掌機 - Miyoo Mini Plus - 如何更新U-Boot Environment CRC32

CRC32結果位於：0x5f000
CRC32計算長度：0x5f004~0x60000
Environment Variables：0x5f004~0x60000

計算方式如下：

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>

static char buf[4096] = {0};

unsigned int crc32b(unsigned char *buf, int len)
{
   int i = 0, j = 0;
   unsigned int byte = 0, crc = 0, mask = 0;

   crc = 0xffffffff;
   for (i=0; i<len; i++) {
      byte = buf[i];
      crc = crc ^ byte;
      for (j = 7; j >= 0; j--) {
         mask = -(crc & 1);
         crc = (crc >> 1) ^ (0xedb88320 & mask);
      }
   }
   return ~crc;
}

int main(int argc, char **argv)
{
    int len = 0, fd = -1;
    
    fd = open("mtdblock0_env_offset", O_RDONLY);
    len = read(fd, buf, sizeof(buf));
    close(fd);

    printf("0x%x\n", crc32b(buf, 0x1000 - 4));
    return 0;
}