Official Go implementation of the Ethereum protocol
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go-ethereum/trie/iterator.go

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8.1 KiB

// 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/>.
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package trie
import (
"bytes"
"fmt"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/logger"
"github.com/ethereum/go-ethereum/logger/glog"
)
// Iterator is a key-value trie iterator to traverse the data contents.
type Iterator struct {
trie *Trie
Key []byte // Current data key on which the iterator is positioned on
Value []byte // Current data value on which the iterator is positioned on
}
// NewIterator creates a new key-value iterator.
func NewIterator(trie *Trie) *Iterator {
return &Iterator{trie: trie, Key: nil}
}
// Next moves the iterator forward with one key-value entry.
func (self *Iterator) Next() bool {
isIterStart := false
if self.Key == nil {
isIterStart = true
self.Key = make([]byte, 32)
}
key := remTerm(compactHexDecode(self.Key))
k := self.next(self.trie.root, key, isIterStart)
self.Key = []byte(decodeCompact(k))
return len(k) > 0
}
func (self *Iterator) next(node interface{}, key []byte, isIterStart bool) []byte {
if node == nil {
return nil
}
switch node := node.(type) {
case fullNode:
if len(key) > 0 {
k := self.next(node[key[0]], key[1:], isIterStart)
if k != nil {
return append([]byte{key[0]}, k...)
}
}
var r byte
if len(key) > 0 {
r = key[0] + 1
}
for i := r; i < 16; i++ {
k := self.key(node[i])
if k != nil {
return append([]byte{i}, k...)
}
}
case shortNode:
k := remTerm(node.Key)
if vnode, ok := node.Val.(valueNode); ok {
switch bytes.Compare([]byte(k), key) {
case 0:
if isIterStart {
self.Value = vnode
return k
}
case 1:
self.Value = vnode
return k
}
} else {
cnode := node.Val
var ret []byte
skey := key[len(k):]
if bytes.HasPrefix(key, k) {
ret = self.next(cnode, skey, isIterStart)
} else if bytes.Compare(k, key[:len(k)]) > 0 {
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return self.key(node)
}
if ret != nil {
return append(k, ret...)
}
}
case hashNode:
rn, err := self.trie.resolveHash(node, nil, nil)
if err != nil && glog.V(logger.Error) {
glog.Errorf("Unhandled trie error: %v", err)
}
return self.next(rn, key, isIterStart)
}
return nil
}
func (self *Iterator) key(node interface{}) []byte {
switch node := node.(type) {
case shortNode:
// Leaf node
k := remTerm(node.Key)
if vnode, ok := node.Val.(valueNode); ok {
self.Value = vnode
return k
}
return append(k, self.key(node.Val)...)
case fullNode:
if node[16] != nil {
self.Value = node[16].(valueNode)
return []byte{16}
}
for i := 0; i < 16; i++ {
k := self.key(node[i])
if k != nil {
return append([]byte{byte(i)}, k...)
}
}
case hashNode:
rn, err := self.trie.resolveHash(node, nil, nil)
if err != nil && glog.V(logger.Error) {
glog.Errorf("Unhandled trie error: %v", err)
}
return self.key(rn)
}
return nil
}
// nodeIteratorState represents the iteration state at one particular node of the
// trie, which can be resumed at a later invocation.
type nodeIteratorState struct {
hash common.Hash // Hash of the node being iterated (nil if not standalone)
node node // Trie node being iterated
parent common.Hash // Hash of the first full ancestor node (nil if current is the root)
child int // Child to be processed next
}
// NodeIterator is an iterator to traverse the trie post-order.
type NodeIterator struct {
trie *Trie // Trie being iterated
stack []*nodeIteratorState // Hierarchy of trie nodes persisting the iteration state
Hash common.Hash // Hash of the current node being iterated (nil if not standalone)
Node node // Current node being iterated (internal representation)
Parent common.Hash // Hash of the first full ancestor node (nil if current is the root)
Leaf bool // Flag whether the current node is a value (data) node
LeafBlob []byte // Data blob contained within a leaf (otherwise nil)
Error error // Failure set in case of an internal error in the iterator
}
// NewNodeIterator creates an post-order trie iterator.
func NewNodeIterator(trie *Trie) *NodeIterator {
if bytes.Compare(trie.Root(), emptyRoot.Bytes()) == 0 {
return new(NodeIterator)
}
return &NodeIterator{trie: trie}
}
// Next moves the iterator to the next node, returning whether there are any
// further nodes. In case of an internal error this method returns false and
// sets the Error field to the encountered failure.
func (it *NodeIterator) Next() bool {
// If the iterator failed previously, don't do anything
if it.Error != nil {
return false
}
// Otherwise step forward with the iterator and report any errors
if err := it.step(); err != nil {
it.Error = err
return false
}
return it.retrieve()
}
// step moves the iterator to the next node of the trie.
func (it *NodeIterator) step() error {
// Abort if we reached the end of the iteration
if it.trie == nil {
return nil
}
// Initialize the iterator if we've just started, or pop off the old node otherwise
if len(it.stack) == 0 {
it.stack = append(it.stack, &nodeIteratorState{node: it.trie.root, child: -1})
if it.stack[0].node == nil {
return fmt.Errorf("root node missing: %x", it.trie.Root())
}
} else {
it.stack = it.stack[:len(it.stack)-1]
if len(it.stack) == 0 {
it.trie = nil
return nil
}
}
// Continue iteration to the next child
for {
parent := it.stack[len(it.stack)-1]
ancestor := parent.hash
if (ancestor == common.Hash{}) {
ancestor = parent.parent
}
if node, ok := parent.node.(fullNode); ok {
// Full node, traverse all children, then the node itself
if parent.child >= len(node) {
break
}
for parent.child++; parent.child < len(node); parent.child++ {
if current := node[parent.child]; current != nil {
it.stack = append(it.stack, &nodeIteratorState{node: current, parent: ancestor, child: -1})
break
}
}
} else if node, ok := parent.node.(shortNode); ok {
// Short node, traverse the pointer singleton child, then the node itself
if parent.child >= 0 {
break
}
parent.child++
it.stack = append(it.stack, &nodeIteratorState{node: node.Val, parent: ancestor, child: -1})
} else if hash, ok := parent.node.(hashNode); ok {
// Hash node, resolve the hash child from the database, then the node itself
if parent.child >= 0 {
break
}
parent.child++
node, err := it.trie.resolveHash(hash, nil, nil)
if err != nil {
return err
}
it.stack = append(it.stack, &nodeIteratorState{hash: common.BytesToHash(hash), node: node, parent: ancestor, child: -1})
} else {
break
}
}
return nil
}
// retrieve pulls and caches the current trie node the iterator is traversing.
// In case of a value node, the additional leaf blob is also populated with the
// data contents for external interpretation.
//
// The method returns whether there are any more data left for inspection.
func (it *NodeIterator) retrieve() bool {
// Clear out any previously set values
it.Hash, it.Node, it.Parent, it.Leaf, it.LeafBlob = common.Hash{}, nil, common.Hash{}, false, nil
// If the iteration's done, return no available data
if it.trie == nil {
return false
}
// Otherwise retrieve the current node and resolve leaf accessors
state := it.stack[len(it.stack)-1]
it.Hash, it.Node, it.Parent = state.hash, state.node, state.parent
if value, ok := it.Node.(valueNode); ok {
it.Leaf, it.LeafBlob = true, []byte(value)
}
return true
}