forked from tikv/pd
/
patricia.go
173 lines (142 loc) · 2.59 KB
/
patricia.go
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package cmux
import (
"bytes"
"io"
)
// patriciaTree is a simple patricia tree that handles []byte instead of string
// and cannot be changed after instantiation.
type patriciaTree struct {
root *ptNode
}
func newPatriciaTree(b ...[]byte) *patriciaTree {
return &patriciaTree{
root: newNode(b),
}
}
func newPatriciaTreeString(strs ...string) *patriciaTree {
b := make([][]byte, len(strs))
for i, s := range strs {
b[i] = []byte(s)
}
return &patriciaTree{
root: newNode(b),
}
}
func (t *patriciaTree) matchPrefix(r io.Reader) bool {
return t.root.match(r, true)
}
func (t *patriciaTree) match(r io.Reader) bool {
return t.root.match(r, false)
}
type ptNode struct {
prefix []byte
next map[byte]*ptNode
terminal bool
}
func newNode(strs [][]byte) *ptNode {
if len(strs) == 0 {
return &ptNode{
prefix: []byte{},
terminal: true,
}
}
if len(strs) == 1 {
return &ptNode{
prefix: strs[0],
terminal: true,
}
}
p, strs := splitPrefix(strs)
n := &ptNode{
prefix: p,
}
nexts := make(map[byte][][]byte)
for _, s := range strs {
if len(s) == 0 {
n.terminal = true
continue
}
nexts[s[0]] = append(nexts[s[0]], s[1:])
}
n.next = make(map[byte]*ptNode)
for first, rests := range nexts {
n.next[first] = newNode(rests)
}
return n
}
func splitPrefix(bss [][]byte) (prefix []byte, rest [][]byte) {
if len(bss) == 0 || len(bss[0]) == 0 {
return prefix, bss
}
if len(bss) == 1 {
return bss[0], [][]byte{{}}
}
for i := 0; ; i++ {
var cur byte
eq := true
for j, b := range bss {
if len(b) <= i {
eq = false
break
}
if j == 0 {
cur = b[i]
continue
}
if cur != b[i] {
eq = false
break
}
}
if !eq {
break
}
prefix = append(prefix, cur)
}
rest = make([][]byte, 0, len(bss))
for _, b := range bss {
rest = append(rest, b[len(prefix):])
}
return prefix, rest
}
func readBytes(r io.Reader, n int) (b []byte, err error) {
b = make([]byte, n)
o := 0
for o < n {
nr, err := r.Read(b[o:])
if err != nil && err != io.EOF {
return b, err
}
o += nr
if err == io.EOF {
break
}
}
return b[:o], nil
}
func (n *ptNode) match(r io.Reader, prefix bool) bool {
if l := len(n.prefix); l > 0 {
b, err := readBytes(r, l)
if err != nil || len(b) != l || !bytes.Equal(b, n.prefix) {
return false
}
}
if prefix && n.terminal {
return true
}
b := make([]byte, 1)
for {
nr, err := r.Read(b)
if nr != 0 {
break
}
if err == io.EOF {
return n.terminal
}
if err != nil {
return false
}
}
nextN, ok := n.next[b[0]]
return ok && nextN.match(r, prefix)
}