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

+######################## 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):
+#   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 #########################
+
+from .charsetprober import CharSetProber
+from .enums import CharacterCategory, ProbingState, SequenceLikelihood
+
+
+class SingleByteCharSetProber(CharSetProber):
+    SAMPLE_SIZE = 64
+    SB_ENOUGH_REL_THRESHOLD = 1024  #  0.25 * SAMPLE_SIZE^2
+    POSITIVE_SHORTCUT_THRESHOLD = 0.95
+    NEGATIVE_SHORTCUT_THRESHOLD = 0.05
+
+    def __init__(self, model, reversed=False, name_prober=None):
+        super(SingleByteCharSetProber, self).__init__()
+        self._model = model
+        # TRUE if we need to reverse every pair in the model lookup
+        self._reversed = reversed
+        # Optional auxiliary prober for name decision
+        self._name_prober = name_prober
+        self._last_order = None
+        self._seq_counters = None
+        self._total_seqs = None
+        self._total_char = None
+        self._freq_char = None
+        self.reset()
+
+    def reset(self):
+        super(SingleByteCharSetProber, self).reset()
+        # char order of last character
+        self._last_order = 255
+        self._seq_counters = [0] * SequenceLikelihood.get_num_categories()
+        self._total_seqs = 0
+        self._total_char = 0
+        # characters that fall in our sampling range
+        self._freq_char = 0
+
+    @property
+    def charset_name(self):
+        if self._name_prober:
+            return self._name_prober.charset_name
+        else:
+            return self._model['charset_name']
+
+    @property
+    def language(self):
+        if self._name_prober:
+            return self._name_prober.language
+        else:
+            return self._model.get('language')
+
+    def feed(self, byte_str):
+        if not self._model['keep_english_letter']:
+            byte_str = self.filter_international_words(byte_str)
+        if not byte_str:
+            return self.state
+        char_to_order_map = self._model['char_to_order_map']
+        for i, c in enumerate(byte_str):
+            # XXX: Order is in range 1-64, so one would think we want 0-63 here,
+            #      but that leads to 27 more test failures than before.
+            order = char_to_order_map[c]
+            # XXX: This was SYMBOL_CAT_ORDER before, with a value of 250, but
+            #      CharacterCategory.SYMBOL is actually 253, so we use CONTROL
+            #      to make it closer to the original intent. The only difference
+            #      is whether or not we count digits and control characters for
+            #      _total_char purposes.
+            if order < CharacterCategory.CONTROL:
+                self._total_char += 1
+            if order < self.SAMPLE_SIZE:
+                self._freq_char += 1
+                if self._last_order < self.SAMPLE_SIZE:
+                    self._total_seqs += 1
+                    if not self._reversed:
+                        i = (self._last_order * self.SAMPLE_SIZE) + order
+                        model = self._model['precedence_matrix'][i]
+                    else:  # reverse the order of the letters in the lookup
+                        i = (order * self.SAMPLE_SIZE) + self._last_order
+                        model = self._model['precedence_matrix'][i]
+                    self._seq_counters[model] += 1
+            self._last_order = order
+
+        charset_name = self._model['charset_name']
+        if self.state == ProbingState.DETECTING:
+            if self._total_seqs > self.SB_ENOUGH_REL_THRESHOLD:
+                confidence = self.get_confidence()
+                if confidence > self.POSITIVE_SHORTCUT_THRESHOLD:
+                    self.logger.debug('%s confidence = %s, we have a winner',
+                                      charset_name, confidence)
+                    self._state = ProbingState.FOUND_IT
+                elif confidence < self.NEGATIVE_SHORTCUT_THRESHOLD:
+                    self.logger.debug('%s confidence = %s, below negative '
+                                      'shortcut threshhold %s', charset_name,
+                                      confidence,
+                                      self.NEGATIVE_SHORTCUT_THRESHOLD)
+                    self._state = ProbingState.NOT_ME
+
+        return self.state
+
+    def get_confidence(self):
+        r = 0.01
+        if self._total_seqs > 0:
+            r = ((1.0 * self._seq_counters[SequenceLikelihood.POSITIVE]) /
+                 self._total_seqs / self._model['typical_positive_ratio'])
+            r = r * self._freq_char / self._total_char
+            if r >= 1.0:
+                r = 0.99
+        return r