85 lines
2.9 KiB
Python
85 lines
2.9 KiB
Python
"""JSON token scanner
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"""
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import re
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from .errors import JSONDecodeError
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def _import_c_make_scanner():
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try:
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from ._speedups import make_scanner
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return make_scanner
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except ImportError:
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return None
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c_make_scanner = _import_c_make_scanner()
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__all__ = ['make_scanner', 'JSONDecodeError']
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NUMBER_RE = re.compile(
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r'(-?(?:0|[1-9]\d*))(\.\d+)?([eE][-+]?\d+)?',
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(re.VERBOSE | re.MULTILINE | re.DOTALL))
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def py_make_scanner(context):
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parse_object = context.parse_object
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parse_array = context.parse_array
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parse_string = context.parse_string
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match_number = NUMBER_RE.match
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encoding = context.encoding
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strict = context.strict
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parse_float = context.parse_float
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parse_int = context.parse_int
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parse_constant = context.parse_constant
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object_hook = context.object_hook
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object_pairs_hook = context.object_pairs_hook
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memo = context.memo
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def _scan_once(string, idx):
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errmsg = 'Expecting value'
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try:
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nextchar = string[idx]
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except IndexError:
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raise JSONDecodeError(errmsg, string, idx)
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if nextchar == '"':
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return parse_string(string, idx + 1, encoding, strict)
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elif nextchar == '{':
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return parse_object((string, idx + 1), encoding, strict,
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_scan_once, object_hook, object_pairs_hook, memo)
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elif nextchar == '[':
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return parse_array((string, idx + 1), _scan_once)
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elif nextchar == 'n' and string[idx:idx + 4] == 'null':
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return None, idx + 4
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elif nextchar == 't' and string[idx:idx + 4] == 'true':
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return True, idx + 4
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elif nextchar == 'f' and string[idx:idx + 5] == 'false':
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return False, idx + 5
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m = match_number(string, idx)
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if m is not None:
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integer, frac, exp = m.groups()
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if frac or exp:
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res = parse_float(integer + (frac or '') + (exp or ''))
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else:
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res = parse_int(integer)
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return res, m.end()
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elif nextchar == 'N' and string[idx:idx + 3] == 'NaN':
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return parse_constant('NaN'), idx + 3
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elif nextchar == 'I' and string[idx:idx + 8] == 'Infinity':
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return parse_constant('Infinity'), idx + 8
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elif nextchar == '-' and string[idx:idx + 9] == '-Infinity':
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return parse_constant('-Infinity'), idx + 9
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else:
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raise JSONDecodeError(errmsg, string, idx)
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def scan_once(string, idx):
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if idx < 0:
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# Ensure the same behavior as the C speedup, otherwise
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# this would work for *some* negative string indices due
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# to the behavior of __getitem__ for strings. #98
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raise JSONDecodeError('Expecting value', string, idx)
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try:
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return _scan_once(string, idx)
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finally:
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memo.clear()
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return scan_once
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make_scanner = c_make_scanner or py_make_scanner
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