Viewing file:  chardistribution.py (9.19 KB) -rw-r--r--
Select action/file-type:
 (+) |  (+) |  (+) | Code (+) | Session (+) |  (+) | SDB (+) |  (+) |  (+) |  (+) |  (+) |  (+) |
######################## 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 (EUCTW_CHAR_TO_FREQ_ORDER, EUCTW_TABLE_SIZE,
EUCTW_TYPICAL_DISTRIBUTION_RATIO)
from .euckrfreq import (EUCKR_CHAR_TO_FREQ_ORDER, EUCKR_TABLE_SIZE,
EUCKR_TYPICAL_DISTRIBUTION_RATIO)
from .gb2312freq import (GB2312_CHAR_TO_FREQ_ORDER, GB2312_TABLE_SIZE,
GB2312_TYPICAL_DISTRIBUTION_RATIO)
from .big5freq import (BIG5_CHAR_TO_FREQ_ORDER, BIG5_TABLE_SIZE,
BIG5_TYPICAL_DISTRIBUTION_RATIO)
from .jisfreq import (JIS_CHAR_TO_FREQ_ORDER, JIS_TABLE_SIZE,
JIS_TYPICAL_DISTRIBUTION_RATIO)
class CharDistributionAnalysis(object):
ENOUGH_DATA_THRESHOLD = 1024
SURE_YES = 0.99
SURE_NO = 0.01
MINIMUM_DATA_THRESHOLD = 3
def __init__(self):
# Mapping table to get frequency order from char order (get from
# GetOrder())
self._char_to_freq_order = None
self._table_size = 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.typical_distribution_ratio = None
self._done = None
self._total_chars = None
self._freq_chars = 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._done = False
self._total_chars = 0 # Total characters encountered
# The number of characters whose frequency order is less than 512
self._freq_chars = 0
def feed(self, char, char_len):
"""feed a character with known length"""
if char_len == 2:
# we only care about 2-bytes character in our distribution analysis
order = self.get_order(char)
else:
order = -1
if order >= 0:
self._total_chars += 1
# order is valid
if order < self._table_size:
if 512 > self._char_to_freq_order[order]:
self._freq_chars += 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._total_chars <= 0 or self._freq_chars <= self.MINIMUM_DATA_THRESHOLD:
return self.SURE_NO
if self._total_chars != self._freq_chars:
r = (self._freq_chars / ((self._total_chars - self._freq_chars)
* self.typical_distribution_ratio))
if r < self.SURE_YES:
return r
# normalize confidence (we don't want to be 100% sure)
return self.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._total_chars > self.ENOUGH_DATA_THRESHOLD
def get_order(self, byte_str):
# 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):
super(EUCTWDistributionAnalysis, self).__init__()
self._char_to_freq_order = EUCTW_CHAR_TO_FREQ_ORDER
self._table_size = EUCTW_TABLE_SIZE
self.typical_distribution_ratio = EUCTW_TYPICAL_DISTRIBUTION_RATIO
def get_order(self, byte_str):
# 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 = byte_str[0]
if first_char >= 0xC4:
return 94 * (first_char - 0xC4) + byte_str[1] - 0xA1
else:
return -1
class EUCKRDistributionAnalysis(CharDistributionAnalysis):
def __init__(self):
super(EUCKRDistributionAnalysis, self).__init__()
self._char_to_freq_order = EUCKR_CHAR_TO_FREQ_ORDER
self._table_size = EUCKR_TABLE_SIZE
self.typical_distribution_ratio = EUCKR_TYPICAL_DISTRIBUTION_RATIO
def get_order(self, byte_str):
# 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 = byte_str[0]
if first_char >= 0xB0:
return 94 * (first_char - 0xB0) + byte_str[1] - 0xA1
else:
return -1
class GB2312DistributionAnalysis(CharDistributionAnalysis):
def __init__(self):
super(GB2312DistributionAnalysis, self).__init__()
self._char_to_freq_order = GB2312_CHAR_TO_FREQ_ORDER
self._table_size = GB2312_TABLE_SIZE
self.typical_distribution_ratio = GB2312_TYPICAL_DISTRIBUTION_RATIO
def get_order(self, byte_str):
# 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 = byte_str[0], byte_str[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):
super(Big5DistributionAnalysis, self).__init__()
self._char_to_freq_order = BIG5_CHAR_TO_FREQ_ORDER
self._table_size = BIG5_TABLE_SIZE
self.typical_distribution_ratio = BIG5_TYPICAL_DISTRIBUTION_RATIO
def get_order(self, byte_str):
# 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 = byte_str[0], byte_str[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):
super(SJISDistributionAnalysis, self).__init__()
self._char_to_freq_order = JIS_CHAR_TO_FREQ_ORDER
self._table_size = JIS_TABLE_SIZE
self.typical_distribution_ratio = JIS_TYPICAL_DISTRIBUTION_RATIO
def get_order(self, byte_str):
# 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 = byte_str[0], byte_str[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):
super(EUCJPDistributionAnalysis, self).__init__()
self._char_to_freq_order = JIS_CHAR_TO_FREQ_ORDER
self._table_size = JIS_TABLE_SIZE
self.typical_distribution_ratio = JIS_TYPICAL_DISTRIBUTION_RATIO
def get_order(self, byte_str):
# 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 = byte_str[0]
if char >= 0xA0:
return 94 * (char - 0xA1) + byte_str[1] - 0xa1
else:
return -1
|