--- /dev/null
+######################## 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)
+
+# Jeff Hodges
+# 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 #########################
+
+module CharDet
+ ENOUGH_DATA_THRESHOLD = 1024
+ SURE_YES = 0.99
+ SURE_NO = 0.01
+
+ class CharDistributionAnalysis
+ def initialize
+ @_mCharToFreqOrder = nil # Mapping table to get frequency order from char order (get from GetOrder())
+ @_mTableSize = nil # Size of above table
+ @_mTypicalDistributionRatio = nil # 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.
+ reset()
+ end
+
+ def reset
+ # # """reset analyser, clear any state"""
+ @_mDone = false # If this flag is set to constants.True, detection is done and conclusion has been made
+ @_mTotalChars = 0 # Total characters encountered
+ @_mFreqChars = 0 # The number of characters whose frequency order is less than 512
+ end
+
+ def feed(aStr, aCharLen)
+ # # """feed a character with known length"""
+ if aCharLen == 2
+ # we only care about 2-bytes character in our distribution analysis
+ order = get_order(aStr)
+ else
+ order = -1
+ end
+ if order >= 0
+ @_mTotalChars += 1
+ # order is valid
+ if order < @_mTableSize
+ if 512 > @_mCharToFreqOrder[order]
+ @_mFreqChars += 1
+ end
+ end
+ end
+ end
+
+ def get_confidence
+ # """return confidence based on existing data"""
+ # if we didn't receive any character in our consideration range, return negative answer
+ if @_mTotalChars <= 0
+ return SURE_NO
+ end
+
+ if @_mTotalChars != @_mFreqChars
+ r = @_mFreqChars / ((@_mTotalChars - @_mFreqChars) * @_mTypicalDistributionRatio)
+ if r < SURE_YES
+ return r
+ end
+ end
+
+ # normalize confidence (we don't want to be 100% sure)
+ return SURE_YES
+ end
+
+ def got_enough_data
+ # It is not necessary to receive all data to draw conclusion. For charset detection,
+ # certain amount of data is enough
+ return @_mTotalChars > ENOUGH_DATA_THRESHOLD
+ end
+
+ def get_order(aStr)
+ # 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
+ end
+ end
+
+ class EUCTWDistributionAnalysis < CharDistributionAnalysis
+ def initialize
+ super()
+ @_mCharToFreqOrder = EUCTWCharToFreqOrder
+ @_mTableSize = EUCTW_TABLE_SIZE
+ @_mTypicalDistributionRatio = EUCTW_TYPICAL_DISTRIBUTION_RATIO
+ end
+
+ def get_order(aStr)
+ # 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
+ if aStr[0..0] >= "\xC4"
+ return 94 * (aStr[0] - 0xC4) + aStr[1] - 0xA1
+ else
+ return -1
+ end
+ end
+ end
+
+ class EUCKRDistributionAnalysis < CharDistributionAnalysis
+ def initialize
+ super()
+ @_mCharToFreqOrder = EUCKRCharToFreqOrder
+ @_mTableSize = EUCKR_TABLE_SIZE
+ @_mTypicalDistributionRatio = EUCKR_TYPICAL_DISTRIBUTION_RATIO
+ end
+
+ def get_order(aStr)
+ # 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
+ if aStr[0..0] >= "\xB0"
+ return 94 * (aStr[0] - 0xB0) + aStr[1] - 0xA1
+ else
+ return -1
+ end
+ end
+ end
+
+ class GB2312DistributionAnalysis < CharDistributionAnalysis
+ def initialize
+ super()
+ @_mCharToFreqOrder = GB2312CharToFreqOrder
+ @_mTableSize = GB2312_TABLE_SIZE
+ @_mTypicalDistributionRatio = GB2312_TYPICAL_DISTRIBUTION_RATIO
+ end
+
+ def get_order(aStr)
+ # 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
+ if (aStr[0..0] >= "\xB0") and (aStr[1..1] >= "\xA1")
+ return 94 * (aStr[0] - 0xB0) + aStr[1] - 0xA1
+ else
+ return -1
+ end
+ end
+ end
+
+ class Big5DistributionAnalysis < CharDistributionAnalysis
+ def initialize
+ super
+ @_mCharToFreqOrder = Big5CharToFreqOrder
+ @_mTableSize = BIG5_TABLE_SIZE
+ @_mTypicalDistributionRatio = BIG5_TYPICAL_DISTRIBUTION_RATIO
+ end
+
+ def get_order(aStr)
+ # 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
+ if aStr[0..0] >= "\xA4"
+ if aStr[1..1] >= "\xA1"
+ return 157 * (aStr[0] - 0xA4) + aStr[1] - 0xA1 + 63
+ else
+ return 157 * (aStr[0] - 0xA4) + aStr[1] - 0x40
+ end
+ else
+ return -1
+ end
+ end
+ end
+
+ class SJISDistributionAnalysis < CharDistributionAnalysis
+ def initialize
+ super()
+ @_mCharToFreqOrder = JISCharToFreqOrder
+ @_mTableSize = JIS_TABLE_SIZE
+ @_mTypicalDistributionRatio = JIS_TYPICAL_DISTRIBUTION_RATIO
+ end
+
+ def get_order(aStr)
+ # 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
+ aStr = aStr[0..1].join if aStr.class == Array
+ if (aStr[0..0] >= "\x81") and (aStr[0..0] <= "\x9F")
+ order = 188 * (aStr[0] - 0x81)
+ elsif (aStr[0..0] >= "\xE0") and (aStr[0..0] <= "\xEF")
+ order = 188 * (aStr[0] - 0xE0 + 31)
+ else
+ return -1
+ end
+ order = order + aStr[1] - 0x40
+ if aStr[1..1] > "\x7F"
+ order =- 1
+ end
+ return order
+ end
+ end
+
+ class EUCJPDistributionAnalysis < CharDistributionAnalysis
+ def initialize
+ super()
+ @_mCharToFreqOrder = JISCharToFreqOrder
+ @_mTableSize = JIS_TABLE_SIZE
+ @_mTypicalDistributionRatio = JIS_TYPICAL_DISTRIBUTION_RATIO
+ end
+
+ def get_order(aStr)
+ # 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
+ if aStr[0..0] >= "\xA0"
+ return 94 * (aStr[0] - 0xA1) + aStr[1] - 0xa1
+ else
+ return -1
+ end
+ end
+ end
+end
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