New server framework, an example, and compressed packet fixed.

server/login.go

@@ -0,0 +1,80 @@
+package server
+
+import (
+	"fmt"
+
+	"github.com/Tnze/go-mc/data/packetid"
+	"github.com/Tnze/go-mc/net"
+	pk "github.com/Tnze/go-mc/net/packet"
+	"github.com/Tnze/go-mc/offline"
+	"github.com/Tnze/go-mc/server/auth"
+	"github.com/google/uuid"
+)
+
+type LoginHandler interface {
+	AcceptLogin(conn *net.Conn, protocol int32) (name string, id uuid.UUID, err error)
+}
+
+type MojangLoginHandler struct {
+	OnlineMode bool
+	Threshold  int
+}
+
+func (d *MojangLoginHandler) AcceptLogin(conn *net.Conn, protocol int32) (name string, id uuid.UUID, err error) {
+	//login start
+	var p pk.Packet
+	err = conn.ReadPacket(&p)
+	if err != nil {
+		return
+	}
+	if p.ID != packetid.LoginStart {
+		err = wrongPacketErr{expect: packetid.LoginStart, get: p.ID}
+		return
+	}
+
+	err = p.Scan((*pk.String)(&name)) //decode username as pk.String
+	if err != nil {
+		return
+	}
+
+	//auth
+	if d.OnlineMode {
+		var resp *auth.Resp
+		//Auth, Encrypt
+		resp, err = auth.Encrypt(conn, name)
+		if err != nil {
+			return
+		}
+		name = resp.Name
+		id = resp.ID
+	} else {
+		// offline-mode UUID
+		id = offline.NameToUUID(name)
+	}
+
+	//set compression
+	if d.Threshold >= 0 {
+		err = conn.WritePacket(pk.Marshal(
+			packetid.Compress, pk.VarInt(d.Threshold),
+		))
+		if err != nil {
+			return
+		}
+		conn.SetThreshold(d.Threshold)
+	}
+
+	// send login success
+	err = conn.WritePacket(pk.Marshal(packetid.Success,
+		pk.UUID(id),
+		pk.String(name),
+	))
+	return
+}
+
+type wrongPacketErr struct {
+	expect, get int32
+}
+
+func (w wrongPacketErr) Error() string {
+	return fmt.Sprintf("wrong packet id: expect %#02X, get %#02X", w.expect, w.get)
+}