1######################## BEGIN LICENSE BLOCK ######################## 2# The Original Code is Mozilla Communicator client code. 3# 4# The Initial Developer of the Original Code is 5# Netscape Communications Corporation. 6# Portions created by the Initial Developer are Copyright (C) 1998 7# the Initial Developer. All Rights Reserved. 8# 9# Contributor(s): 10# Mark Pilgrim - port to Python 11# 12# This library is free software; you can redistribute it and/or 13# modify it under the terms of the GNU Lesser General Public 14# License as published by the Free Software Foundation; either 15# version 2.1 of the License, or (at your option) any later version. 16# 17# This library is distributed in the hope that it will be useful, 18# but WITHOUT ANY WARRANTY; without even the implied warranty of 19# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 20# Lesser General Public License for more details. 21# 22# You should have received a copy of the GNU Lesser General Public 23# License along with this library; if not, write to the Free Software 24# Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 25# 02110-1301 USA 26######################### END LICENSE BLOCK ######################### 27 28from .euctwfreq import (EUCTW_CHAR_TO_FREQ_ORDER, EUCTW_TABLE_SIZE, 29 EUCTW_TYPICAL_DISTRIBUTION_RATIO) 30from .euckrfreq import (EUCKR_CHAR_TO_FREQ_ORDER, EUCKR_TABLE_SIZE, 31 EUCKR_TYPICAL_DISTRIBUTION_RATIO) 32from .gb2312freq import (GB2312_CHAR_TO_FREQ_ORDER, GB2312_TABLE_SIZE, 33 GB2312_TYPICAL_DISTRIBUTION_RATIO) 34from .big5freq import (BIG5_CHAR_TO_FREQ_ORDER, BIG5_TABLE_SIZE, 35 BIG5_TYPICAL_DISTRIBUTION_RATIO) 36from .jisfreq import (JIS_CHAR_TO_FREQ_ORDER, JIS_TABLE_SIZE, 37 JIS_TYPICAL_DISTRIBUTION_RATIO) 38 39 40class CharDistributionAnalysis(object): 41 ENOUGH_DATA_THRESHOLD = 1024 42 SURE_YES = 0.99 43 SURE_NO = 0.01 44 MINIMUM_DATA_THRESHOLD = 3 45 46 def __init__(self): 47 # Mapping table to get frequency order from char order (get from 48 # GetOrder()) 49 self._char_to_freq_order = None 50 self._table_size = None # Size of above table 51 # This is a constant value which varies from language to language, 52 # used in calculating confidence. See 53 # http://www.mozilla.org/projects/intl/UniversalCharsetDetection.html 54 # for further detail. 55 self.typical_distribution_ratio = None 56 self._done = None 57 self._total_chars = None 58 self._freq_chars = None 59 self.reset() 60 61 def reset(self): 62 """reset analyser, clear any state""" 63 # If this flag is set to True, detection is done and conclusion has 64 # been made 65 self._done = False 66 self._total_chars = 0 # Total characters encountered 67 # The number of characters whose frequency order is less than 512 68 self._freq_chars = 0 69 70 def feed(self, char, char_len): 71 """feed a character with known length""" 72 if char_len == 2: 73 # we only care about 2-bytes character in our distribution analysis 74 order = self.get_order(char) 75 else: 76 order = -1 77 if order >= 0: 78 self._total_chars += 1 79 # order is valid 80 if order < self._table_size: 81 if 512 > self._char_to_freq_order[order]: 82 self._freq_chars += 1 83 84 def get_confidence(self): 85 """return confidence based on existing data""" 86 # if we didn't receive any character in our consideration range, 87 # return negative answer 88 if self._total_chars <= 0 or self._freq_chars <= self.MINIMUM_DATA_THRESHOLD: 89 return self.SURE_NO 90 91 if self._total_chars != self._freq_chars: 92 r = (self._freq_chars / ((self._total_chars - self._freq_chars) 93 * self.typical_distribution_ratio)) 94 if r < self.SURE_YES: 95 return r 96 97 # normalize confidence (we don't want to be 100% sure) 98 return self.SURE_YES 99 100 def got_enough_data(self): 101 # It is not necessary to receive all data to draw conclusion. 102 # For charset detection, certain amount of data is enough 103 return self._total_chars > self.ENOUGH_DATA_THRESHOLD 104 105 def get_order(self, byte_str): 106 # We do not handle characters based on the original encoding string, 107 # but convert this encoding string to a number, here called order. 108 # This allows multiple encodings of a language to share one frequency 109 # table. 110 return -1 111 112 113class EUCTWDistributionAnalysis(CharDistributionAnalysis): 114 def __init__(self): 115 super(EUCTWDistributionAnalysis, self).__init__() 116 self._char_to_freq_order = EUCTW_CHAR_TO_FREQ_ORDER 117 self._table_size = EUCTW_TABLE_SIZE 118 self.typical_distribution_ratio = EUCTW_TYPICAL_DISTRIBUTION_RATIO 119 120 def get_order(self, byte_str): 121 # for euc-TW encoding, we are interested 122 # first byte range: 0xc4 -- 0xfe 123 # second byte range: 0xa1 -- 0xfe 124 # no validation needed here. State machine has done that 125 first_char = byte_str[0] 126 if first_char >= 0xC4: 127 return 94 * (first_char - 0xC4) + byte_str[1] - 0xA1 128 else: 129 return -1 130 131 132class EUCKRDistributionAnalysis(CharDistributionAnalysis): 133 def __init__(self): 134 super(EUCKRDistributionAnalysis, self).__init__() 135 self._char_to_freq_order = EUCKR_CHAR_TO_FREQ_ORDER 136 self._table_size = EUCKR_TABLE_SIZE 137 self.typical_distribution_ratio = EUCKR_TYPICAL_DISTRIBUTION_RATIO 138 139 def get_order(self, byte_str): 140 # for euc-KR encoding, we are interested 141 # first byte range: 0xb0 -- 0xfe 142 # second byte range: 0xa1 -- 0xfe 143 # no validation needed here. State machine has done that 144 first_char = byte_str[0] 145 if first_char >= 0xB0: 146 return 94 * (first_char - 0xB0) + byte_str[1] - 0xA1 147 else: 148 return -1 149 150 151class GB2312DistributionAnalysis(CharDistributionAnalysis): 152 def __init__(self): 153 super(GB2312DistributionAnalysis, self).__init__() 154 self._char_to_freq_order = GB2312_CHAR_TO_FREQ_ORDER 155 self._table_size = GB2312_TABLE_SIZE 156 self.typical_distribution_ratio = GB2312_TYPICAL_DISTRIBUTION_RATIO 157 158 def get_order(self, byte_str): 159 # for GB2312 encoding, we are interested 160 # first byte range: 0xb0 -- 0xfe 161 # second byte range: 0xa1 -- 0xfe 162 # no validation needed here. State machine has done that 163 first_char, second_char = byte_str[0], byte_str[1] 164 if (first_char >= 0xB0) and (second_char >= 0xA1): 165 return 94 * (first_char - 0xB0) + second_char - 0xA1 166 else: 167 return -1 168 169 170class Big5DistributionAnalysis(CharDistributionAnalysis): 171 def __init__(self): 172 super(Big5DistributionAnalysis, self).__init__() 173 self._char_to_freq_order = BIG5_CHAR_TO_FREQ_ORDER 174 self._table_size = BIG5_TABLE_SIZE 175 self.typical_distribution_ratio = BIG5_TYPICAL_DISTRIBUTION_RATIO 176 177 def get_order(self, byte_str): 178 # for big5 encoding, we are interested 179 # first byte range: 0xa4 -- 0xfe 180 # second byte range: 0x40 -- 0x7e , 0xa1 -- 0xfe 181 # no validation needed here. State machine has done that 182 first_char, second_char = byte_str[0], byte_str[1] 183 if first_char >= 0xA4: 184 if second_char >= 0xA1: 185 return 157 * (first_char - 0xA4) + second_char - 0xA1 + 63 186 else: 187 return 157 * (first_char - 0xA4) + second_char - 0x40 188 else: 189 return -1 190 191 192class SJISDistributionAnalysis(CharDistributionAnalysis): 193 def __init__(self): 194 super(SJISDistributionAnalysis, self).__init__() 195 self._char_to_freq_order = JIS_CHAR_TO_FREQ_ORDER 196 self._table_size = JIS_TABLE_SIZE 197 self.typical_distribution_ratio = JIS_TYPICAL_DISTRIBUTION_RATIO 198 199 def get_order(self, byte_str): 200 # for sjis encoding, we are interested 201 # first byte range: 0x81 -- 0x9f , 0xe0 -- 0xfe 202 # second byte range: 0x40 -- 0x7e, 0x81 -- oxfe 203 # no validation needed here. State machine has done that 204 first_char, second_char = byte_str[0], byte_str[1] 205 if (first_char >= 0x81) and (first_char <= 0x9F): 206 order = 188 * (first_char - 0x81) 207 elif (first_char >= 0xE0) and (first_char <= 0xEF): 208 order = 188 * (first_char - 0xE0 + 31) 209 else: 210 return -1 211 order = order + second_char - 0x40 212 if second_char > 0x7F: 213 order = -1 214 return order 215 216 217class EUCJPDistributionAnalysis(CharDistributionAnalysis): 218 def __init__(self): 219 super(EUCJPDistributionAnalysis, self).__init__() 220 self._char_to_freq_order = JIS_CHAR_TO_FREQ_ORDER 221 self._table_size = JIS_TABLE_SIZE 222 self.typical_distribution_ratio = JIS_TYPICAL_DISTRIBUTION_RATIO 223 224 def get_order(self, byte_str): 225 # for euc-JP encoding, we are interested 226 # first byte range: 0xa0 -- 0xfe 227 # second byte range: 0xa1 -- 0xfe 228 # no validation needed here. State machine has done that 229 char = byte_str[0] 230 if char >= 0xA0: 231 return 94 * (char - 0xA1) + byte_str[1] - 0xa1 232 else: 233 return -1 234