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1 """JSON token scanner
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2 """
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3 import re
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4 try:
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5 from _json import make_scanner as c_make_scanner
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6 except ImportError:
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7 c_make_scanner = None
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8
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9 __all__ = ['make_scanner']
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10
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11 NUMBER_RE = re.compile(
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12 r'(-?(?:0|[1-9]\d*))(\.\d+)?([eE][-+]?\d+)?',
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13 (re.VERBOSE | re.MULTILINE | re.DOTALL))
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14
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15 def py_make_scanner(context):
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16 parse_object = context.parse_object
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17 parse_array = context.parse_array
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18 parse_string = context.parse_string
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19 match_number = NUMBER_RE.match
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20 strict = context.strict
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21 parse_float = context.parse_float
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22 parse_int = context.parse_int
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23 parse_constant = context.parse_constant
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24 object_hook = context.object_hook
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25 object_pairs_hook = context.object_pairs_hook
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26 memo = context.memo
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27
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28 def _scan_once(string, idx):
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29 try:
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30 nextchar = string[idx]
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31 except IndexError:
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32 raise StopIteration(idx) from None
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33
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34 if nextchar == '"':
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35 return parse_string(string, idx + 1, strict)
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36 elif nextchar == '{':
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37 return parse_object((string, idx + 1), strict,
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38 _scan_once, object_hook, object_pairs_hook, memo)
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39 elif nextchar == '[':
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40 return parse_array((string, idx + 1), _scan_once)
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41 elif nextchar == 'n' and string[idx:idx + 4] == 'null':
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42 return None, idx + 4
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43 elif nextchar == 't' and string[idx:idx + 4] == 'true':
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44 return True, idx + 4
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45 elif nextchar == 'f' and string[idx:idx + 5] == 'false':
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46 return False, idx + 5
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47
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48 m = match_number(string, idx)
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49 if m is not None:
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50 integer, frac, exp = m.groups()
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51 if frac or exp:
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52 res = parse_float(integer + (frac or '') + (exp or ''))
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53 else:
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54 res = parse_int(integer)
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55 return res, m.end()
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56 elif nextchar == 'N' and string[idx:idx + 3] == 'NaN':
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57 return parse_constant('NaN'), idx + 3
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58 elif nextchar == 'I' and string[idx:idx + 8] == 'Infinity':
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59 return parse_constant('Infinity'), idx + 8
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60 elif nextchar == '-' and string[idx:idx + 9] == '-Infinity':
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61 return parse_constant('-Infinity'), idx + 9
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62 else:
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63 raise StopIteration(idx)
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64
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65 def scan_once(string, idx):
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66 try:
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67 return _scan_once(string, idx)
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68 finally:
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69 memo.clear()
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70
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71 return scan_once
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72
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73 make_scanner = c_make_scanner or py_make_scanner
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