diff options
Diffstat (limited to 'vendor/github.com/bahlo/generic-list-go/list.go')
-rw-r--r-- | vendor/github.com/bahlo/generic-list-go/list.go | 235 |
1 files changed, 235 insertions, 0 deletions
diff --git a/vendor/github.com/bahlo/generic-list-go/list.go b/vendor/github.com/bahlo/generic-list-go/list.go new file mode 100644 index 000000000..a06a7c612 --- /dev/null +++ b/vendor/github.com/bahlo/generic-list-go/list.go @@ -0,0 +1,235 @@ +// 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[T any] 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[T] + + // The list to which this element belongs. + list *List[T] + + // The value stored with this element. + Value T +} + +// Next returns the next list element or nil. +func (e *Element[T]) Next() *Element[T] { + 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[T]) Prev() *Element[T] { + 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[T any] struct { + root Element[T] // 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[T]) Init() *List[T] { + l.root.next = &l.root + l.root.prev = &l.root + l.len = 0 + return l +} + +// New returns an initialized list. +func New[T any]() *List[T] { return new(List[T]).Init() } + +// Len returns the number of elements of list l. +// The complexity is O(1). +func (l *List[T]) Len() int { return l.len } + +// Front returns the first element of list l or nil if the list is empty. +func (l *List[T]) Front() *Element[T] { + 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[T]) Back() *Element[T] { + if l.len == 0 { + return nil + } + return l.root.prev +} + +// lazyInit lazily initializes a zero List value. +func (l *List[T]) lazyInit() { + if l.root.next == nil { + l.Init() + } +} + +// insert inserts e after at, increments l.len, and returns e. +func (l *List[T]) insert(e, at *Element[T]) *Element[T] { + e.prev = at + e.next = at.next + e.prev.next = e + e.next.prev = e + e.list = l + l.len++ + return e +} + +// insertValue is a convenience wrapper for insert(&Element{Value: v}, at). +func (l *List[T]) insertValue(v T, at *Element[T]) *Element[T] { + return l.insert(&Element[T]{Value: v}, at) +} + +// remove removes e from its list, decrements l.len +func (l *List[T]) remove(e *Element[T]) { + 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 moves e to next to at. +func (l *List[T]) move(e, at *Element[T]) { + 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 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[T]) Remove(e *Element[T]) T { + 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[T]) PushFront(v T) *Element[T] { + 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[T]) PushBack(v T) *Element[T] { + 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[T]) InsertBefore(v T, mark *Element[T]) *Element[T] { + 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[T]) InsertAfter(v T, mark *Element[T]) *Element[T] { + 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[T]) MoveToFront(e *Element[T]) { + if e.list != l || l.root.next == e { + return + } + // see comment in List.Remove about initialization of l + l.move(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[T]) MoveToBack(e *Element[T]) { + 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 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[T]) MoveBefore(e, mark *Element[T]) { + if e.list != l || e == mark || mark.list != l { + return + } + l.move(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[T]) MoveAfter(e, mark *Element[T]) { + if e.list != l || e == mark || mark.list != l { + return + } + l.move(e, mark) +} + +// PushBackList inserts a copy of another list at the back of list l. +// The lists l and other may be the same. They must not be nil. +func (l *List[T]) PushBackList(other *List[T]) { + 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 another list at the front of list l. +// The lists l and other may be the same. They must not be nil. +func (l *List[T]) PushFrontList(other *List[T]) { + l.lazyInit() + for i, e := other.Len(), other.Back(); i > 0; i, e = i-1, e.Prev() { + l.insertValue(e.Value, &l.root) + } +} |