# documentación de Django - 1.10.7

# Código fuente para django.http.response

    from __future__ import unicode_literals

    import datetime
    import json
    import re
    import sys
    import time
    from email.header import Header

    from django.conf import settings
    from django.core import signals, signing
    from django.core.exceptions import DisallowedRedirect
    from django.core.serializers.json import DjangoJSONEncoder
    from django.http.cookie import SimpleCookie
    from django.utils import six, timezone
    from django.utils.encoding import (
        force_bytes, force_str, force_text, iri_to_uri,
    )
    from django.utils.http import cookie_date
    from django.utils.six.moves import map
    from django.utils.six.moves.http_client import responses
    from django.utils.six.moves.urllib.parse import urlparse

    _charset_from_content_type_re = re.compile(r';\s*charset=(?P<charset>[^\s;]+)', re.I)

    class BadHeaderError(ValueError):
        pass

    class HttpResponseBase(six.Iterator):
        """
        An HTTP response base class with dictionary-accessed headers.

        This class doesn't handle content. It should not be used directly.
        Use the HttpResponse and StreamingHttpResponse subclasses instead.
        """

        status_code = 200

        def __init__(self, content_type=None, status=None, reason=None, charset=None):
            # _headers is a mapping of the lower-case name to the original case of
            # the header (required for working with legacy systems) and the header
            # value. Both the name of the header and its value are ASCII strings.
            self._headers = {}
            self._closable_objects = []
            # This parameter is set by the handler. It's necessary to preserve the
            # historical behavior of request_finished.
            self._handler_class = None
            self.cookies = SimpleCookie()
            self.closed = False
            if status is not None:
                self.status_code = status
            self._reason_phrase = reason
            self._charset = charset
            if content_type is None:
                content_type = '%s; charset=%s' % (settings.DEFAULT_CONTENT_TYPE,
                                                   self.charset)
            self['Content-Type'] = content_type

        @property
        def reason_phrase(self):
            if self._reason_phrase is not None:
                return self._reason_phrase
            # Leave self._reason_phrase unset in order to use the default
            # reason phrase for status code.
            return responses.get(self.status_code, 'Unknown Status Code')

        @reason_phrase.setter
        def reason_phrase(self, value):
            self._reason_phrase = value

        @property
        def charset(self):
            if self._charset is not None:
                return self._charset
            content_type = self.get('Content-Type', '')
            matched = _charset_from_content_type_re.search(content_type)
            if matched:
                # Extract the charset and strip its double quotes
                return matched.group('charset').replace('"', '')
            return settings.DEFAULT_CHARSET

        @charset.setter
        def charset(self, value):
            self._charset = value

        def serialize_headers(self):
            """HTTP headers as a bytestring."""
            def to_bytes(val, encoding):
                return val if isinstance(val, bytes) else val.encode(encoding)

            headers = [
                (b': '.join([to_bytes(key, 'ascii'), to_bytes(value, 'latin-1')]))
                for key, value in self._headers.values()
            ]
            return b'\r\n'.join(headers)

        if six.PY3:
            __bytes__ = serialize_headers
        else:
            __str__ = serialize_headers

        def _convert_to_charset(self, value, charset, mime_encode=False):
            """Converts headers key/value to ascii/latin-1 native strings.

            `charset` must be 'ascii' or 'latin-1'. If `mime_encode` is True and
            `value` can't be represented in the given charset, MIME-encoding
            is applied.
            """
            if not isinstance(value, (bytes, six.text_type)):
                value = str(value)
            if ((isinstance(value, bytes) and (b'\n' in value or b'\r' in value)) or
                    isinstance(value, six.text_type) and ('\n' in value or '\r' in value)):
                raise BadHeaderError("Header values can't contain newlines (got %r)" % value)
            try:
                if six.PY3:
                    if isinstance(value, str):
                        # Ensure string is valid in given charset
                        value.encode(charset)
                    else:
                        # Convert bytestring using given charset
                        value = value.decode(charset)
                else:
                    if isinstance(value, str):
                        # Ensure string is valid in given charset
                        value.decode(charset)
                    else:
                        # Convert unicode string to given charset
                        value = value.encode(charset)
            except UnicodeError as e:
                if mime_encode:
                    # Wrapping in str() is a workaround for #12422 under Python 2.
                    value = str(Header(value, 'utf-8', maxlinelen=sys.maxsize).encode())
                else:
                    e.reason += ', HTTP response headers must be in %s format' % charset
                    raise
            return value

        def __setitem__(self, header, value):
            header = self._convert_to_charset(header, 'ascii')
            value = self._convert_to_charset(value, 'latin-1', mime_encode=True)
            self._headers[header.lower()] = (header, value)

        def __delitem__(self, header):
            try:
                del self._headers[header.lower()]
            except KeyError:
                pass

        def __getitem__(self, header):
            return self._headers[header.lower()][1]

        def has_header(self, header):
            """Case-insensitive check for a header."""
            return header.lower() in self._headers

        __contains__ = has_header

        def items(self):
            return self._headers.values()

        def get(self, header, alternate=None):
            return self._headers.get(header.lower(), (None, alternate))[1]

        def set_cookie(self, key, value='', max_age=None, expires=None, path='/',
                       domain=None, secure=False, httponly=False):
            """
            Sets a cookie.

            ``expires`` can be:
            - a string in the correct format,
            - a naive ``datetime.datetime`` object in UTC,
            - an aware ``datetime.datetime`` object in any time zone.
            If it is a ``datetime.datetime`` object then ``max_age`` will be calculated.
            """
            value = force_str(value)
            self.cookies[key] = value
            if expires is not None:
                if isinstance(expires, datetime.datetime):
                    if timezone.is_aware(expires):
                        expires = timezone.make_naive(expires, timezone.utc)
                    delta = expires - expires.utcnow()
                    # Add one second so the date matches exactly (a fraction of
                    # time gets lost between converting to a timedelta and
                    # then the date string).
                    delta = delta + datetime.timedelta(seconds=1)
                    # Just set max_age - the max_age logic will set expires.
                    expires = None
                    max_age = max(0, delta.days * 86400 + delta.seconds)
                else:
                    self.cookies[key]['expires'] = expires
            else:
                self.cookies[key]['expires'] = ''
            if max_age is not None:
                self.cookies[key]['max-age'] = max_age
                # IE requires expires, so set it if hasn't been already.
                if not expires:
                    self.cookies[key]['expires'] = cookie_date(time.time() +
                                                               max_age)
            if path is not None:
                self.cookies[key]['path'] = path
            if domain is not None:
                self.cookies[key]['domain'] = domain
            if secure:
                self.cookies[key]['secure'] = True
            if httponly:
                self.cookies[key]['httponly'] = True

        def setdefault(self, key, value):
            """Sets a header unless it has already been set."""
            if key not in self:
                self[key] = value

        def set_signed_cookie(self, key, value, salt='', **kwargs):
            value = signing.get_cookie_signer(salt=key + salt).sign(value)
            return self.set_cookie(key, value, **kwargs)

        def delete_cookie(self, key, path='/', domain=None):
            self.set_cookie(key, max_age=0, path=path, domain=domain,
                            expires='Thu, 01-Jan-1970 00:00:00 GMT')

        # Common methods used by subclasses

        def make_bytes(self, value):
            """Turn a value into a bytestring encoded in the output charset."""
            # Per PEP 3333, this response body must be bytes. To avoid returning
            # an instance of a subclass, this function returns `bytes(value)`.
            # This doesn't make a copy when `value` already contains bytes.

            # Handle string types -- we can't rely on force_bytes here because:
            # - under Python 3 it attempts str conversion first
            # - when self._charset != 'utf-8' it re-encodes the content
            if isinstance(value, bytes):
                return bytes(value)
            if isinstance(value, six.text_type):
                return bytes(value.encode(self.charset))

            # Handle non-string types (#16494)
            return force_bytes(value, self.charset)

        # These methods partially implement the file-like object interface.
        # See https://docs.python.org/3/library/io.html#io.IOBase

        # The WSGI server must call this method upon completion of the request.
        # See http://blog.dscpl.com.au/2012/10/obligations-for-calling-close-on.html
        def close(self):
            for closable in self._closable_objects:
                try:
                    closable.close()
                except Exception:
                    pass
            self.closed = True
            signals.request_finished.send(sender=self._handler_class)

        def write(self, content):
            raise IOError("This %s instance is not writable" % self.__class__.__name__)

        def flush(self):
            pass

        def tell(self):
            raise IOError("This %s instance cannot tell its position" % self.__class__.__name__)

        # These methods partially implement a stream-like object interface.
        # See https://docs.python.org/library/io.html#io.IOBase

        def readable(self):
            return False

        def seekable(self):
            return False

        def writable(self):
            return False

        def writelines(self, lines):
            raise IOError("This %s instance is not writable" % self.__class__.__name__)

    class HttpResponse(HttpResponseBase):
        """
        An HTTP response class with a string as content.

        This content that can be read, appended to or replaced.
        """

        streaming = False

        def __init__(self, content=b'', *args, **kwargs):
            super(HttpResponse, self).__init__(*args, **kwargs)
            # Content is a bytestring. See the `content` property methods.
            self.content = content

        def __repr__(self):
            return '<%(cls)s status_code=%(status_code)d, "%(content_type)s">' % {
                'cls': self.__class__.__name__,
                'status_code': self.status_code,
                'content_type': self['Content-Type'],
            }

        def serialize(self):
            """Full HTTP message, including headers, as a bytestring."""
            return self.serialize_headers() + b'\r\n\r\n' + self.content

        if six.PY3:
            __bytes__ = serialize
        else:
            __str__ = serialize

        @property
        def content(self):
            return b''.join(self._container)

        @content.setter
        def content(self, value):
            # Consume iterators upon assignment to allow repeated iteration.
            if hasattr(value, '__iter__') and not isinstance(value, (bytes, six.string_types)):
                content = b''.join(self.make_bytes(chunk) for chunk in value)
                if hasattr(value, 'close'):
                    try:
                        value.close()
                    except Exception:
                        pass
            else:
                content = self.make_bytes(value)
            # Create a list of properly encoded bytestrings to support write().
            self._container = [content]

        def __iter__(self):
            return iter(self._container)

        def write(self, content):
            self._container.append(self.make_bytes(content))

        def tell(self):
            return len(self.content)

        def getvalue(self):
            return self.content

        def writable(self):
            return True

        def writelines(self, lines):
            for line in lines:
                self.write(line)

    class StreamingHttpResponse(HttpResponseBase):
        """
        A streaming HTTP response class with an iterator as content.

        This should only be iterated once, when the response is streamed to the
        client. However, it can be appended to or replaced with a new iterator
        that wraps the original content (or yields entirely new content).
        """

        streaming = True

        def __init__(self, streaming_content=(), *args, **kwargs):
            super(StreamingHttpResponse, self).__init__(*args, **kwargs)
            # `streaming_content` should be an iterable of bytestrings.
            # See the `streaming_content` property methods.
            self.streaming_content = streaming_content

        @property
        def content(self):
            raise AttributeError(
                "This %s instance has no `content` attribute. Use "
                "`streaming_content` instead." % self.__class__.__name__
            )

        @property
        def streaming_content(self):
            return map(self.make_bytes, self._iterator)

        @streaming_content.setter
        def streaming_content(self, value):
            self._set_streaming_content(value)

        def _set_streaming_content(self, value):
            # Ensure we can never iterate on "value" more than once.
            self._iterator = iter(value)
            if hasattr(value, 'close'):
                self._closable_objects.append(value)

        def __iter__(self):
            return self.streaming_content

        def getvalue(self):
            return b''.join(self.streaming_content)

    class FileResponse(StreamingHttpResponse):
        """
        A streaming HTTP response class optimized for files.
        """
        block_size = 4096

        def _set_streaming_content(self, value):
            if hasattr(value, 'read'):
                self.file_to_stream = value
                filelike = value
                if hasattr(filelike, 'close'):
                    self._closable_objects.append(filelike)
                value = iter(lambda: filelike.read(self.block_size), b'')
            else:
                self.file_to_stream = None
            super(FileResponse, self)._set_streaming_content(value)

    class HttpResponseRedirectBase(HttpResponse):
        allowed_schemes = ['http', 'https', 'ftp']

        def __init__(self, redirect_to, *args, **kwargs):
            parsed = urlparse(force_text(redirect_to))
            if parsed.scheme and parsed.scheme not in self.allowed_schemes:
                raise DisallowedRedirect("Unsafe redirect to URL with protocol '%s'" % parsed.scheme)
            super(HttpResponseRedirectBase, self).__init__(*args, **kwargs)
            self['Location'] = iri_to_uri(redirect_to)

        url = property(lambda self: self['Location'])

        def __repr__(self):
            return '<%(cls)s status_code=%(status_code)d, "%(content_type)s", url="%(url)s">' % {
                'cls': self.__class__.__name__,
                'status_code': self.status_code,
                'content_type': self['Content-Type'],
                'url': self.url,
            }

    class HttpResponseRedirect(HttpResponseRedirectBase):
        status_code = 302

    class HttpResponsePermanentRedirect(HttpResponseRedirectBase):
        status_code = 301

    class HttpResponseNotModified(HttpResponse):
        status_code = 304

        def __init__(self, *args, **kwargs):
            super(HttpResponseNotModified, self).__init__(*args, **kwargs)
            del self['content-type']

        @HttpResponse.content.setter
        def content(self, value):
            if value:
                raise AttributeError("You cannot set content to a 304 (Not Modified) response")
            self._container = []

    class HttpResponseBadRequest(HttpResponse):
        status_code = 400

    class HttpResponseNotFound(HttpResponse):
        status_code = 404

    class HttpResponseForbidden(HttpResponse):
        status_code = 403

    class HttpResponseNotAllowed(HttpResponse):
        status_code = 405

        def __init__(self, permitted_methods, *args, **kwargs):
            super(HttpResponseNotAllowed, self).__init__(*args, **kwargs)
            self['Allow'] = ', '.join(permitted_methods)

        def __repr__(self):
            return '<%(cls)s [%(methods)s] status_code=%(status_code)d, "%(content_type)s">' % {
                'cls': self.__class__.__name__,
                'status_code': self.status_code,
                'content_type': self['Content-Type'],
                'methods': self['Allow'],
            }

    class HttpResponseGone(HttpResponse):
        status_code = 410

    class HttpResponseServerError(HttpResponse):
        status_code = 500

    class Http404(Exception):
        pass

    class JsonResponse(HttpResponse):
        """
        An HTTP response class that consumes data to be serialized to JSON.

        :param data: Data to be dumped into json. By default only ``dict`` objects
          are allowed to be passed due to a security flaw before EcmaScript 5. See
          the ``safe`` parameter for more information.
        :param encoder: Should be an json encoder class. Defaults to
          ``django.core.serializers.json.DjangoJSONEncoder``.
        :param safe: Controls if only ``dict`` objects may be serialized. Defaults
          to ``True``.
        :param json_dumps_params: A dictionary of kwargs passed to json.dumps().
        """

        def __init__(self, data, encoder=DjangoJSONEncoder, safe=True,
                     json_dumps_params=None, **kwargs):
            if safe and not isinstance(data, dict):
                raise TypeError(
                    'In order to allow non-dict objects to be serialized set the '
                    'safe parameter to False.'
                )
            if json_dumps_params is None:
                json_dumps_params = {}
            kwargs.setdefault('content_type', 'application/json')
            data = json.dumps(data, cls=encoder, **json_dumps_params)
            super(JsonResponse, self).__init__(content=data, **kwargs)