Implementation of JSONEncoder

Json_encoder.py

"""Implementation of JSONEncoder
"""
from __future__ import absolute_import
import re
from operator import itemgetter
from decimal import Decimal
from .compat import u, unichr, binary_type, string_types, integer_types, PY3
def _import_speedups():
    try:
        from . import _speedups
        return _speedups.encode_basestring_ascii, _speedups.make_encoder
    except ImportError:
        return None, None
c_encode_basestring_ascii, c_make_encoder = _import_speedups()

from simplejson.decoder import PosInf

#ESCAPE = re.compile(ur'[\x00-\x1f\\"\b\f\n\r\t\u2028\u2029]')
# This is required because u() will mangle the string and ur'' isn't valid
# python3 syntax
ESCAPE = re.compile(u'[\\x00-\\x1f\\\\"\\b\\f\\n\\r\\t\u2028\u2029]')
ESCAPE_ASCII = re.compile(r'([\\"]|[^\ -~])')
HAS_UTF8 = re.compile(r'[\x80-\xff]')
ESCAPE_DCT = {
    '\\': '\\\\',
    '"': '\\"',
    '\b': '\\b',
    '\f': '\\f',
    '\n': '\\n',
    '\r': '\\r',
    '\t': '\\t',
}
for i in range(0x20):
    #ESCAPE_DCT.setdefault(chr(i), '\\u{0:04x}'.format(i))
    ESCAPE_DCT.setdefault(chr(i), '\\u%04x' % (i,))
for i in [0x2028, 0x2029]:
    ESCAPE_DCT.setdefault(unichr(i), '\\u%04x' % (i,))

FLOAT_REPR = repr

def encode_basestring(s, _PY3=PY3, _q=u('"')):
    """Return a JSON representation of a Python string

    """
    if _PY3:
        if isinstance(s, binary_type):
            s = s.decode('utf-8')
    else:
        if isinstance(s, str) and HAS_UTF8.search(s) is not None:
            s = s.decode('utf-8')
    def replace(match):
        return ESCAPE_DCT[match.group(0)]
    return _q + ESCAPE.sub(replace, s) + _q


def py_encode_basestring_ascii(s, _PY3=PY3):
    """Return an ASCII-only JSON representation of a Python string

    """
    if _PY3:
        if isinstance(s, binary_type):
            s = s.decode('utf-8')
    else:
        if isinstance(s, str) and HAS_UTF8.search(s) is not None:
            s = s.decode('utf-8')
    def replace(match):
        s = match.group(0)
        try:
            return ESCAPE_DCT[s]
        except KeyError:
            n = ord(s)
            if n < 0x10000:
                #return '\\u{0:04x}'.format(n)
                return '\\u%04x' % (n,)
            else:
                # surrogate pair
                n -= 0x10000
                s1 = 0xd800 | ((n >> 10) & 0x3ff)
                s2 = 0xdc00 | (n & 0x3ff)
                #return '\\u{0:04x}\\u{1:04x}'.format(s1, s2)
                return '\\u%04x\\u%04x' % (s1, s2)
    return '"' + str(ESCAPE_ASCII.sub(replace, s)) + '"'


encode_basestring_ascii = (
    c_encode_basestring_ascii or py_encode_basestring_ascii)

class JSONEncoder(object):
    """Extensible JSON <http://json.org> encoder for Python data structures.

    Supports the following objects and types by default:

    +-------------------+---------------+
    | Python            | JSON          |
    +===================+===============+
    | dict, namedtuple  | object        |
    +-------------------+---------------+
    | list, tuple       | array         |
    +-------------------+---------------+
    | str, unicode      | string        |
    +-------------------+---------------+
    | int, long, float  | number        |
    +-------------------+---------------+
    | True              | true          |
    +-------------------+---------------+
    | False             | false         |
    +-------------------+---------------+
    | None              | null          |
    +-------------------+---------------+

    To extend this to recognize other objects, subclass and implement a
    ``.default()`` method with another method that returns a serializable
    object for ``o`` if possible, otherwise it should call the superclass
    implementation (to raise ``TypeError``).

    """
    item_separator = ', '
    key_separator = ': '
    def __init__(self, skipkeys=False, ensure_ascii=True,
            check_circular=True, allow_nan=True, sort_keys=False,
            indent=None, separators=None, encoding='utf-8', default=None,
            use_decimal=True, namedtuple_as_object=True,
            tuple_as_array=True, bigint_as_string=False,
            item_sort_key=None):
        """Constructor for JSONEncoder, with sensible defaults.

        If skipkeys is false, then it is a TypeError to attempt
        encoding of keys that are not str, int, long, float or None.  If
        skipkeys is True, such items are simply skipped.

        If ensure_ascii is true, the output is guaranteed to be str
        objects with all incoming unicode characters escaped.  If
        ensure_ascii is false, the output will be unicode object.

        If check_circular is true, then lists, dicts, and custom encoded
        objects will be checked for circular references during encoding to
        prevent an infinite recursion (which would cause an OverflowError).
        Otherwise, no such check takes place.

        If allow_nan is true, then NaN, Infinity, and -Infinity will be
        encoded as such.  This behavior is not JSON specification compliant,
        but is consistent with most JavaScript based encoders and decoders.
        Otherwise, it will be a ValueError to encode such floats.

        If sort_keys is true, then the output of dictionaries will be
        sorted by key; this is useful for regression tests to ensure
        that JSON serializations can be compared on a day-to-day basis.

        If indent is a string, then JSON array elements and object members
        will be pretty-printed with a newline followed by that string repeated
        for each level of nesting. ``None`` (the default) selects the most compact
        representation without any newlines. For backwards compatibility with
        versions of simplejson earlier than 2.1.0, an integer is also accepted
        and is converted to a string with that many spaces.

        If specified, separators should be a (item_separator, key_separator)
        tuple.  The default is (', ', ': ').  To get the most compact JSON
        representation you should specify (',', ':') to eliminate whitespace.

        If specified, default is a function that gets called for objects
        that can't otherwise be serialized.  It should return a JSON encodable
        version of the object or raise a ``TypeError``.

        If encoding is not None, then all input strings will be
        transformed into unicode using that encoding prior to JSON-encoding.
        The default is UTF-8.

        If use_decimal is true (not the default), ``decimal.Decimal`` will
        be supported directly by the encoder. For the inverse, decode JSON
        with ``parse_float=decimal.Decimal``.

        If namedtuple_as_object is true (the default), objects with
        ``_asdict()`` methods will be encoded as JSON objects.

        If tuple_as_array is true (the default), tuple (and subclasses) will
        be encoded as JSON arrays.

        If bigint_as_string is true (not the default), ints 2**53 and higher
        or lower than -2**53 will be encoded as strings. This is to avoid the
        rounding that happens in Javascript otherwise.

        If specified, item_sort_key is a callable used to sort the items in
        each dictionary. This is useful if you want to sort items other than
        in alphabetical order by key.
        """

        self.skipkeys = skipkeys
        self.ensure_ascii = ensure_ascii
        self.check_circular = check_circular
        self.allow_nan = allow_nan
        self.sort_keys = sort_keys
        self.use_decimal = use_decimal
        self.namedtuple_as_object = namedtuple_as_object
        self.tuple_as_array = tuple_as_array
        self.bigint_as_string = bigint_as_string
        self.item_sort_key = item_sort_key
        if indent is not None and not isinstance(indent, string_types):
            indent = indent * ' '
        self.indent = indent
        if separators is not None:
            self.item_separator, self.key_separator = separators
        elif indent is not None:
            self.item_separator = ','
        if default is not None:
            self.default = default
        self.encoding = encoding

    def default(self, o):
        """Implement this method in a subclass such that it returns
        a serializable object for ``o``, or calls the base implementation
        (to raise a ``TypeError``).

        For example, to support arbitrary iterators, you could
        implement default like this::

            def default(self, o):
                try:
                    iterable = iter(o)
                except TypeError:
                    pass
                else:
                    return list(iterable)
                return JSONEncoder.default(self, o)

        """
        raise TypeError(repr(o) + " is not JSON serializable")

    def encode(self, o):
        """Return a JSON string representation of a Python data structure.

        >>> from simplejson import JSONEncoder
        >>> JSONEncoder().encode({"foo": ["bar", "baz"]})
        '{"foo": ["bar", "baz"]}'

        """
        # This is for extremely simple cases and benchmarks.
        if isinstance(o, binary_type):
            _encoding = self.encoding
            if (_encoding is not None and not (_encoding == 'utf-8')):
                o = o.decode(_encoding)
        if isinstance(o, string_types):
            if self.ensure_ascii:
                return encode_basestring_ascii(o)
            else:
                return encode_basestring(o)
        # This doesn't pass the iterator directly to ''.join() because the
        # exceptions aren't as detailed.  The list call should be roughly
        # equivalent to the PySequence_Fast that ''.join() would do.
        chunks = self.iterencode(o, _one_shot=True)
        if not isinstance(chunks, (list, tuple)):
            chunks = list(chunks)
        if self.ensure_ascii:
            return ''.join(chunks)
        else:
            return u''.join(chunks)

    def iterencode(self, o, _one_shot=False):
        """Encode the given object and yield each string
        representation as available.

        For example::

            for chunk in JSONEncoder().iterencode(bigobject):
                mysocket.write(chunk)

        """
        if self.check_circular:
            markers = {}
        else:
            markers = None
        if self.ensure_ascii:
            _encoder = encode_basestring_ascii
        else:
            _encoder = encode_basestring
        if self.encoding != 'utf-8':
            def _encoder(o, _orig_encoder=_encoder, _encoding=self.encoding):
                if isinstance(o, binary_type):
                    o = o.decode(_encoding)
                return _orig_encoder(o)

        def floatstr(o, allow_nan=self.allow_nan,
                _repr=FLOAT_REPR, _inf=PosInf, _neginf=-PosInf):
            # Check for specials. Note that this type of test is processor
            # and/or platform-specific, so do tests which don't depend on
            # the internals.

            if o != o:
                text = 'NaN'
            elif o == _inf:
                text = 'Infinity'
            elif o == _neginf:
                text = '-Infinity'
            else:
                return _repr(o)

            if not allow_nan:
                raise ValueError(
                    "Out of range float values are not JSON compliant: " +
                    repr(o))

            return text


        key_memo = {}
        if (_one_shot and c_make_encoder is not None
                and self.indent is None):
            _iterencode = c_make_encoder(
                markers, self.default, _encoder, self.indent,
                self.key_separator, self.item_separator, self.sort_keys,
                self.skipkeys, self.allow_nan, key_memo, self.use_decimal,
                self.namedtuple_as_object, self.tuple_as_array,
                self.bigint_as_string, self.item_sort_key,
                self.encoding,
                Decimal)
        else:
            _iterencode = _make_iterencode(
                markers, self.default, _encoder, self.indent, floatstr,
                self.key_separator, self.item_separator, self.sort_keys,
                self.skipkeys, _one_shot, self.use_decimal,
                self.namedtuple_as_object, self.tuple_as_array,
                self.bigint_as_string, self.item_sort_key,
                self.encoding,
                Decimal=Decimal)
        try:
            return _iterencode(o, 0)
        finally:
            key_memo.clear()


class JSONEncoderForHTML(JSONEncoder):
    """An encoder that produces JSON safe to embed in HTML.

    To embed JSON content in, say, a script tag on a web page, the
    characters &, < and > should be escaped. They cannot be escaped
    with the usual entities (e.g. &amp;) because they are not expanded
    within <script> tags.
    """

    def encode(self, o):
        # Override JSONEncoder.encode because it has hacks for
        # performance that make things more complicated.
        chunks = self.iterencode(o, True)
        if self.ensure_ascii:
            return ''.join(chunks)
        else:
            return u''.join(chunks)

    def iterencode(self, o, _one_shot=False):
        chunks = super(JSONEncoderForHTML, self).iterencode(o, _one_shot)
        for chunk in chunks:
            chunk = chunk.replace('&', '\\u0026')
            chunk = chunk.replace('<', '\\u003c')
            chunk = chunk.replace('>', '\\u003e')
            yield chunk


def _make_iterencode(markers, _default, _encoder, _indent, _floatstr,
        _key_separator, _item_separator, _sort_keys, _skipkeys, _one_shot,
        _use_decimal, _namedtuple_as_object, _tuple_as_array,
        _bigint_as_string, _item_sort_key, _encoding,
        ## HACK: hand-optimized bytecode; turn globals into locals
        _PY3=PY3,
        ValueError=ValueError,
        string_types=string_types,
        Decimal=Decimal,
        dict=dict,
        float=float,
        id=id,
        integer_types=integer_types,
        isinstance=isinstance,
        list=list,
        str=str,
        tuple=tuple,
    ):
    if _item_sort_key and not callable(_item_sort_key):
        raise TypeError("item_sort_key must be None or callable")
    elif _sort_keys and not _item_sort_key:
        _item_sort_key = itemgetter(0)

    def _iterencode_list(lst, _current_indent_level):
        if not lst:
            yield '[]'
            return
        if markers is not None:
            markerid = id(lst)
            if markerid in markers:
                raise ValueError("Circular reference detected")
            markers[markerid] = lst
        buf = '['
        if _indent is not None:
            _current_indent_level += 1
            newline_indent = '\n' + (_indent * _current_indent_level)
            separator = _item_separator + newline_indent
            buf += newline_indent
        else:
            newline_indent = None
            separator = _item_separator
        first = True
        for value in lst:
            if first:
                first = False
            else:
                buf = separator
            if (isinstance(value, string_types) or
                (_PY3 and isinstance(value, binary_type))):
                yield buf + _encoder(value)
            elif value is None:
                yield buf + 'null'
            elif value is True:
                yield buf + 'true'
            elif value is False:
                yield buf + 'false'
            elif isinstance(value, integer_types):
                yield ((buf + str(value))
                       if (not _bigint_as_string or
                           (-1 << 53) < value < (1 << 53))
                           else (buf + '"' + str(value) + '"'))
            elif isinstance(value, float):
                yield buf + _floatstr(value)
            elif _use_decimal and isinstance(value, Decimal):
                yield buf + str(value)
            else:
                yield buf
                if isinstance(value, list):
                    chunks = _iterencode_list(value, _current_indent_level)
                else:
                    _asdict = _namedtuple_as_object and getattr(value, '_asdict', None)
                    if _asdict and callable(_asdict):
                        chunks = _iterencode_dict(_asdict(),
                                                  _current_indent_level)
                    elif _tuple_as_array and isinstance(value, tuple):
                        chunks = _iterencode_list(value, _current_indent_level)
                    elif isinstance(value, dict):
                        chunks = _iterencode_dict(value, _current_indent_level)
                    else:
                        chunks = _iterencode(value, _current_indent_level)
                for chunk in chunks:
                    yield chunk
        if newline_indent is not None:
            _current_indent_level -= 1
            yield '\n' + (_indent * _current_indent_level)
        yield ']'
        if markers is not None:
            del markers[markerid]

    def _stringify_key(key):
        if isinstance(key, string_types): # pragma: no cover
            pass
        elif isinstance(key, binary_type):
            key = key.decode(_encoding)
        elif isinstance(key, float):
            key = _floatstr(key)
        elif key is True:
            key = 'true'
        elif key is False:
            key = 'false'
        elif key is None:
            key = 'null'
        elif isinstance(key, integer_types):
            key = str(key)
        elif _use_decimal and isinstance(key, Decimal):
            key = str(key)
        elif _skipkeys:
            key = None
        else:
            raise TypeError("key " + repr(key) + " is not a string")
        return key

    def _iterencode_dict(dct, _current_indent_level):
        if not dct:
            yield '{}'
            return
        if markers is not None:
            markerid = id(dct)
            if markerid in markers:
                raise ValueError("Circular reference detected")
            markers[markerid] = dct
        yield '{'
        if _indent is not None:
            _current_indent_level += 1
            newline_indent = '\n' + (_indent * _current_indent_level)
            item_separator = _item_separator + newline_indent
            yield newline_indent
        else:
            newline_indent = None
            item_separator = _item_separator
        first = True
        if _PY3:
            iteritems = dct.items()
        else:
            iteritems = dct.iteritems()
        if _item_sort_key:
            items = []
            for k, v in dct.items():
                if not isinstance(k, string_types):
                    k = _stringify_key(k)
                    if k is None:
                        continue
                items.append((k, v))
            items.sort(key=_item_sort_key)
        else:
            items = iteritems
        for key, value in items:
            if not (_item_sort_key or isinstance(key, string_types)):
                key = _stringify_key(key)
                if key is None:
                    # _skipkeys must be True
                    continue
            if first:
                first = False
            else:
                yield item_separator
            yield _encoder(key)
            yield _key_separator
            if (isinstance(value, string_types) or
                (_PY3 and isinstance(value, binary_type))):
                yield _encoder(value)
            elif value is None:
                yield 'null'
            elif value is True:
                yield 'true'
            elif value is False:
                yield 'false'
            elif isinstance(value, integer_types):
                yield (str(value)
                       if (not _bigint_as_string or
                           (-1 << 53) < value < (1 << 53))
                           else ('"' + str(value) + '"'))
            elif isinstance(value, float):
                yield _floatstr(value)
            elif _use_decimal and isinstance(value, Decimal):
                yield str(value)
            else:
                if isinstance(value, list):
                    chunks = _iterencode_list(value, _current_indent_level)
                else:
                    _asdict = _namedtuple_as_object and getattr(value, '_asdict', None)
                    if _asdict and callable(_asdict):
                        chunks = _iterencode_dict(_asdict(),
                                                  _current_indent_level)
                    elif _tuple_as_array and isinstance(value, tuple):
                        chunks = _iterencode_list(value, _current_indent_level)
                    elif isinstance(value, dict):
                        chunks = _iterencode_dict(value, _current_indent_level)
                    else:
                        chunks = _iterencode(value, _current_indent_level)
                for chunk in chunks:
                    yield chunk
        if newline_indent is not None:
            _current_indent_level -= 1
            yield '\n' + (_indent * _current_indent_level)
        yield '}'
        if markers is not None:
            del markers[markerid]

    def _iterencode(o, _current_indent_level):
        if (isinstance(o, string_types) or
            (_PY3 and isinstance(o, binary_type))):
            yield _encoder(o)
        elif o is None:
            yield 'null'
        elif o is True:
            yield 'true'
        elif o is False:
            yield 'false'
        elif isinstance(o, integer_types):
            yield (str(o)
                   if (not _bigint_as_string or
                       (-1 << 53) < o < (1 << 53))
                       else ('"' + str(o) + '"'))
        elif isinstance(o, float):
            yield _floatstr(o)
        elif isinstance(o, list):
            for chunk in _iterencode_list(o, _current_indent_level):
                yield chunk
        else:
            _asdict = _namedtuple_as_object and getattr(o, '_asdict', None)
            if _asdict and callable(_asdict):
                for chunk in _iterencode_dict(_asdict(), _current_indent_level):
                    yield chunk
            elif (_tuple_as_array and isinstance(o, tuple)):
                for chunk in _iterencode_list(o, _current_indent_level):
                    yield chunk
            elif isinstance(o, dict):
                for chunk in _iterencode_dict(o, _current_indent_level):
                    yield chunk
            elif _use_decimal and isinstance(o, Decimal):
                yield str(o)
            else:
                if markers is not None:
                    markerid = id(o)
                    if markerid in markers:
                        raise ValueError("Circular reference detected")
                    markers[markerid] = o
                o = _default(o)
                for chunk in _iterencode(o, _current_indent_level):
                    yield chunk
                if markers is not None:
                    del markers[markerid]

    return _iterencode