70 lines
2.2 KiB
Python
70 lines
2.2 KiB
Python
"""Small helper class to provide a small slice of a stream."""
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from six.moves import http_client
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class StreamSlice(object):
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"""Provides a slice-like object for streams.
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:type stream: readable file-like object
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:param stream: the stream to be buffered
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:type max_bytes: integer
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:param max_bytes: maximum number of bytes to return in the slice
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"""
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def __init__(self, stream, max_bytes):
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self._stream = stream
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self._remaining_bytes = max_bytes
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self._max_bytes = max_bytes
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def __repr__(self):
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return 'Slice of stream %s with %s/%s bytes not yet read' % (
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self._stream, self._remaining_bytes, self._max_bytes)
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def __len__(self):
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return self._max_bytes
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def __nonzero__(self):
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# For 32-bit python2.x, len() cannot exceed a 32-bit number; avoid
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# accidental len() calls from httplib in the form of "if this_object:".
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return bool(self._max_bytes)
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@property
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def length(self):
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"""Maximum number of bytes to return in the slice.
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.. note::
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For 32-bit python2.x, len() cannot exceed a 32-bit number.
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:rtype: integer
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"""
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return self._max_bytes
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def read(self, size=None):
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"""Read bytes from the slice.
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Compared to other streams, there is one case where we may
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unexpectedly raise an exception on read: if the underlying stream
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is exhausted (i.e. returns no bytes on read), and the size of this
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slice indicates we should still be able to read more bytes, we
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raise :exc:`IncompleteRead`.
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:type size: integer or None
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:param size: If provided, read no more than size bytes from the stream.
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:rtype: bytes
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:returns: bytes read from this slice.
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:raises: :exc:`IncompleteRead`
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"""
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if size is not None:
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read_size = min(size, self._remaining_bytes)
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else:
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read_size = self._remaining_bytes
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data = self._stream.read(read_size)
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if read_size > 0 and not data:
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raise http_client.IncompleteRead(
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self._max_bytes - self._remaining_bytes, self._max_bytes)
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self._remaining_bytes -= len(data)
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return data
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