1 // Copyright 2010-2020 Espressif Systems (Shanghai) PTE LTD 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 #pragma once 16 17 #ifdef __cplusplus 18 extern "C" { 19 #endif 20 21 #include <stdint.h> 22 23 /** Notes about CRC API 24 * The ESP32 ROM include some CRC tables and CRC APIs to speed up CRC calculation. 25 * The CRC APIs include CRC8, CRC16, CRC32 algorithms for both little endian and big endian modes. 26 * Here are the polynomials for the algorithms: 27 * CRC-8 x8+x2+x1+1 0x07 28 * CRC16-CCITT x16+x12+x5+1 0x1021 29 * CRC32 x32+x26+x23+x22+x16+x12+x11+x10+x8+x7+x5+x4+x2+x1+1 0x04c11db7 30 * 31 * These group of CRC APIs are designed to calculate the data in buffers either continuous or not. 32 * To make it easy, we had added a `~` at the beginning and the end of the functions. 33 * To calculate non-continuous buffers, we can write the code like this: 34 * init = ~init; 35 * crc = crc32_le(init, buf0, length0); 36 * crc = crc32_le(crc, buf1, length1); 37 * crc = ~crc; 38 * 39 * However, it is not easy to select which API to use and give the correct parameters. 40 * A specific CRC algorithm will include this parameters: width, polynomials, init, refin, refout, xorout 41 * refin and refout show the endian of the algorithm: 42 * if both of them are true, please use the little endian API. 43 * if both of them are false, please use the big endian API. 44 * xorout is the value which you need to be xored to the raw result. 45 * However, these group of APIs need one '~' before and after the APIs. 46 * 47 * Here are some examples for CRC16: 48 * CRC-16/CCITT, poly = 0x1021, init = 0x0000, refin = true, refout = true, xorout = 0x0000 49 * crc = ~crc16_le((uint16_t)~0x0000, buf, length); 50 * 51 * CRC-16/CCITT-FALSE, poly = 0x1021, init = 0xffff, refin = false, refout = false, xorout = 0x0000 52 * crc = ~crc16_be((uint16_t)~0xffff, buf, length); 53 * 54 * CRC-16/X25, poly = 0x1021, init = 0xffff, refin = true, refout = true, xorout = 0xffff 55 * crc = (~crc16_le((uint16_t)~(0xffff), buf, length))^0xffff; 56 * 57 * CRC-16/XMODEM, poly= 0x1021, init = 0x0000, refin = false, refout = false, xorout = 0x0000 58 * crc = ~crc16_be((uint16_t)~0x0000, buf, length); 59 * 60 */ 61 62 /** 63 * @brief CRC32 value in little endian. 64 * 65 * @param crc: Initial CRC value (result of last calculation or 0 for the first time) 66 * @param buf: Data buffer that used to calculate the CRC value 67 * @param len: Length of the data buffer 68 * @return CRC32 value 69 */ 70 uint32_t esp_rom_crc32_le(uint32_t crc, uint8_t const *buf, uint32_t len); 71 72 /** 73 * @brief CRC32 value in big endian. 74 * 75 * @param crc: Initial CRC value (result of last calculation or 0 for the first time) 76 * @param buf: Data buffer that used to calculate the CRC value 77 * @param len: Length of the data buffer 78 * @return CRC32 value 79 */ 80 uint32_t esp_rom_crc32_be(uint32_t crc, uint8_t const *buf, uint32_t len); 81 82 /** 83 * @brief CRC16 value in little endian. 84 * 85 * @param crc: Initial CRC value (result of last calculation or 0 for the first time) 86 * @param buf: Data buffer that used to calculate the CRC value 87 * @param len: Length of the data buffer 88 * @return CRC16 value 89 */ 90 uint16_t esp_rom_crc16_le(uint16_t crc, uint8_t const *buf, uint32_t len); 91 92 /** 93 * @brief CRC16 value in big endian. 94 * 95 * @param crc: Initial CRC value (result of last calculation or 0 for the first time) 96 * @param buf: Data buffer that used to calculate the CRC value 97 * @param len: Length of the data buffer 98 * @return CRC16 value 99 */ 100 uint16_t esp_rom_crc16_be(uint16_t crc, uint8_t const *buf, uint32_t len); 101 102 /** 103 * @brief CRC8 value in little endian. 104 * 105 * @param crc: Initial CRC value (result of last calculation or 0 for the first time) 106 * @param buf: Data buffer that used to calculate the CRC value 107 * @param len: Length of the data buffer 108 * @return CRC8 value 109 */ 110 uint8_t esp_rom_crc8_le(uint8_t crc, uint8_t const *buf, uint32_t len); 111 112 /** 113 * @brief CRC8 value in big endian. 114 * 115 * @param crc: Initial CRC value (result of last calculation or 0 for the first time) 116 * @param buf: Data buffer that used to calculate the CRC value 117 * @param len: Length of the data buffer 118 * @return CRC8 value 119 */ 120 uint8_t esp_rom_crc8_be(uint8_t crc, uint8_t const *buf, uint32_t len); 121 122 #ifdef __cplusplus 123 } 124 #endif 125
