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stbi/Lib/site-packages/pip/_vendor/chardet/chardistribution.py

+######################## 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