components/esp_rom/include/esp_rom_crc.h (ESP-IDF)

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

// Copyright 2010-2020 Espressif Systems (Shanghai) PTE LTD // // 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. #pragma once #ifdef __cplusplus extern "C" { #endif #include <stdint.h> /** Notes about CRC API * The ESP32 ROM include some CRC tables and CRC APIs to speed up CRC calculation. * The CRC APIs include CRC8, CRC16, CRC32 algorithms for both little endian and big endian modes. * Here are the polynomials for the algorithms: * CRC-8 x8+x2+x1+1 0x07 * CRC16-CCITT x16+x12+x5+1 0x1021 * CRC32 x32+x26+x23+x22+x16+x12+x11+x10+x8+x7+x5+x4+x2+x1+1 0x04c11db7 * * These group of CRC APIs are designed to calculate the data in buffers either continuous or not. * To make it easy, we had added a `~` at the beginning and the end of the functions. * To calculate non-continuous buffers, we can write the code like this: * init = ~init; * crc = crc32_le(init, buf0, length0); * crc = crc32_le(crc, buf1, length1); * crc = ~crc; * * However, it is not easy to select which API to use and give the correct parameters. * A specific CRC algorithm will include this parameters: width, polynomials, init, refin, refout, xorout * refin and refout show the endian of the algorithm: * if both of them are true, please use the little endian API. * if both of them are false, please use the big endian API. * xorout is the value which you need to be xored to the raw result. * However, these group of APIs need one '~' before and after the APIs. * * Here are some examples for CRC16: * CRC-16/CCITT, poly = 0x1021, init = 0x0000, refin = true, refout = true, xorout = 0x0000 * crc = ~crc16_le((uint16_t)~0x0000, buf, length); * * CRC-16/CCITT-FALSE, poly = 0x1021, init = 0xffff, refin = false, refout = false, xorout = 0x0000 * crc = ~crc16_be((uint16_t)~0xffff, buf, length); * * CRC-16/X25, poly = 0x1021, init = 0xffff, refin = true, refout = true, xorout = 0xffff * crc = (~crc16_le((uint16_t)~(0xffff), buf, length))^0xffff; * * CRC-16/XMODEM, poly= 0x1021, init = 0x0000, refin = false, refout = false, xorout = 0x0000 * crc = ~crc16_be((uint16_t)~0x0000, buf, length); * */ /** * @brief CRC32 value in little endian. * * @param crc: Initial CRC value (result of last calculation or 0 for the first time) * @param buf: Data buffer that used to calculate the CRC value * @param len: Length of the data buffer * @return CRC32 value */ uint32_t esp_rom_crc32_le(uint32_t crc, uint8_t const *buf, uint32_t len); /** * @brief CRC32 value in big endian. * * @param crc: Initial CRC value (result of last calculation or 0 for the first time) * @param buf: Data buffer that used to calculate the CRC value * @param len: Length of the data buffer * @return CRC32 value */ uint32_t esp_rom_crc32_be(uint32_t crc, uint8_t const *buf, uint32_t len); /** * @brief CRC16 value in little endian. * * @param crc: Initial CRC value (result of last calculation or 0 for the first time) * @param buf: Data buffer that used to calculate the CRC value * @param len: Length of the data buffer * @return CRC16 value */ uint16_t esp_rom_crc16_le(uint16_t crc, uint8_t const *buf, uint32_t len); /** * @brief CRC16 value in big endian. * * @param crc: Initial CRC value (result of last calculation or 0 for the first time) * @param buf: Data buffer that used to calculate the CRC value * @param len: Length of the data buffer * @return CRC16 value */ uint16_t esp_rom_crc16_be(uint16_t crc, uint8_t const *buf, uint32_t len); /** * @brief CRC8 value in little endian. * * @param crc: Initial CRC value (result of last calculation or 0 for the first time) * @param buf: Data buffer that used to calculate the CRC value * @param len: Length of the data buffer * @return CRC8 value */ uint8_t esp_rom_crc8_le(uint8_t crc, uint8_t const *buf, uint32_t len); /** * @brief CRC8 value in big endian. * * @param crc: Initial CRC value (result of last calculation or 0 for the first time) * @param buf: Data buffer that used to calculate the CRC value * @param len: Length of the data buffer * @return CRC8 value */ uint8_t esp_rom_crc8_be(uint8_t crc, uint8_t const *buf, uint32_t len); #ifdef __cplusplus } #endif