// Copyright 2014 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 trie
import (
"fmt"
"io"
"strings"
"github.com/dexon-foundation/dexon/common"
"github.com/dexon-foundation/dexon/rlp"
)
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
cache() (hashNode, bool)
canUnload(cachegen, cachelimit uint16) bool
}
type (
fullNode struct {
Children [17]node // Actual trie node data to encode/decode (needs custom encoder)
flags nodeFlag
}
shortNode struct {
Key []byte
Val node
flags nodeFlag
}
hashNode []byte
valueNode []byte
)
// nilValueNode is used when collapsing internal trie nodes for hashing, since
// unset children need to serialize correctly.
var nilValueNode = valueNode(nil)
// EncodeRLP encodes a full node into the consensus RLP format.
func (n *fullNode) EncodeRLP(w io.Writer) error {
var nodes [17]node
for i, child := range &n.Children {
if child != nil {
nodes[i] = child
} else {
nodes[i] = nilValueNode
}
}
return rlp.Encode(w, nodes)
}
func (n *fullNode) copy() *fullNode { copy := *n; return © }
func (n *shortNode) copy() *shortNode { copy := *n; return © }
// nodeFlag contains caching-related metadata about a node.
type nodeFlag struct {
hash hashNode // cached hash of the node (may be nil)
gen uint16 // cache generation counter
dirty bool // whether the node has changes that must be written to the database
}
// canUnload tells whether a node can be unloaded.
func (n *nodeFlag) canUnload(cachegen, cachelimit uint16) bool {
return !n.dirty && cachegen-n.gen >= cachelimit
}
func (n *fullNode) canUnload(gen, limit uint16) bool { return n.flags.canUnload(gen, limit) }
func (n *shortNode) canUnload(gen, limit uint16) bool { return n.flags.canUnload(gen, limit) }
func (n hashNode) canUnload(uint16, uint16) bool { return false }
func (n valueNode) canUnload(uint16, uint16) bool { return false }
func (n *fullNode) cache() (hashNode, bool) { return n.flags.hash, n.flags.dirty }
func (n *shortNode) cache() (hashNode, bool) { return n.flags.hash, n.flags.dirty }
func (n hashNode) cache() (hashNode, bool) { return nil, true }
func (n valueNode) cache() (hashNode, bool) { return nil, true }
// Pretty printing.
func (n *fullNode) String() string { return n.fstring("") }
func (n *shortNode) String() string { return n.fstring("") }
func (n hashNode) String() string { return n.fstring("") }
func (n valueNode) String() string { return n.fstring("") }
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))
}
func mustDecodeNode(hash, buf []byte, cachegen uint16) node {
n, err := decodeNode(hash, buf, cachegen)
if err != nil {
panic(fmt.Sprintf("node %x: %v", hash, err))
}
return n
}
// decodeNode parses the RLP encoding of a trie node.
func decodeNode(hash, buf []byte, cachegen uint16) (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, cachegen)
return n, wrapError(err, "short")
case 17:
n, err := decodeFull(hash, elems, cachegen)
return n, wrapError(err, "full")
default:
return nil, fmt.Errorf("invalid number of list elements: %v", c)
}
}
func decodeShort(hash, elems []byte, cachegen uint16) (node, error) {
kbuf, rest, err := rlp.SplitString(elems)
if err != nil {
return nil, err
}
flag := nodeFlag{hash: hash, gen: cachegen}
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, cachegen)
if err != nil {
return nil, wrapError(err, "val")
}
return &shortNode{key, r, flag}, nil
}
func decodeFull(hash, elems []byte, cachegen uint16) (*fullNode, error) {
n := &fullNode{flags: nodeFlag{hash: hash, gen: cachegen}}
for i := 0; i < 16; i++ {
cld, rest, err := decodeRef(elems, cachegen)
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
}
const hashLen = len(common.Hash{})
func decodeRef(buf []byte, cachegen uint16) (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, cachegen)
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))
}
}
// 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 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}}
}
func (err *decodeError) Error() string {
return fmt.Sprintf("%v (decode path: %s)", err.what, strings.Join(err.stack, "<-"))
}
