222 lines
4.6 KiB
Go
222 lines
4.6 KiB
Go
package stack
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// ElementMapper provides an identity mapping by default.
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//
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// This can be replaced to provide a struct that maps elements to linker
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// objects, if they are not the same. An ElementMapper is not typically
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// required if: Linker is left as is, Element is left as is, or Linker and
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// Element are the same type.
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type tupleElementMapper struct{}
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// linkerFor maps an Element to a Linker.
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//
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// This default implementation should be inlined.
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//
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//go:nosplit
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func (tupleElementMapper) linkerFor(elem *tuple) *tuple { return elem }
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// List is an intrusive list. Entries can be added to or removed from the list
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// in O(1) time and with no additional memory allocations.
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//
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// The zero value for List is an empty list ready to use.
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//
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// To iterate over a list (where l is a List):
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// for e := l.Front(); e != nil; e = e.Next() {
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// // do something with e.
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// }
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//
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// +stateify savable
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type tupleList struct {
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head *tuple
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tail *tuple
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}
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// Reset resets list l to the empty state.
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func (l *tupleList) Reset() {
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l.head = nil
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l.tail = nil
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}
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// Empty returns true iff the list is empty.
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//
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//go:nosplit
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func (l *tupleList) Empty() bool {
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return l.head == nil
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}
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// Front returns the first element of list l or nil.
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//
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//go:nosplit
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func (l *tupleList) Front() *tuple {
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return l.head
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}
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// Back returns the last element of list l or nil.
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//
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//go:nosplit
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func (l *tupleList) Back() *tuple {
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return l.tail
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}
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// Len returns the number of elements in the list.
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//
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// NOTE: This is an O(n) operation.
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//
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//go:nosplit
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func (l *tupleList) Len() (count int) {
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for e := l.Front(); e != nil; e = (tupleElementMapper{}.linkerFor(e)).Next() {
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count++
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}
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return count
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}
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// PushFront inserts the element e at the front of list l.
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//
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//go:nosplit
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func (l *tupleList) PushFront(e *tuple) {
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linker := tupleElementMapper{}.linkerFor(e)
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linker.SetNext(l.head)
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linker.SetPrev(nil)
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if l.head != nil {
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tupleElementMapper{}.linkerFor(l.head).SetPrev(e)
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} else {
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l.tail = e
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}
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l.head = e
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}
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// PushBack inserts the element e at the back of list l.
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//
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//go:nosplit
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func (l *tupleList) PushBack(e *tuple) {
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linker := tupleElementMapper{}.linkerFor(e)
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linker.SetNext(nil)
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linker.SetPrev(l.tail)
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if l.tail != nil {
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tupleElementMapper{}.linkerFor(l.tail).SetNext(e)
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} else {
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l.head = e
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}
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l.tail = e
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}
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// PushBackList inserts list m at the end of list l, emptying m.
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//
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//go:nosplit
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func (l *tupleList) PushBackList(m *tupleList) {
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if l.head == nil {
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l.head = m.head
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l.tail = m.tail
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} else if m.head != nil {
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tupleElementMapper{}.linkerFor(l.tail).SetNext(m.head)
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tupleElementMapper{}.linkerFor(m.head).SetPrev(l.tail)
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l.tail = m.tail
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}
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m.head = nil
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m.tail = nil
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}
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// InsertAfter inserts e after b.
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//
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//go:nosplit
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func (l *tupleList) InsertAfter(b, e *tuple) {
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bLinker := tupleElementMapper{}.linkerFor(b)
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eLinker := tupleElementMapper{}.linkerFor(e)
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a := bLinker.Next()
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eLinker.SetNext(a)
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eLinker.SetPrev(b)
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bLinker.SetNext(e)
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if a != nil {
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tupleElementMapper{}.linkerFor(a).SetPrev(e)
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} else {
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l.tail = e
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}
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}
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// InsertBefore inserts e before a.
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//
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//go:nosplit
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func (l *tupleList) InsertBefore(a, e *tuple) {
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aLinker := tupleElementMapper{}.linkerFor(a)
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eLinker := tupleElementMapper{}.linkerFor(e)
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b := aLinker.Prev()
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eLinker.SetNext(a)
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eLinker.SetPrev(b)
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aLinker.SetPrev(e)
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if b != nil {
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tupleElementMapper{}.linkerFor(b).SetNext(e)
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} else {
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l.head = e
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}
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}
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// Remove removes e from l.
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//
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//go:nosplit
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func (l *tupleList) Remove(e *tuple) {
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linker := tupleElementMapper{}.linkerFor(e)
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prev := linker.Prev()
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next := linker.Next()
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if prev != nil {
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tupleElementMapper{}.linkerFor(prev).SetNext(next)
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} else if l.head == e {
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l.head = next
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}
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if next != nil {
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tupleElementMapper{}.linkerFor(next).SetPrev(prev)
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} else if l.tail == e {
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l.tail = prev
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}
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linker.SetNext(nil)
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linker.SetPrev(nil)
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}
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// Entry is a default implementation of Linker. Users can add anonymous fields
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// of this type to their structs to make them automatically implement the
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// methods needed by List.
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//
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// +stateify savable
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type tupleEntry struct {
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next *tuple
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prev *tuple
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}
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// Next returns the entry that follows e in the list.
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//
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//go:nosplit
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func (e *tupleEntry) Next() *tuple {
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return e.next
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}
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// Prev returns the entry that precedes e in the list.
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//
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//go:nosplit
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func (e *tupleEntry) Prev() *tuple {
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return e.prev
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}
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// SetNext assigns 'entry' as the entry that follows e in the list.
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//
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//go:nosplit
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func (e *tupleEntry) SetNext(elem *tuple) {
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e.next = elem
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}
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// SetPrev assigns 'entry' as the entry that precedes e in the list.
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//
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//go:nosplit
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func (e *tupleEntry) SetPrev(elem *tuple) {
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e.prev = elem
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}
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