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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
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