buildkit/vendor/github.com/hashicorp/go-immutable-radix/node.go

353 lines
6.9 KiB
Go

package iradix
import (
"bytes"
"sort"
)
// WalkFn is used when walking the tree. Takes a
// key and value, returning if iteration should
// be terminated.
type WalkFn func(k []byte, v interface{}) bool
// leafNode is used to represent a value
type leafNode struct {
mutateCh chan struct{}
key []byte
val interface{}
}
// edge is used to represent an edge node
type edge struct {
label byte
node *Node
}
// Node is an immutable node in the radix tree
type Node struct {
// mutateCh is closed if this node is modified
mutateCh chan struct{}
// leaf is used to store possible leaf
leaf *leafNode
// prefix is the common prefix we ignore
prefix []byte
// Edges should be stored in-order for iteration.
// We avoid a fully materialized slice to save memory,
// since in most cases we expect to be sparse
edges edges
}
func (n *Node) isLeaf() bool {
return n.leaf != nil
}
func (n *Node) addEdge(e edge) {
num := len(n.edges)
idx := sort.Search(num, func(i int) bool {
return n.edges[i].label >= e.label
})
n.edges = append(n.edges, e)
if idx != num {
copy(n.edges[idx+1:], n.edges[idx:num])
n.edges[idx] = e
}
}
func (n *Node) replaceEdge(e edge) {
num := len(n.edges)
idx := sort.Search(num, func(i int) bool {
return n.edges[i].label >= e.label
})
if idx < num && n.edges[idx].label == e.label {
n.edges[idx].node = e.node
return
}
panic("replacing missing edge")
}
func (n *Node) getEdge(label byte) (int, *Node) {
num := len(n.edges)
idx := sort.Search(num, func(i int) bool {
return n.edges[i].label >= label
})
if idx < num && n.edges[idx].label == label {
return idx, n.edges[idx].node
}
return -1, nil
}
func (n *Node) delEdge(label byte) {
num := len(n.edges)
idx := sort.Search(num, func(i int) bool {
return n.edges[i].label >= label
})
if idx < num && n.edges[idx].label == label {
copy(n.edges[idx:], n.edges[idx+1:])
n.edges[len(n.edges)-1] = edge{}
n.edges = n.edges[:len(n.edges)-1]
}
}
func (n *Node) GetWatch(k []byte) (<-chan struct{}, interface{}, bool) {
search := k
watch := n.mutateCh
for {
// Check for key exhaustion
if len(search) == 0 {
if n.isLeaf() {
return n.leaf.mutateCh, n.leaf.val, true
}
break
}
// Look for an edge
_, n = n.getEdge(search[0])
if n == nil {
break
}
// Update to the finest granularity as the search makes progress
watch = n.mutateCh
// Consume the search prefix
if bytes.HasPrefix(search, n.prefix) {
search = search[len(n.prefix):]
} else {
break
}
}
return watch, nil, false
}
func (n *Node) Get(k []byte) (interface{}, bool) {
_, val, ok := n.GetWatch(k)
return val, ok
}
// LongestPrefix is like Get, but instead of an
// exact match, it will return the longest prefix match.
func (n *Node) LongestPrefix(k []byte) ([]byte, interface{}, bool) {
var last *leafNode
search := k
for {
// Look for a leaf node
if n.isLeaf() {
last = n.leaf
}
// Check for key exhaution
if len(search) == 0 {
break
}
// Look for an edge
_, n = n.getEdge(search[0])
if n == nil {
break
}
// Consume the search prefix
if bytes.HasPrefix(search, n.prefix) {
search = search[len(n.prefix):]
} else {
break
}
}
if last != nil {
return last.key, last.val, true
}
return nil, nil, false
}
// Minimum is used to return the minimum value in the tree
func (n *Node) Minimum() ([]byte, interface{}, bool) {
for {
if n.isLeaf() {
return n.leaf.key, n.leaf.val, true
}
if len(n.edges) > 0 {
n = n.edges[0].node
} else {
break
}
}
return nil, nil, false
}
// Maximum is used to return the maximum value in the tree
func (n *Node) Maximum() ([]byte, interface{}, bool) {
for {
if num := len(n.edges); num > 0 {
n = n.edges[num-1].node
continue
}
if n.isLeaf() {
return n.leaf.key, n.leaf.val, true
} else {
break
}
}
return nil, nil, false
}
// Iterator is used to return an iterator at
// the given node to walk the tree
func (n *Node) Iterator() *Iterator {
return &Iterator{node: n}
}
// rawIterator is used to return a raw iterator at the given node to walk the
// tree.
func (n *Node) rawIterator() *rawIterator {
iter := &rawIterator{node: n}
iter.Next()
return iter
}
// Walk is used to walk the tree
func (n *Node) Walk(fn WalkFn) {
recursiveWalk(n, fn)
}
// WalkPrefix is used to walk the tree under a prefix
func (n *Node) WalkPrefix(prefix []byte, fn WalkFn) {
search := prefix
for {
// Check for key exhaution
if len(search) == 0 {
recursiveWalk(n, fn)
return
}
// Look for an edge
_, n = n.getEdge(search[0])
if n == nil {
break
}
// Consume the search prefix
if bytes.HasPrefix(search, n.prefix) {
search = search[len(n.prefix):]
} else if bytes.HasPrefix(n.prefix, search) {
// Child may be under our search prefix
recursiveWalk(n, fn)
return
} else {
break
}
}
}
// WalkPath is used to walk the tree, but only visiting nodes
// from the root down to a given leaf. Where WalkPrefix walks
// all the entries *under* the given prefix, this walks the
// entries *above* the given prefix.
func (n *Node) WalkPath(path []byte, fn WalkFn) {
search := path
for {
// Visit the leaf values if any
if n.leaf != nil && fn(n.leaf.key, n.leaf.val) {
return
}
// Check for key exhaution
if len(search) == 0 {
return
}
// Look for an edge
_, n = n.getEdge(search[0])
if n == nil {
return
}
// Consume the search prefix
if bytes.HasPrefix(search, n.prefix) {
search = search[len(n.prefix):]
} else {
break
}
}
}
func (n *Node) Seek(prefix []byte) *Seeker {
search := prefix
p := &pos{n: n}
for {
// Check for key exhaution
if len(search) == 0 {
return &Seeker{p}
}
num := len(n.edges)
idx := sort.Search(num, func(i int) bool {
return n.edges[i].label >= search[0]
})
p.current = idx
if idx < len(n.edges) {
n = n.edges[idx].node
if bytes.HasPrefix(search, n.prefix) && len(n.edges) > 0 {
search = search[len(n.prefix):]
p.current++
p = &pos{n: n, prev: p}
continue
}
}
p.current++
return &Seeker{p}
}
}
type Seeker struct {
*pos
}
type pos struct {
n *Node
current int
prev *pos
isLeaf bool
}
func (s *Seeker) Next() (k []byte, v interface{}, ok bool) {
if s.current >= len(s.n.edges) {
if s.prev == nil {
return nil, nil, false
}
s.pos = s.prev
return s.Next()
}
edge := s.n.edges[s.current]
s.current++
if edge.node.leaf != nil && !s.isLeaf {
s.isLeaf = true
s.current--
return edge.node.leaf.key, edge.node.leaf.val, true
}
s.isLeaf = false
s.pos = &pos{n: edge.node, prev: s.pos}
return s.Next()
}
// recursiveWalk is used to do a pre-order walk of a node
// recursively. Returns true if the walk should be aborted
func recursiveWalk(n *Node, fn WalkFn) bool {
// Visit the leaf values if any
if n.leaf != nil && fn(n.leaf.key, n.leaf.val) {
return true
}
// Recurse on the children
for _, e := range n.edges {
if recursiveWalk(e.node, fn) {
return true
}
}
return false
}