无符号int转换C ++

Question

I'm trying to figure out a serial program with C++. I'm sending a char array that consists of several uint8_t and several uint16_t that I'm trying to split up and send.

char buf[3];
uint16_t var=1500;

What's the difference (if any) between these:

buf[0]= var & 0xFF; buf[1]= var >> 8;

and

buf[0]= (uint8_t)(var & 0xFF); buf[1]= var >> 8;

The other end is expecting 16bit integers with LSB first and for some reason I just don't think I'm getting the expected serial write. I know there are a multitude of reasons this could be happening, but I'm just trying to wrap my head around the concept here.

Answer 1

Most serial protocols want data in big-endian order. In that case you should just do *reinterpret_cast<short*>(buf) = htons(var) . If you really need little-endian, use htole16 , defined in string/endian.h .