输入函数，函数（req * AppendEntriesRequest）编码（w io.Writer）（int，error）{

func (req *AppendEntriesRequest) Encode(w io.Writer) (int, error) {
    pb := &protobuf.AppendEntriesRequest{
        Term:         proto.Uint64(req.Term),
        PrevLogIndex: proto.Uint64(req.PrevLogIndex),
        PrevLogTerm:  proto.Uint64(req.PrevLogTerm),
        CommitIndex:  proto.Uint64(req.CommitIndex),
        LeaderName:   proto.String(req.LeaderName),
        Entries:      req.Entries,
    }

    p, err := proto.Marshal(pb)
    if err != nil {
        return -1, err
    }

    return w.Write(p)
}

For this function, is "w" input? what about req? Kinda confused here. Thanks

that is a Go Method

AppendEntriesRequest is a type and req *AppendEntriesRequest is a pointer to that type. You can compare req in other languages as this or self

w io.Writer is the input of the function.

(int, error) are the return values.

You can invoke this method by instantiating a AppendEntriesRequest structure:

r := &AppendEntriesRequest{}
n, err := r.Encode(...)