def reset(self) -> None: """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: Union[bytes, bytearray], char_len: int) -> None: """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) -> float: """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) -> bool: # 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, _: Union[bytes, bytearray]) -> int: # 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) -> None: 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: Union[bytes, bytearray]) -> int: # 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) -> None: 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: Union[bytes, bytearray]) -> int: # 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) -> None: 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: Union[bytes, bytearray]) -> int: 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) -> None: 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: Union[bytes, bytearray]) -> int: # 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) -> None: 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: Union[bytes, bytearray]) -> int: # 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) -> None: 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: Union[bytes, bytearray]) -> int: # 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) -> None: 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: Union[bytes, bytearray]) -> int: # 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