# Lint as: python2, python3
# Copyright 2018 The TensorFlow 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.
# ==============================================================================
r"""Utilities for creating TFRecords of TF examples for the Open Images dataset.
"""
from __future__ import absolute_import
from __future__ import division
from __future__ import print_function

from six.moves import range
import tensorflow as tf


def open_sharded_output_tfrecords(exit_stack, base_path, num_shards):
  """Opens all TFRecord shards for writing and adds them to an exit stack.

  Args:
    exit_stack: A context2.ExitStack used to automatically closed the TFRecords
      opened in this function.
    base_path: The base path for all shards
    num_shards: The number of shards

  Returns:
    The list of opened TFRecords. Position k in the list corresponds to shard k.
  """
  tf_record_output_filenames = [
      '{}-{:05d}-of-{:05d}'.format(base_path, idx, num_shards)
      for idx in range(num_shards)
  ]

  tfrecords = [
      exit_stack.enter_context(tf.python_io.TFRecordWriter(file_name))
      for file_name in tf_record_output_filenames
  ]

  return tfrecords
