| // Copyright 2020 The Pigweed Authors |
| // |
| // 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. |
| |
| // Provides an implementation of the CCITT CRC16 for the polynomial |
| // |
| // x^16 + x^12 + x^5 + 1 |
| // |
| // Polynomial 0x1021, initial value 0xFFFF. See https://www.zlib.net/crc_v3.txt. |
| #pragma once |
| |
| #include <stddef.h> |
| #include <stdint.h> |
| |
| #ifdef __cplusplus |
| extern "C" { |
| #endif // __cplusplus |
| |
| // C API for calculating the CCITT CRC16 of an array of data. |
| uint16_t pw_ChecksumCcittCrc16(const void* data, |
| size_t size_bytes, |
| uint16_t initial_value); |
| |
| #ifdef __cplusplus |
| } // extern "C" |
| |
| #include <span> |
| |
| namespace pw::checksum { |
| |
| inline constexpr uint16_t kCcittCrc16DefaultInitialValue = 0xFFFF; |
| |
| // Calculates the CCITT CRC16 for the provided data. To update an existing CRC, |
| // pass the previous value as the initial_value argument. |
| inline uint16_t CcittCrc16( |
| std::span<const std::byte> data, |
| uint16_t initial_value = kCcittCrc16DefaultInitialValue) { |
| return pw_ChecksumCcittCrc16(data.data(), data.size_bytes(), initial_value); |
| } |
| |
| // Calculates the CCITT CRC16 for a single byte. This is useful for updating a |
| // CRC byte-by-byte. |
| inline uint16_t CcittCrc16( |
| std::byte value, uint16_t initial_value = kCcittCrc16DefaultInitialValue) { |
| return pw_ChecksumCcittCrc16(&value, sizeof(value), initial_value); |
| } |
| |
| } // namespace pw::checksum |
| |
| #endif // __cplusplus |