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# Copyright 2011, Google Inc.
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions are
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# met:
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#
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# * Redistributions of source code must retain the above copyright
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# notice, this list of conditions and the following disclaimer.
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# * Redistributions in binary form must reproduce the above
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# copyright notice, this list of conditions and the following disclaimer
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# in the documentation and/or other materials provided with the
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# distribution.
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# * Neither the name of Google Inc. nor the names of its
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# contributors may be used to endorse or promote products derived from
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# this software without specific prior written permission.
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# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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"""Reader objects to abstract out different body response types.
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This module is package-private. It is not expected that these will
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have any clients outside of httpplus.
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"""
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import httplib
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import itertools
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import logging
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logger = logging.getLogger(__name__)
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class ReadNotReady(Exception):
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"""Raised when read() is attempted but not enough data is loaded."""
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class HTTPRemoteClosedError(httplib.HTTPException):
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"""The server closed the remote socket in the middle of a response."""
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class AbstractReader(object):
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"""Abstract base class for response readers.
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Subclasses must implement _load, and should implement _close if
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it's not an error for the server to close their socket without
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some termination condition being detected during _load.
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"""
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def __init__(self):
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self._finished = False
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self._done_chunks = []
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@property
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def available_data(self):
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return sum(map(len, self._done_chunks))
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def done(self):
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return self._finished
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def read(self, amt):
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if self.available_data < amt and not self._finished:
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raise ReadNotReady()
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need = [amt]
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def pred(s):
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needed = need[0] > 0
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need[0] -= len(s)
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return needed
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blocks = list(itertools.takewhile(pred, self._done_chunks))
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self._done_chunks = self._done_chunks[len(blocks):]
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over_read = sum(map(len, blocks)) - amt
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if over_read > 0 and blocks:
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logger.debug('need to reinsert %d data into done chunks', over_read)
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last = blocks[-1]
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blocks[-1], reinsert = last[:-over_read], last[-over_read:]
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self._done_chunks.insert(0, reinsert)
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result = ''.join(blocks)
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assert len(result) == amt or (self._finished and len(result) < amt)
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return result
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def _load(self, data): # pragma: no cover
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"""Subclasses must implement this.
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As data is available to be read out of this object, it should
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be placed into the _done_chunks list. Subclasses should not
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rely on data remaining in _done_chunks forever, as it may be
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reaped if the client is parsing data as it comes in.
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"""
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raise NotImplementedError
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def _close(self):
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"""Default implementation of close.
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The default implementation assumes that the reader will mark
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the response as finished on the _finished attribute once the
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entire response body has been read. In the event that this is
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not true, the subclass should override the implementation of
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close (for example, close-is-end responses have to set
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self._finished in the close handler.)
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"""
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if not self._finished:
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raise HTTPRemoteClosedError(
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'server appears to have closed the socket mid-response')
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class AbstractSimpleReader(AbstractReader):
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"""Abstract base class for simple readers that require no response decoding.
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Examples of such responses are Connection: Close (close-is-end)
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and responses that specify a content length.
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"""
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def _load(self, data):
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if data:
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assert not self._finished, (
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'tried to add data (%r) to a closed reader!' % data)
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logger.debug('%s read an additional %d data', self.name, len(data))
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self._done_chunks.append(data)
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class CloseIsEndReader(AbstractSimpleReader):
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"""Reader for responses that specify Connection: Close for length."""
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name = 'close-is-end'
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def _close(self):
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logger.info('Marking close-is-end reader as closed.')
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self._finished = True
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class ContentLengthReader(AbstractSimpleReader):
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"""Reader for responses that specify an exact content length."""
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name = 'content-length'
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def __init__(self, amount):
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AbstractReader.__init__(self)
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self._amount = amount
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if amount == 0:
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self._finished = True
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self._amount_seen = 0
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def _load(self, data):
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AbstractSimpleReader._load(self, data)
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self._amount_seen += len(data)
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if self._amount_seen >= self._amount:
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self._finished = True
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logger.debug('content-length read complete')
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class ChunkedReader(AbstractReader):
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"""Reader for chunked transfer encoding responses."""
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def __init__(self, eol):
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AbstractReader.__init__(self)
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self._eol = eol
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self._leftover_skip_amt = 0
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self._leftover_data = ''
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def _load(self, data):
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assert not self._finished, 'tried to add data to a closed reader!'
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logger.debug('chunked read an additional %d data', len(data))
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position = 0
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if self._leftover_data:
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logger.debug('chunked reader trying to finish block from leftover data')
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# TODO: avoid this string concatenation if possible
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data = self._leftover_data + data
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position = self._leftover_skip_amt
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self._leftover_data = ''
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self._leftover_skip_amt = 0
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datalen = len(data)
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while position < datalen:
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split = data.find(self._eol, position)
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if split == -1:
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self._leftover_data = data
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self._leftover_skip_amt = position
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return
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amt = int(data[position:split], base=16)
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block_start = split + len(self._eol)
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# If the whole data chunk plus the eol trailer hasn't
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# loaded, we'll wait for the next load.
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if block_start + amt + len(self._eol) > len(data):
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self._leftover_data = data
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self._leftover_skip_amt = position
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return
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if amt == 0:
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self._finished = True
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logger.debug('closing chunked reader due to chunk of length 0')
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return
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self._done_chunks.append(data[block_start:block_start + amt])
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position = block_start + amt + len(self._eol)
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# no-check-code
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