完成了内存存储的书写

6.3.md

@@ -1,4 +1,119 @@
 #6.3 session存储
+上一节我们介绍了Session管理器的实现原理，定义了如何实现session存储的接口，这小节我们讲通过一个例子来实现内存的session存储，其他类似数据库或者文件的存储，用户可以根据相应的接口定义来实现，内存的实现请看下面的例子代码
+
+	package memory
+	
+	import (
+		"session/session"
+		"time"
+	)
+	
+	var d = &Provider{}
+	
+	type SessionStore struct {
+		sid          string                      //session id唯一标示	  	
+		timeAccessed time.Time                   //最后访问时间	  	
+		value        map[interface{}]interface{} //session里面存储的值
+	}
+	
+	func (this *SessionStore) Set(key, value interface{}) bool {
+		this.value[key] = value
+		d.SessionUpdate(this.sid)
+		return true
+	}
+	
+	func (this *SessionStore) Get(key interface{}) interface{} {
+		d.SessionUpdate(this.sid)
+		if v, ok := this.value[key]; ok {
+			return v
+		} else {
+			return ""
+		}
+	}
+	
+	func (this *SessionStore) Del(key interface{}) bool {
+		delete(this.value, key)
+		d.SessionUpdate(this.sid)
+		return true
+	}
+	
+	type Provider struct {
+		lock     sync.Mutex               //用来锁
+		sessions map[string]*SessionStore //用来存储在内存
+		list     *list.List               //用来做gc
+	}
+	
+	func (this *Provider) SessionInit(sid string) (session.Session, error) {
+		this.lock.Lock()
+		defer this.lock.Unlock()
+		v := make(map[interface{}]interface{}, 0)
+		newsess := &SessionStore{"sid": sid, "timeAccessed": time.Now(), "value": v}
+		this.sessions[sid] = newsess
+		this.list.Push(newsess)
+		return newsess
+	}
+	
+	func (this *Provider) SessionRead(sid string) (session.Session, error) {
+		if s, ok := this.sessions[sid]; ok {
+			return s, nil
+		} else {
+			sess, err := this.SessionInit(sid)
+			return sess, err
+		}
+	}
+	
+	func (this *Provider) SessionDestroy(sid string) bool {
+		if s, ok := this.sessions[sid]; ok {
+			delete(this.table, sid)
+			this.list.Remove(s)
+			return true
+		} else {
+			return false
+		}
+	}
+	
+	func (this *Provider) SessionGC(maxlifetime int64) {
+		this.lock.Lock()
+		defer this.lock.Unlock()
+	
+		for {
+			element := this.list.Back()
+			if element == nil {
+				break
+			}
+			if (element.Value.(*SessionStore).timeAccessed.Unix() + maxlifetime) < time.Now().Unix() {
+				this.list.Remove(element)
+				delete(this.table, element.Value.(*SessionStore).sid)
+			} else {
+				break
+			}
+		}
+	}
+	
+	func (this *Provider) SessionUpdate(sid string) bool {
+		this.lock.Lock()
+		defer this.lock.Unlock()
+		if element, ok := this.sessions[sid]; ok {
+			element.Value.(*SessionStore).value = s.value
+			this.moveToFront(element)
+			return true
+		} else {
+			return false
+		}
+	}
+	
+	func (this *Provider) moveToFront(element *list.Element) {
+		this.lock.Lock()
+		defer this.lock.Unlock()
+		element.Value.(*SessionStore).timeAccessed = time.Now()
+		this.list.MoveToFront(element)
+	}
+	
+	func init() {
+		session.Register("memory", d)
+	}
+
+上面这个代码实现了一个内存存储实现的session机制
 ## links
    * [目录](<preface.md>)
    * 上一节: [Go如何使用session](<6.2.md>)