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+######################## 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 .euctwfreq import (EUCTWCharToFreqOrder, EUCTW_TABLE_SIZE,
+ EUCTW_TYPICAL_DISTRIBUTION_RATIO)
+from .euckrfreq import (EUCKRCharToFreqOrder, EUCKR_TABLE_SIZE,
+ EUCKR_TYPICAL_DISTRIBUTION_RATIO)
+from .gb2312freq import (GB2312CharToFreqOrder, GB2312_TABLE_SIZE,
+ GB2312_TYPICAL_DISTRIBUTION_RATIO)
+from .big5freq import (Big5CharToFreqOrder, BIG5_TABLE_SIZE,
+ BIG5_TYPICAL_DISTRIBUTION_RATIO)
+from .jisfreq import (JISCharToFreqOrder, JIS_TABLE_SIZE,
+ JIS_TYPICAL_DISTRIBUTION_RATIO)
+from .compat import wrap_ord
+
+ENOUGH_DATA_THRESHOLD = 1024
+SURE_YES = 0.99
+SURE_NO = 0.01
+MINIMUM_DATA_THRESHOLD = 3
+
+
+class CharDistributionAnalysis:
+ def __init__(self):
+ # Mapping table to get frequency order from char order (get from
+ # GetOrder())
+ self._mCharToFreqOrder = None
+ self._mTableSize = 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._mTypicalDistributionRatio = 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._mDone = False
+ self._mTotalChars = 0 # Total characters encountered
+ # The number of characters whose frequency order is less than 512
+ self._mFreqChars = 0
+
+ def feed(self, aBuf, aCharLen):
+ """feed a character with known length"""
+ if aCharLen == 2:
+ # we only care about 2-bytes character in our distribution analysis
+ order = self.get_order(aBuf)
+ else:
+ order = -1
+ if order >= 0:
+ self._mTotalChars += 1
+ # order is valid
+ if order < self._mTableSize:
+ if 512 > self._mCharToFreqOrder[order]:
+ self._mFreqChars += 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._mTotalChars <= 0 or self._mFreqChars <= MINIMUM_DATA_THRESHOLD:
+ return SURE_NO
+
+ if self._mTotalChars != self._mFreqChars:
+ r = (self._mFreqChars / ((self._mTotalChars - self._mFreqChars)
+ * self._mTypicalDistributionRatio))
+ if r < SURE_YES:
+ return r
+
+ # normalize confidence (we don't want to be 100% sure)
+ return 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._mTotalChars > ENOUGH_DATA_THRESHOLD
+
+ def get_order(self, aBuf):
+ # 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):
+ CharDistributionAnalysis.__init__(self)
+ self._mCharToFreqOrder = EUCTWCharToFreqOrder
+ self._mTableSize = EUCTW_TABLE_SIZE
+ self._mTypicalDistributionRatio = EUCTW_TYPICAL_DISTRIBUTION_RATIO
+
+ def get_order(self, aBuf):
+ # 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 = wrap_ord(aBuf[0])
+ if first_char >= 0xC4:
+ return 94 * (first_char - 0xC4) + wrap_ord(aBuf[1]) - 0xA1
+ else:
+ return -1
+
+
+class EUCKRDistributionAnalysis(CharDistributionAnalysis):
+ def __init__(self):
+ CharDistributionAnalysis.__init__(self)
+ self._mCharToFreqOrder = EUCKRCharToFreqOrder
+ self._mTableSize = EUCKR_TABLE_SIZE
+ self._mTypicalDistributionRatio = EUCKR_TYPICAL_DISTRIBUTION_RATIO
+
+ def get_order(self, aBuf):
+ # 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 = wrap_ord(aBuf[0])
+ if first_char >= 0xB0:
+ return 94 * (first_char - 0xB0) + wrap_ord(aBuf[1]) - 0xA1
+ else:
+ return -1
+
+
+class GB2312DistributionAnalysis(CharDistributionAnalysis):
+ def __init__(self):
+ CharDistributionAnalysis.__init__(self)
+ self._mCharToFreqOrder = GB2312CharToFreqOrder
+ self._mTableSize = GB2312_TABLE_SIZE
+ self._mTypicalDistributionRatio = GB2312_TYPICAL_DISTRIBUTION_RATIO
+
+ def get_order(self, aBuf):
+ # 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 = wrap_ord(aBuf[0]), wrap_ord(aBuf[1])
+ if (first_char >= 0xB0) and (second_char >= 0xA1):
+ return 94 * (first_char - 0xB0) + second_char - 0xA1
+ else:
+ return -1
+
+
+class Big5DistributionAnalysis(CharDistributionAnalysis):
+ def __init__(self):
+ CharDistributionAnalysis.__init__(self)
+ self._mCharToFreqOrder = Big5CharToFreqOrder
+ self._mTableSize = BIG5_TABLE_SIZE
+ self._mTypicalDistributionRatio = BIG5_TYPICAL_DISTRIBUTION_RATIO
+
+ def get_order(self, aBuf):
+ # 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 = wrap_ord(aBuf[0]), wrap_ord(aBuf[1])
+ if first_char >= 0xA4:
+ if second_char >= 0xA1:
+ return 157 * (first_char - 0xA4) + second_char - 0xA1 + 63
+ else:
+ return 157 * (first_char - 0xA4) + second_char - 0x40
+ else:
+ return -1
+
+
+class SJISDistributionAnalysis(CharDistributionAnalysis):
+ def __init__(self):
+ CharDistributionAnalysis.__init__(self)
+ self._mCharToFreqOrder = JISCharToFreqOrder
+ self._mTableSize = JIS_TABLE_SIZE
+ self._mTypicalDistributionRatio = JIS_TYPICAL_DISTRIBUTION_RATIO
+
+ def get_order(self, aBuf):
+ # 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 = wrap_ord(aBuf[0]), wrap_ord(aBuf[1])
+ if (first_char >= 0x81) and (first_char <= 0x9F):
+ order = 188 * (first_char - 0x81)
+ elif (first_char >= 0xE0) and (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):
+ CharDistributionAnalysis.__init__(self)
+ self._mCharToFreqOrder = JISCharToFreqOrder
+ self._mTableSize = JIS_TABLE_SIZE
+ self._mTypicalDistributionRatio = JIS_TYPICAL_DISTRIBUTION_RATIO
+
+ def get_order(self, aBuf):
+ # 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 = wrap_ord(aBuf[0])
+ if char >= 0xA0:
+ return 94 * (char - 0xA1) + wrap_ord(aBuf[1]) - 0xa1
+ else:
+ return -1