union数据转换 & 四字节转float

1.利用union进行数据转换

union即为联合，它是一种特殊的类。通过关键字union进行定义，可以进行数据转换

16进制字符串字节转化为十进制数

 typedef union DATA_TO_BYTE
 {
 uint16_t data16;
 unsigned char b[2];
 }TO_TWO_BYTE;
 TO_TWO_BYTE x;
 x.b[0] = (unsigned char)0x00;//低8位
 x.b[1] = (unsigned char)0x16;//高8位
 std::cout<<x.data16<<std::endl;

输出结果为5632

2.四字节与float转换

参考链接：https://blog.csdn.net/senkkes/article/details/50353316

  // char to float
  char sBuf[4];
  sBuf[0] = 0xc9;
  sBuf[1] = 0x4f;
  sBuf[2] = 0x7d;
  sBuf[3] = 0x43;
  float zx = *(float *)(sBuf);
  std::cout<< zx <<std::endl;//终端输出为253.312

  // float to char
  float wTemp = 50;
  char  sBuf1[4];
  char* temp;
  memset(sBuf1, 0, sizeof(sBuf1));

  temp     = (char *)(&wTemp);
  sBuf1[0] = temp[0];
  sBuf1[1] = temp[1];
  sBuf1[2] = temp[2];
  sBuf1[3] = temp[3];