了解Go中的切片分配

Question

In the below code snippet, what exactly is the line after the if block doing

slice = slice[0:l+len(data)]?

func Append(slice, data []byte) []byte {
    l := len(slice)
    if l + len(data) > cap(slice) {  // reallocate
        // Allocate double what's needed, for future growth.
        newSlice := make([]byte, (l+len(data))*2)
        // The copy function is predeclared and works for any slice type.
        copy(newSlice, slice)
        slice = newSlice
    }
    slice = slice[0:l+len(data)]  // <-- What is this doing ?
    for i, c := range data {
        slice[l+i] = c
    }
    return slice
}

Answer 1

I guess

slice = slice[0:l+len(data)] 

changes slice length, so you can add new elements.

You can extend a slice's length by re-slicing it, provided it has sufficient capacity.

reference