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lower_bound_iterator.go
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/
lower_bound_iterator.go
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// Copyright (c) HashiCorp, Inc.
// SPDX-License-Identifier: BUSL-1.1
package adaptive
import (
"bytes"
)
// Iterator is used to iterate over a set of nodes from the node
// down to a specified path. This will iterate over the same values that
// the Node.WalkPath method will.
type LowerBoundIterator[T any] struct {
path []byte
node Node[T]
stack []Node[T]
depth int
pos Node[T]
seenMismatch bool
}
// Front returns the current node that has been iterated to.
func (i *LowerBoundIterator[T]) Front() Node[T] {
return i.pos
}
func (i *LowerBoundIterator[T]) Path() string {
return string(i.path)
}
func (i *LowerBoundIterator[T]) Next() ([]byte, T, bool) {
var zero T
// Iterate through the stack until it's empty
for len(i.stack) > 0 {
node := i.stack[len(i.stack)-1]
i.stack = i.stack[:len(i.stack)-1]
if node == nil {
return nil, zero, false
}
switch node.(type) {
case *Node4[T]:
n4 := node.(*Node4[T])
n4L := n4.leaf
for itr := int(n4.numChildren) - 1; itr >= 0; itr-- {
i.stack = append(i.stack, n4.children[itr])
}
if n4L != nil {
return getKey(n4L.key), n4L.value, true
}
case *Node16[T]:
n16 := node.(*Node16[T])
n16L := n16.leaf
for itr := int(n16.numChildren) - 1; itr >= 0; itr-- {
i.stack = append(i.stack, n16.children[itr])
}
if n16L != nil {
return getKey(n16.leaf.key), n16.leaf.value, true
}
case *Node48[T]:
n48 := node.(*Node48[T])
n48L := n48.leaf
for itr := 255; itr >= 0; itr-- {
idx := n48.keys[itr]
if idx == 0 {
continue
}
nodeCh := n48.children[idx-1]
if nodeCh == nil {
continue
}
i.stack = append(i.stack, nodeCh)
}
if n48L != nil {
return getKey(n48L.key), n48L.value, true
}
case *Node256[T]:
n256 := node.(*Node256[T])
n256L := n256.leaf
for itr := 255; itr >= 0; itr-- {
nodeCh := n256.children[itr]
if nodeCh == nil {
continue
}
i.stack = append(i.stack, nodeCh)
}
if n256L != nil {
return getKey(n256L.key), n256L.value, true
}
case *NodeLeaf[T]:
leafCh := node.(*NodeLeaf[T])
return getKey(leafCh.key), leafCh.value, true
}
}
return nil, zero, false
}
func (i *LowerBoundIterator[T]) recurseMin(n Node[T]) Node[T] {
// Traverse to the minimum child
if n.isLeaf() {
return n
}
nCh := n.getNumChildren()
if nCh > 1 {
// Add all the other edges to the stack (the min node will be added as
// we recurse)
var allCh []Node[T]
for itr := nCh - 1; itr >= 1; itr-- {
allCh = append(allCh, n.getChild(int(itr)))
}
i.stack = append(allCh, i.stack...)
}
if nCh > 0 {
return i.recurseMin(n.getChild(0))
}
// Shouldn't be possible
return nil
}
func (i *LowerBoundIterator[T]) SeekLowerBound(prefixKey []byte) {
node := i.node
i.stack = []Node[T]{}
if len(prefixKey) == 0 {
i.stack = []Node[T]{node}
return
}
prefix := getTreeKey(prefixKey)
found := func(n Node[T]) {
nL := n.getNodeLeaf()
if nL == nil {
i.stack = append(
i.stack,
n,
)
return
}
if bytes.Compare(nL.key, i.path) >= 0 {
i.stack = append(
i.stack,
n,
)
return
}
}
findMin := func(n Node[T]) {
if n != nil {
found(n)
return
}
n = i.recurseMin(n)
}
i.path = prefix
depth := 0
i.node = node
i.seenMismatch = false
var parent Node[T]
for {
// Check if the node matches the prefix
if node == nil {
if parent != nil && parent.getNodeLeaf() != nil {
i.stack = append(i.stack, parent.getNodeLeaf())
}
return
}
var prefixCmp int
if !node.isLeaf() {
if int(node.getPartialLen()) < len(prefix) {
prefixCmp = bytes.Compare(node.getPartial()[:node.getPartialLen()], prefix[depth:min(len(prefix), depth+int(node.getPartialLen()))])
} else {
prefixCmp = bytes.Compare(node.getPartial()[:node.getPartialLen()], prefix[depth:])
}
}
if prefixCmp > 0 && !i.seenMismatch {
// Prefix is larger, that means the lower bound is greater than the search
// and from now on we need to follow the minimum path to the smallest
// leaf under this subtree.
nL := node.getNodeLeaf()
if nL != nil {
if bytes.Compare(nL.key, i.path) >= 0 {
findMin(node)
}
} else {
findMin(node)
}
if parent != nil && parent.getNodeLeaf() != nil {
if bytes.Compare(parent.getNodeLeaf().getKey(), i.path) >= 0 {
i.stack = append(i.stack, parent.getNodeLeaf())
}
return
}
return
}
if prefixCmp < 0 && !i.seenMismatch {
// Prefix is smaller than search prefix, that means there is no lower
// bound
i.node = nil
if parent != nil && parent.getNodeLeaf() != nil {
if bytes.Compare(parent.getNodeLeaf().getKey(), i.path) >= 0 {
i.stack = append(i.stack, parent.getNodeLeaf())
}
}
return
}
if node.isLeaf() && node.getNodeLeaf() != nil && bytes.Compare(node.getNodeLeaf().getKey(), prefix) >= 0 {
found(node)
if parent != nil && parent.getNodeLeaf() != nil {
if bytes.Compare(parent.getNodeLeaf().getKey(), i.path) >= 0 {
i.stack = append(i.stack, parent.getNodeLeaf())
}
}
return
}
// Determine the child index to proceed based on the next byte of the prefix
// If the node has a prefix, compare it with the prefix
if node.getArtNodeType() != leafType {
mismatchIdx := prefixMismatch[T](node, prefix, len(prefix), depth)
if mismatchIdx < int(node.getPartialLen()) && !i.seenMismatch {
// If there's a mismatch, set the node to nil to break the loop
node = nil
return
}
if mismatchIdx > 0 {
i.seenMismatch = true
}
depth += int(node.getPartialLen())
}
if depth >= len(prefix) {
nL := node.getNodeLeaf()
if nL != nil {
if bytes.Compare(nL.getKey(), i.path) >= 0 {
i.stack = append(i.stack, node)
}
} else {
i.stack = append(i.stack, node)
}
if parent != nil && parent.getNodeLeaf() != nil {
if bytes.Compare(parent.getNodeLeaf().getKey(), i.path) >= 0 {
i.stack = append(i.stack, parent.getNodeLeaf())
}
}
return
}
idx := node.getLowerBoundCh(prefix[depth])
if idx == -1 && !i.seenMismatch {
return
}
if i.seenMismatch && idx != -1 {
idx = 0
}
if idx == -1 {
if node.getNodeLeaf() != nil {
if bytes.Compare(node.getNodeLeaf().getKey(), i.path) >= 0 {
i.stack = append(i.stack, node)
}
} else {
for itr := int(node.getNumChildren()) - 1; itr >= idx+1; itr-- {
nCh := node.getChild(itr)
nChL := nCh.getNodeLeaf()
if nChL == nil {
i.stack = append(i.stack, node.getChild(itr))
} else {
if bytes.Compare(nChL.key, i.path) >= 0 {
i.stack = append(i.stack, node.getChild(itr))
}
}
}
}
if parent.getNodeLeaf() != nil && bytes.Compare(parent.getNodeLeaf().getKey(), i.path) >= 0 {
i.stack = append(i.stack, parent.getNodeLeaf())
}
node = nil
return
}
if i.seenMismatch && parent != nil && parent.getNodeLeaf() != nil {
nL := node.getNodeLeaf()
addedNode := false
if nL != nil {
if bytes.Compare(nL.getKey(), i.path) >= 0 {
i.stack = append(i.stack, node)
addedNode = true
}
}
if !addedNode {
for itr := int(node.getNumChildren()) - 1; itr >= 0; itr-- {
if node.getChild(itr) != nil {
nCh := node.getChild(itr)
nChL := nCh.getNodeLeaf()
if nChL == nil {
i.stack = append(i.stack, node.getChild(itr))
} else {
if bytes.Compare(nChL.key, i.path) >= 0 {
i.stack = append(i.stack, node.getChild(itr))
}
}
}
}
}
if bytes.Compare(parent.getNodeLeaf().getKey(), i.path) >= 0 {
i.stack = append(i.stack, parent.getNodeLeaf())
}
return
}
for itr := int(node.getNumChildren()) - 1; itr >= idx+1; itr-- {
if node.getChild(itr) != nil {
nCh := node.getChild(itr)
nChL := nCh.getNodeLeaf()
if nChL == nil {
i.stack = append(i.stack, node.getChild(itr))
} else {
if bytes.Compare(nChL.key, i.path) >= 0 {
i.stack = append(i.stack, node.getChild(itr))
}
}
}
}
if idx >= 0 && node.getKeyAtIdx(idx) != prefix[depth] {
i.seenMismatch = true
}
if idx == -1 {
return
}
parent = node
// Move to the next level in the tree
node = node.getChild(idx)
depth++
}
}