mirror of
https://github.com/wlynxg/NetHive.git
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feat: implement a list with generics
This commit is contained in:
lynx
235
pkgs/list/list.go
Normal file
235
pkgs/list/list.go
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@@ -0,0 +1,235 @@
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// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package list implements a doubly linked list.
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//
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// To iterate over a list (where l is a *List):
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//
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// for e := l.Front(); e != nil; e = e.Next() {
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// // do something with e.Value
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// }
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package list
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// Element is an element of a linked list.
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type Element[V any] struct {
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// Next and previous pointers in the doubly-linked list of elements.
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// To simplify the implementation, internally a list l is implemented
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// as a ring, such that &l.root is both the next element of the last
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// list element (l.Back()) and the previous element of the first list
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// element (l.Front()).
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next, prev *Element[V]
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// The list to which this element belongs.
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list *List[V]
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// The value stored with this element.
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Value V
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}
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// Next returns the next list element or nil.
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func (e *Element[V]) Next() *Element[V] {
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if p := e.next; e.list != nil && p != &e.list.root {
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return p
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}
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return nil
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}
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// Prev returns the previous list element or nil.
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func (e *Element[V]) Prev() *Element[V] {
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if p := e.prev; e.list != nil && p != &e.list.root {
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return p
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}
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return nil
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}
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// List represents a doubly linked list.
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// The zero value for List is an empty list ready to use.
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type List[V any] struct {
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root Element[V] // sentinel list element, only &root, root.prev, and root.next are used
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len int // current list length excluding (this) sentinel element
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}
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// Init initializes or clears list l.
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func (l *List[V]) Init() *List[V] {
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l.root.next = &l.root
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l.root.prev = &l.root
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l.len = 0
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return l
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}
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// New returns an initialized list.
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func New[V any]() *List[V] { return new(List[V]).Init() }
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// Len returns the number of elements of list l.
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// The complexity is O(1).
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func (l *List[V]) Len() int { return l.len }
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// Front returns the first element of list l or nil if the list is empty.
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func (l *List[V]) Front() *Element[V] {
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if l.len == 0 {
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return nil
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}
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return l.root.next
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}
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// Back returns the last element of list l or nil if the list is empty.
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func (l *List[V]) Back() *Element[V] {
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if l.len == 0 {
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return nil
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}
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return l.root.prev
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}
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// lazyInit lazily initializes a zero List value.
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func (l *List[V]) lazyInit() {
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if l.root.next == nil {
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l.Init()
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}
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}
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// insert inserts e after at, increments l.len, and returns e.
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func (l *List[V]) insert(e, at *Element[V]) *Element[V] {
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e.prev = at
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e.next = at.next
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e.prev.next = e
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e.next.prev = e
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e.list = l
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l.len++
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return e
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}
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// insertValue is a convenience wrapper for insert(&Element{Value: v}, at).
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func (l *List[V]) insertValue(v V, at *Element[V]) *Element[V] {
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return l.insert(&Element[V]{Value: v}, at)
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}
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// remove removes e from its list, decrements l.len
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func (l *List[V]) remove(e *Element[V]) {
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e.prev.next = e.next
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e.next.prev = e.prev
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e.next = nil // avoid memory leaks
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e.prev = nil // avoid memory leaks
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e.list = nil
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l.len--
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}
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// move moves e to next to at.
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func (l *List[V]) move(e, at *Element[V]) {
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if e == at {
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return
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}
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e.prev.next = e.next
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e.next.prev = e.prev
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e.prev = at
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e.next = at.next
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e.prev.next = e
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e.next.prev = e
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}
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// Remove removes e from l if e is an element of list l.
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// It returns the element value e.Value.
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// The element must not be nil.
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func (l *List[V]) Remove(e *Element[V]) V {
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if e.list == l {
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// if e.list == l, l must have been initialized when e was inserted
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// in l or l == nil (e is a zero Element) and l.remove will crash
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l.remove(e)
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}
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return e.Value
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}
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// PushFront inserts a new element e with value v at the front of list l and returns e.
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func (l *List[V]) PushFront(v V) *Element[V] {
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l.lazyInit()
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return l.insertValue(v, &l.root)
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}
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// PushBack inserts a new element e with value v at the back of list l and returns e.
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func (l *List[V]) PushBack(v V) *Element[V] {
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l.lazyInit()
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return l.insertValue(v, l.root.prev)
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}
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// InsertBefore inserts a new element e with value v immediately before mark and returns e.
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// If mark is not an element of l, the list is not modified.
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// The mark must not be nil.
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func (l *List[V]) InsertBefore(v V, mark *Element[V]) *Element[V] {
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if mark.list != l {
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return nil
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}
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// see comment in List.Remove about initialization of l
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return l.insertValue(v, mark.prev)
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}
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// InsertAfter inserts a new element e with value v immediately after mark and returns e.
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// If mark is not an element of l, the list is not modified.
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// The mark must not be nil.
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func (l *List[V]) InsertAfter(v V, mark *Element[V]) *Element[V] {
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if mark.list != l {
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return nil
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}
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// see comment in List.Remove about initialization of l
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return l.insertValue(v, mark)
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}
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// MoveToFront moves element e to the front of list l.
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// If e is not an element of l, the list is not modified.
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// The element must not be nil.
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func (l *List[V]) MoveToFront(e *Element[V]) {
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if e.list != l || l.root.next == e {
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return
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}
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// see comment in List.Remove about initialization of l
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l.move(e, &l.root)
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}
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// MoveToBack moves element e to the back of list l.
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// If e is not an element of l, the list is not modified.
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// The element must not be nil.
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func (l *List[V]) MoveToBack(e *Element[V]) {
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if e.list != l || l.root.prev == e {
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return
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}
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// see comment in List.Remove about initialization of l
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l.move(e, l.root.prev)
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}
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// MoveBefore moves element e to its new position before mark.
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// If e or mark is not an element of l, or e == mark, the list is not modified.
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// The element and mark must not be nil.
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func (l *List[V]) MoveBefore(e, mark *Element[V]) {
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if e.list != l || e == mark || mark.list != l {
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return
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}
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l.move(e, mark.prev)
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}
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// MoveAfter moves element e to its new position after mark.
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// If e or mark is not an element of l, or e == mark, the list is not modified.
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// The element and mark must not be nil.
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func (l *List[V]) MoveAfter(e, mark *Element[V]) {
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if e.list != l || e == mark || mark.list != l {
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return
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}
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l.move(e, mark)
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}
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// PushBackList inserts a copy of another list at the back of list l.
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// The lists l and other may be the same. They must not be nil.
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func (l *List[V]) PushBackList(other *List[V]) {
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l.lazyInit()
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for i, e := other.Len(), other.Front(); i > 0; i, e = i-1, e.Next() {
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l.insertValue(e.Value, l.root.prev)
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}
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}
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// PushFrontList inserts a copy of another list at the front of list l.
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// The lists l and other may be the same. They must not be nil.
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func (l *List[V]) PushFrontList(other *List[V]) {
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l.lazyInit()
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for i, e := other.Len(), other.Back(); i > 0; i, e = i-1, e.Prev() {
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l.insertValue(e.Value, &l.root)
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}
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}
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342
pkgs/list/list_test.go
Normal file
342
pkgs/list/list_test.go
Normal file
@@ -0,0 +1,342 @@
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// Copyright 2009 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package list
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import "testing"
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func checkListLen[V any](t *testing.T, l *List[V], len int) bool {
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if n := l.Len(); n != len {
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t.Errorf("l.Len() = %d, want %d", n, len)
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return false
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}
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return true
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}
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func checkListPointers[V any](t *testing.T, l *List[V], es []*Element[V]) {
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root := &l.root
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if !checkListLen(t, l, len(es)) {
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return
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}
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// zero length lists must be the zero value or properly initialized (sentinel circle)
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if len(es) == 0 {
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if l.root.next != nil && l.root.next != root || l.root.prev != nil && l.root.prev != root {
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t.Errorf("l.root.next = %p, l.root.prev = %p; both should both be nil or %p", l.root.next, l.root.prev, root)
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}
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return
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}
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// len(es) > 0
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// check internal and external prev/next connections
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for i, e := range es {
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prev := root
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Prev := (*Element[V])(nil)
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if i > 0 {
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prev = es[i-1]
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Prev = prev
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}
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if p := e.prev; p != prev {
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t.Errorf("elt[%d](%p).prev = %p, want %p", i, e, p, prev)
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}
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if p := e.Prev(); p != Prev {
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t.Errorf("elt[%d](%p).Prev() = %p, want %p", i, e, p, Prev)
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}
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next := root
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Next := (*Element[V])(nil)
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if i < len(es)-1 {
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next = es[i+1]
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Next = next
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}
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if n := e.next; n != next {
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t.Errorf("elt[%d](%p).next = %p, want %p", i, e, n, next)
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}
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if n := e.Next(); n != Next {
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t.Errorf("elt[%d](%p).Next() = %p, want %p", i, e, n, Next)
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}
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}
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}
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func TestList(t *testing.T) {
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l := New[any]()
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checkListPointers(t, l, []*Element[any]{})
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// Single element list
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e := l.PushFront("a")
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checkListPointers(t, l, []*Element[any]{e})
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l.MoveToFront(e)
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checkListPointers(t, l, []*Element[any]{e})
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l.MoveToBack(e)
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checkListPointers(t, l, []*Element[any]{e})
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l.Remove(e)
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checkListPointers(t, l, []*Element[any]{})
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// Bigger list
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e2 := l.PushFront(2)
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e1 := l.PushFront(1)
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e3 := l.PushBack(3)
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e4 := l.PushBack("banana")
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checkListPointers(t, l, []*Element[any]{e1, e2, e3, e4})
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l.Remove(e2)
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checkListPointers(t, l, []*Element[any]{e1, e3, e4})
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l.MoveToFront(e3) // move from middle
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checkListPointers(t, l, []*Element[any]{e3, e1, e4})
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l.MoveToFront(e1)
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l.MoveToBack(e3) // move from middle
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checkListPointers(t, l, []*Element[any]{e1, e4, e3})
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l.MoveToFront(e3) // move from back
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checkListPointers(t, l, []*Element[any]{e3, e1, e4})
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l.MoveToFront(e3) // should be no-op
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checkListPointers(t, l, []*Element[any]{e3, e1, e4})
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l.MoveToBack(e3) // move from front
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checkListPointers(t, l, []*Element[any]{e1, e4, e3})
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l.MoveToBack(e3) // should be no-op
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checkListPointers(t, l, []*Element[any]{e1, e4, e3})
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e2 = l.InsertBefore(2, e1) // insert before front
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checkListPointers(t, l, []*Element[any]{e2, e1, e4, e3})
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l.Remove(e2)
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e2 = l.InsertBefore(2, e4) // insert before middle
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checkListPointers(t, l, []*Element[any]{e1, e2, e4, e3})
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l.Remove(e2)
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e2 = l.InsertBefore(2, e3) // insert before back
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checkListPointers(t, l, []*Element[any]{e1, e4, e2, e3})
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l.Remove(e2)
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e2 = l.InsertAfter(2, e1) // insert after front
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checkListPointers(t, l, []*Element[any]{e1, e2, e4, e3})
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l.Remove(e2)
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e2 = l.InsertAfter(2, e4) // insert after middle
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checkListPointers(t, l, []*Element[any]{e1, e4, e2, e3})
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l.Remove(e2)
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e2 = l.InsertAfter(2, e3) // insert after back
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checkListPointers(t, l, []*Element[any]{e1, e4, e3, e2})
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l.Remove(e2)
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// Check standard iteration.
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sum := 0
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for e := l.Front(); e != nil; e = e.Next() {
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if i, ok := e.Value.(int); ok {
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sum += i
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}
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}
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if sum != 4 {
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t.Errorf("sum over l = %d, want 4", sum)
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}
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// Clear all elements by iterating
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var next *Element[any]
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for e := l.Front(); e != nil; e = next {
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next = e.Next()
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l.Remove(e)
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}
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checkListPointers(t, l, []*Element[any]{})
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}
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func checkList[V comparable](t *testing.T, l *List[V], es []any) {
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if !checkListLen(t, l, len(es)) {
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return
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}
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i := 0
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for e := l.Front(); e != nil; e = e.Next() {
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le := e.Value
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if le != es[i] {
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t.Errorf("elt[%d].Value = %v, want %v", i, le, es[i])
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}
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i++
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}
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}
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func TestExtending(t *testing.T) {
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l1 := New[int]()
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l2 := New[int]()
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l1.PushBack(1)
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l1.PushBack(2)
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l1.PushBack(3)
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l2.PushBack(4)
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l2.PushBack(5)
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l3 := New[int]()
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l3.PushBackList(l1)
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checkList(t, l3, []any{1, 2, 3})
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l3.PushBackList(l2)
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checkList(t, l3, []any{1, 2, 3, 4, 5})
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l3 = New[int]()
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l3.PushFrontList(l2)
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checkList(t, l3, []any{4, 5})
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l3.PushFrontList(l1)
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checkList(t, l3, []any{1, 2, 3, 4, 5})
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checkList(t, l1, []any{1, 2, 3})
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checkList(t, l2, []any{4, 5})
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l3 = New[int]()
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l3.PushBackList(l1)
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checkList(t, l3, []any{1, 2, 3})
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l3.PushBackList(l3)
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checkList(t, l3, []any{1, 2, 3, 1, 2, 3})
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l3 = New[int]()
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l3.PushFrontList(l1)
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checkList(t, l3, []any{1, 2, 3})
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l3.PushFrontList(l3)
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checkList(t, l3, []any{1, 2, 3, 1, 2, 3})
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l3 = New[int]()
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l1.PushBackList(l3)
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checkList(t, l1, []any{1, 2, 3})
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l1.PushFrontList(l3)
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checkList(t, l1, []any{1, 2, 3})
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}
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func TestRemove(t *testing.T) {
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l := New[any]()
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e1 := l.PushBack(1)
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e2 := l.PushBack(2)
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checkListPointers(t, l, []*Element[any]{e1, e2})
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e := l.Front()
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l.Remove(e)
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checkListPointers(t, l, []*Element[any]{e2})
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l.Remove(e)
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checkListPointers(t, l, []*Element[any]{e2})
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}
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func TestIssue4103(t *testing.T) {
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l1 := New[any]()
|
||||
l1.PushBack(1)
|
||||
l1.PushBack(2)
|
||||
|
||||
l2 := New[any]()
|
||||
l2.PushBack(3)
|
||||
l2.PushBack(4)
|
||||
|
||||
e := l1.Front()
|
||||
l2.Remove(e) // l2 should not change because e is not an element of l2
|
||||
if n := l2.Len(); n != 2 {
|
||||
t.Errorf("l2.Len() = %d, want 2", n)
|
||||
}
|
||||
|
||||
l1.InsertBefore(8, e)
|
||||
if n := l1.Len(); n != 3 {
|
||||
t.Errorf("l1.Len() = %d, want 3", n)
|
||||
}
|
||||
}
|
||||
|
||||
func TestIssue6349(t *testing.T) {
|
||||
l := New[any]()
|
||||
l.PushBack(1)
|
||||
l.PushBack(2)
|
||||
|
||||
e := l.Front()
|
||||
l.Remove(e)
|
||||
if e.Value != 1 {
|
||||
t.Errorf("e.value = %d, want 1", e.Value)
|
||||
}
|
||||
if e.Next() != nil {
|
||||
t.Errorf("e.Next() != nil")
|
||||
}
|
||||
if e.Prev() != nil {
|
||||
t.Errorf("e.Prev() != nil")
|
||||
}
|
||||
}
|
||||
|
||||
func TestMove(t *testing.T) {
|
||||
l := New[any]()
|
||||
e1 := l.PushBack(1)
|
||||
e2 := l.PushBack(2)
|
||||
e3 := l.PushBack(3)
|
||||
e4 := l.PushBack(4)
|
||||
|
||||
l.MoveAfter(e3, e3)
|
||||
checkListPointers(t, l, []*Element[any]{e1, e2, e3, e4})
|
||||
l.MoveBefore(e2, e2)
|
||||
checkListPointers(t, l, []*Element[any]{e1, e2, e3, e4})
|
||||
|
||||
l.MoveAfter(e3, e2)
|
||||
checkListPointers(t, l, []*Element[any]{e1, e2, e3, e4})
|
||||
l.MoveBefore(e2, e3)
|
||||
checkListPointers(t, l, []*Element[any]{e1, e2, e3, e4})
|
||||
|
||||
l.MoveBefore(e2, e4)
|
||||
checkListPointers(t, l, []*Element[any]{e1, e3, e2, e4})
|
||||
e2, e3 = e3, e2
|
||||
|
||||
l.MoveBefore(e4, e1)
|
||||
checkListPointers(t, l, []*Element[any]{e4, e1, e2, e3})
|
||||
e1, e2, e3, e4 = e4, e1, e2, e3
|
||||
|
||||
l.MoveAfter(e4, e1)
|
||||
checkListPointers(t, l, []*Element[any]{e1, e4, e2, e3})
|
||||
e2, e3, e4 = e4, e2, e3
|
||||
|
||||
l.MoveAfter(e2, e3)
|
||||
checkListPointers(t, l, []*Element[any]{e1, e3, e2, e4})
|
||||
}
|
||||
|
||||
// Test PushFront, PushBack, PushFrontList, PushBackList with uninitialized List
|
||||
func TestZeroList(t *testing.T) {
|
||||
var l1 = new(List[any])
|
||||
l1.PushFront(1)
|
||||
checkList(t, l1, []any{1})
|
||||
|
||||
var l2 = new(List[any])
|
||||
l2.PushBack(1)
|
||||
checkList(t, l2, []any{1})
|
||||
|
||||
var l3 = new(List[any])
|
||||
l3.PushFrontList(l1)
|
||||
checkList(t, l3, []any{1})
|
||||
|
||||
var l4 = new(List[any])
|
||||
l4.PushBackList(l2)
|
||||
checkList(t, l4, []any{1})
|
||||
}
|
||||
|
||||
// Test that a list l is not modified when calling InsertBefore with a mark that is not an element of l.
|
||||
func TestInsertBeforeUnknownMark(t *testing.T) {
|
||||
var l List[any]
|
||||
l.PushBack(1)
|
||||
l.PushBack(2)
|
||||
l.PushBack(3)
|
||||
l.InsertBefore(1, new(Element[any]))
|
||||
checkList(t, &l, []any{1, 2, 3})
|
||||
}
|
||||
|
||||
// Test that a list l is not modified when calling InsertAfter with a mark that is not an element of l.
|
||||
func TestInsertAfterUnknownMark(t *testing.T) {
|
||||
var l List[any]
|
||||
l.PushBack(1)
|
||||
l.PushBack(2)
|
||||
l.PushBack(3)
|
||||
l.InsertAfter(1, new(Element[any]))
|
||||
checkList(t, &l, []any{1, 2, 3})
|
||||
}
|
||||
|
||||
// Test that a list l is not modified when calling MoveAfter or MoveBefore with a mark that is not an element of l.
|
||||
func TestMoveUnknownMark(t *testing.T) {
|
||||
var l1 List[any]
|
||||
e1 := l1.PushBack(1)
|
||||
|
||||
var l2 List[any]
|
||||
e2 := l2.PushBack(2)
|
||||
|
||||
l1.MoveAfter(e1, e2)
|
||||
checkList(t, &l1, []any{1})
|
||||
checkList(t, &l2, []any{2})
|
||||
|
||||
l1.MoveBefore(e1, e2)
|
||||
checkList(t, &l1, []any{1})
|
||||
checkList(t, &l2, []any{2})
|
||||
}
|
||||
Reference in New Issue
Block a user