Lib/json/scanner.py

   1 """JSON token scanner
   2 """
   3 import re
   4 try:
   5     from _json import make_scanner as c_make_scanner
   6 except ImportError:
   7     c_make_scanner = None
   8
   9 __all__ = ['make_scanner']
  10
  11 NUMBER_RE = re.compile(
  12     r'(-?(?:0|[1-9]\d*))(\.\d+)?([eE][-+]?\d+)?',
  13     (re.VERBOSE | re.MULTILINE | re.DOTALL))
  14
  15 def py_make_scanner(context):
  16     parse_object = context.parse_object
  17     parse_array = context.parse_array
  18     parse_string = context.parse_string
  19     match_number = NUMBER_RE.match
  20     encoding = context.encoding
  21     strict = context.strict
  22     parse_float = context.parse_float
  23     parse_int = context.parse_int
  24     parse_constant = context.parse_constant
  25     object_hook = context.object_hook
  26     object_pairs_hook = context.object_pairs_hook
  27
  28     def _scan_once(string, idx):
  29         try:
  30             nextchar = string[idx]
  31         except IndexError:
  32             raise StopIteration
  33
  34         if nextchar == '"':
  35             return parse_string(string, idx + 1, encoding, strict)
  36         elif nextchar == '{':
  37             return parse_object((string, idx + 1), encoding, strict,
  38                 _scan_once, object_hook, object_pairs_hook)
  39         elif nextchar == '[':
  40             return parse_array((string, idx + 1), _scan_once)
  41         elif nextchar == 'n' and string[idx:idx + 4] == 'null':
  42             return None, idx + 4
  43         elif nextchar == 't' and string[idx:idx + 4] == 'true':
  44             return True, idx + 4
  45         elif nextchar == 'f' and string[idx:idx + 5] == 'false':
  46             return False, idx + 5
  47
  48         m = match_number(string, idx)
  49         if m is not None:
  50             integer, frac, exp = m.groups()
  51             if frac or exp:
  52                 res = parse_float(integer + (frac or '') + (exp or ''))
  53             else:
  54                 res = parse_int(integer)
  55             return res, m.end()
  56         elif nextchar == 'N' and string[idx:idx + 3] == 'NaN':
  57             return parse_constant('NaN'), idx + 3
  58         elif nextchar == 'I' and string[idx:idx + 8] == 'Infinity':
  59             return parse_constant('Infinity'), idx + 8
  60         elif nextchar == '-' and string[idx:idx + 9] == '-Infinity':
  61             return parse_constant('-Infinity'), idx + 9
  62         else:
  63             raise StopIteration
  64
  65     return _scan_once
  66
  67 make_scanner = c_make_scanner or py_make_scanner