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Filename : response.py
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# urllib3/response.py
# Copyright 2008-2013 Andrey Petrov and contributors (see CONTRIBUTORS.txt)
#
# This module is part of urllib3 and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php


import logging
import zlib
import io

from ._collections import HTTPHeaderDict
from .exceptions import DecodeError
from .packages.six import string_types as basestring, binary_type
from .util import is_fp_closed


log = logging.getLogger(__name__)


class DeflateDecoder(object):

    def __init__(self):
        self._first_try = True
        self._data = binary_type()
        self._obj = zlib.decompressobj()

    def __getattr__(self, name):
        return getattr(self._obj, name)

    def decompress(self, data):
        if not self._first_try:
            return self._obj.decompress(data)

        self._data += data
        try:
            return self._obj.decompress(data)
        except zlib.error:
            self._first_try = False
            self._obj = zlib.decompressobj(-zlib.MAX_WBITS)
            try:
                return self.decompress(self._data)
            finally:
                self._data = None


def _get_decoder(mode):
    if mode == 'gzip':
        return zlib.decompressobj(16 + zlib.MAX_WBITS)

    return DeflateDecoder()


class HTTPResponse(io.IOBase):
    """
    HTTP Response container.

    Backwards-compatible to httplib's HTTPResponse but the response ``body`` is
    loaded and decoded on-demand when the ``data`` property is accessed.

    Extra parameters for behaviour not present in httplib.HTTPResponse:

    :param preload_content:
        If True, the response's body will be preloaded during construction.

    :param decode_content:
        If True, attempts to decode specific content-encoding's based on headers
        (like 'gzip' and 'deflate') will be skipped and raw data will be used
        instead.

    :param original_response:
        When this HTTPResponse wrapper is generated from an httplib.HTTPResponse
        object, it's convenient to include the original for debug purposes. It's
        otherwise unused.
    """

    CONTENT_DECODERS = ['gzip', 'deflate']
    REDIRECT_STATUSES = [301, 302, 303, 307, 308]

    def __init__(self, body='', headers=None, status=0, version=0, reason=None,
                 strict=0, preload_content=True, decode_content=True,
                 original_response=None, pool=None, connection=None):

        self.headers = HTTPHeaderDict()
        if headers:
            self.headers.update(headers)
        self.status = status
        self.version = version
        self.reason = reason
        self.strict = strict
        self.decode_content = decode_content

        self._decoder = None
        self._body = body if body and isinstance(body, basestring) else None
        self._fp = None
        self._original_response = original_response
        self._fp_bytes_read = 0

        self._pool = pool
        self._connection = connection

        if hasattr(body, 'read'):
            self._fp = body

        if preload_content and not self._body:
            self._body = self.read(decode_content=decode_content)

    def get_redirect_location(self):
        """
        Should we redirect and where to?

        :returns: Truthy redirect location string if we got a redirect status
            code and valid location. ``None`` if redirect status and no
            location. ``False`` if not a redirect status code.
        """
        if self.status in self.REDIRECT_STATUSES:
            return self.headers.get('location')

        return False

    def release_conn(self):
        if not self._pool or not self._connection:
            return

        self._pool._put_conn(self._connection)
        self._connection = None

    @property
    def data(self):
        # For backwords-compat with earlier urllib3 0.4 and earlier.
        if self._body:
            return self._body

        if self._fp:
            return self.read(cache_content=True)

    def tell(self):
        """
        Obtain the number of bytes pulled over the wire so far. May differ from
        the amount of content returned by :meth:``HTTPResponse.read`` if bytes
        are encoded on the wire (e.g, compressed).
        """
        return self._fp_bytes_read

    def read(self, amt=None, decode_content=None, cache_content=False):
        """
        Similar to :meth:`httplib.HTTPResponse.read`, but with two additional
        parameters: ``decode_content`` and ``cache_content``.

        :param amt:
            How much of the content to read. If specified, caching is skipped
            because it doesn't make sense to cache partial content as the full
            response.

        :param decode_content:
            If True, will attempt to decode the body based on the
            'content-encoding' header.

        :param cache_content:
            If True, will save the returned data such that the same result is
            returned despite of the state of the underlying file object. This
            is useful if you want the ``.data`` property to continue working
            after having ``.read()`` the file object. (Overridden if ``amt`` is
            set.)
        """
        # Note: content-encoding value should be case-insensitive, per RFC 2616
        # Section 3.5
        content_encoding = self.headers.get('content-encoding', '').lower()
        if self._decoder is None:
            if content_encoding in self.CONTENT_DECODERS:
                self._decoder = _get_decoder(content_encoding)
        if decode_content is None:
            decode_content = self.decode_content

        if self._fp is None:
            return

        flush_decoder = False

        try:
            if amt is None:
                # cStringIO doesn't like amt=None
                data = self._fp.read()
                flush_decoder = True
            else:
                cache_content = False
                data = self._fp.read(amt)
                if amt != 0 and not data:  # Platform-specific: Buggy versions of Python.
                    # Close the connection when no data is returned
                    #
                    # This is redundant to what httplib/http.client _should_
                    # already do.  However, versions of python released before
                    # December 15, 2012 (http://bugs.python.org/issue16298) do not
                    # properly close the connection in all cases. There is no harm
                    # in redundantly calling close.
                    self._fp.close()
                    flush_decoder = True

            self._fp_bytes_read += len(data)

            try:
                if decode_content and self._decoder:
                    data = self._decoder.decompress(data)
            except (IOError, zlib.error) as e:
                raise DecodeError(
                    "Received response with content-encoding: %s, but "
                    "failed to decode it." % content_encoding,
                    e)

            if flush_decoder and decode_content and self._decoder:
                buf = self._decoder.decompress(binary_type())
                data += buf + self._decoder.flush()

            if cache_content:
                self._body = data

            return data

        finally:
            if self._original_response and self._original_response.isclosed():
                self.release_conn()

    def stream(self, amt=2**16, decode_content=None):
        """
        A generator wrapper for the read() method. A call will block until
        ``amt`` bytes have been read from the connection or until the
        connection is closed.

        :param amt:
            How much of the content to read. The generator will return up to
            much data per iteration, but may return less. This is particularly
            likely when using compressed data. However, the empty string will
            never be returned.

        :param decode_content:
            If True, will attempt to decode the body based on the
            'content-encoding' header.
        """
        while not is_fp_closed(self._fp):
            data = self.read(amt=amt, decode_content=decode_content)

            if data:
                yield data


    @classmethod
    def from_httplib(ResponseCls, r, **response_kw):
        """
        Given an :class:`httplib.HTTPResponse` instance ``r``, return a
        corresponding :class:`urllib3.response.HTTPResponse` object.

        Remaining parameters are passed to the HTTPResponse constructor, along
        with ``original_response=r``.
        """

        headers = HTTPHeaderDict()
        for k, v in r.getheaders():
            headers.add(k, v)

        # HTTPResponse objects in Python 3 don't have a .strict attribute
        strict = getattr(r, 'strict', 0)
        return ResponseCls(body=r,
                           headers=headers,
                           status=r.status,
                           version=r.version,
                           reason=r.reason,
                           strict=strict,
                           original_response=r,
                           **response_kw)

    # Backwards-compatibility methods for httplib.HTTPResponse
    def getheaders(self):
        return self.headers

    def getheader(self, name, default=None):
        return self.headers.get(name, default)

    # Overrides from io.IOBase
    def close(self):
        if not self.closed:
            self._fp.close()

    @property
    def closed(self):
        if self._fp is None:
            return True
        elif hasattr(self._fp, 'closed'):
            return self._fp.closed
        elif hasattr(self._fp, 'isclosed'):  # Python 2
            return self._fp.isclosed()
        else:
            return True

    def fileno(self):
        if self._fp is None:
            raise IOError("HTTPResponse has no file to get a fileno from")
        elif hasattr(self._fp, "fileno"):
            return self._fp.fileno()
        else:
            raise IOError("The file-like object  this HTTPResponse is wrapped "
                          "around has no file descriptor")

    def flush(self):
        if self._fp is not None and hasattr(self._fp, 'flush'):
            return self._fp.flush()

    def readable(self):
        return True