标准 CRC32 参数如下：
非标准 CRC32:
多项式的值：0x04C11DB7 ,
初始值：0xFFFFFFFF，
结果异或值： 0x0，
数据输入反转 关闭，
数据输出反转 关闭。
源码是非标准CRC32, 可以更改里面的参数 变成 标准 CRC32;
/********************************************************************** * * Filename: crc32.c * * Description: Slow and fast implementations of the CRC32 standards. * * Notes: The parameters for each supported CRC standard are * defined in the header file crc.h. The implementations * here should stand up to further additions to that list. * * * Copyright (c) 2000 by Michael Barr. This software is placed into * the public domain and may be used for any purpose. However, this * notice must not be changed or removed and no warranty is either * expressed or implied by its publication or distribution. **********************************************************************/ /** * @file crc32.c * @brief Implementation of crc32.h */ #include "crc32.h" #define FALSE 0 #define TRUE !FALSE typedef unsigned long crc; #define CRC_NAME "CRC-32" // 多项式 #define POLYNOMIAL 0x04C11DB7 //#define POLYNOMIAL 0xEDB88320 //#define POLYNOMIAL 0xDB710641 //#define POLYNOMIAL 0x82608ED8 // 初始值 #define INITIAL_REMAINDER 0xFFFFFFFF // 结果异或值 #define FINAL_XOR_VALUE 0x0UL // 输入反转 关闭 #define REFLECT_DATA FALSE // 输出反转 关闭 #define REFLECT_REMAINDER FALSE /* * Derive parameters from the standard-specific parameters in crc32.h. */ #define WIDTH (8 * sizeof(crc)) #define TOPBIT (1U << (WIDTH - 1)) #if (REFLECT_DATA == TRUE) #undef REFLECT_DATA #define REFLECT_DATA(X) ((unsigned char) reflect((X), 8)) #else #undef REFLECT_DATA #define REFLECT_DATA(X) (X) #endif #if (REFLECT_REMAINDER == TRUE) #undef REFLECT_REMAINDER #define REFLECT_REMAINDER(X) ((crc) reflect((X), WIDTH)) #else #undef REFLECT_REMAINDER #define REFLECT_REMAINDER(X) (X) #endif /********************************************************************* * * Function: reflect() * * Description: Reorder the bits of a binary sequence, by reflecting * them about the middle position. * * Notes: No checking is done that nBits <= 32. * * Returns: The reflection of the original data. * *********************************************************************/ static unsigned long reflect(unsigned long data, unsigned char nBits) { unsigned long reflection = 0x00000000; unsigned char bit; /* * Reflect the data about the center bit. */ for (bit = 0; bit < nBits; ++bit) { /* * If the LSB bit is set, set the reflection of it. */ if (data & 0x01) { reflection |= (1 << ((nBits - 1) - bit)); } data = (data >> 1); } return (reflection); } /* reflect() */ /********************************************************************* * * Function: crc32() * * Description: Compute the CRC of a given message. * * Notes: * * Returns: The CRC of the message. * *********************************************************************/ uint32_t crc32(const void *data, int nBytes) { crc remainder = INITIAL_REMAINDER; int byte; unsigned char bit; unsigned char const *message = data; /* * Perform modulo-2 division, a byte at a time. */ for (byte = 0; byte < nBytes; ++byte) { /* * Bring the next byte into the remainder. */ remainder ^= (REFLECT_DATA(message[byte]) << (WIDTH - 8)); /* * Perform modulo-2 division, a bit at a time. */ for (bit = 8; bit > 0; --bit) { /* * Try to divide the current data bit. */ if (remainder & TOPBIT) { remainder = (remainder << 1) ^ POLYNOMIAL; } else { remainder = (remainder << 1); } } } /* * The final remainder is the CRC result. */ return (REFLECT_REMAINDER(remainder) ^ FINAL_XOR_VALUE); } /* crc32() */ /********************************************************************* * * Function: crc32_continue() * * Description: Compute the CRC of a given message. * * Notes: * * Returns: The CRC of the message. * *********************************************************************/ uint32_t crc32_continue(uint32_t prev_crc, const void *data, int nBytes) { crc remainder = REFLECT_REMAINDER(prev_crc ^ FINAL_XOR_VALUE); int byte; unsigned char bit; unsigned char const *message = data; /* * Perform modulo-2 division, a byte at a time. */ for (byte = 0; byte < nBytes; ++byte) { /* * Bring the next byte into the remainder. */ remainder ^= (REFLECT_DATA(message[byte]) << (WIDTH - 8)); /* * Perform modulo-2 division, a bit at a time. */ for (bit = 8; bit > 0; --bit) { /* * Try to divide the current data bit. */ if (remainder & TOPBIT) { remainder = (remainder << 1) ^ POLYNOMIAL; } else { remainder = (remainder << 1); } } } /* * The final remainder is the CRC result. */ return (REFLECT_REMAINDER(remainder) ^ FINAL_XOR_VALUE); } /* crc32_continue() */ /************************************************************************************************** * @fn crc16 * * @brief Run the CRC16 Polynomial calculation over the byte parameter. * * input parameters * * @param crc - Running CRC calculated so far. * @param val - Value on which to run the CRC16. * * output parameters * * None. * * @return crc - Updated for the run. ************************************************************************************************** */ uint16_t crc16(uint16_t crc, uint8_t val) { const uint16_t poly = 0x1021; uint8_t cnt; for (cnt = 0; cnt < 8; cnt++, val <<= 1) { uint8_t msb = (crc & 0x8000) ? 1 : 0; crc <<= 1; if (val & 0x80) crc |= 0x0001; if (msb) crc ^= poly; } return crc; }
/********************************************************************** * * Filename: crc.h * * Description: A header file describing the various CRC standards. * * Notes: * * * Copyright (c) 2000 by Michael Barr. This software is placed into * the public domain and may be used for any purpose. However, this * notice must not be changed or removed and no warranty is either * expressed or implied by its publication or distribution. **********************************************************************/ /** * @file crc.h * @brief CRC functions */ #ifndef _crc_h #define _crc_h #include "stdint.h" #ifdef __cplusplus extern "C" { #endif uint32_t crc32(const void *data, int nBytes); uint32_t crc32_continue(uint32_t prev_crc, const void *data, int nBytes); uint16_t crc16(uint16_t crc, uint8_t val); #ifdef __cplusplus } #endif #endif