Spaceship Go

Compare

First, we can compare two bytes. That is, having a function that tells us whether these two bytes are the same or not.

func Compare(a, b []byte) int

The function Compare does this for us. It checks whether two byte slices are the same, and returns the result as an integer. The function performs a lexicographic comparison and returns 0 if they are the same, -1 if a < b and +1 if a > b.

It's interesting to note how this function is implemented. Diving into Go's source code we can see the following:

func Compare(a, b []byte) int {

	return bytealg.Compare(a, b)

}

Something as simple as just comparing bytes, involves going down to assembly language. The function Compare calls the function Compare in the package bytealg, which defines Compare like this:

//go:noescape

func Compare(a, b []byte) int

The directive //go:noespace tells the compiler that the values passed to the function must be stored in the stack. And addtionally that the function implementation is not written in Go. This means that the byte comparison function is implemented in a lower laguage, like assembly.

Check Compiler directives if you want to get more details in this topic.