venv/lib/python3.11/site-packages/pip/_vendor/pygments/scanner.py

   1 """
   2     pygments.scanner
   3     ~~~~~~~~~~~~~~~~
   4
   5     This library implements a regex based scanner. Some languages
   6     like Pascal are easy to parse but have some keywords that
   7     depend on the context. Because of this it's impossible to lex
   8     that just by using a regular expression lexer like the
   9     `RegexLexer`.
  10
  11     Have a look at the `DelphiLexer` to get an idea of how to use
  12     this scanner.
  13
  14     :copyright: Copyright 2006-2023 by the Pygments team, see AUTHORS.
  15     :license: BSD, see LICENSE for details.
  16 """
  17 import re
  18
  19
  20 class EndOfText(RuntimeError):
  21     """
  22     Raise if end of text is reached and the user
  23     tried to call a match function.
  24     """
  25
  26
  27 class Scanner:
  28     """
  29     Simple scanner
  30
  31     All method patterns are regular expression strings (not
  32     compiled expressions!)
  33     """
  34
  35     def __init__(self, text, flags=0):
  36         """
  37         :param text:    The text which should be scanned
  38         :param flags:   default regular expression flags
  39         """
  40         self.data = text
  41         self.data_length = len(text)
  42         self.start_pos = 0
  43         self.pos = 0
  44         self.flags = flags
  45         self.last = None
  46         self.match = None
  47         self._re_cache = {}
  48
  49     def eos(self):
  50         """`True` if the scanner reached the end of text."""
  51         return self.pos >= self.data_length
  52     eos = property(eos, eos.__doc__)
  53
  54     def check(self, pattern):
  55         """
  56         Apply `pattern` on the current position and return
  57         the match object. (Doesn't touch pos). Use this for
  58         lookahead.
  59         """
  60         if self.eos:
  61             raise EndOfText()
  62         if pattern not in self._re_cache:
  63             self._re_cache[pattern] = re.compile(pattern, self.flags)
  64         return self._re_cache[pattern].match(self.data, self.pos)
  65
  66     def test(self, pattern):
  67         """Apply a pattern on the current position and check
  68         if it patches. Doesn't touch pos.
  69         """
  70         return self.check(pattern) is not None
  71
  72     def scan(self, pattern):
  73         """
  74         Scan the text for the given pattern and update pos/match
  75         and related fields. The return value is a boolean that
  76         indicates if the pattern matched. The matched value is
  77         stored on the instance as ``match``, the last value is
  78         stored as ``last``. ``start_pos`` is the position of the
  79         pointer before the pattern was matched, ``pos`` is the
  80         end position.
  81         """
  82         if self.eos:
  83             raise EndOfText()
  84         if pattern not in self._re_cache:
  85             self._re_cache[pattern] = re.compile(pattern, self.flags)
  86         self.last = self.match
  87         m = self._re_cache[pattern].match(self.data, self.pos)
  88         if m is None:
  89             return False
  90         self.start_pos = m.start()
  91         self.pos = m.end()
  92         self.match = m.group()
  93         return True
  94
  95     def get_char(self):
  96         """Scan exactly one char."""
  97         self.scan('.')
  98
  99     def __repr__(self):
 100         return '<%s %d/%d>' % (
 101             self.__class__.__name__,
 102             self.pos,
 103             self.data_length
 104         )