262 lines
9.8 KiB
Python
262 lines
9.8 KiB
Python
######################## BEGIN LICENSE BLOCK ########################
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# The Original Code is Mozilla Communicator client 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) 1998
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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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#
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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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from typing import Tuple, Union
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from .big5freq import (
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BIG5_CHAR_TO_FREQ_ORDER,
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BIG5_TABLE_SIZE,
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BIG5_TYPICAL_DISTRIBUTION_RATIO,
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)
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from .euckrfreq import (
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EUCKR_CHAR_TO_FREQ_ORDER,
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EUCKR_TABLE_SIZE,
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EUCKR_TYPICAL_DISTRIBUTION_RATIO,
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)
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from .euctwfreq import (
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EUCTW_CHAR_TO_FREQ_ORDER,
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EUCTW_TABLE_SIZE,
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EUCTW_TYPICAL_DISTRIBUTION_RATIO,
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)
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from .gb2312freq import (
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GB2312_CHAR_TO_FREQ_ORDER,
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GB2312_TABLE_SIZE,
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GB2312_TYPICAL_DISTRIBUTION_RATIO,
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)
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from .jisfreq import (
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JIS_CHAR_TO_FREQ_ORDER,
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JIS_TABLE_SIZE,
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JIS_TYPICAL_DISTRIBUTION_RATIO,
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)
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from .johabfreq import JOHAB_TO_EUCKR_ORDER_TABLE
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class CharDistributionAnalysis:
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ENOUGH_DATA_THRESHOLD = 1024
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SURE_YES = 0.99
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SURE_NO = 0.01
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MINIMUM_DATA_THRESHOLD = 3
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def __init__(self) -> None:
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# Mapping table to get frequency order from char order (get from
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# GetOrder())
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self._char_to_freq_order: Tuple[int, ...] = tuple()
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self._table_size = 0 # Size of above table
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# This is a constant value which varies from language to language,
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# used in calculating confidence. See
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# http://www.mozilla.org/projects/intl/UniversalCharsetDetection.html
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# for further detail.
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self.typical_distribution_ratio = 0.0
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self._done = False
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self._total_chars = 0
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self._freq_chars = 0
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self.reset()
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def reset(self) -> None:
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"""reset analyser, clear any state"""
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# If this flag is set to True, detection is done and conclusion has
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# been made
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self._done = False
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self._total_chars = 0 # Total characters encountered
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# The number of characters whose frequency order is less than 512
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self._freq_chars = 0
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def feed(self, char: Union[bytes, bytearray], char_len: int) -> None:
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"""feed a character with known length"""
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if char_len == 2:
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# we only care about 2-bytes character in our distribution analysis
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order = self.get_order(char)
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else:
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order = -1
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if order >= 0:
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self._total_chars += 1
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# order is valid
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if order < self._table_size:
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if 512 > self._char_to_freq_order[order]:
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self._freq_chars += 1
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def get_confidence(self) -> float:
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"""return confidence based on existing data"""
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# if we didn't receive any character in our consideration range,
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# return negative answer
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if self._total_chars <= 0 or self._freq_chars <= self.MINIMUM_DATA_THRESHOLD:
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return self.SURE_NO
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if self._total_chars != self._freq_chars:
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r = self._freq_chars / (
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(self._total_chars - self._freq_chars) * self.typical_distribution_ratio
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)
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if r < self.SURE_YES:
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return r
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# normalize confidence (we don't want to be 100% sure)
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return self.SURE_YES
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def got_enough_data(self) -> bool:
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# It is not necessary to receive all data to draw conclusion.
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# For charset detection, certain amount of data is enough
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return self._total_chars > self.ENOUGH_DATA_THRESHOLD
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def get_order(self, _: Union[bytes, bytearray]) -> int:
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# We do not handle characters based on the original encoding string,
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# but convert this encoding string to a number, here called order.
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# This allows multiple encodings of a language to share one frequency
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# table.
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return -1
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class EUCTWDistributionAnalysis(CharDistributionAnalysis):
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def __init__(self) -> None:
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super().__init__()
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self._char_to_freq_order = EUCTW_CHAR_TO_FREQ_ORDER
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self._table_size = EUCTW_TABLE_SIZE
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self.typical_distribution_ratio = EUCTW_TYPICAL_DISTRIBUTION_RATIO
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def get_order(self, byte_str: Union[bytes, bytearray]) -> int:
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# for euc-TW encoding, we are interested
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# first byte range: 0xc4 -- 0xfe
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# second byte range: 0xa1 -- 0xfe
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# no validation needed here. State machine has done that
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first_char = byte_str[0]
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if first_char >= 0xC4:
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return 94 * (first_char - 0xC4) + byte_str[1] - 0xA1
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return -1
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class EUCKRDistributionAnalysis(CharDistributionAnalysis):
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def __init__(self) -> None:
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super().__init__()
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self._char_to_freq_order = EUCKR_CHAR_TO_FREQ_ORDER
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self._table_size = EUCKR_TABLE_SIZE
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self.typical_distribution_ratio = EUCKR_TYPICAL_DISTRIBUTION_RATIO
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def get_order(self, byte_str: Union[bytes, bytearray]) -> int:
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# for euc-KR encoding, we are interested
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# first byte range: 0xb0 -- 0xfe
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# second byte range: 0xa1 -- 0xfe
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# no validation needed here. State machine has done that
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first_char = byte_str[0]
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if first_char >= 0xB0:
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return 94 * (first_char - 0xB0) + byte_str[1] - 0xA1
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return -1
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class JOHABDistributionAnalysis(CharDistributionAnalysis):
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def __init__(self) -> None:
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super().__init__()
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self._char_to_freq_order = EUCKR_CHAR_TO_FREQ_ORDER
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self._table_size = EUCKR_TABLE_SIZE
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self.typical_distribution_ratio = EUCKR_TYPICAL_DISTRIBUTION_RATIO
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def get_order(self, byte_str: Union[bytes, bytearray]) -> int:
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first_char = byte_str[0]
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if 0x88 <= first_char < 0xD4:
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code = first_char * 256 + byte_str[1]
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return JOHAB_TO_EUCKR_ORDER_TABLE.get(code, -1)
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return -1
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class GB2312DistributionAnalysis(CharDistributionAnalysis):
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def __init__(self) -> None:
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super().__init__()
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self._char_to_freq_order = GB2312_CHAR_TO_FREQ_ORDER
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self._table_size = GB2312_TABLE_SIZE
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self.typical_distribution_ratio = GB2312_TYPICAL_DISTRIBUTION_RATIO
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def get_order(self, byte_str: Union[bytes, bytearray]) -> int:
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# for GB2312 encoding, we are interested
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# first byte range: 0xb0 -- 0xfe
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# second byte range: 0xa1 -- 0xfe
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# no validation needed here. State machine has done that
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first_char, second_char = byte_str[0], byte_str[1]
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if (first_char >= 0xB0) and (second_char >= 0xA1):
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return 94 * (first_char - 0xB0) + second_char - 0xA1
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return -1
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class Big5DistributionAnalysis(CharDistributionAnalysis):
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def __init__(self) -> None:
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super().__init__()
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self._char_to_freq_order = BIG5_CHAR_TO_FREQ_ORDER
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self._table_size = BIG5_TABLE_SIZE
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self.typical_distribution_ratio = BIG5_TYPICAL_DISTRIBUTION_RATIO
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def get_order(self, byte_str: Union[bytes, bytearray]) -> int:
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# for big5 encoding, we are interested
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# first byte range: 0xa4 -- 0xfe
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# second byte range: 0x40 -- 0x7e , 0xa1 -- 0xfe
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# no validation needed here. State machine has done that
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first_char, second_char = byte_str[0], byte_str[1]
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if first_char >= 0xA4:
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if second_char >= 0xA1:
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return 157 * (first_char - 0xA4) + second_char - 0xA1 + 63
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return 157 * (first_char - 0xA4) + second_char - 0x40
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return -1
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class SJISDistributionAnalysis(CharDistributionAnalysis):
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def __init__(self) -> None:
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super().__init__()
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self._char_to_freq_order = JIS_CHAR_TO_FREQ_ORDER
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self._table_size = JIS_TABLE_SIZE
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self.typical_distribution_ratio = JIS_TYPICAL_DISTRIBUTION_RATIO
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def get_order(self, byte_str: Union[bytes, bytearray]) -> int:
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# for sjis encoding, we are interested
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# first byte range: 0x81 -- 0x9f , 0xe0 -- 0xfe
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# second byte range: 0x40 -- 0x7e, 0x81 -- oxfe
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# no validation needed here. State machine has done that
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first_char, second_char = byte_str[0], byte_str[1]
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if 0x81 <= first_char <= 0x9F:
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order = 188 * (first_char - 0x81)
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elif 0xE0 <= first_char <= 0xEF:
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order = 188 * (first_char - 0xE0 + 31)
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else:
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return -1
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order = order + second_char - 0x40
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if second_char > 0x7F:
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order = -1
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return order
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class EUCJPDistributionAnalysis(CharDistributionAnalysis):
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def __init__(self) -> None:
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super().__init__()
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self._char_to_freq_order = JIS_CHAR_TO_FREQ_ORDER
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self._table_size = JIS_TABLE_SIZE
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self.typical_distribution_ratio = JIS_TYPICAL_DISTRIBUTION_RATIO
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def get_order(self, byte_str: Union[bytes, bytearray]) -> int:
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# for euc-JP encoding, we are interested
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# first byte range: 0xa0 -- 0xfe
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# second byte range: 0xa1 -- 0xfe
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# no validation needed here. State machine has done that
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char = byte_str[0]
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if char >= 0xA0:
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return 94 * (char - 0xA1) + byte_str[1] - 0xA1
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return -1
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