text: # Copyright 2020 The TensorFlow Hub Authors. All Rights Reserved.
  #
  # 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.
  # ==============================================================================
  """Utilities for file operations."""
  
  
  import os
  import tarfile
  
  import tensorflow as tf
  
  
  def extract_file(tgz,
                   tarinfo,
                   dst_path,
                   buffer_size=10 << 20,
                   log_function=None):
    """Extracts 'tarinfo' from 'tgz' and writes to 'dst_path'."""
    src = tgz.extractfile(tarinfo)
    if src is None:
      return
    dst = tf.compat.v1.gfile.GFile(dst_path, "wb")
    while 1:
      buf = src.read(buffer_size)
      if not buf:
        break
      dst.write(buf)
      if log_function is not None:
        log_function(len(buf))
    dst.close()
    src.close()
  
  
  def extract_tarfile_to_destination(fileobj, dst_path, log_function=None):
    """Extract a tarfile. Optional: log the progress."""
    with tarfile.open(mode="r|*", fileobj=fileobj) as tgz:
      for tarinfo in tgz:
        abs_target_path = merge_relative_path(dst_path, tarinfo.name)
  
        if tarinfo.isfile():
          extract_file(tgz, tarinfo, abs_target_path, log_function=log_function)
        elif tarinfo.isdir():
          tf.compat.v1.gfile.MakeDirs(abs_target_path)
        else:
          # We do not support symlinks and other uncommon objects.
          raise ValueError("Unexpected object type in tar archive: %s" %
                           tarinfo.type)
  
  
  def merge_relative_path(dst_path, rel_path):
    """Merge a relative tar file to a destination (which can be "gs://...")."""
    # Convert rel_path to be relative and normalize it to remove ".", "..", "//",
    # which are valid directories in fileystems like "gs://".
    norm_rel_path = os.path.normpath(rel_path.lstrip("/"))
  
    if norm_rel_path == ".":
      return dst_path
  
    # Check that the norm rel path does not starts with "..".
    if norm_rel_path.startswith(".."):
      raise ValueError("Relative path %r is invalid." % rel_path)
  
    merged = os.path.join(dst_path, norm_rel_path)
  
    # After merging verify that the merged path keeps the original dst_path.
    if not merged.startswith(dst_path):
      raise ValueError("Relative path %r is invalid. Failed to merge with %r." %
                       (rel_path, dst_path))
    return merged
  