参考:https://www.chenxublog.com/2020/03/08/c-fast-convert-hex-char-array.html
void char_to_hex(char *src, int len, char *des)
{
char hex_table[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'};
while (len--)
{
*(des++) = hex_table[(*src) >> 4];
*(des++) = hex_table[*(src++) & 0x0f];
}
}