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itializes 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 n |