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