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latin1prober.rb
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latin1prober.rb
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######################## BEGIN LICENSE BLOCK ########################
# The Original Code is Mozilla Universal charset detector code.
#
# The Initial Developer of the Original Code is
# Netscape Communications Corporation.
# Portions created by the Initial Developer are Copyright (C) 2001
# the Initial Developer. All Rights Reserved.
#
# Contributor(s):
# Jeff Hodges - port to Ruby
# Mark Pilgrim - port to Python
# Shy Shalom - original C code
#
# 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
FREQ_CAT_NUM = 4
UDF = 0 # undefined
OTH = 1 # other
ASC = 2 # ascii capital letter
ASS = 3 # ascii small letter
ACV = 4 # accent capital vowel
ACO = 5 # accent capital other
ASV = 6 # accent small vowel
ASO = 7 # accent small other
CLASS_NUM = 8 # total classes
Latin1_CharToClass = [
OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, # 00 - 07
OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, # 08 - 0F
OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, # 10 - 17
OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, # 18 - 1F
OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, # 20 - 27
OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, # 28 - 2F
OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, # 30 - 37
OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, # 38 - 3F
OTH, ASC, ASC, ASC, ASC, ASC, ASC, ASC, # 40 - 47
ASC, ASC, ASC, ASC, ASC, ASC, ASC, ASC, # 48 - 4F
ASC, ASC, ASC, ASC, ASC, ASC, ASC, ASC, # 50 - 57
ASC, ASC, ASC, OTH, OTH, OTH, OTH, OTH, # 58 - 5F
OTH, ASS, ASS, ASS, ASS, ASS, ASS, ASS, # 60 - 67
ASS, ASS, ASS, ASS, ASS, ASS, ASS, ASS, # 68 - 6F
ASS, ASS, ASS, ASS, ASS, ASS, ASS, ASS, # 70 - 77
ASS, ASS, ASS, OTH, OTH, OTH, OTH, OTH, # 78 - 7F
OTH, UDF, OTH, ASO, OTH, OTH, OTH, OTH, # 80 - 87
OTH, OTH, ACO, OTH, ACO, UDF, ACO, UDF, # 88 - 8F
UDF, OTH, OTH, OTH, OTH, OTH, OTH, OTH, # 90 - 97
OTH, OTH, ASO, OTH, ASO, UDF, ASO, ACO, # 98 - 9F
OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, # A0 - A7
OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, # A8 - AF
OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, # B0 - B7
OTH, OTH, OTH, OTH, OTH, OTH, OTH, OTH, # B8 - BF
ACV, ACV, ACV, ACV, ACV, ACV, ACO, ACO, # C0 - C7
ACV, ACV, ACV, ACV, ACV, ACV, ACV, ACV, # C8 - CF
ACO, ACO, ACV, ACV, ACV, ACV, ACV, OTH, # D0 - D7
ACV, ACV, ACV, ACV, ACV, ACO, ACO, ACO, # D8 - DF
ASV, ASV, ASV, ASV, ASV, ASV, ASO, ASO, # E0 - E7
ASV, ASV, ASV, ASV, ASV, ASV, ASV, ASV, # E8 - EF
ASO, ASO, ASV, ASV, ASV, ASV, ASV, OTH, # F0 - F7
ASV, ASV, ASV, ASV, ASV, ASO, ASO, ASO, # F8 - FF
]
# 0 : illegal
# 1 : very unlikely
# 2 : normal
# 3 : very likely
Latin1ClassModel = [
# UDF OTH ASC ASS ACV ACO ASV ASO
0, 0, 0, 0, 0, 0, 0, 0, # UDF
0, 3, 3, 3, 3, 3, 3, 3, # OTH
0, 3, 3, 3, 3, 3, 3, 3, # ASC
0, 3, 3, 3, 1, 1, 3, 3, # ASS
0, 3, 3, 3, 1, 2, 1, 2, # ACV
0, 3, 3, 3, 3, 3, 3, 3, # ACO
0, 3, 1, 3, 1, 1, 1, 3, # ASV
0, 3, 1, 3, 1, 1, 3, 3, # ASO
]
class Latin1Prober < CharSetProber
def initialize
super
reset()
end
def reset
@_mLastCharClass = OTH
@_mFreqCounter = [0] * FREQ_CAT_NUM
super
end
def get_charset_name
return "windows-1252"
end
def feed(aBuf)
aBuf = filter_with_english_letters(aBuf)
aBuf.each_byte do |b|
c = b.chr
charClass = Latin1_CharToClass[c[0]]
freq = Latin1ClassModel[(@_mLastCharClass * CLASS_NUM) + charClass]
if freq == 0
@_mState = ENotMe
break
end
@_mFreqCounter[freq] += 1
@_mLastCharClass = charClass
end
return get_state()
end
def get_confidence
if get_state() == ENotMe
return 0.01
end
total = @_mFreqCounter.inject{|a,b| a+b}
if total < 0.01
confidence = 0.0
else
confidence = (@_mFreqCounter[3] / total) - (@_mFreqCounter[1] * 20.0 / total)
end
if confidence < 0.0
confidence = 0.0
end
# lower the confidence of latin1 so that other more accurate detector
# can take priority.
confidence = confidence * 0.5
return confidence
end
end
end