1"""JSON token scanner
2"""
3import re
4try:
5    from _json import make_scanner as c_make_scanner
6except ImportError:
7    c_make_scanner = None
8
9__all__ = ['make_scanner']
10
11NUMBER_RE = re.compile(
12    r'(-?(?:0|[1-9]\d*))(\.\d+)?([eE][-+]?\d+)?',
13    (re.VERBOSE | re.MULTILINE | re.DOTALL))
14
15def 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    strict = context.strict
21    parse_float = context.parse_float
22    parse_int = context.parse_int
23    parse_constant = context.parse_constant
24    object_hook = context.object_hook
25    object_pairs_hook = context.object_pairs_hook
26    memo = context.memo
27
28    def _scan_once(string, idx):
29        try:
30            nextchar = string[idx]
31        except IndexError:
32            raise StopIteration(idx)
33
34        if nextchar == '"':
35            return parse_string(string, idx + 1, strict)
36        elif nextchar == '{':
37            return parse_object((string, idx + 1), strict,
38                _scan_once, object_hook, object_pairs_hook, memo)
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(idx)
64
65    def scan_once(string, idx):
66        try:
67            return _scan_once(string, idx)
68        finally:
69            memo.clear()
70
71    return _scan_once
72
73make_scanner = c_make_scanner or py_make_scanner
74