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dirty_set_impl.go
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dirty_set_impl.go
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package fsutil
import (
__generics_imported0 "github.com/ttpreport/gvisor-ligolo/pkg/sentry/memmap"
)
import (
"bytes"
"fmt"
)
// trackGaps is an optional parameter.
//
// If trackGaps is 1, the Set will track maximum gap size recursively,
// enabling the GapIterator.{Prev,Next}LargeEnoughGap functions. In this
// case, Key must be an unsigned integer.
//
// trackGaps must be 0 or 1.
const DirtytrackGaps = 0
var _ = uint8(DirtytrackGaps << 7) // Will fail if not zero or one.
// dynamicGap is a type that disappears if trackGaps is 0.
type DirtydynamicGap [DirtytrackGaps]uint64
// Get returns the value of the gap.
//
// Precondition: trackGaps must be non-zero.
func (d *DirtydynamicGap) Get() uint64 {
return d[:][0]
}
// Set sets the value of the gap.
//
// Precondition: trackGaps must be non-zero.
func (d *DirtydynamicGap) Set(v uint64) {
d[:][0] = v
}
const (
// minDegree is the minimum degree of an internal node in a Set B-tree.
//
// - Any non-root node has at least minDegree-1 segments.
//
// - Any non-root internal (non-leaf) node has at least minDegree children.
//
// - The root node may have fewer than minDegree-1 segments, but it may
// only have 0 segments if the tree is empty.
//
// Our implementation requires minDegree >= 3. Higher values of minDegree
// usually improve performance, but increase memory usage for small sets.
DirtyminDegree = 3
DirtymaxDegree = 2 * DirtyminDegree
)
// A Set is a mapping of segments with non-overlapping Range keys. The zero
// value for a Set is an empty set. Set values are not safely movable nor
// copyable. Set is thread-compatible.
//
// +stateify savable
type DirtySet struct {
root Dirtynode `state:".(*DirtySegmentDataSlices)"`
}
// IsEmpty returns true if the set contains no segments.
func (s *DirtySet) IsEmpty() bool {
return s.root.nrSegments == 0
}
// IsEmptyRange returns true iff no segments in the set overlap the given
// range. This is semantically equivalent to s.SpanRange(r) == 0, but may be
// more efficient.
func (s *DirtySet) IsEmptyRange(r __generics_imported0.MappableRange) bool {
switch {
case r.Length() < 0:
panic(fmt.Sprintf("invalid range %v", r))
case r.Length() == 0:
return true
}
_, gap := s.Find(r.Start)
if !gap.Ok() {
return false
}
return r.End <= gap.End()
}
// Span returns the total size of all segments in the set.
func (s *DirtySet) Span() uint64 {
var sz uint64
for seg := s.FirstSegment(); seg.Ok(); seg = seg.NextSegment() {
sz += seg.Range().Length()
}
return sz
}
// SpanRange returns the total size of the intersection of segments in the set
// with the given range.
func (s *DirtySet) SpanRange(r __generics_imported0.MappableRange) uint64 {
switch {
case r.Length() < 0:
panic(fmt.Sprintf("invalid range %v", r))
case r.Length() == 0:
return 0
}
var sz uint64
for seg := s.LowerBoundSegment(r.Start); seg.Ok() && seg.Start() < r.End; seg = seg.NextSegment() {
sz += seg.Range().Intersect(r).Length()
}
return sz
}
// FirstSegment returns the first segment in the set. If the set is empty,
// FirstSegment returns a terminal iterator.
func (s *DirtySet) FirstSegment() DirtyIterator {
if s.root.nrSegments == 0 {
return DirtyIterator{}
}
return s.root.firstSegment()
}
// LastSegment returns the last segment in the set. If the set is empty,
// LastSegment returns a terminal iterator.
func (s *DirtySet) LastSegment() DirtyIterator {
if s.root.nrSegments == 0 {
return DirtyIterator{}
}
return s.root.lastSegment()
}
// FirstGap returns the first gap in the set.
func (s *DirtySet) FirstGap() DirtyGapIterator {
n := &s.root
for n.hasChildren {
n = n.children[0]
}
return DirtyGapIterator{n, 0}
}
// LastGap returns the last gap in the set.
func (s *DirtySet) LastGap() DirtyGapIterator {
n := &s.root
for n.hasChildren {
n = n.children[n.nrSegments]
}
return DirtyGapIterator{n, n.nrSegments}
}
// Find returns the segment or gap whose range contains the given key. If a
// segment is found, the returned Iterator is non-terminal and the
// returned GapIterator is terminal. Otherwise, the returned Iterator is
// terminal and the returned GapIterator is non-terminal.
func (s *DirtySet) Find(key uint64) (DirtyIterator, DirtyGapIterator) {
n := &s.root
for {
lower := 0
upper := n.nrSegments
for lower < upper {
i := lower + (upper-lower)/2
if r := n.keys[i]; key < r.End {
if key >= r.Start {
return DirtyIterator{n, i}, DirtyGapIterator{}
}
upper = i
} else {
lower = i + 1
}
}
i := lower
if !n.hasChildren {
return DirtyIterator{}, DirtyGapIterator{n, i}
}
n = n.children[i]
}
}
// FindSegment returns the segment whose range contains the given key. If no
// such segment exists, FindSegment returns a terminal iterator.
func (s *DirtySet) FindSegment(key uint64) DirtyIterator {
seg, _ := s.Find(key)
return seg
}
// LowerBoundSegment returns the segment with the lowest range that contains a
// key greater than or equal to min. If no such segment exists,
// LowerBoundSegment returns a terminal iterator.
func (s *DirtySet) LowerBoundSegment(min uint64) DirtyIterator {
seg, gap := s.Find(min)
if seg.Ok() {
return seg
}
return gap.NextSegment()
}
// UpperBoundSegment returns the segment with the highest range that contains a
// key less than or equal to max. If no such segment exists, UpperBoundSegment
// returns a terminal iterator.
func (s *DirtySet) UpperBoundSegment(max uint64) DirtyIterator {
seg, gap := s.Find(max)
if seg.Ok() {
return seg
}
return gap.PrevSegment()
}
// FindGap returns the gap containing the given key. If no such gap exists
// (i.e. the set contains a segment containing that key), FindGap returns a
// terminal iterator.
func (s *DirtySet) FindGap(key uint64) DirtyGapIterator {
_, gap := s.Find(key)
return gap
}
// LowerBoundGap returns the gap with the lowest range that is greater than or
// equal to min.
func (s *DirtySet) LowerBoundGap(min uint64) DirtyGapIterator {
seg, gap := s.Find(min)
if gap.Ok() {
return gap
}
return seg.NextGap()
}
// UpperBoundGap returns the gap with the highest range that is less than or
// equal to max.
func (s *DirtySet) UpperBoundGap(max uint64) DirtyGapIterator {
seg, gap := s.Find(max)
if gap.Ok() {
return gap
}
return seg.PrevGap()
}
// Add inserts the given segment into the set and returns true. If the new
// segment can be merged with adjacent segments, Add will do so. If the new
// segment would overlap an existing segment, Add returns false. If Add
// succeeds, all existing iterators are invalidated.
func (s *DirtySet) Add(r __generics_imported0.MappableRange, val DirtyInfo) bool {
if r.Length() <= 0 {
panic(fmt.Sprintf("invalid segment range %v", r))
}
gap := s.FindGap(r.Start)
if !gap.Ok() {
return false
}
if r.End > gap.End() {
return false
}
s.Insert(gap, r, val)
return true
}
// AddWithoutMerging inserts the given segment into the set and returns true.
// If it would overlap an existing segment, AddWithoutMerging does nothing and
// returns false. If AddWithoutMerging succeeds, all existing iterators are
// invalidated.
func (s *DirtySet) AddWithoutMerging(r __generics_imported0.MappableRange, val DirtyInfo) bool {
if r.Length() <= 0 {
panic(fmt.Sprintf("invalid segment range %v", r))
}
gap := s.FindGap(r.Start)
if !gap.Ok() {
return false
}
if r.End > gap.End() {
return false
}
s.InsertWithoutMergingUnchecked(gap, r, val)
return true
}
// Insert inserts the given segment into the given gap. If the new segment can
// be merged with adjacent segments, Insert will do so. Insert returns an
// iterator to the segment containing the inserted value (which may have been
// merged with other values). All existing iterators (including gap, but not
// including the returned iterator) are invalidated.
//
// If the gap cannot accommodate the segment, or if r is invalid, Insert panics.
//
// Insert is semantically equivalent to a InsertWithoutMerging followed by a
// Merge, but may be more efficient. Note that there is no unchecked variant of
// Insert since Insert must retrieve and inspect gap's predecessor and
// successor segments regardless.
func (s *DirtySet) Insert(gap DirtyGapIterator, r __generics_imported0.MappableRange, val DirtyInfo) DirtyIterator {
if r.Length() <= 0 {
panic(fmt.Sprintf("invalid segment range %v", r))
}
prev, next := gap.PrevSegment(), gap.NextSegment()
if prev.Ok() && prev.End() > r.Start {
panic(fmt.Sprintf("new segment %v overlaps predecessor %v", r, prev.Range()))
}
if next.Ok() && next.Start() < r.End {
panic(fmt.Sprintf("new segment %v overlaps successor %v", r, next.Range()))
}
if prev.Ok() && prev.End() == r.Start {
if mval, ok := (dirtySetFunctions{}).Merge(prev.Range(), prev.Value(), r, val); ok {
shrinkMaxGap := DirtytrackGaps != 0 && gap.Range().Length() == gap.node.maxGap.Get()
prev.SetEndUnchecked(r.End)
prev.SetValue(mval)
if shrinkMaxGap {
gap.node.updateMaxGapLeaf()
}
if next.Ok() && next.Start() == r.End {
val = mval
if mval, ok := (dirtySetFunctions{}).Merge(prev.Range(), val, next.Range(), next.Value()); ok {
prev.SetEndUnchecked(next.End())
prev.SetValue(mval)
return s.Remove(next).PrevSegment()
}
}
return prev
}
}
if next.Ok() && next.Start() == r.End {
if mval, ok := (dirtySetFunctions{}).Merge(r, val, next.Range(), next.Value()); ok {
shrinkMaxGap := DirtytrackGaps != 0 && gap.Range().Length() == gap.node.maxGap.Get()
next.SetStartUnchecked(r.Start)
next.SetValue(mval)
if shrinkMaxGap {
gap.node.updateMaxGapLeaf()
}
return next
}
}
return s.InsertWithoutMergingUnchecked(gap, r, val)
}
// InsertWithoutMerging inserts the given segment into the given gap and
// returns an iterator to the inserted segment. All existing iterators
// (including gap, but not including the returned iterator) are invalidated.
//
// If the gap cannot accommodate the segment, or if r is invalid,
// InsertWithoutMerging panics.
func (s *DirtySet) InsertWithoutMerging(gap DirtyGapIterator, r __generics_imported0.MappableRange, val DirtyInfo) DirtyIterator {
if r.Length() <= 0 {
panic(fmt.Sprintf("invalid segment range %v", r))
}
if gr := gap.Range(); !gr.IsSupersetOf(r) {
panic(fmt.Sprintf("cannot insert segment range %v into gap range %v", r, gr))
}
return s.InsertWithoutMergingUnchecked(gap, r, val)
}
// InsertWithoutMergingUnchecked inserts the given segment into the given gap
// and returns an iterator to the inserted segment. All existing iterators
// (including gap, but not including the returned iterator) are invalidated.
//
// Preconditions:
// - r.Start >= gap.Start().
// - r.End <= gap.End().
func (s *DirtySet) InsertWithoutMergingUnchecked(gap DirtyGapIterator, r __generics_imported0.MappableRange, val DirtyInfo) DirtyIterator {
gap = gap.node.rebalanceBeforeInsert(gap)
splitMaxGap := DirtytrackGaps != 0 && (gap.node.nrSegments == 0 || gap.Range().Length() == gap.node.maxGap.Get())
copy(gap.node.keys[gap.index+1:], gap.node.keys[gap.index:gap.node.nrSegments])
copy(gap.node.values[gap.index+1:], gap.node.values[gap.index:gap.node.nrSegments])
gap.node.keys[gap.index] = r
gap.node.values[gap.index] = val
gap.node.nrSegments++
if splitMaxGap {
gap.node.updateMaxGapLeaf()
}
return DirtyIterator{gap.node, gap.index}
}
// Remove removes the given segment and returns an iterator to the vacated gap.
// All existing iterators (including seg, but not including the returned
// iterator) are invalidated.
func (s *DirtySet) Remove(seg DirtyIterator) DirtyGapIterator {
if seg.node.hasChildren {
victim := seg.PrevSegment()
seg.SetRangeUnchecked(victim.Range())
seg.SetValue(victim.Value())
nextAdjacentNode := seg.NextSegment().node
if DirtytrackGaps != 0 {
nextAdjacentNode.updateMaxGapLeaf()
}
return s.Remove(victim).NextGap()
}
copy(seg.node.keys[seg.index:], seg.node.keys[seg.index+1:seg.node.nrSegments])
copy(seg.node.values[seg.index:], seg.node.values[seg.index+1:seg.node.nrSegments])
dirtySetFunctions{}.ClearValue(&seg.node.values[seg.node.nrSegments-1])
seg.node.nrSegments--
if DirtytrackGaps != 0 {
seg.node.updateMaxGapLeaf()
}
return seg.node.rebalanceAfterRemove(DirtyGapIterator{seg.node, seg.index})
}
// RemoveAll removes all segments from the set. All existing iterators are
// invalidated.
func (s *DirtySet) RemoveAll() {
s.root = Dirtynode{}
}
// RemoveRange removes all segments in the given range. An iterator to the
// newly formed gap is returned, and all existing iterators are invalidated.
func (s *DirtySet) RemoveRange(r __generics_imported0.MappableRange) DirtyGapIterator {
seg, gap := s.Find(r.Start)
if seg.Ok() {
seg = s.Isolate(seg, r)
gap = s.Remove(seg)
}
for seg = gap.NextSegment(); seg.Ok() && seg.Start() < r.End; seg = gap.NextSegment() {
seg = s.Isolate(seg, r)
gap = s.Remove(seg)
}
return gap
}
// Merge attempts to merge two neighboring segments. If successful, Merge
// returns an iterator to the merged segment, and all existing iterators are
// invalidated. Otherwise, Merge returns a terminal iterator.
//
// If first is not the predecessor of second, Merge panics.
func (s *DirtySet) Merge(first, second DirtyIterator) DirtyIterator {
if first.NextSegment() != second {
panic(fmt.Sprintf("attempt to merge non-neighboring segments %v, %v", first.Range(), second.Range()))
}
return s.MergeUnchecked(first, second)
}
// MergeUnchecked attempts to merge two neighboring segments. If successful,
// MergeUnchecked returns an iterator to the merged segment, and all existing
// iterators are invalidated. Otherwise, MergeUnchecked returns a terminal
// iterator.
//
// Precondition: first is the predecessor of second: first.NextSegment() ==
// second, first == second.PrevSegment().
func (s *DirtySet) MergeUnchecked(first, second DirtyIterator) DirtyIterator {
if first.End() == second.Start() {
if mval, ok := (dirtySetFunctions{}).Merge(first.Range(), first.Value(), second.Range(), second.Value()); ok {
first.SetEndUnchecked(second.End())
first.SetValue(mval)
return s.Remove(second).PrevSegment()
}
}
return DirtyIterator{}
}
// MergeAll attempts to merge all adjacent segments in the set. All existing
// iterators are invalidated.
func (s *DirtySet) MergeAll() {
seg := s.FirstSegment()
if !seg.Ok() {
return
}
next := seg.NextSegment()
for next.Ok() {
if mseg := s.MergeUnchecked(seg, next); mseg.Ok() {
seg, next = mseg, mseg.NextSegment()
} else {
seg, next = next, next.NextSegment()
}
}
}
// MergeRange attempts to merge all adjacent segments that contain a key in the
// specific range. All existing iterators are invalidated.
func (s *DirtySet) MergeRange(r __generics_imported0.MappableRange) {
seg := s.LowerBoundSegment(r.Start)
if !seg.Ok() {
return
}
next := seg.NextSegment()
for next.Ok() && next.Range().Start < r.End {
if mseg := s.MergeUnchecked(seg, next); mseg.Ok() {
seg, next = mseg, mseg.NextSegment()
} else {
seg, next = next, next.NextSegment()
}
}
}
// MergeAdjacent attempts to merge the segment containing r.Start with its
// predecessor, and the segment containing r.End-1 with its successor.
func (s *DirtySet) MergeAdjacent(r __generics_imported0.MappableRange) {
first := s.FindSegment(r.Start)
if first.Ok() {
if prev := first.PrevSegment(); prev.Ok() {
s.Merge(prev, first)
}
}
last := s.FindSegment(r.End - 1)
if last.Ok() {
if next := last.NextSegment(); next.Ok() {
s.Merge(last, next)
}
}
}
// Split splits the given segment at the given key and returns iterators to the
// two resulting segments. All existing iterators (including seg, but not
// including the returned iterators) are invalidated.
//
// If the segment cannot be split at split (because split is at the start or
// end of the segment's range, so splitting would produce a segment with zero
// length, or because split falls outside the segment's range altogether),
// Split panics.
func (s *DirtySet) Split(seg DirtyIterator, split uint64) (DirtyIterator, DirtyIterator) {
if !seg.Range().CanSplitAt(split) {
panic(fmt.Sprintf("can't split %v at %v", seg.Range(), split))
}
return s.SplitUnchecked(seg, split)
}
// SplitUnchecked splits the given segment at the given key and returns
// iterators to the two resulting segments. All existing iterators (including
// seg, but not including the returned iterators) are invalidated.
//
// Preconditions: seg.Start() < key < seg.End().
func (s *DirtySet) SplitUnchecked(seg DirtyIterator, split uint64) (DirtyIterator, DirtyIterator) {
val1, val2 := (dirtySetFunctions{}).Split(seg.Range(), seg.Value(), split)
end2 := seg.End()
seg.SetEndUnchecked(split)
seg.SetValue(val1)
seg2 := s.InsertWithoutMergingUnchecked(seg.NextGap(), __generics_imported0.MappableRange{split, end2}, val2)
return seg2.PrevSegment(), seg2
}
// SplitAt splits the segment straddling split, if one exists. SplitAt returns
// true if a segment was split and false otherwise. If SplitAt splits a
// segment, all existing iterators are invalidated.
func (s *DirtySet) SplitAt(split uint64) bool {
if seg := s.FindSegment(split); seg.Ok() && seg.Range().CanSplitAt(split) {
s.SplitUnchecked(seg, split)
return true
}
return false
}
// Isolate ensures that the given segment's range does not escape r by
// splitting at r.Start and r.End if necessary, and returns an updated iterator
// to the bounded segment. All existing iterators (including seg, but not
// including the returned iterators) are invalidated.
func (s *DirtySet) Isolate(seg DirtyIterator, r __generics_imported0.MappableRange) DirtyIterator {
if seg.Range().CanSplitAt(r.Start) {
_, seg = s.SplitUnchecked(seg, r.Start)
}
if seg.Range().CanSplitAt(r.End) {
seg, _ = s.SplitUnchecked(seg, r.End)
}
return seg
}
// ApplyContiguous applies a function to a contiguous range of segments,
// splitting if necessary. The function is applied until the first gap is
// encountered, at which point the gap is returned. If the function is applied
// across the entire range, a terminal gap is returned. All existing iterators
// are invalidated.
//
// N.B. The Iterator must not be invalidated by the function.
func (s *DirtySet) ApplyContiguous(r __generics_imported0.MappableRange, fn func(seg DirtyIterator)) DirtyGapIterator {
seg, gap := s.Find(r.Start)
if !seg.Ok() {
return gap
}
for {
seg = s.Isolate(seg, r)
fn(seg)
if seg.End() >= r.End {
return DirtyGapIterator{}
}
gap = seg.NextGap()
if !gap.IsEmpty() {
return gap
}
seg = gap.NextSegment()
if !seg.Ok() {
return DirtyGapIterator{}
}
}
}
// +stateify savable
type Dirtynode struct {
// An internal binary tree node looks like:
//
// K
// / \
// Cl Cr
//
// where all keys in the subtree rooted by Cl (the left subtree) are less
// than K (the key of the parent node), and all keys in the subtree rooted
// by Cr (the right subtree) are greater than K.
//
// An internal B-tree node's indexes work out to look like:
//
// K0 K1 K2 ... Kn-1
// / \/ \/ \ ... / \
// C0 C1 C2 C3 ... Cn-1 Cn
//
// where n is nrSegments.
nrSegments int
// parent is a pointer to this node's parent. If this node is root, parent
// is nil.
parent *Dirtynode
// parentIndex is the index of this node in parent.children.
parentIndex int
// Flag for internal nodes that is technically redundant with "children[0]
// != nil", but is stored in the first cache line. "hasChildren" rather
// than "isLeaf" because false must be the correct value for an empty root.
hasChildren bool
// The longest gap within this node. If the node is a leaf, it's simply the
// maximum gap among all the (nrSegments+1) gaps formed by its nrSegments keys
// including the 0th and nrSegments-th gap possibly shared with its upper-level
// nodes; if it's a non-leaf node, it's the max of all children's maxGap.
maxGap DirtydynamicGap
// Nodes store keys and values in separate arrays to maximize locality in
// the common case (scanning keys for lookup).
keys [DirtymaxDegree - 1]__generics_imported0.MappableRange
values [DirtymaxDegree - 1]DirtyInfo
children [DirtymaxDegree]*Dirtynode
}
// firstSegment returns the first segment in the subtree rooted by n.
//
// Preconditions: n.nrSegments != 0.
func (n *Dirtynode) firstSegment() DirtyIterator {
for n.hasChildren {
n = n.children[0]
}
return DirtyIterator{n, 0}
}
// lastSegment returns the last segment in the subtree rooted by n.
//
// Preconditions: n.nrSegments != 0.
func (n *Dirtynode) lastSegment() DirtyIterator {
for n.hasChildren {
n = n.children[n.nrSegments]
}
return DirtyIterator{n, n.nrSegments - 1}
}
func (n *Dirtynode) prevSibling() *Dirtynode {
if n.parent == nil || n.parentIndex == 0 {
return nil
}
return n.parent.children[n.parentIndex-1]
}
func (n *Dirtynode) nextSibling() *Dirtynode {
if n.parent == nil || n.parentIndex == n.parent.nrSegments {
return nil
}
return n.parent.children[n.parentIndex+1]
}
// rebalanceBeforeInsert splits n and its ancestors if they are full, as
// required for insertion, and returns an updated iterator to the position
// represented by gap.
func (n *Dirtynode) rebalanceBeforeInsert(gap DirtyGapIterator) DirtyGapIterator {
if n.nrSegments < DirtymaxDegree-1 {
return gap
}
if n.parent != nil {
gap = n.parent.rebalanceBeforeInsert(gap)
}
if n.parent == nil {
left := &Dirtynode{
nrSegments: DirtyminDegree - 1,
parent: n,
parentIndex: 0,
hasChildren: n.hasChildren,
}
right := &Dirtynode{
nrSegments: DirtyminDegree - 1,
parent: n,
parentIndex: 1,
hasChildren: n.hasChildren,
}
copy(left.keys[:DirtyminDegree-1], n.keys[:DirtyminDegree-1])
copy(left.values[:DirtyminDegree-1], n.values[:DirtyminDegree-1])
copy(right.keys[:DirtyminDegree-1], n.keys[DirtyminDegree:])
copy(right.values[:DirtyminDegree-1], n.values[DirtyminDegree:])
n.keys[0], n.values[0] = n.keys[DirtyminDegree-1], n.values[DirtyminDegree-1]
DirtyzeroValueSlice(n.values[1:])
if n.hasChildren {
copy(left.children[:DirtyminDegree], n.children[:DirtyminDegree])
copy(right.children[:DirtyminDegree], n.children[DirtyminDegree:])
DirtyzeroNodeSlice(n.children[2:])
for i := 0; i < DirtyminDegree; i++ {
left.children[i].parent = left
left.children[i].parentIndex = i
right.children[i].parent = right
right.children[i].parentIndex = i
}
}
n.nrSegments = 1
n.hasChildren = true
n.children[0] = left
n.children[1] = right
if DirtytrackGaps != 0 {
left.updateMaxGapLocal()
right.updateMaxGapLocal()
}
if gap.node != n {
return gap
}
if gap.index < DirtyminDegree {
return DirtyGapIterator{left, gap.index}
}
return DirtyGapIterator{right, gap.index - DirtyminDegree}
}
copy(n.parent.keys[n.parentIndex+1:], n.parent.keys[n.parentIndex:n.parent.nrSegments])
copy(n.parent.values[n.parentIndex+1:], n.parent.values[n.parentIndex:n.parent.nrSegments])
n.parent.keys[n.parentIndex], n.parent.values[n.parentIndex] = n.keys[DirtyminDegree-1], n.values[DirtyminDegree-1]
copy(n.parent.children[n.parentIndex+2:], n.parent.children[n.parentIndex+1:n.parent.nrSegments+1])
for i := n.parentIndex + 2; i < n.parent.nrSegments+2; i++ {
n.parent.children[i].parentIndex = i
}
sibling := &Dirtynode{
nrSegments: DirtyminDegree - 1,
parent: n.parent,
parentIndex: n.parentIndex + 1,
hasChildren: n.hasChildren,
}
n.parent.children[n.parentIndex+1] = sibling
n.parent.nrSegments++
copy(sibling.keys[:DirtyminDegree-1], n.keys[DirtyminDegree:])
copy(sibling.values[:DirtyminDegree-1], n.values[DirtyminDegree:])
DirtyzeroValueSlice(n.values[DirtyminDegree-1:])
if n.hasChildren {
copy(sibling.children[:DirtyminDegree], n.children[DirtyminDegree:])
DirtyzeroNodeSlice(n.children[DirtyminDegree:])
for i := 0; i < DirtyminDegree; i++ {
sibling.children[i].parent = sibling
sibling.children[i].parentIndex = i
}
}
n.nrSegments = DirtyminDegree - 1
if DirtytrackGaps != 0 {
n.updateMaxGapLocal()
sibling.updateMaxGapLocal()
}
if gap.node != n {
return gap
}
if gap.index < DirtyminDegree {
return gap
}
return DirtyGapIterator{sibling, gap.index - DirtyminDegree}
}
// rebalanceAfterRemove "unsplits" n and its ancestors if they are deficient
// (contain fewer segments than required by B-tree invariants), as required for
// removal, and returns an updated iterator to the position represented by gap.
//
// Precondition: n is the only node in the tree that may currently violate a
// B-tree invariant.
func (n *Dirtynode) rebalanceAfterRemove(gap DirtyGapIterator) DirtyGapIterator {
for {
if n.nrSegments >= DirtyminDegree-1 {
return gap
}
if n.parent == nil {
return gap
}
if sibling := n.prevSibling(); sibling != nil && sibling.nrSegments >= DirtyminDegree {
copy(n.keys[1:], n.keys[:n.nrSegments])
copy(n.values[1:], n.values[:n.nrSegments])
n.keys[0] = n.parent.keys[n.parentIndex-1]
n.values[0] = n.parent.values[n.parentIndex-1]
n.parent.keys[n.parentIndex-1] = sibling.keys[sibling.nrSegments-1]
n.parent.values[n.parentIndex-1] = sibling.values[sibling.nrSegments-1]
dirtySetFunctions{}.ClearValue(&sibling.values[sibling.nrSegments-1])
if n.hasChildren {
copy(n.children[1:], n.children[:n.nrSegments+1])
n.children[0] = sibling.children[sibling.nrSegments]
sibling.children[sibling.nrSegments] = nil
n.children[0].parent = n
n.children[0].parentIndex = 0
for i := 1; i < n.nrSegments+2; i++ {
n.children[i].parentIndex = i
}
}
n.nrSegments++
sibling.nrSegments--
if DirtytrackGaps != 0 {
n.updateMaxGapLocal()
sibling.updateMaxGapLocal()
}
if gap.node == sibling && gap.index == sibling.nrSegments {
return DirtyGapIterator{n, 0}
}
if gap.node == n {
return DirtyGapIterator{n, gap.index + 1}
}
return gap
}
if sibling := n.nextSibling(); sibling != nil && sibling.nrSegments >= DirtyminDegree {
n.keys[n.nrSegments] = n.parent.keys[n.parentIndex]
n.values[n.nrSegments] = n.parent.values[n.parentIndex]
n.parent.keys[n.parentIndex] = sibling.keys[0]
n.parent.values[n.parentIndex] = sibling.values[0]
copy(sibling.keys[:sibling.nrSegments-1], sibling.keys[1:])
copy(sibling.values[:sibling.nrSegments-1], sibling.values[1:])
dirtySetFunctions{}.ClearValue(&sibling.values[sibling.nrSegments-1])
if n.hasChildren {
n.children[n.nrSegments+1] = sibling.children[0]
copy(sibling.children[:sibling.nrSegments], sibling.children[1:])
sibling.children[sibling.nrSegments] = nil
n.children[n.nrSegments+1].parent = n
n.children[n.nrSegments+1].parentIndex = n.nrSegments + 1
for i := 0; i < sibling.nrSegments; i++ {
sibling.children[i].parentIndex = i
}
}
n.nrSegments++
sibling.nrSegments--
if DirtytrackGaps != 0 {
n.updateMaxGapLocal()
sibling.updateMaxGapLocal()
}
if gap.node == sibling {
if gap.index == 0 {
return DirtyGapIterator{n, n.nrSegments}
}
return DirtyGapIterator{sibling, gap.index - 1}
}
return gap
}
p := n.parent
if p.nrSegments == 1 {
left, right := p.children[0], p.children[1]
p.nrSegments = left.nrSegments + right.nrSegments + 1
p.hasChildren = left.hasChildren
p.keys[left.nrSegments] = p.keys[0]
p.values[left.nrSegments] = p.values[0]
copy(p.keys[:left.nrSegments], left.keys[:left.nrSegments])
copy(p.values[:left.nrSegments], left.values[:left.nrSegments])
copy(p.keys[left.nrSegments+1:], right.keys[:right.nrSegments])
copy(p.values[left.nrSegments+1:], right.values[:right.nrSegments])
if left.hasChildren {
copy(p.children[:left.nrSegments+1], left.children[:left.nrSegments+1])
copy(p.children[left.nrSegments+1:], right.children[:right.nrSegments+1])
for i := 0; i < p.nrSegments+1; i++ {
p.children[i].parent = p
p.children[i].parentIndex = i
}
} else {
p.children[0] = nil
p.children[1] = nil
}
if gap.node == left {
return DirtyGapIterator{p, gap.index}
}
if gap.node == right {
return DirtyGapIterator{p, gap.index + left.nrSegments + 1}
}
return gap
}
// Merge n and either sibling, along with the segment separating the
// two, into whichever of the two nodes comes first. This is the
// reverse of the non-root splitting case in
// node.rebalanceBeforeInsert.
var left, right *Dirtynode
if n.parentIndex > 0 {
left = n.prevSibling()
right = n
} else {
left = n
right = n.nextSibling()
}
if gap.node == right {
gap = DirtyGapIterator{left, gap.index + left.nrSegments + 1}
}
left.keys[left.nrSegments] = p.keys[left.parentIndex]
left.values[left.nrSegments] = p.values[left.parentIndex]
copy(left.keys[left.nrSegments+1:], right.keys[:right.nrSegments])
copy(left.values[left.nrSegments+1:], right.values[:right.nrSegments])
if left.hasChildren {
copy(left.children[left.nrSegments+1:], right.children[:right.nrSegments+1])
for i := left.nrSegments + 1; i < left.nrSegments+right.nrSegments+2; i++ {
left.children[i].parent = left
left.children[i].parentIndex = i
}
}
left.nrSegments += right.nrSegments + 1
copy(p.keys[left.parentIndex:], p.keys[left.parentIndex+1:p.nrSegments])
copy(p.values[left.parentIndex:], p.values[left.parentIndex+1:p.nrSegments])
dirtySetFunctions{}.ClearValue(&p.values[p.nrSegments-1])
copy(p.children[left.parentIndex+1:], p.children[left.parentIndex+2:p.nrSegments+1])
for i := 0; i < p.nrSegments; i++ {
p.children[i].parentIndex = i
}
p.children[p.nrSegments] = nil
p.nrSegments--
if DirtytrackGaps != 0 {
left.updateMaxGapLocal()
}
n = p
}
}
// updateMaxGapLeaf updates maxGap bottom-up from the calling leaf until no
// necessary update.
//
// Preconditions: n must be a leaf node, trackGaps must be 1.
func (n *Dirtynode) updateMaxGapLeaf() {
if n.hasChildren {
panic(fmt.Sprintf("updateMaxGapLeaf should always be called on leaf node: %v", n))
}
max := n.calculateMaxGapLeaf()
if max == n.maxGap.Get() {
return
}
oldMax := n.maxGap.Get()
n.maxGap.Set(max)
if max > oldMax {
for p := n.parent; p != nil; p = p.parent {
if p.maxGap.Get() >= max {
break
}
p.maxGap.Set(max)
}
return
}
for p := n.parent; p != nil; p = p.parent {
if p.maxGap.Get() > oldMax {
break
}
parentNewMax := p.calculateMaxGapInternal()
if p.maxGap.Get() == parentNewMax {
break
}
p.maxGap.Set(parentNewMax)
}
}
// updateMaxGapLocal updates maxGap of the calling node solely with no
// propagation to ancestor nodes.
//
// Precondition: trackGaps must be 1.
func (n *Dirtynode) updateMaxGapLocal() {
if !n.hasChildren {
n.maxGap.Set(n.calculateMaxGapLeaf())
} else {
n.maxGap.Set(n.calculateMaxGapInternal())
}
}
// calculateMaxGapLeaf iterates the gaps within a leaf node and calculate the
// max.
//
// Preconditions: n must be a leaf node.
func (n *Dirtynode) calculateMaxGapLeaf() uint64 {
max := DirtyGapIterator{n, 0}.Range().Length()
for i := 1; i <= n.nrSegments; i++ {
if current := (DirtyGapIterator{n, i}).Range().Length(); current > max {
max = current
}
}
return max
}
// calculateMaxGapInternal iterates children's maxGap within an internal node n
// and calculate the max.
//