"""Implementation of JSONDecoder """ from __future__ import absolute_import import re import sys import struct from .compat import PY3, unichr from .scanner import make_scanner, JSONDecodeError def _import_c_scanstring(): try: from ._speedups import scanstring return scanstring except ImportError: return None c_scanstring = _import_c_scanstring() # NOTE (3.1.0): JSONDecodeError may still be imported from this module for # compatibility, but it was never in the __all__ __all__ = ['JSONDecoder'] FLAGS = re.VERBOSE | re.MULTILINE | re.DOTALL def _floatconstants(): if sys.version_info < (2, 6): _BYTES = '7FF80000000000007FF0000000000000'.decode('hex') nan, inf = struct.unpack('>dd', _BYTES) else: nan = float('nan') inf = float('inf') return nan, inf, -inf NaN, PosInf, NegInf = _floatconstants() _CONSTANTS = { '-Infinity': NegInf, 'Infinity': PosInf, 'NaN': NaN, } STRINGCHUNK = re.compile(r'(.*?)(["\\\x00-\x1f])', FLAGS) BACKSLASH = { '"': u'"', '\\': u'\\', '/': u'/', 'b': u'\b', 'f': u'\f', 'n': u'\n', 'r': u'\r', 't': u'\t', } DEFAULT_ENCODING = "utf-8" if hasattr(sys, 'get_int_max_str_digits'): bounded_int = int else: def bounded_int(s, INT_MAX_STR_DIGITS=4300): """Backport of the integer string length conversion limitation https://docs.python.org/3/library/stdtypes.html#int-max-str-digits """ if len(s) > INT_MAX_STR_DIGITS: raise ValueError("Exceeds the limit (%s) for integer string conversion: value has %s digits" % (INT_MAX_STR_DIGITS, len(s))) return int(s) def scan_four_digit_hex(s, end, _m=re.compile(r'^[0-9a-fA-F]{4}$').match): """Scan a four digit hex number from s[end:end + 4] """ msg = "Invalid \\uXXXX escape sequence" esc = s[end:end + 4] if not _m(esc): raise JSONDecodeError(msg, s, end - 2) try: return int(esc, 16), end + 4 except ValueError: raise JSONDecodeError(msg, s, end - 2) def py_scanstring(s, end, encoding=None, strict=True, _b=BACKSLASH, _m=STRINGCHUNK.match, _join=u''.join, _PY3=PY3, _maxunicode=sys.maxunicode, _scan_four_digit_hex=scan_four_digit_hex): """Scan the string s for a JSON string. End is the index of the character in s after the quote that started the JSON string. Unescapes all valid JSON string escape sequences and raises ValueError on attempt to decode an invalid string. If strict is False then literal control characters are allowed in the string. Returns a tuple of the decoded string and the index of the character in s after the end quote.""" if encoding is None: encoding = DEFAULT_ENCODING chunks = [] _append = chunks.append begin = end - 1 while 1: chunk = _m(s, end) if chunk is None: raise JSONDecodeError( "Unterminated string starting at", s, begin) prev_end = end end = chunk.end() content, terminator = chunk.groups() # Content is contains zero or more unescaped string characters if content: if not _PY3 and not isinstance(content, unicode): content = unicode(content, encoding) _append(content) # Terminator is the end of string, a literal control character, # or a backslash denoting that an escape sequence follows if terminator == '"': break elif terminator != '\\': if strict: msg = "Invalid control character %r at" raise JSONDecodeError(msg, s, prev_end) else: _append(terminator) continue try: esc = s[end] except IndexError: raise JSONDecodeError( "Unterminated string starting at", s, begin) # If not a unicode escape sequence, must be in the lookup table if esc != 'u': try: char = _b[esc] except KeyError: msg = "Invalid \\X escape sequence %r" raise JSONDecodeError(msg, s, end) end += 1 else: # Unicode escape sequence uni, end = _scan_four_digit_hex(s, end + 1) # Check for surrogate pair on UCS-4 systems # Note that this will join high/low surrogate pairs # but will also pass unpaired surrogates through if (_maxunicode > 65535 and uni & 0xfc00 == 0xd800 and s[end:end + 2] == '\\u'): uni2, end2 = _scan_four_digit_hex(s, end + 2) if uni2 & 0xfc00 == 0xdc00: uni = 0x10000 + (((uni - 0xd800) << 10) | (uni2 - 0xdc00)) end = end2 char = unichr(uni) # Append the unescaped character _append(char) return _join(chunks), end # Use speedup if available scanstring = c_scanstring or py_scanstring WHITESPACE = re.compile(r'[ \t\n\r]*', FLAGS) WHITESPACE_STR = ' \t\n\r' def JSONObject(state, encoding, strict, scan_once, object_hook, object_pairs_hook, memo=None, _w=WHITESPACE.match, _ws=WHITESPACE_STR): (s, end) = state # Backwards compatibility if memo is None: memo = {} memo_get = memo.setdefault pairs = [] # Use a slice to prevent IndexError from being raised, the following # check will raise a more specific ValueError if the string is empty nextchar = s[end:end + 1] # Normally we expect nextchar == '"' if nextchar != '"': if nextchar in _ws: end = _w(s, end).end() nextchar = s[end:end + 1] # Trivial empty object if nextchar == '}': if object_pairs_hook is not None: result = object_pairs_hook(pairs) return result, end + 1 pairs = {} if object_hook is not None: pairs = object_hook(pairs) return pairs, end + 1 elif nextchar != '"': raise JSONDecodeError( "Expecting property name enclosed in double quotes or '}'", s, end) end += 1 while True: key, end = scanstring(s, end, encoding, strict) key = memo_get(key, key) # To skip some function call overhead we optimize the fast paths where # the JSON key separator is ": " or just ":". if s[end:end + 1] != ':': end = _w(s, end).end() if s[end:end + 1] != ':': raise JSONDecodeError("Expecting ':' delimiter", s, end) end += 1 try: if s[end] in _ws: end += 1 if s[end] in _ws: end = _w(s, end + 1).end() except IndexError: pass value, end = scan_once(s, end) pairs.append((key, value)) try: nextchar = s[end] if nextchar in _ws: end = _w(s, end + 1).end() nextchar = s[end] except IndexError: nextchar = '' end += 1 if nextchar == '}': break elif nextchar != ',': raise JSONDecodeError("Expecting ',' delimiter or '}'", s, end - 1) try: nextchar = s[end] if nextchar in _ws: end += 1 nextchar = s[end] if nextchar in _ws: end = _w(s, end + 1).end() nextchar = s[end] except IndexError: nextchar = '' end += 1 if nextchar != '"': raise JSONDecodeError( "Expecting property name enclosed in double quotes", s, end - 1) if object_pairs_hook is not None: result = object_pairs_hook(pairs) return result, end pairs = dict(pairs) if object_hook is not None: pairs = object_hook(pairs) return pairs, end def JSONArray(state, scan_once, _w=WHITESPACE.match, _ws=WHITESPACE_STR): (s, end) = state values = [] nextchar = s[end:end + 1] if nextchar in _ws: end = _w(s, end + 1).end() nextchar = s[end:end + 1] # Look-ahead for trivial empty array if nextchar == ']': return values, end + 1 elif nextchar == '': raise JSONDecodeError("Expecting value or ']'", s, end) _append = values.append while True: value, end = scan_once(s, end) _append(value) nextchar = s[end:end + 1] if nextchar in _ws: end = _w(s, end + 1).end() nextchar = s[end:end + 1] end += 1 if nextchar == ']': break elif nextchar != ',': raise JSONDecodeError("Expecting ',' delimiter or ']'", s, end - 1) try: if s[end] in _ws: end += 1 if s[end] in _ws: end = _w(s, end + 1).end() except IndexError: pass return values, end class JSONDecoder(object): """Simple JSON decoder Performs the following translations in decoding by default: +---------------+-------------------+ | JSON | Python | +===============+===================+ | object | dict | +---------------+-------------------+ | array | list | +---------------+-------------------+ | string | str, unicode | +---------------+-------------------+ | number (int) | int, long | +---------------+-------------------+ | number (real) | float | +---------------+-------------------+ | true | True | +---------------+-------------------+ | false | False | +---------------+-------------------+ | null | None | +---------------+-------------------+ When allow_nan=True, it also understands ``NaN``, ``Infinity``, and ``-Infinity`` as their corresponding ``float`` values, which is outside the JSON spec. """ def __init__(self, encoding=None, object_hook=None, parse_float=None, parse_int=None, parse_constant=None, strict=True, object_pairs_hook=None, allow_nan=False): """ *encoding* determines the encoding used to interpret any :class:`str` objects decoded by this instance (``'utf-8'`` by default). It has no effect when decoding :class:`unicode` objects. Note that currently only encodings that are a superset of ASCII work, strings of other encodings should be passed in as :class:`unicode`. *object_hook*, if specified, will be called with the result of every JSON object decoded and its return value will be used in place of the given :class:`dict`. This can be used to provide custom deserializations (e.g. to support JSON-RPC class hinting). *object_pairs_hook* is an optional function that will be called with the result of any object literal decode with an ordered list of pairs. The return value of *object_pairs_hook* will be used instead of the :class:`dict`. This feature can be used to implement custom decoders that rely on the order that the key and value pairs are decoded (for example, :func:`collections.OrderedDict` will remember the order of insertion). If *object_hook* is also defined, the *object_pairs_hook* takes priority. *parse_float*, if specified, will be called with the string of every JSON float to be decoded. By default, this is equivalent to ``float(num_str)``. This can be used to use another datatype or parser for JSON floats (e.g. :class:`decimal.Decimal`). *parse_int*, if specified, will be called with the string of every JSON int to be decoded. By default, this is equivalent to ``int(num_str)``. This can be used to use another datatype or parser for JSON integers (e.g. :class:`float`). *allow_nan*, if True (default false), will allow the parser to accept the non-standard floats ``NaN``, ``Infinity``, and ``-Infinity``. *parse_constant*, if specified, will be called with one of the following strings: ``'-Infinity'``, ``'Infinity'``, ``'NaN'``. It is not recommended to use this feature, as it is rare to parse non-compliant JSON containing these values. *strict* controls the parser's behavior when it encounters an invalid control character in a string. The default setting of ``True`` means that unescaped control characters are parse errors, if ``False`` then control characters will be allowed in strings. """ if encoding is None: encoding = DEFAULT_ENCODING self.encoding = encoding self.object_hook = object_hook self.object_pairs_hook = object_pairs_hook self.parse_float = parse_float or float self.parse_int = parse_int or bounded_int self.parse_constant = parse_constant or (allow_nan and _CONSTANTS.__getitem__ or None) self.strict = strict self.parse_object = JSONObject self.parse_array = JSONArray self.parse_string = scanstring self.memo = {} self.scan_once = make_scanner(self) def decode(self, s, _w=WHITESPACE.match, _PY3=PY3): """Return the Python representation of ``s`` (a ``str`` or ``unicode`` instance containing a JSON document) """ if _PY3 and isinstance(s, bytes): s = str(s, self.encoding) obj, end = self.raw_decode(s) end = _w(s, end).end() if end != len(s): raise JSONDecodeError("Extra data", s, end, len(s)) return obj def raw_decode(self, s, idx=0, _w=WHITESPACE.match, _PY3=PY3): """Decode a JSON document from ``s`` (a ``str`` or ``unicode`` beginning with a JSON document) and return a 2-tuple of the Python representation and the index in ``s`` where the document ended. Optionally, ``idx`` can be used to specify an offset in ``s`` where the JSON document begins. This can be used to decode a JSON document from a string that may have extraneous data at the end. """ if idx < 0: # Ensure that raw_decode bails on negative indexes, the regex # would otherwise mask this behavior. #98 raise JSONDecodeError('Expecting value', s, idx) if _PY3 and not isinstance(s, str): raise TypeError("Input string must be text, not bytes") # strip UTF-8 bom if len(s) > idx: ord0 = ord(s[idx]) if ord0 == 0xfeff: idx += 1 elif ord0 == 0xef and s[idx:idx + 3] == '\xef\xbb\xbf': idx += 3 return self.scan_once(s, idx=_w(s, idx).end())