view mercurial/httpclient/_readers.py @ 26265:077f20eed4b2

obsolete: clarify that 'successorssets' returns the latest successors

We do not return the first successors we found, we returns the latest (non
obsolete  (mostly)) one following the obsolete link transitively. We update the
documentation to make this clean.

# Copyright 2011, Google Inc.
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#
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# modification, are permitted provided that the following conditions are
# met:
#
#     * Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
#     * Redistributions in binary form must reproduce the above
# copyright notice, this list of conditions and the following disclaimer
# in the documentation and/or other materials provided with the
# distribution.
#     * Neither the name of Google Inc. nor the names of its
# contributors may be used to endorse or promote products derived from
# this software without specific prior written permission.

# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
"""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.
"""

import 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 = ''.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