| #!/usr/bin/env python |
| """Small helper class to provide a small slice of a stream. |
| |
| This class reads ahead to detect if we are at the end of the stream. |
| """ |
| |
| from apitools.base.py import exceptions |
| |
| |
| # TODO(user): Consider replacing this with a StringIO. |
| class BufferedStream(object): |
| |
| """Buffers a stream, reading ahead to determine if we're at the end.""" |
| |
| def __init__(self, stream, start, size): |
| self.__stream = stream |
| self.__start_pos = start |
| self.__buffer_pos = 0 |
| self.__buffered_data = self.__stream.read(size) |
| self.__stream_at_end = len(self.__buffered_data) < size |
| self.__end_pos = self.__start_pos + len(self.__buffered_data) |
| |
| def __str__(self): |
| return ('Buffered stream %s from position %s-%s with %s ' |
| 'bytes remaining' % (self.__stream, self.__start_pos, |
| self.__end_pos, self._bytes_remaining)) |
| |
| def __len__(self): |
| return len(self.__buffered_data) |
| |
| @property |
| def stream_exhausted(self): |
| return self.__stream_at_end |
| |
| @property |
| def stream_end_position(self): |
| return self.__end_pos |
| |
| @property |
| def _bytes_remaining(self): |
| return len(self.__buffered_data) - self.__buffer_pos |
| |
| def read(self, size=None): # pylint: disable=invalid-name |
| """Reads from the buffer.""" |
| if size is None or size < 0: |
| raise exceptions.NotYetImplementedError( |
| 'Illegal read of size %s requested on BufferedStream. ' |
| 'Wrapped stream %s is at position %s-%s, ' |
| '%s bytes remaining.' % |
| (size, self.__stream, self.__start_pos, self.__end_pos, |
| self._bytes_remaining)) |
| |
| data = '' |
| if self._bytes_remaining: |
| size = min(size, self._bytes_remaining) |
| data = self.__buffered_data[ |
| self.__buffer_pos:self.__buffer_pos + size] |
| self.__buffer_pos += size |
| return data |
