# Copyright 2018 Google LLC
#
# 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
#
#     https://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.

import warnings

_SLOW_CRC32C_WARNING = (
    "As the c extension couldn't be imported, `google-crc32c` is using a " 
    "pure python implementation that is significantly slower. If possible, "
    "please configure a c build environment and compile the extension"
)

# Default to C exstension Implementation, falling back to pure python.
try:
    from google_crc32c import cext as impl
    implementation = "c"
except ImportError as exc:
    from google_crc32c import python as impl  # type: ignore
    warnings.warn(_SLOW_CRC32C_WARNING, RuntimeWarning)
    implementation = "python"

extend = impl.extend
value = impl.value

Checksum = impl.Checksum

__all__ = ["extend", "value", "Checksum", "implementation"]