Provide official ListPingHandler implementation

server/playerlist.go

@@ -0,0 +1,90 @@
+package server
+
+import (
+	"container/list"
+	"sync"
+
+	"github.com/Tnze/go-mc/chat"
+)
+
+// PlayerList is an implement of ListPingHandler based on linked-list.
+// This struct should not be copied after used.
+type PlayerList struct {
+	name        string
+	protocol    int
+	maxPlayer   int
+	description *chat.Message
+	players     *list.List
+	// Only the linked-list is protected by this Mutex.
+	// Because others field never change after created.
+	playersLock sync.Mutex
+}
+
+// NewPlayerList create a PlayerList which implement ListPingHandler.
+func NewPlayerList(name string, protocol, maxPlayers int, motd *chat.Message) *PlayerList {
+	return &PlayerList{
+		name:        name,
+		protocol:    protocol,
+		maxPlayer:   maxPlayers,
+		description: motd,
+		players:     list.New(),
+	}
+}
+
+// TryInsert trying to insert player into PlayerList.
+// Return nil if the server is full (length of list larger than maxPlayers),
+// otherwise return a function which is used to remove the player from PlayerList
+func (p *PlayerList) TryInsert(player PlayerSample) (remove func()) {
+	p.playersLock.Lock()
+	defer p.playersLock.Unlock()
+
+	if p.players.Len() >= p.maxPlayer {
+		return nil
+	}
+
+	elem := p.players.PushBack(player)
+	return func() {
+		p.playersLock.Lock()
+		p.players.Remove(elem)
+		p.playersLock.Unlock()
+	}
+}
+
+func (p *PlayerList) Name() string {
+	return p.name
+}
+
+func (p *PlayerList) Protocol() int {
+	return p.protocol
+}
+
+func (p *PlayerList) MaxPlayer() int {
+	return p.maxPlayer
+}
+
+func (p *PlayerList) OnlinePlayer() int {
+	p.playersLock.Lock()
+	defer p.playersLock.Unlock()
+	return p.players.Len()
+}
+
+func (p *PlayerList) PlayerSamples() (sample []PlayerSample) {
+	p.playersLock.Lock()
+	defer p.playersLock.Unlock()
+	// Up to 10 players can be returned
+	length := p.players.Len()
+	if length > 10 {
+		length = 10
+	}
+	sample = make([]PlayerSample, length)
+	v := p.players.Front()
+	for i := 0; i < length; i++ {
+		sample[i] = v.Value.(PlayerSample)
+		v = v.Next()
+	}
+	return
+}
+
+func (p *PlayerList) Description() *chat.Message {
+	return p.description
+}