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node.go
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node.go
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// Copyright 2015 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
package mpt
import (
"bytes"
"fmt"
"github.com/ethereum/go-ethereum/rlp"
"io"
"strings"
)
var indices = []string{"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "a", "b", "c", "d", "e", "f", "[17]"}
type node interface {
fstring(string) string
}
// nodeFlag contains caching-related metadata about a node.
type nodeFlag struct {
hash hashNode // cached hash of the node (may be nil)
dirty bool // whether the node has changes that must be written to the database
}
type (
fullNode struct {
Children [17]node
flags nodeFlag
}
shortNode struct {
Key []byte
Val node
flags nodeFlag
}
hashNode []byte
valueNode []byte
)
func (n *fullNode) fstring(ind string) string {
resp := fmt.Sprintf("[\n%s ", ind)
for i, node := range &n.Children {
if node == nil {
resp += fmt.Sprintf("%s: <nil> ", indices[i])
} else {
resp += fmt.Sprintf("%s: %v", indices[i], node.fstring(ind+" "))
}
}
return resp + fmt.Sprintf("\n%s] ", ind)
}
func (n *shortNode) fstring(ind string) string {
return fmt.Sprintf("{%x: %v} ", n.Key, n.Val.fstring(ind+" "))
}
func (n hashNode) fstring(ind string) string {
return fmt.Sprintf("<%x> ", []byte(n))
}
func (n valueNode) fstring(ind string) string {
return fmt.Sprintf("%x ", []byte(n))
}
// decodeNode parses the RLP encoding of a trie node.
func decodeNode(hash, buf []byte) (node, error) {
if len(buf) == 0 {
return nil, io.ErrUnexpectedEOF
}
elems, _, err := rlp.SplitList(buf)
if err != nil {
return nil, fmt.Errorf("decode error: %v", err)
}
switch c, _ := rlp.CountValues(elems); c {
case 2:
n, err := decodeShort(hash, elems)
return n, wrapError(err, "short")
case 17:
n, err := decodeFull(hash, elems)
return n, wrapError(err, "full")
default:
return nil, fmt.Errorf("invalid number of list elements: %v", c)
}
}
func decodeShort(hash, elems []byte) (node, error) {
kbuf, rest, err := rlp.SplitString(elems)
if err != nil {
return nil, err
}
flag := nodeFlag{hash: hash}
key := compactToHex(kbuf)
if hasTerm(key) {
// value node
val, _, err := rlp.SplitString(rest)
if err != nil {
return nil, fmt.Errorf("invalid value node: %v", err)
}
return &shortNode{key, append(valueNode{}, val...), flag}, nil
}
r, _, err := decodeRef(rest)
if err != nil {
return nil, wrapError(err, "val")
}
return &shortNode{key, r, flag}, nil
}
// hasTerm returns whether a hex key has the terminator flag.
func hasTerm(s []byte) bool {
return len(s) > 0 && s[len(s)-1] == 16
}
func compactToHex(compact []byte) []byte {
if len(compact) == 0 {
return compact
}
base := keybytesToHex(compact)
// delete terminator flag
if base[0] < 2 {
base = base[:len(base)-1]
}
// apply odd flag
chop := 2 - base[0]&1
return base[chop:]
}
func keybytesToHex(str []byte) []byte {
l := len(str)*2 + 1
var nibbles = make([]byte, l)
for i, b := range str {
nibbles[i*2] = b / 16
nibbles[i*2+1] = b % 16
}
nibbles[l-1] = 16
return nibbles
}
func decodeRef(buf []byte) (node, []byte, error) {
kind, val, rest, err := rlp.Split(buf)
if err != nil {
return nil, buf, err
}
switch {
case kind == rlp.List:
// 'embedded' node reference. The encoding must be smaller
// than a hash in order to be valid.
if size := len(buf) - len(rest); size > hashLen {
err := fmt.Errorf("oversized embedded node (size is %d bytes, want size < %d)", size, hashLen)
return nil, buf, err
}
n, err := decodeNode(nil, buf)
return n, rest, err
case kind == rlp.String && len(val) == 0:
// empty node
return nil, rest, nil
case kind == rlp.String && len(val) == 32:
return append(hashNode{}, val...), rest, nil
default:
return nil, nil, fmt.Errorf("invalid RLP string size %d (want 0 or 32)", len(val))
}
}
const hashLen = 32
func decodeFull(hash, elems []byte) (*fullNode, error) {
n := &fullNode{flags: nodeFlag{hash: hash}}
for i := 0; i < 16; i++ {
cld, rest, err := decodeRef(elems)
if err != nil {
return n, wrapError(err, fmt.Sprintf("[%d]", i))
}
n.Children[i], elems = cld, rest
}
val, _, err := rlp.SplitString(elems)
if err != nil {
return n, err
}
if len(val) > 0 {
n.Children[16] = append(valueNode{}, val...)
}
return n, nil
}
func wrapError(err error, ctx string) error {
if err == nil {
return nil
}
if decErr, ok := err.(*decodeError); ok {
decErr.stack = append(decErr.stack, ctx)
return decErr
}
return &decodeError{err, []string{ctx}}
}
// wraps a decoding error with information about the path to the
// invalid child node (for debugging encoding issues).
type decodeError struct {
what error
stack []string
}
func (err *decodeError) Error() string {
return fmt.Sprintf("%v (decode path: %s)", err.what, strings.Join(err.stack, "<-"))
}
func get(tn node, key []byte, skipResolved bool) ([]byte, node) {
for {
switch n := tn.(type) {
case *shortNode:
if len(key) < len(n.Key) || !bytes.Equal(n.Key, key[:len(n.Key)]) {
return nil, nil
}
tn = n.Val
key = key[len(n.Key):]
if !skipResolved {
return key, tn
}
case *fullNode:
tn = n.Children[key[0]]
key = key[1:]
if !skipResolved {
return key, tn
}
case hashNode:
return key, n
case nil:
return key, nil
case valueNode:
return nil, n
default:
panic(fmt.Sprintf("%T: invalid node: %v", tn, tn))
}
}
}