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1"""
2Implementation of JSONDecoder
3"""
4import re
5
6from scanner import Scanner, pattern
7
8FLAGS = re.VERBOSE | re.MULTILINE | re.DOTALL
9
10def _floatconstants():
11    import struct
12    import sys
13    _BYTES = '7FF80000000000007FF0000000000000'.decode('hex')
14    if sys.byteorder != 'big':
15        _BYTES = _BYTES[:8][::-1] + _BYTES[8:][::-1]
16    nan, inf = struct.unpack('dd', _BYTES)
17    return nan, inf, -inf
18
19NaN, PosInf, NegInf = _floatconstants()
20
21def linecol(doc, pos):
22    lineno = doc.count('\n', 0, pos) + 1
23    if lineno == 1:
24        colno = pos
25    else:
26        colno = pos - doc.rindex('\n', 0, pos)
27    return lineno, colno
28
29def errmsg(msg, doc, pos, end=None):
30    lineno, colno = linecol(doc, pos)
31    if end is None:
32        return '%s: line %d column %d (char %d)' % (msg, lineno, colno, pos)
33    endlineno, endcolno = linecol(doc, end)
34    return '%s: line %d column %d - line %d column %d (char %d - %d)' % (
35        msg, lineno, colno, endlineno, endcolno, pos, end)
36
37_CONSTANTS = {
38    '-Infinity': NegInf,
39    'Infinity': PosInf,
40    'NaN': NaN,
41    'true': True,
42    'false': False,
43    'null': None,
44}
45
46def JSONConstant(match, context, c=_CONSTANTS):
47    return c[match.group(0)], None
48pattern('(-?Infinity|NaN|true|false|null)')(JSONConstant)
49
50def JSONNumber(match, context):
51    match = JSONNumber.regex.match(match.string, *match.span())
52    integer, frac, exp = match.groups()
53    if frac or exp:
54        res = float(integer + (frac or '') + (exp or ''))
55    else:
56        res = int(integer)
57    return res, None
58pattern(r'(-?(?:0|[1-9]\d*))(\.\d+)?([eE][-+]?\d+)?')(JSONNumber)
59
60STRINGCHUNK = re.compile(r'(.*?)(["\\])', FLAGS)
61BACKSLASH = {
62    '"': u'"', '\\': u'\\', '/': u'/',
63    'b': u'\b', 'f': u'\f', 'n': u'\n', 'r': u'\r', 't': u'\t',
64}
65
66DEFAULT_ENCODING = "utf-8"
67
68def scanstring(s, end, encoding=None, _b=BACKSLASH, _m=STRINGCHUNK.match):
69    if encoding is None:
70        encoding = DEFAULT_ENCODING
71    chunks = []
72    _append = chunks.append
73    begin = end - 1
74    while 1:
75        chunk = _m(s, end)
76        if chunk is None:
77            raise ValueError(
78                errmsg("Unterminated string starting at", s, begin))
79        end = chunk.end()
80        content, terminator = chunk.groups()
81        if content:
82            if not isinstance(content, unicode):
83                content = unicode(content, encoding)
84            _append(content)
85        if terminator == '"':
86            break
87        try:
88            esc = s[end]
89        except IndexError:
90            raise ValueError(
91                errmsg("Unterminated string starting at", s, begin))
92        if esc != 'u':
93            try:
94                m = _b[esc]
95            except KeyError:
96                raise ValueError(
97                    errmsg("Invalid \\escape: %r" % (esc,), s, end))
98            end += 1
99        else:
100            esc = s[end + 1:end + 5]
101            try:
102                m = unichr(int(esc, 16))
103                if len(esc) != 4 or not esc.isalnum():
104                    raise ValueError
105            except ValueError:
106                raise ValueError(errmsg("Invalid \\uXXXX escape", s, end))
107            end += 5
108        _append(m)
109    return u''.join(chunks), end
110
111def JSONString(match, context):
112    encoding = getattr(context, 'encoding', None)
113    return scanstring(match.string, match.end(), encoding)
114pattern(r'"')(JSONString)
115
116WHITESPACE = re.compile(r'\s*', FLAGS)
117
118def JSONObject(match, context, _w=WHITESPACE.match):
119    pairs = {}
120    s = match.string
121    end = _w(s, match.end()).end()
122    nextchar = s[end:end + 1]
123    # trivial empty object
124    if nextchar == '}':
125        return pairs, end + 1
126    if nextchar != '"':
127        raise ValueError(errmsg("Expecting property name", s, end))
128    end += 1
129    encoding = getattr(context, 'encoding', None)
130    iterscan = JSONScanner.iterscan
131    while True:
132        key, end = scanstring(s, end, encoding)
133        end = _w(s, end).end()
134        if s[end:end + 1] != ':':
135            raise ValueError(errmsg("Expecting : delimiter", s, end))
136        end = _w(s, end + 1).end()
137        try:
138            value, end = iterscan(s, idx=end, context=context).next()
139        except StopIteration:
140            raise ValueError(errmsg("Expecting object", s, end))
141        pairs[key] = value
142        end = _w(s, end).end()
143        nextchar = s[end:end + 1]
144        end += 1
145        if nextchar == '}':
146            break
147        if nextchar != ',':
148            raise ValueError(errmsg("Expecting , delimiter", s, end - 1))
149        end = _w(s, end).end()
150        nextchar = s[end:end + 1]
151        end += 1
152        if nextchar != '"':
153            raise ValueError(errmsg("Expecting property name", s, end - 1))
154    object_hook = getattr(context, 'object_hook', None)
155    if object_hook is not None:
156        pairs = object_hook(pairs)
157    return pairs, end
158pattern(r'{')(JSONObject)
159
160def JSONArray(match, context, _w=WHITESPACE.match):
161    values = []
162    s = match.string
163    end = _w(s, match.end()).end()
164    # look-ahead for trivial empty array
165    nextchar = s[end:end + 1]
166    if nextchar == ']':
167        return values, end + 1
168    iterscan = JSONScanner.iterscan
169    while True:
170        try:
171            value, end = iterscan(s, idx=end, context=context).next()
172        except StopIteration:
173            raise ValueError(errmsg("Expecting object", s, end))
174        values.append(value)
175        end = _w(s, end).end()
176        nextchar = s[end:end + 1]
177        end += 1
178        if nextchar == ']':
179            break
180        if nextchar != ',':
181            raise ValueError(errmsg("Expecting , delimiter", s, end))
182        end = _w(s, end).end()
183    return values, end
184pattern(r'\[')(JSONArray)
185
186ANYTHING = [
187    JSONObject,
188    JSONArray,
189    JSONString,
190    JSONConstant,
191    JSONNumber,
192]
193
194JSONScanner = Scanner(ANYTHING)
195
196class JSONDecoder(object):
197    """
198    Simple JSON <http://json.org> decoder
199
200    Performs the following translations in decoding:
201
202    +---------------+-------------------+
203    | JSON          | Python            |
204    +===============+===================+
205    | object        | dict              |
206    +---------------+-------------------+
207    | array         | list              |
208    +---------------+-------------------+
209    | string        | unicode           |
210    +---------------+-------------------+
211    | number (int)  | int, long         |
212    +---------------+-------------------+
213    | number (real) | float             |
214    +---------------+-------------------+
215    | true          | True              |
216    +---------------+-------------------+
217    | false         | False             |
218    +---------------+-------------------+
219    | null          | None              |
220    +---------------+-------------------+
221
222    It also understands ``NaN``, ``Infinity``, and ``-Infinity`` as
223    their corresponding ``float`` values, which is outside the JSON spec.
224    """
225
226    _scanner = Scanner(ANYTHING)
227    __all__ = ['__init__', 'decode', 'raw_decode']
228
229    def __init__(self, encoding=None, object_hook=None):
230        """
231        ``encoding`` determines the encoding used to interpret any ``str``
232        objects decoded by this instance (utf-8 by default).  It has no
233        effect when decoding ``unicode`` objects.
234
235        Note that currently only encodings that are a superset of ASCII work,
236        strings of other encodings should be passed in as ``unicode``.
237
238        ``object_hook``, if specified, will be called with the result
239        of every JSON object decoded and its return value will be used in
240        place of the given ``dict``.  This can be used to provide custom
241        deserializations (e.g. to support JSON-RPC class hinting).
242        """
243        self.encoding = encoding
244        self.object_hook = object_hook
245
246    def decode(self, s, _w=WHITESPACE.match):
247        """
248        Return the Python representation of ``s`` (a ``str`` or ``unicode``
249        instance containing a JSON document)
250        """
251        obj, end = self.raw_decode(s, idx=_w(s, 0).end())
252        end = _w(s, end).end()
253        if end != len(s):
254            raise ValueError(errmsg("Extra data", s, end, len(s)))
255        return obj
256
257    def raw_decode(self, s, **kw):
258        """
259        Decode a JSON document from ``s`` (a ``str`` or ``unicode`` beginning
260        with a JSON document) and return a 2-tuple of the Python
261        representation and the index in ``s`` where the document ended.
262
263        This can be used to decode a JSON document from a string that may
264        have extraneous data at the end.
265        """
266        kw.setdefault('context', self)
267        try:
268            obj, end = self._scanner.iterscan(s, **kw).next()
269        except StopIteration:
270            raise ValueError("No JSON object could be decoded")
271        return obj, end
272
273__all__ = ['JSONDecoder']
274