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"""Reader objects to abstract out different body response types.

This module is package-private. It is not expected that these will

have any clients outside of httpplus.

"""

from __future__ import absolute_import

try:

    import httplib

    httplib.HTTPException

except ImportError:

    import http.client as httplib

import logging

logger = logging.getLogger(__name__)

class ReadNotReady(Exception):

    """Raised when read() is attempted but not enough data is loaded."""

class HTTPRemoteClosedError(httplib.HTTPException):

    """The server closed the remote socket in the middle of a response."""

class AbstractReader(object):

    """Abstract base class for response readers.

    Subclasses must implement _load, and should implement _close if

    it's not an error for the server to close their socket without

    some termination condition being detected during _load.

    """

    def __init__(self):

        self._finished = False

        self._done_chunks = []

        self.available_data = 0

    def _addchunk(self, data):

        self._done_chunks.append(data)

        self.available_data += len(data)

    def _pushchunk(self, data):

        self._done_chunks.insert(0, data)

        self.available_data += len(data)

    def _popchunk(self):

        b = self._done_chunks.pop(0)

        self.available_data -= len(b)

        return b

    def done(self):

        """Returns true if the response body is entirely read."""

        return self._finished

    def read(self, amt):

        """Read amt bytes from the response body."""

        if self.available_data < amt and not self._finished:

            raise ReadNotReady()

        blocks = []

        need = amt

        while self._done_chunks:

            b = self._popchunk()

            if len(b) > need:

                nb = b[:need]

                self._pushchunk(b[need:])

                b = nb

            blocks.append(b)

            need -= len(b)

            if need == 0:

                break

        result = b''.join(blocks)

        assert len(result) == amt or (self._finished and len(result) < amt)

        return result

    def readto(self, delimstr, blocks = None):

        """return available data chunks up to the first one in which

        delimstr occurs. No data will be returned after delimstr --

        the chunk in which it occurs will be split and the remainder

        pushed back onto the available data queue. If blocks is

        supplied chunks will be added to blocks, otherwise a new list

        will be allocated.

        """

        if blocks is None:

            blocks = []

        while self._done_chunks:

            b = self._popchunk()

            i = b.find(delimstr) + len(delimstr)

            if i:

                if i < len(b):

                    self._pushchunk(b[i:])

                blocks.append(b[:i])

                break

            else:

                blocks.append(b)

        return blocks

    def _load(self, data): # pragma: no cover

        """Subclasses must implement this.

        As data is available to be read out of this object, it should

        be placed into the _done_chunks list. Subclasses should not

        rely on data remaining in _done_chunks forever, as it may be

        reaped if the client is parsing data as it comes in.

        """

        raise NotImplementedError

    def _close(self):

        """Default implementation of close.

        The default implementation assumes that the reader will mark

        the response as finished on the _finished attribute once the

        entire response body has been read. In the event that this is

        not true, the subclass should override the implementation of

        close (for example, close-is-end responses have to set

        self._finished in the close handler.)

        """

        if not self._finished:

            raise HTTPRemoteClosedError(

                'server appears to have closed the socket mid-response')

class AbstractSimpleReader(AbstractReader):

    """Abstract base class for simple readers that require no response decoding.

    Examples of such responses are Connection: Close (close-is-end)

    and responses that specify a content length.

    """

    def _load(self, data):

        if data:

            assert not self._finished, (

                'tried to add data (%r) to a closed reader!' % data)

        logger.debug('%s read an additional %d data',

                     self.name, len(data)) # pylint: disable=E1101

        self._addchunk(data)

class CloseIsEndReader(AbstractSimpleReader):

    """Reader for responses that specify Connection: Close for length."""

    name = 'close-is-end'

    def _close(self):

        logger.info('Marking close-is-end reader as closed.')

        self._finished = True

class ContentLengthReader(AbstractSimpleReader):

    """Reader for responses that specify an exact content length."""

    name = 'content-length'

    def __init__(self, amount):

        AbstractSimpleReader.__init__(self)

        self._amount = amount

        if amount == 0:

            self._finished = True

        self._amount_seen = 0

    def _load(self, data):

        AbstractSimpleReader._load(self, data)

        self._amount_seen += len(data)

        if self._amount_seen >= self._amount:

            self._finished = True

            logger.debug('content-length read complete')

class ChunkedReader(AbstractReader):

    """Reader for chunked transfer encoding responses."""

    def __init__(self, eol):

        AbstractReader.__init__(self)

        self._eol = eol

        self._leftover_skip_amt = 0

        self._leftover_data = ''

    def _load(self, data):

        assert not self._finished, 'tried to add data to a closed reader!'

        logger.debug('chunked read an additional %d data', len(data))

        position = 0

        if self._leftover_data:

            logger.debug(

                'chunked reader trying to finish block from leftover data')

            # TODO: avoid this string concatenation if possible

            data = self._leftover_data + data

            position = self._leftover_skip_amt

            self._leftover_data = ''

            self._leftover_skip_amt = 0

        datalen = len(data)

        while position < datalen:

            split = data.find(self._eol, position)

            if split == -1:

                self._leftover_data = data

                self._leftover_skip_amt = position

                return

            amt = int(data[position:split], base=16)

            block_start = split + len(self._eol)

            # If the whole data chunk plus the eol trailer hasn't

            # loaded, we'll wait for the next load.

            if block_start + amt + len(self._eol) > len(data):

                self._leftover_data = data

                self._leftover_skip_amt = position

                return

            if amt == 0:

                self._finished = True

                logger.debug('closing chunked reader due to chunk of length 0')

                return

            self._addchunk(data[block_start:block_start + amt])

            position = block_start + amt + len(self._eol)

# no-check-code