package main
 
import (
	"container/list"
	"fmt"
)
 
func main() {
	// 构造链表对象
	pers := list.New()
 
	// Persion 普通人对象
	type Persion struct {
		Name string
		Age  int
	}
 
	// 链表对象数据填充
	pers.PushBack(&Persion{"wang", 27})
	pers.PushFront(&Persion{"zhi", 27})
 
	// 开始遍历处理
	for e := pers.Front(); e != nil; e = e.Next() {
		per, ok := e.Value.(*Persion)
		if !ok {
			panic(fmt.Sprint("Persion List faild", e.Value))
		}
		fmt.Println(per)
	}
 
	for e := pers.Front(); e != nil; {
		next := e.Next()
		pers.Remove(e)
		e = next
	}
	fmt.Println(pers.Len())
}

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
 
// Package list implements a doubly linked list.
//
// To iterate over a list (where l is a *List):
//	for e := l.Front(); e != nil; e = e.Next() {
//		// do something with e.Value
//	}
//
package list
 
// Element is an element of a linked list.
type Element struct {
	// Next and previous pointers in the doubly-linked list of elements.
	// To simplify the implementation, internally a list l is implemented
	// as a ring, such that &l.root is both the next element of the last
	// list element (l.Back()) and the previous element of the first list
	// element (l.Front()).
	next, prev *Element
 
	// The list to which this element belongs.
	list *List
 
	// The value stored with this element.
	Value interface{}
}
 
// Next returns the next list element or nil.
func (e *Element) Next() *Element {
	if p := e.next; e.list != nil && p != &e.list.root {
		return p
	}
	return nil
}
 
// Prev returns the previous list element or nil.
func (e *Element) Prev() *Element {
	if p := e.prev; e.list != nil && p != &e.list.root {
		return p
	}
	return nil
}
 
// List represents a doubly linked list.
// The zero value for List is an empty list ready to use.
type List struct {
	root Element // sentinel list element, only &root, root.prev, and root.next are used
	len  int     // current list length excluding (this) sentinel element
}
 
// Init initializes or clears list l.
func (l *List) Init() *List {
	l.root.next = &l.root
	l.root.prev = &l.root
	l.len = 0
	return l
}
 
// New returns an initialized list.
func New() *List { return new(List).Init() }
 
// Len returns the number of elements of list l.
// The complexity is O(1).
func (l *List) Len() int { return l.len }
 
// Front returns the first element of list l or nil if the list is empty.
func (l *List) Front() *Element {
	if l.len == 0 {
		return nil
	}
	return l.root.next
}
 
// Back returns the last element of list l or nil if the list is empty.
func (l *List) Back() *Element {
	if l.len == 0 {
		return nil
	}
	return l.root.prev
}
 
// lazyInit lazily initializes a zero List value.
func (l *List) lazyInit() {
	if l.root.next == nil {
		l.Init()
	}
}
 
// insert inserts e after at, increments l.len, and returns e.
func (l *List) insert(e, at *Element) *Element {
	n := at.next
	at.next = e
	e.prev = at
	e.next = n
	n.prev = e
	e.list = l
	l.len++
	return e
}
 
// insertValue is a convenience wrapper for insert(&Element{Value: v}, at).
func (l *List) insertValue(v interface{}, at *Element) *Element {
	return l.insert(&Element{Value: v}, at)
}
 
// remove removes e from its list, decrements l.len, and returns e.
func (l *List) remove(e *Element) *Element {
	e.prev.next = e.next
	e.next.prev = e.prev
	e.next = nil // avoid memory leaks
	e.prev = nil // avoid memory leaks
	e.list = nil
	l.len--
	return e
}
 
// Remove removes e from l if e is an element of list l.
// It returns the element value e.Value.
// The element must not be nil.
func (l *List) Remove(e *Element) interface{} {
	if e.list == l {
		// if e.list == l, l must have been initialized when e was inserted
		// in l or l == nil (e is a zero Element) and l.remove will crash
		l.remove(e)
	}
	return e.Value
}
 
// PushFront inserts a new element e with value v at the front of list l and returns e.
func (l *List) PushFront(v interface{}) *Element {
	l.lazyInit()
	return l.insertValue(v, &l.root)
}
 
// PushBack inserts a new element e with value v at the back of list l and returns e.
func (l *List) PushBack(v interface{}) *Element {
	l.lazyInit()
	return l.insertValue(v, l.root.prev)
}
 
// InsertBefore inserts a new element e with value v immediately before mark and returns e.
// If mark is not an element of l, the list is not modified.
// The mark must not be nil.
func (l *List) InsertBefore(v interface{}, mark *Element) *Element {
	if mark.list != l {
		return nil
	}
	// see comment in List.Remove about initialization of l
	return l.insertValue(v, mark.prev)
}
 
// InsertAfter inserts a new element e with value v immediately after mark and returns e.
// If mark is not an element of l, the list is not modified.
// The mark must not be nil.
func (l *List) InsertAfter(v interface{}, mark *Element) *Element {
	if mark.list != l {
		return nil
	}
	// see comment in List.Remove about initialization of l
	return l.insertValue(v, mark)
}
 
// MoveToFront moves element e to the front of list l.
// If e is not an element of l, the list is not modified.
// The element must not be nil.
func (l *List) MoveToFront(e *Element) {
	if e.list != l || l.root.next == e {
		return
	}
	// see comment in List.Remove about initialization of l
	l.insert(l.remove(e), &l.root)
}
 
// MoveToBack moves element e to the back of list l.
// If e is not an element of l, the list is not modified.
// The element must not be nil.
func (l *List) MoveToBack(e *Element) {
	if e.list != l || l.root.prev == e {
		return
	}
	// see comment in List.Remove about initialization of l
	l.insert(l.remove(e), l.root.prev)
}
 
// MoveBefore moves element e to its new position before mark.
// If e or mark is not an element of l, or e == mark, the list is not modified.
// The element and mark must not be nil.
func (l *List) MoveBefore(e, mark *Element) {
	if e.list != l || e == mark || mark.list != l {
		return
	}
	l.insert(l.remove(e), mark.prev)
}
 
// MoveAfter moves element e to its new position after mark.
// If e or mark is not an element of l, or e == mark, the list is not modified.
// The element and mark must not be nil.
func (l *List) MoveAfter(e, mark *Element) {
	if e.list != l || e == mark || mark.list != l {
		return
	}
	l.insert(l.remove(e), mark)
}
 
// PushBackList inserts a copy of an other list at the back of list l.
// The lists l and other may be the same. They must not be nil.
func (l *List) PushBackList(other *List) {
	l.lazyInit()
	for i, e := other.Len(), other.Front(); i > 0; i, e = i-1, e.Next() {
		l.insertValue(e.Value, l.root.prev)
	}
}
 
// PushFrontList inserts a copy of an other list at the front of list l.
// The lists l and other may be the same. They must not be nil.
func (l *List) PushFrontList(other *List) {
	l.lazyInit()
	for i, e := other.Len(), other.Back(); i > 0; i, e = i-1, e.Prev() {
		l.insertValue(e.Value, &l.root)
	}
}

// Element is an element of a linked list.
type Element struct {
	// Next and previous pointers in the doubly-linked list of elements.
	// To simplify the implementation, internally a list l is implemented
	// as a ring, such that &l.root is both the next element of the last
	// list element (l.Back()) and the previous element of the first list
	// element (l.Front()).
	next, prev *Element
 
	// The list to which this element belongs.
	list *List
 
	// The value stored with this element.
	Value interface{}
}
 
// Next returns the next list element or nil.
func (e *Element) Next() *Element {
	if p := e.next; e.list != nil && p != &e.list.root {
		return p
	}
	return nil
}
 
// Prev returns the previous list element or nil.
func (e *Element) Prev() *Element {
	if p := e.prev; e.list != nil && p != &e.list.root {
		return p
	}
	return nil
}
 
// List represents a doubly linked list.
// The zero value for List is an empty list ready to use.
type List struct {
	root Element // sentinel list element, only &root, root.prev, and root.next are used
	len  int     // current list length excluding (this) sentinel element
}

// PushBackList inserts a copy of an other list at the back of list l.
// The lists l and other may be the same. They must not be nil.
func (l *List) PushBackList(other *List) {
	l.lazyInit()
	for i, e := other.Len(), other.Front(); i > 0; i, e = i-1, e.Next() {
		l.insertValue(e.Value, l.root.prev)
	}
}

// PushBackList inserts a copy of an other list at the back of list l.
// The lists l and other may be the same. They must not be nil.
func (l *List) PushBackList(other *List) {
	l.lazyInit()
	for e := other.Front(); e != nil; e = e.Next() {
		l.insertValue(e.Value, l.root.prev)
	}
}

package cache
 
import (
	"container/list"
	"sync"
)
 
// entry 存储实体内容
type entry struct {
	key   interface{}
	value interface{}
}
 
// Cache LRU 缓存实现
type Cache struct {
	// x 保证 LRU 访问安全
	m sync.Mutex
 
	// max 表示缓存容量的最大值, 0 表示无限缓存
	max uint
 
	// list 循环双向链表
	list *list.List
 
	// pond 缓存的池子
	pond map[interface{}]*list.Element
}
 
// New 新建一个 LRU 缓存对象
func New(max uint) *Cache {
	return &Cache{
		max:  max,
		list: list.New(),
		pond: make(map[interface{}]*list.Element),
	}
}
 
// remove 通过 *list.Element 删除
func (c *Cache) remove(e *list.Element) {
	n, ok := c.list.Remove(e).(*entry)
	if ok {
		delete(c.pond, n.key)
	}
}
 
// Set 添加缓存
func (c *Cache) Set(key, value interface{}) {
	c.m.Lock()
	defer c.m.Unlock()
 
	if e, ok := c.pond[key]; ok {
		if value == nil {
			// Set key nil <=> Remove key
			c.remove(e)
		} else {
			e.Value = value
			c.list.MoveToFront(e)
		}
		return
	}
 
	// 如果是首次添加
	c.pond[key] = c.list.PushFront(&entry{key, value})
 
	// 如果超出池子缓存开始清理
	if c.max != 0 && uint(c.list.Len()) > c.max {
		c.remove(c.list.Back())
	}
}
 
// Get 获取缓存
func (c *Cache) Get(key interface{}) (interface{}, bool) {
	c.m.Lock()
	defer c.m.Unlock()
 
	if e, ok := c.pond[key]; ok {
		c.list.MoveToFront(e)
		return e.Value.(*entry).value, true
	}
	return nil, false
}

	c := cache.New(1)
	c.Set("123", "123")
	c.Set("234", "234")
	fmt.Println(c.Get("123"))
	fmt.Println(c.Get("234"))