text: # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #      http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  """FileObjectAdapter class.
  
  Used in conjunction with PythonOutputStream/PythonInputStream to allow a C++
  OutputStream/InputStream to interact with a Python file-like object.
  """
  
  from __future__ import absolute_import
  from __future__ import division
  # Placeholder for import for type annotations
  from __future__ import print_function
  
  import io
  from typing import BinaryIO
  
  from tink.cc.pybind import tink_bindings
  
  
  class FileObjectAdapter(tink_bindings.PythonFileObjectAdapter):
    """Adapts a Python file object for use in C++."""
  
    def __init__(self, file_object: BinaryIO):
      # Required to fix CLIF "Value invalidated due to capture by std::unique_ptr"
      super(FileObjectAdapter, self).__init__()
      self._file_object = file_object
  
    def write(self, data: bytes) -> int:
      """Writes to underlying file object and returns number of bytes written."""
      try:
        written = self._file_object.write(data)
        return 0 if written is None else written
      except io.BlockingIOError as e:
        return e.characters_written
  
    def close(self) -> None:
      self._file_object.close()
  
    def read(self, size: int) -> bytes:
      """Reads at most 'size' bytes from the underlying file object.
  
      Args:
        size: A non-negative integer, maximum number of bytes to read.
  
      Returns:
        Bytes that were read. An empty bytes object is returned if no bytes are
        available at the moment.
  
      Raises:
        EOFError if the file object is already at EOF.
      """
      if size < 0:
        raise ValueError('size must be non-negative')
  
      try:
        data = self._file_object.read(size)
        if data is None:
          return b''
        elif not data and size > 0:
          raise EOFError('EOF')
        return data
      except io.BlockingIOError:
        return b''
  