C语言常用的工具函数（自用一）

文章目录

• C语言常用的工具函数（自用一）
• • 1、查表法计算crc
  • • 1.1、crc16
    • 1.2、crc5
  • 2、字符转换
  • 3、长整型和8位字节数组转换
  • • 3.1、将长整型中的某几位转为8位字节数组
    • 3.2、将8位字节数组转为长整型中的某几位
  • 4、延时相关函数（基于stm32）
  • • 4.1、SysTick和nop延时
    • 4.2、DWT ns延时
  • 5、位循环移动

C语言常用的工具函数（自用一）

---

1、查表法计算crc

1.1、crc16

#define CRC16_WIDTH     16
#define POLYNOMIAL_16   0x1021
#define CRC16_PRELOAD   0xFFFF

//查表法计算crc16
const uint16_t crc16OffsetTable[256]= {
0x0000,0x1021,0x2042,0x3063,0x4084,0x50a5,0x60c6,0x70e7,
0x8108,0x9129,0xa14a,0xb16b,0xc18c,0xd1ad,0xe1ce,0xf1ef,
0x1231,0x0210,0x3273,0x2252,0x52b5,0x4294,0x72f7,0x62d6,
0x9339,0x8318,0xb37b,0xa35a,0xd3bd,0xc39c,0xf3ff,0xe3de,
0x2462,0x3443,0x0420,0x1401,0x64e6,0x74c7,0x44a4,0x5485,
0xa56a,0xb54b,0x8528,0x9509,0xe5ee,0xf5cf,0xc5ac,0xd58d,
0x3653,0x2672,0x1611,0x0630,0x76d7,0x66f6,0x5695,0x46b4,
0xb75b,0xa77a,0x9719,0x8738,0xf7df,0xe7fe,0xd79d,0xc7bc,
0x48c4,0x58e5,0x6886,0x78a7,0x0840,0x1861,0x2802,0x3823,
0xc9cc,0xd9ed,0xe98e,0xf9af,0x8948,0x9969,0xa90a,0xb92b,
0x5af5,0x4ad4,0x7ab7,0x6a96,0x1a71,0x0a50,0x3a33,0x2a12,
0xdbfd,0xcbdc,0xfbbf,0xeb9e,0x9b79,0x8b58,0xbb3b,0xab1a,
0x6ca6,0x7c87,0x4ce4,0x5cc5,0x2c22,0x3c03,0x0c60,0x1c41,
0xedae,0xfd8f,0xcdec,0xddcd,0xad2a,0xbd0b,0x8d68,0x9d49,
0x7e97,0x6eb6,0x5ed5,0x4ef4,0x3e13,0x2e32,0x1e51,0x0e70,
0xff9f,0xefbe,0xdfdd,0xcffc,0xbf1b,0xaf3a,0x9f59,0x8f78,
0x9188,0x81a9,0xb1ca,0xa1eb,0xd10c,0xc12d,0xf14e,0xe16f,
0x1080,0x00a1,0x30c2,0x20e3,0x5004,0x4025,0x7046,0x6067,
0x83b9,0x9398,0xa3fb,0xb3da,0xc33d,0xd31c,0xe37f,0xf35e,
0x02b1,0x1290,0x22f3,0x32d2,0x4235,0x5214,0x6277,0x7256,
0xb5ea,0xa5cb,0x95a8,0x8589,0xf56e,0xe54f,0xd52c,0xc50d,
0x34e2,0x24c3,0x14a0,0x0481,0x7466,0x6447,0x5424,0x4405,
0xa7db,0xb7fa,0x8799,0x97b8,0xe75f,0xf77e,0xc71d,0xd73c,
0x26d3,0x36f2,0x0691,0x16b0,0x6657,0x7676,0x4615,0x5634,
0xd94c,0xc96d,0xf90e,0xe92f,0x99c8,0x89e9,0xb98a,0xa9ab,
0x5844,0x4865,0x7806,0x6827,0x18c0,0x08e1,0x3882,0x28a3,
0xcb7d,0xdb5c,0xeb3f,0xfb1e,0x8bf9,0x9bd8,0xabbb,0xbb9a,
0x4a75,0x5a54,0x6a37,0x7a16,0x0af1,0x1ad0,0x2ab3,0x3a92,
0xfd2e,0xed0f,0xdd6c,0xcd4d,0xbdaa,0xad8b,0x9de8,0x8dc9,
0x7c26,0x6c07,0x5c64,0x4c45,0x3ca2,0x2c83,0x1ce0,0x0cc1,
0xef1f,0xff3e,0xcf5d,0xdf7c,0xaf9b,0xbfba,0x8fd9,0x9ff8,
0x6e17,0x7e36,0x4e55,0x5e74,0x2e93,0x3eb2,0x0ed1,0x1ef0
};

/**

- @brief  按字节进行crc16计算.
- @note
- @param  *data 要计算crc16的数组.
- len 数组中的有效计算字节数
    *
- @retval 返回uint16_t类型的crc结果
- @author yangFei
- @date   20220324
- @note   
  */
  uint16_t crc16Bytewise(const uint8_t *data, uint16_t len)
  {
    uint16_t crc = CRC16_PRELOAD;
    uint8_t *sbuf = (uint8_t *)data;
    for (uint32_t counter=0 ; counter<len; ++counter) 
    {
        crc = (crc<<8) ^ crc16OffsetTable[(uint8_t)((crc>>8) ^ *sbuf++)];
    }
    return ~crc;
}

/**

- @brief  按位进行crc16计算.
- @note
- @param  *data 要计算crc16的数组.
- bits 数组中的有效计算位
    *
- @retval 返回uint16_t类型的crc结果
- @author yangFei
- @date   20220324
- @note   
  */
  uint16_t crc16Bitwise(const uint8_t *data, uint16_t bits)
  {
    uint32_t nbFullBytes = bits/8;
    uint16_t crc16 = crc16Bytewise(data, nbFullBytes);

    uint32_t nbExtraBits = bits%8;
    if (nbExtraBits) {
        uint8_t buf[nbFullBytes+1];

        crc16 = ~crc16;
        buf[nbFullBytes] = data[nbFullBytes] & (uint8_t)(0xFF00 >> nbExtraBits);
        crc16 ^= (buf[nbFullBytes] << (CRC16_WIDTH-8));

        // Repeat polynomial calculation (avoid loop for best performance)
        switch (nbExtraBits) {
            case 7: crc16 = (crc16 & (1<<(CRC16_WIDTH-1))) ? (crc16 << 1) ^ POLYNOMIAL_16 : (crc16 << 1);   // Fall through
            case 6: crc16 = (crc16 & (1<<(CRC16_WIDTH-1))) ? (crc16 << 1) ^ POLYNOMIAL_16 : (crc16 << 1);   // Fall through
            case 5: crc16 = (crc16 & (1<<(CRC16_WIDTH-1))) ? (crc16 << 1) ^ POLYNOMIAL_16 : (crc16 << 1);   // Fall through
            case 4: crc16 = (crc16 & (1<<(CRC16_WIDTH-1))) ? (crc16 << 1) ^ POLYNOMIAL_16 : (crc16 << 1);   // Fall through
            case 3: crc16 = (crc16 & (1<<(CRC16_WIDTH-1))) ? (crc16 << 1) ^ POLYNOMIAL_16 : (crc16 << 1);   // Fall through
            case 2: crc16 = (crc16 & (1<<(CRC16_WIDTH-1))) ? (crc16 << 1) ^ POLYNOMIAL_16 : (crc16 << 1);   // Fall through
            case 1: crc16 = (crc16 & (1<<(CRC16_WIDTH-1))) ? (crc16 << 1) ^ POLYNOMIAL_16 : (crc16 << 1);   // Fall through
        }
        crc16 = ~crc16;
    }

    return crc16;
}

1.2、crc5

/**

- @brief  CRC-5计算.
- @note
- @param  data 帧有效数据.
- bits 冗余校验比特数
    *
- @retval 5位校验结果
- @author yangFei
- @date   20220324
- @note   只适用于RFID协议中的校验，不具备适用性；crc5Bitwise(0x818180,17) = 0x1d
  */
  uint8_t crc5Bitwise(uint32_t data, uint16_t bits)
  {
    uint32_t crc;
    uint32_t crc_n;

    crc = (0x09 << 19);  //19+5 = 24

    while(bits--)
    {
        crc_n  = (crc << 1) & 0xFFFFFFFF;
        crc_n ^= ((data ^ crc) & (1<<23)) ? (0x29 << (19)) : 0;
        crc    = crc_n;
        data  = (data << 1) & 0xFFFFFFFF;
    }
    crc >>= 19;
    crc ^= 0x0000001F;
    crc = ~crc;
    crc &= 0x0000001F;

    return (uint8_t)crc;
}

2、字符转换

/**
  * @brief  字符转换位16进制.
  * @note
  * @param  a  传入的字符.
  *
  * @retval 返回字符对应的16进制
  * @author yangFei
  * @date   20220324
  * @note   小写
  */
uint8_t char2hex(uint8_t a)
{
    uint8_t temp;

    if((a>='0')&(a<='9'))
        return (a-'0');
    else
    {
        switch(a)
        {
        case 'a':
            temp = 10;
            break;

        case 'b':
            temp = 11;
            break;

        case 'c':
            temp = 12;
            break;

        case 'd':
            temp = 13;
            break;

        case 'e':
            temp = 14;
            break;

        case 'f':
            temp = 15;
            break;

        }

        return temp;
    }
}

3、长整型和8位字节数组转换

3.1、将长整型中的某几位转为8位字节数组

/**
	* @brief  将长整型中的某几位转为8位字节数组.
  * @note
  * @param  long_bit  长整型数据
  * @param 	*short_bit 8位字节数组
  * @param 	bit_len 要转换的位长度
  *
  * @retval 0：转换成功    1：转换失败
  * @author yangFei
  * @date   20220328
  * @note   默认高位在前
  */
uint8_t long_short_arr(uint64_t long_bit, uint8_t *short_bit, uint8_t bit_len)
{
      uint8_t short_bytes;

      short_bytes = bit_len / 8;
      if(bit_len % 8)
      {
        short_bytes += 1;
      }

      if(short_bytes > 8)
      {
        return 1;
      }

      for(uint8_t i=0; i<short_bytes; i++) 
      {
        short_bit[short_bytes-1-i] = (long_bit >> (i*8)) & 0xff;
      }

      return 0;
}

3.2、将8位字节数组转为长整型中的某几位

/**
	* @brief  将某几位为8位字节数组转为长整型.
  * @note
  * @param 	*short_bit 8位字节数组
  * @param 	bit_len 要转换的位长度
  *
  * @retval 转换后的长整型
  * @author yangFei
  * @date   20220328
  * @note   默认高位在前
  */
uint64_t short_arr_long(uint8_t *short_bit, uint8_t bit_len)
{
      uint8_t short_bytes;
      uint64_t long_data = 0;

      short_bytes = bit_len / 8;

      if(bit_len % 8)
      {
        short_bytes += 1;
      }

      for(uint8_t i=0; i<short_bytes; i++) 
      {
        long_data |= (short_bit[i] << ((short_bytes-1-i) * 8));
      }

      return long_data;
}

4、延时相关函数（基于stm32）

4.1、SysTick和nop延时

/**
  * @brief  死循环us延时.
  * @note
  * @param  nus 微秒数.
  *
  * @retval 
  * @author yangFei
  * @date   20220324
  * @note   若使用SysTick仍然有不可接受的误差，使用__NOP().
  */
void delay_us(uint32_t nus)
{
#define clock (SystemCoreClock / 1000000)

    uint32_t ticks;
    uint32_t told,tnow,tcnt = 0;
    uint32_t reload = SysTick->LOAD;	//LOAD的值
    ticks = clock * nus; 			//需要的节拍数
//    CPU_CRITICAL_ENTER();       /* close interrupt            */

    told = SysTick->VAL;        	//刚进入时的计数器值
    while(1)
    {
        tnow = SysTick->VAL;
        if(tnow != told)
        {
            if(tnow < told) tcnt += told - tnow; //这里注意一下SYSTICK是一个递减的计数器就可以了
            else tcnt += reload - tnow + told;
            told = tnow;
            if(tcnt >= ticks)break; //时间超过/等于要延迟的时间,则退出.
        }
    };

//    //CPU_CRITICAL_EXIT();			//恢复关中断前状态
		
//		for(uint32_t i=0; i<nus; i++)//需要手动根据时钟计算需要几个__NOP()   80M情况下大概20个 是3.2us
//		{
//		//        __NOP();
//		//        __NOP();
//		//        __NOP();
//		//        __NOP();
//		//			
//		//        __NOP();
//		//        __NOP();
//		//        __NOP();
//		//        __NOP();
//			
//			
//				__NOP();
//				__NOP();
//				__NOP();
//				__NOP();
//				__NOP();
//				__NOP();
//				__NOP();
//				__NOP();
//				__NOP();
//				__NOP();
//				__NOP();
//				__NOP();
//				__NOP();
//				__NOP();
//				__NOP();
//				__NOP();
//		}
}

4.2、DWT ns延时

#define NS_TO_CYCLES(ns)        (((ns)*2)/25)

#define INIT_DWT()             { CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;    \
                                 DWT->CTRL |= DWT_CTRL_CYCCNTENA_Msk;               \
                                 RESET_DWT();                                       \
                                 }
#define RESET_DWT()             DWT->CYCCNT = 0
#define GET_DWT()               (DWT->CYCCNT)

/**
  * @brief  DWT ns延时
  * @note
  * @param  nsec ns延时.
  *
  * @retval 
  * @author yangFei
  * @date   20220401
  * @note   调用此函数前需调用INIT_DWT();   RESET_DWT();
  */
void nsdelay(uint32_t nsec)
{
	RESET_DWT();  
	
    uint32_t cycles = NS_TO_CYCLES(nsec)-(nsec < 8000 ? 25 : 20);    // -25/-20: compensate function call overhead
    do
    {
        __NOP();            // Avoid code optimization
    } while(GET_DWT() < cycles);    
}

5、位循环移动

//循环左移 
#define ROTATE_LEFT(x,  n) ((x) << (n)) | ((x) >> ((8*sizeof(x)) - (n)))
//循环右移 
#define ROTATE_RIGHT(x,  n) ((x) >> (n)) | ((x) << ((8*sizeof(x)) - (n)))