crc/internal/crc32c.h

0001 // Copyright 2022 The Abseil Authors
0002 //
0003 // Licensed under the Apache License, Version 2.0 (the "License");
0004 // you may not use this file except in compliance with the License.
0005 // You may obtain a copy of the License at
0006 //
0007 //     https://www.apache.org/licenses/LICENSE-2.0
0008 //
0009 // Unless required by applicable law or agreed to in writing, software
0010 // distributed under the License is distributed on an "AS IS" BASIS,
0011 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
0012 // See the License for the specific language governing permissions and
0013 // limitations under the License.
0014
0015 #ifndef ABSL_CRC_INTERNAL_CRC32C_H_
0016 #define ABSL_CRC_INTERNAL_CRC32C_H_
0017
0018 #include "absl/base/config.h"
0019 #include "absl/crc/crc32c.h"
0020
0021 namespace absl {
0022 ABSL_NAMESPACE_BEGIN
0023 namespace crc_internal {
0024
0025 // Modifies a CRC32 value by removing `length` bytes with a value of 0 from
0026 // the end of the string.
0027 //
0028 // This is the inverse operation of ExtendCrc32cByZeroes().
0029 //
0030 // This operation has a runtime cost of O(log(`length`))
0031 //
0032 // Internal implementation detail, exposed for testing only.
0033 crc32c_t UnextendCrc32cByZeroes(crc32c_t initial_crc, size_t length);
0034
0035 }  // namespace crc_internal
0036 ABSL_NAMESPACE_END
0037 }  // namespace absl
0038
0039 #endif  // ABSL_CRC_INTERNAL_CRC32C_H_