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executable file 278 lines (247 sloc) 9.105 kB
"""
Implementation of JSONDecoder
"""
import re
from scanner import Scanner, pattern
FLAGS = re.VERBOSE | re.MULTILINE | re.DOTALL
def _floatconstants():
import struct
import sys
_BYTES = '7FF80000000000007FF0000000000000'.decode('hex')
if sys.byteorder != 'big':
# NOTE(kgibbs): These lines must be added to make this file work under
# Python 2.2, which is commonly used at Google.
bytes_list = list(_BYTES)
bytes_first_half = bytes_list[:8]; bytes_first_half.reverse()
bytes_second_half = bytes_list[8:]; bytes_second_half.reverse()
_BYTES = "".join(bytes_first_half + bytes_second_half)
# NOTE(kgibbs): End changes.
nan, inf = struct.unpack('dd', _BYTES)
return nan, inf, -inf
NaN, PosInf, NegInf = _floatconstants()
def linecol(doc, pos):
lineno = doc.count('\n', 0, pos) + 1
if lineno == 1:
colno = pos
else:
colno = pos - doc.rindex('\n', 0, pos)
return lineno, colno
def errmsg(msg, doc, pos, end=None):
lineno, colno = linecol(doc, pos)
if end is None:
return '%s: line %d column %d (char %d)' % (msg, lineno, colno, pos)
endlineno, endcolno = linecol(doc, end)
return '%s: line %d column %d - line %d column %d (char %d - %d)' % (
msg, lineno, colno, endlineno, endcolno, pos, end)
_CONSTANTS = {
'-Infinity': NegInf,
'Infinity': PosInf,
'NaN': NaN,
'true': True,
'false': False,
'null': None,
}
def JSONConstant(match, context, c=_CONSTANTS):
return c[match.group(0)], None
pattern('(-?Infinity|NaN|true|false|null)')(JSONConstant)
def JSONNumber(match, context):
match = JSONNumber.regex.match(match.string, *match.span())
integer, frac, exp = match.groups()
if frac or exp:
res = float(integer + (frac or '') + (exp or ''))
else:
res = int(integer)
return res, None
pattern(r'(-?(?:0|[1-9]\d*))(\.\d+)?([eE][-+]?\d+)?')(JSONNumber)
STRINGCHUNK = re.compile(r'(.*?)(["\\])', FLAGS)
BACKSLASH = {
'"': u'"', '\\': u'\\', '/': u'/',
'b': u'\b', 'f': u'\f', 'n': u'\n', 'r': u'\r', 't': u'\t',
}
DEFAULT_ENCODING = "utf-8"
def scanstring(s, end, encoding=None, _b=BACKSLASH, _m=STRINGCHUNK.match):
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 ValueError(
errmsg("Unterminated string starting at", s, begin))
end = chunk.end()
content, terminator = chunk.groups()
if content:
if not isinstance(content, unicode):
content = unicode(content, encoding)
_append(content)
if terminator == '"':
break
try:
esc = s[end]
except IndexError:
raise ValueError(
errmsg("Unterminated string starting at", s, begin))
if esc != 'u':
try:
m = _b[esc]
except KeyError:
raise ValueError(
errmsg("Invalid \\escape: %r" % (esc,), s, end))
end += 1
else:
esc = s[end + 1:end + 5]
try:
m = unichr(int(esc, 16))
if len(esc) != 4 or not esc.isalnum():
raise ValueError
except ValueError:
raise ValueError(errmsg("Invalid \\uXXXX escape", s, end))
end += 5
_append(m)
return u''.join(chunks), end
def JSONString(match, context):
encoding = getattr(context, 'encoding', None)
return scanstring(match.string, match.end(), encoding)
pattern(r'"')(JSONString)
WHITESPACE = re.compile(r'\s*', FLAGS)
def JSONObject(match, context, _w=WHITESPACE.match):
pairs = {}
s = match.string
end = _w(s, match.end()).end()
nextchar = s[end:end + 1]
# trivial empty object
if nextchar == '}':
return pairs, end + 1
if nextchar != '"':
raise ValueError(errmsg("Expecting property name", s, end))
end += 1
encoding = getattr(context, 'encoding', None)
while True:
key, end = scanstring(s, end, encoding)
end = _w(s, end).end()
if s[end:end + 1] != ':':
raise ValueError(errmsg("Expecting : delimiter", s, end))
end = _w(s, end + 1).end()
try:
value, end = JSONScanner.iterscan(s, idx=end).next()
except StopIteration:
raise ValueError(errmsg("Expecting object", s, end))
pairs[key] = value
end = _w(s, end).end()
nextchar = s[end:end + 1]
end += 1
if nextchar == '}':
break
if nextchar != ',':
raise ValueError(errmsg("Expecting , delimiter", s, end - 1))
end = _w(s, end).end()
nextchar = s[end:end + 1]
end += 1
if nextchar != '"':
raise ValueError(errmsg("Expecting property name", s, end - 1))
object_hook = getattr(context, 'object_hook', None)
if object_hook is not None:
pairs = object_hook(pairs)
return pairs, end
pattern(r'{')(JSONObject)
def JSONArray(match, context, _w=WHITESPACE.match):
values = []
s = match.string
end = _w(s, match.end()).end()
# look-ahead for trivial empty array
nextchar = s[end:end + 1]
if nextchar == ']':
return values, end + 1
while True:
try:
value, end = JSONScanner.iterscan(s, idx=end).next()
except StopIteration:
raise ValueError(errmsg("Expecting object", s, end))
values.append(value)
end = _w(s, end).end()
nextchar = s[end:end + 1]
end += 1
if nextchar == ']':
break
if nextchar != ',':
raise ValueError(errmsg("Expecting , delimiter", s, end))
end = _w(s, end).end()
return values, end
pattern(r'\[')(JSONArray)
ANYTHING = [
JSONObject,
JSONArray,
JSONString,
JSONConstant,
JSONNumber,
]
JSONScanner = Scanner(ANYTHING)
class JSONDecoder(object):
"""
Simple JSON <http://json.org> decoder
Performs the following translations in decoding:
+---------------+-------------------+
| JSON | Python |
+===============+===================+
| object | dict |
+---------------+-------------------+
| array | list |
+---------------+-------------------+
| string | unicode |
+---------------+-------------------+
| number (int) | int, long |
+---------------+-------------------+
| number (real) | float |
+---------------+-------------------+
| true | True |
+---------------+-------------------+
| false | False |
+---------------+-------------------+
| null | None |
+---------------+-------------------+
It also understands ``NaN``, ``Infinity``, and ``-Infinity`` as
their corresponding ``float`` values, which is outside the JSON spec.
"""
_scanner = Scanner(ANYTHING)
__all__ = ['__init__', 'decode', 'raw_decode']
def __init__(self, encoding=None, object_hook=None):
"""
``encoding`` determines the encoding used to interpret any ``str``
objects decoded by this instance (utf-8 by default). It has no
effect when decoding ``unicode`` objects.
Note that currently only encodings that are a superset of ASCII work,
strings of other encodings should be passed in as ``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 ``dict``. This can be used to provide custom
deserializations (e.g. to support JSON-RPC class hinting).
"""
self.encoding = encoding
self.object_hook = object_hook
def decode(self, s, _w=WHITESPACE.match):
"""
Return the Python representation of ``s`` (a ``str`` or ``unicode``
instance containing a JSON document)
"""
obj, end = self.raw_decode(s, idx=_w(s, 0).end())
end = _w(s, end).end()
if end != len(s):
raise ValueError(errmsg("Extra data", s, end, len(s)))
return obj
def raw_decode(self, s, **kw):
"""
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.
This can be used to decode a JSON document from a string that may
have extraneous data at the end.
"""
kw.setdefault('context', self)
try:
obj, end = self._scanner.iterscan(s, **kw).next()
except StopIteration:
raise ValueError("No JSON object could be decoded")
return obj, end
__all__ = ['JSONDecoder']
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