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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