golang container list实现

golang源码中的container列表实现。

源码实现

// Element 表示列表中的一个节点
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()).

    // 指向下一个节点和前一个节点的指针
	next, prev *Element

	// The list to which this element belongs.
    // List指针表示该节点所属的列表
	list *List

	// The value stored with this element.
    // 节点的值
	Value any
}

// Next 返回下一个节点口的指针
func (e *Element) Next() *Element {
    // 如果e.list != nil 且下一个节点不是root则返回e.next
	if p := e.next; e.list != nil && p != &e.list.root {
		return p
	}
	return nil
}

// Prev 返回上一个节点的指针
func (e *Element) Prev() *Element {
    // 如果e.list != nil 且下一个节点不是root则返回e.prev
	if p := e.prev; e.list != nil && p != &e.list.root {
		return p
	}
	return nil
}

// List 表示一个双向链表
// 链表的最后一个节点的next指针和链表的第一个节点的prev指针都指向root
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 初始化或清除一个列表
func (l *List) Init() *List {
	l.root.next = &l.root
	l.root.prev = &l.root
	l.len = 0
	return l
}

// New 初始化一个列表并返回其指针
func New() *List { return new(List).Init() }

// Len 返回列表的长度
func (l *List) Len() int { return l.len }

// Front 返回列表的第一个节点指针
func (l *List) Front() *Element {
	if l.len == 0 {
		return nil
	}
	return l.root.next
}

// Back 返回列表的最后一个指针
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 在节点at之后插入节点e, 并返回节点e指针
func (l *List) insert(e, at *Element) *Element {
	e.prev = at
	e.next = at.next
	e.prev.next = e
	e.next.prev = e
	e.list = l
	l.len++
	return e
}
// insertValue 对insert的封装
func (l *List) insertValue(v any, at *Element) *Element {
	return l.insert(&Element{Value: v}, at)
}

// remove 将节点从列表中移除
func (l *List) remove(e *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--
}

// move 将节点e移动到节点at之后
func (l *List) move(e, at *Element) {
	if e == at {
		return
	}
	e.prev.next = e.next
	e.next.prev = e.prev

	e.prev = at
	e.next = at.next
	e.prev.next = e
	e.next.prev = e
}

// Remove 将节点从列表中移除
func (l *List) Remove(e *Element) any {
	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 将节点插入到列表头
func (l *List) PushFront(v any) *Element {
	l.lazyInit()
	return l.insertValue(v, &l.root)
}

// PushBack 将节点插入到列表尾部
func (l *List) PushBack(v any) *Element {
	l.lazyInit()
	return l.insertValue(v, l.root.prev)
}

// InsertBefore 将v插入到节点mark之前
func (l *List) InsertBefore(v any, 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 将v插入到节点mark之后
func (l *List) InsertAfter(v any, mark *Element) *Element {
	if mark.list != l {
		return nil
	}
	// see comment in List.Remove about initialization of l
	return l.insertValue(v, mark)
}

// MoveToFront 将节点e移动到列表头
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.move(e, &l.root)
}

// MoveToBack 将节点e移动到列表末尾
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.move(e, l.root.prev)
}

// MoveBefore 将节点e移动到mark之前
func (l *List) MoveBefore(e, mark *Element) {
	if e.list != l || e == mark || mark.list != l {
		return
	}
	l.move(e, mark.prev)
} 

// MoveAfter 将节点e移动到mark之后
func (l *List) MoveAfter(e, mark *Element) {
	if e.list != l || e == mark || mark.list != l {
		return
	}
	l.move(e, mark)
}

// PushBackList 将一个列表中的所有元素加入l中，在l之后
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 将一个列表中的所有元素加入l中，在l之前
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)
	}
}

使用示例

package main

import (
	"container/list"
	"fmt"
)

func main() {
	l := list.New()
	e4 := l.PushBack(4)
	e1 := l.PushFront(1)
	l.InsertBefore(3, e4)
	l.InsertAfter(2, e1)

	// Iterate through list and print its contents.
	for e := l.Front(); e != nil; e = e.Next() {
		fmt.Println(e.Value)
	}
}

---

REF:

1. container/list/list.go