summaryrefslogtreecommitdiffstats
path: root/Lib/json/decoder.py
blob: 44635a00e74f61f9f49f24d1027522e58ae5285e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
"""Implementation of JSONDecoder
"""
import re
import sys
import struct

from json.scanner import make_scanner
try:
    from _json import scanstring as c_scanstring
except ImportError:
    c_scanstring = None

__all__ = ['JSONDecoder']

FLAGS = re.VERBOSE | re.MULTILINE | re.DOTALL

def _floatconstants():
    _BYTES = '7FF80000000000007FF0000000000000'.decode('hex')
    if sys.byteorder != 'big':
        _BYTES = _BYTES[:8][::-1] + _BYTES[8:][::-1]
    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):
    # Note that this function is called from _json
    lineno, colno = linecol(doc, pos)
    if end is None:
        fmt = '{0}: line {1} column {2} (char {3})'
        return fmt.format(msg, lineno, colno, pos)
        #fmt = '%s: line %d column %d (char %d)'
        #return fmt % (msg, lineno, colno, pos)
    endlineno, endcolno = linecol(doc, end)
    fmt = '{0}: line {1} column {2} - line {3} column {4} (char {5} - {6})'
    return fmt.format(msg, lineno, colno, endlineno, endcolno, pos, end)
    #fmt = '%s: line %d column %d - line %d column %d (char %d - %d)'
    #return fmt % (msg, lineno, colno, endlineno, endcolno, pos, end)


_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"

def py_scanstring(s, end, encoding=None, strict=True,
        _b=BACKSLASH, _m=STRINGCHUNK.match):
    """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 ValueError(
                errmsg("Unterminated string starting at", s, begin))
        end = chunk.end()
        content, terminator = chunk.groups()
        # Content is contains zero or more unescaped string characters
        if content:
            if 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" % (terminator,)
                msg = "Invalid control character {0!r} at".format(terminator)
                raise ValueError(errmsg(msg, s, end))
            else:
                _append(terminator)
                continue
        try:
            esc = s[end]
        except IndexError:
            raise ValueError(
                errmsg("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 \\escape: " + repr(esc)
                raise ValueError(errmsg(msg, s, end))
            end += 1
        else:
            # Unicode escape sequence
            esc = s[end + 1:end + 5]
            next_end = end + 5
            if len(esc) != 4:
                msg = "Invalid \\uXXXX escape"
                raise ValueError(errmsg(msg, s, end))
            uni = int(esc, 16)
            # Check for surrogate pair on UCS-4 systems
            if 0xd800 <= uni <= 0xdbff and sys.maxunicode > 65535:
                msg = "Invalid \\uXXXX\\uXXXX surrogate pair"
                if not s[end + 5:end + 7] == '\\u':
                    raise ValueError(errmsg(msg, s, end))
                esc2 = s[end + 7:end + 11]
                if len(esc2) != 4:
                    raise ValueError(errmsg(msg, s, end))
                uni2 = int(esc2, 16)
                uni = 0x10000 + (((uni - 0xd800) << 10) | (uni2 - 0xdc00))
                next_end += 6
            char = unichr(uni)
            end = next_end
        # Append the unescaped character
        _append(char)
    return u''.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((s, end), encoding, strict, scan_once, object_hook,
               object_pairs_hook, _w=WHITESPACE.match, _ws=WHITESPACE_STR):
    pairs = []
    pairs_append = pairs.append
    # 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 == '}':
            return pairs, end + 1
        elif nextchar != '"':
            raise ValueError(errmsg("Expecting property name", s, end))
    end += 1
    while True:
        key, end = scanstring(s, end, encoding, strict)

        # 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 ValueError(errmsg("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

        try:
            value, end = scan_once(s, end)
        except StopIteration:
            raise ValueError(errmsg("Expecting object", 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 ValueError(errmsg("Expecting , delimiter", 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 ValueError(errmsg("Expecting property name", 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((s, end), scan_once, _w=WHITESPACE.match, _ws=WHITESPACE_STR):
    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
    _append = values.append
    while True:
        try:
            value, end = scan_once(s, end)
        except StopIteration:
            raise ValueError(errmsg("Expecting object", 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 ValueError(errmsg("Expecting , delimiter", s, end))

        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 <http://json.org> decoder

    Performs the following translations in decoding by default:

    +---------------+-------------------+
    | 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.

    """

    def __init__(self, encoding=None, object_hook=None, parse_float=None,
            parse_int=None, parse_constant=None, strict=True,
            object_pairs_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).

        ``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. 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. float).

        ``parse_constant``, if specified, will be called with one of the
        following strings: -Infinity, Infinity, NaN.
        This can be used to raise an exception if invalid JSON numbers
        are encountered.

        """
        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 int
        self.parse_constant = parse_constant or _CONSTANTS.__getitem__
        self.strict = strict
        self.parse_object = JSONObject
        self.parse_array = JSONArray
        self.parse_string = scanstring
        self.scan_once = make_scanner(self)

    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, idx=0):
        """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.

        """
        try:
            obj, end = self.scan_once(s, idx)
        except StopIteration:
            raise ValueError("No JSON object could be decoded")
        return obj, end