400 lines
14 KiB
Python
400 lines
14 KiB
Python
"""Implementation of JSONDecoder
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"""
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from __future__ import absolute_import
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import re
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import sys
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import struct
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from .compat import fromhex, b, u, text_type, binary_type, PY3, unichr
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from .scanner import make_scanner, JSONDecodeError
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def _import_c_scanstring():
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try:
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from ._speedups import scanstring
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return scanstring
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except ImportError:
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return None
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c_scanstring = _import_c_scanstring()
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# NOTE (3.1.0): JSONDecodeError may still be imported from this module for
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# compatibility, but it was never in the __all__
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__all__ = ['JSONDecoder']
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FLAGS = re.VERBOSE | re.MULTILINE | re.DOTALL
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def _floatconstants():
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_BYTES = fromhex('7FF80000000000007FF0000000000000')
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# The struct module in Python 2.4 would get frexp() out of range here
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# when an endian is specified in the format string. Fixed in Python 2.5+
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if sys.byteorder != 'big':
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_BYTES = _BYTES[:8][::-1] + _BYTES[8:][::-1]
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nan, inf = struct.unpack('dd', _BYTES)
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return nan, inf, -inf
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NaN, PosInf, NegInf = _floatconstants()
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_CONSTANTS = {
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'-Infinity': NegInf,
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'Infinity': PosInf,
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'NaN': NaN,
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}
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STRINGCHUNK = re.compile(r'(.*?)(["\\\x00-\x1f])', FLAGS)
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BACKSLASH = {
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'"': u('"'), '\\': u('\u005c'), '/': u('/'),
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'b': u('\b'), 'f': u('\f'), 'n': u('\n'), 'r': u('\r'), 't': u('\t'),
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}
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DEFAULT_ENCODING = "utf-8"
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def py_scanstring(s, end, encoding=None, strict=True,
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_b=BACKSLASH, _m=STRINGCHUNK.match, _join=u('').join,
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_PY3=PY3, _maxunicode=sys.maxunicode):
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"""Scan the string s for a JSON string. End is the index of the
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character in s after the quote that started the JSON string.
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Unescapes all valid JSON string escape sequences and raises ValueError
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on attempt to decode an invalid string. If strict is False then literal
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control characters are allowed in the string.
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Returns a tuple of the decoded string and the index of the character in s
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after the end quote."""
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if encoding is None:
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encoding = DEFAULT_ENCODING
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chunks = []
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_append = chunks.append
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begin = end - 1
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while 1:
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chunk = _m(s, end)
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if chunk is None:
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raise JSONDecodeError(
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"Unterminated string starting at", s, begin)
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end = chunk.end()
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content, terminator = chunk.groups()
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# Content is contains zero or more unescaped string characters
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if content:
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if not _PY3 and not isinstance(content, text_type):
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content = text_type(content, encoding)
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_append(content)
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# Terminator is the end of string, a literal control character,
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# or a backslash denoting that an escape sequence follows
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if terminator == '"':
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break
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elif terminator != '\\':
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if strict:
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msg = "Invalid control character %r at"
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raise JSONDecodeError(msg, s, end)
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else:
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_append(terminator)
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continue
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try:
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esc = s[end]
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except IndexError:
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raise JSONDecodeError(
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"Unterminated string starting at", s, begin)
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# If not a unicode escape sequence, must be in the lookup table
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if esc != 'u':
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try:
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char = _b[esc]
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except KeyError:
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msg = "Invalid \\X escape sequence %r"
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raise JSONDecodeError(msg, s, end)
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end += 1
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else:
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# Unicode escape sequence
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msg = "Invalid \\uXXXX escape sequence"
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esc = s[end + 1:end + 5]
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escX = esc[1:2]
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if len(esc) != 4 or escX == 'x' or escX == 'X':
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raise JSONDecodeError(msg, s, end - 1)
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try:
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uni = int(esc, 16)
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except ValueError:
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raise JSONDecodeError(msg, s, end - 1)
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end += 5
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# Check for surrogate pair on UCS-4 systems
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# Note that this will join high/low surrogate pairs
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# but will also pass unpaired surrogates through
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if (_maxunicode > 65535 and
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uni & 0xfc00 == 0xd800 and
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s[end:end + 2] == '\\u'):
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esc2 = s[end + 2:end + 6]
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escX = esc2[1:2]
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if len(esc2) == 4 and not (escX == 'x' or escX == 'X'):
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try:
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uni2 = int(esc2, 16)
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except ValueError:
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raise JSONDecodeError(msg, s, end)
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if uni2 & 0xfc00 == 0xdc00:
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uni = 0x10000 + (((uni - 0xd800) << 10) |
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(uni2 - 0xdc00))
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end += 6
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char = unichr(uni)
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# Append the unescaped character
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_append(char)
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return _join(chunks), end
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# Use speedup if available
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scanstring = c_scanstring or py_scanstring
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WHITESPACE = re.compile(r'[ \t\n\r]*', FLAGS)
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WHITESPACE_STR = ' \t\n\r'
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def JSONObject(state, encoding, strict, scan_once, object_hook,
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object_pairs_hook, memo=None,
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_w=WHITESPACE.match, _ws=WHITESPACE_STR):
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(s, end) = state
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# Backwards compatibility
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if memo is None:
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memo = {}
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memo_get = memo.setdefault
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pairs = []
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# Use a slice to prevent IndexError from being raised, the following
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# check will raise a more specific ValueError if the string is empty
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nextchar = s[end:end + 1]
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# Normally we expect nextchar == '"'
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if nextchar != '"':
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if nextchar in _ws:
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end = _w(s, end).end()
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nextchar = s[end:end + 1]
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# Trivial empty object
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if nextchar == '}':
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if object_pairs_hook is not None:
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result = object_pairs_hook(pairs)
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return result, end + 1
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pairs = {}
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if object_hook is not None:
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pairs = object_hook(pairs)
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return pairs, end + 1
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elif nextchar != '"':
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raise JSONDecodeError(
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"Expecting property name enclosed in double quotes",
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s, end)
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end += 1
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while True:
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key, end = scanstring(s, end, encoding, strict)
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key = memo_get(key, key)
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# To skip some function call overhead we optimize the fast paths where
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# the JSON key separator is ": " or just ":".
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if s[end:end + 1] != ':':
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end = _w(s, end).end()
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if s[end:end + 1] != ':':
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raise JSONDecodeError("Expecting ':' delimiter", s, end)
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end += 1
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try:
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if s[end] in _ws:
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end += 1
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if s[end] in _ws:
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end = _w(s, end + 1).end()
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except IndexError:
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pass
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value, end = scan_once(s, end)
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pairs.append((key, value))
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try:
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nextchar = s[end]
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if nextchar in _ws:
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end = _w(s, end + 1).end()
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nextchar = s[end]
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except IndexError:
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nextchar = ''
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end += 1
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if nextchar == '}':
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break
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elif nextchar != ',':
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raise JSONDecodeError("Expecting ',' delimiter or '}'", s, end - 1)
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try:
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nextchar = s[end]
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if nextchar in _ws:
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end += 1
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nextchar = s[end]
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if nextchar in _ws:
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end = _w(s, end + 1).end()
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nextchar = s[end]
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except IndexError:
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nextchar = ''
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end += 1
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if nextchar != '"':
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raise JSONDecodeError(
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"Expecting property name enclosed in double quotes",
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s, end - 1)
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if object_pairs_hook is not None:
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result = object_pairs_hook(pairs)
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return result, end
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pairs = dict(pairs)
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if object_hook is not None:
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pairs = object_hook(pairs)
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return pairs, end
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def JSONArray(state, scan_once, _w=WHITESPACE.match, _ws=WHITESPACE_STR):
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(s, end) = state
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values = []
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nextchar = s[end:end + 1]
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if nextchar in _ws:
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end = _w(s, end + 1).end()
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nextchar = s[end:end + 1]
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# Look-ahead for trivial empty array
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if nextchar == ']':
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return values, end + 1
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elif nextchar == '':
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raise JSONDecodeError("Expecting value or ']'", s, end)
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_append = values.append
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while True:
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value, end = scan_once(s, end)
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_append(value)
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nextchar = s[end:end + 1]
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if nextchar in _ws:
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end = _w(s, end + 1).end()
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nextchar = s[end:end + 1]
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end += 1
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if nextchar == ']':
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break
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elif nextchar != ',':
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raise JSONDecodeError("Expecting ',' delimiter or ']'", s, end - 1)
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try:
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if s[end] in _ws:
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end += 1
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if s[end] in _ws:
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end = _w(s, end + 1).end()
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except IndexError:
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pass
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return values, end
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class JSONDecoder(object):
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"""Simple JSON <http://json.org> decoder
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Performs the following translations in decoding by default:
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+---------------+-------------------+
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| JSON | Python |
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+===============+===================+
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| object | dict |
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+---------------+-------------------+
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| array | list |
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+---------------+-------------------+
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| string | str, unicode |
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+---------------+-------------------+
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| number (int) | int, long |
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+---------------+-------------------+
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| number (real) | float |
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+---------------+-------------------+
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| true | True |
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+---------------+-------------------+
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| false | False |
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+---------------+-------------------+
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| null | None |
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+---------------+-------------------+
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It also understands ``NaN``, ``Infinity``, and ``-Infinity`` as
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their corresponding ``float`` values, which is outside the JSON spec.
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"""
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def __init__(self, encoding=None, object_hook=None, parse_float=None,
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parse_int=None, parse_constant=None, strict=True,
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object_pairs_hook=None):
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"""
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*encoding* determines the encoding used to interpret any
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:class:`str` objects decoded by this instance (``'utf-8'`` by
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default). It has no effect when decoding :class:`unicode` objects.
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Note that currently only encodings that are a superset of ASCII work,
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strings of other encodings should be passed in as :class:`unicode`.
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*object_hook*, if specified, will be called with the result of every
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JSON object decoded and its return value will be used in place of the
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given :class:`dict`. This can be used to provide custom
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deserializations (e.g. to support JSON-RPC class hinting).
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*object_pairs_hook* is an optional function that will be called with
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the result of any object literal decode with an ordered list of pairs.
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The return value of *object_pairs_hook* will be used instead of the
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:class:`dict`. This feature can be used to implement custom decoders
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that rely on the order that the key and value pairs are decoded (for
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example, :func:`collections.OrderedDict` will remember the order of
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insertion). If *object_hook* is also defined, the *object_pairs_hook*
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takes priority.
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*parse_float*, if specified, will be called with the string of every
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JSON float to be decoded. By default, this is equivalent to
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``float(num_str)``. This can be used to use another datatype or parser
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for JSON floats (e.g. :class:`decimal.Decimal`).
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*parse_int*, if specified, will be called with the string of every
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JSON int to be decoded. By default, this is equivalent to
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``int(num_str)``. This can be used to use another datatype or parser
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for JSON integers (e.g. :class:`float`).
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*parse_constant*, if specified, will be called with one of the
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following strings: ``'-Infinity'``, ``'Infinity'``, ``'NaN'``. This
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can be used to raise an exception if invalid JSON numbers are
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encountered.
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*strict* controls the parser's behavior when it encounters an
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invalid control character in a string. The default setting of
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``True`` means that unescaped control characters are parse errors, if
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``False`` then control characters will be allowed in strings.
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"""
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if encoding is None:
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encoding = DEFAULT_ENCODING
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self.encoding = encoding
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self.object_hook = object_hook
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self.object_pairs_hook = object_pairs_hook
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self.parse_float = parse_float or float
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self.parse_int = parse_int or int
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self.parse_constant = parse_constant or _CONSTANTS.__getitem__
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self.strict = strict
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self.parse_object = JSONObject
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self.parse_array = JSONArray
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self.parse_string = scanstring
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self.memo = {}
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self.scan_once = make_scanner(self)
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def decode(self, s, _w=WHITESPACE.match, _PY3=PY3):
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"""Return the Python representation of ``s`` (a ``str`` or ``unicode``
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instance containing a JSON document)
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"""
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if _PY3 and isinstance(s, binary_type):
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s = s.decode(self.encoding)
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obj, end = self.raw_decode(s)
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end = _w(s, end).end()
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if end != len(s):
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raise JSONDecodeError("Extra data", s, end, len(s))
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return obj
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def raw_decode(self, s, idx=0, _w=WHITESPACE.match, _PY3=PY3):
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"""Decode a JSON document from ``s`` (a ``str`` or ``unicode``
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beginning with a JSON document) and return a 2-tuple of the Python
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representation and the index in ``s`` where the document ended.
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Optionally, ``idx`` can be used to specify an offset in ``s`` where
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the JSON document begins.
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This can be used to decode a JSON document from a string that may
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have extraneous data at the end.
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"""
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if idx < 0:
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# Ensure that raw_decode bails on negative indexes, the regex
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# would otherwise mask this behavior. #98
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raise JSONDecodeError('Expecting value', s, idx)
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if _PY3 and not isinstance(s, text_type):
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raise TypeError("Input string must be text, not bytes")
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# strip UTF-8 bom
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if len(s) > idx:
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ord0 = ord(s[idx])
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if ord0 == 0xfeff:
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idx += 1
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elif ord0 == 0xef and s[idx:idx + 3] == '\xef\xbb\xbf':
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idx += 3
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return self.scan_once(s, idx=_w(s, idx).end())
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