import the decoder portion of simplejson-1.7.1 too

src/allmydata/util/json_decoder.py

@@ -0,0 +1,300 @@
+"""
+Implementation of JSONDecoder
+"""
+
+# this is simplejson/decoder.py, from Bob Ippolito's simplejson-1.7.1
+#  (http://undefined.org/python/#simplejson)
+# which is distributed under the BSD license as copied here:
+#
+# Copyright (c) 2006 Bob Ippolito
+# 
+# Permission is hereby granted, free of charge, to any person obtaining a copy of
+# this software and associated documentation files (the "Software"), to deal in
+# the Software without restriction, including without limitation the rights to
+# use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+# of the Software, and to permit persons to whom the Software is furnished to do
+# so, subject to the following conditions:
+# 
+# The above copyright notice and this permission notice shall be included in all
+# copies or substantial portions of the Software.
+# 
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+
+# we extract just the decoder here because that's all we need.
+
+import re
+
+from simplejson.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':
+        _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):
+    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)
+    iterscan = JSONScanner.iterscan
+    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 = iterscan(s, idx=end, context=context).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
+    iterscan = JSONScanner.iterscan
+    while True:
+        try:
+            value, end = iterscan(s, idx=end, context=context).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']