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// 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.
// The list package implements a doubly linked list.
package list
// Element is an element in the linked list.
type Element struct {
// Next and previous pointers in the doubly-linked list of elements.
// The front of the list has prev = nil, and the back has next = nil.
next, prev *Element;
// A unique ID for the list to which this element belongs.
id *byte;
// The contents of this list element.
Value interface{};
}
// Next returns the next list element or nil.
func (e *Element) Next() *Element {
return e.next;
}
// Prev returns the previous list element or nil.
func (e *Element) Prev() *Element {
return e.prev;
}
// List represents a doubly linked list.
type List struct {
front, back *Element;
len int;
id *byte;
}
// Init initializes or clears a List.
func (l *List) Init() *List {
l.front = nil;
l.back = nil;
l.len = 0;
l.id = new(byte);
return l;
}
// New returns an initialized list.
func New() *List {
return new(List).Init();
}
// Front returns the first element in the list.
func (l *List) Front() *Element {
return l.front;
}
// Back returns the last element in the list.
func (l *List) Back() *Element {
return l.back;
}
// Remove removes the element from the list.
func (l *List) Remove(e *Element) {
if e.id != l.id {
return;
}
if e.prev == nil {
l.front = e.next;
} else {
e.prev.next = e.next;
}
if e.next == nil {
l.back = e.prev;
} else {
e.next.prev = e.prev;
}
e.prev = nil;
e.next = nil;
l.len--;
}
func (l *List) insertBefore(e *Element, mark *Element) {
if mark.prev == nil {
// new front of the list
l.front = e;
} else {
mark.prev.next = e;
}
e.prev = mark.prev;
mark.prev = e;
e.next = mark;
l.len++;
}
func (l *List) insertAfter(e *Element, mark *Element) {
if mark.next == nil {
// new back of the list
l.back = e;
} else {
mark.next.prev = e;
}
e.next = mark.next;
mark.next = e;
e.prev = mark;
l.len++;
}
func (l *List) insertFront(e *Element) {
if l.front == nil {
// empty list
l.front, l.back = e, e;
e.prev, e.next = nil, nil;
l.len = 1;
return;
}
l.insertBefore(e, l.front);
}
func (l *List) insertBack(e *Element) {
if l.back == nil {
// empty list
l.front, l.back = e, e;
e.prev, e.next = nil, nil;
l.len = 1;
return;
}
l.insertAfter(e, l.back);
}
// PushFront inserts the value at the front of the list and returns a new Element containing the value.
func (l *List) PushFront(value interface{}) *Element {
if l.id == nil {
l.Init();
}
e := &Element{nil, nil, l.id, value};
l.insertFront(e);
return e;
}
// PushBack inserts the value at the back of the list and returns a new Element containing the value.
func (l *List) PushBack(value interface{}) *Element {
if l.id == nil {
l.Init();
}
e := &Element{nil, nil, l.id, value};
l.insertBack(e);
return e;
}
// InsertBefore inserts the value immediately before mark and returns a new Element containing the value.
func (l *List) InsertBefore(value interface{}, mark *Element) *Element {
if mark.id != l.id {
return nil;
}
e := &Element{nil, nil, l.id, value};
l.insertBefore(e, mark);
return e;
}
// InsertAfter inserts the value immediately after mark and returns a new Element containing the value.
func (l *List) InsertAfter(value interface{}, mark *Element) *Element {
if mark.id != l.id {
return nil;
}
e := &Element{nil, nil, l.id, value};
l.insertAfter(e, mark);
return e;
}
// MoveToFront moves the element to the front of the list.
func (l *List) MoveToFront(e *Element) {
if e.id != l.id || l.front == e {
return;
}
l.Remove(e);
l.insertFront(e);
}
// MoveToBack moves the element to the back of the list.
func (l *List) MoveToBack(e *Element) {
if e.id != l.id || l.back == e {
return;
}
l.Remove(e);
l.insertBack(e);
}
// Len returns the number of elements in the list.
func (l *List) Len() int {
return l.len;
}
func (l *List) iterate(c chan<- interface{}) {
for e := l.front; e != nil; e = e.next {
c <- e.Value;
}
close(c);
}
func (l *List) Iter() <-chan interface{} {
c := make(chan interface{});
go l.iterate(c);
return c;
}
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