将结构布局为字节

Question

I can't find a way to layout structure to a byte array programming by GO. I'm programming extension for GoBGP service. I want to set community for the route via GoBGP API. More about BGP and communities.

My situation:

I'm trying to send the 32bit number. First, 16bits are interpreted as AS number, other 16bits- communities. API has an interface for uint32 to set all this data. I want to have a simple structure like:

type routeCommunity struct {
   AS        uint16
   Community uint16
}

I'm struggling to pass this structure data to a uint32 variable. I would like to layout it to a byte array and then I could just make uint32 from it.

In C++ I would have a pointer of structure pointing to a char array and continued to work with that structure and in the end, I would send char array.

How to make it happen in Golang??

Answer 1

You can pass your structure to a uint32 variable using "unsafe" package:

func (rc *routeCommunity) bits() uint32 {
    return *(*uint32)(unsafe.Pointer(rc))
}

https://play.golang.org/p/AQeeoYUn7o0

UPD:

Keep in mind the bits position depends on an order of the structure fields. Low two bytes of the variable contain the first field value and high two bytes contain the second one.