4047ccad2f
The 'step' method is split into two parts, 'peek' and 'push'. peek returns the next state but doesn't make it current. The end of iteration was previously tracked by setting 'trie' to nil. End of iteration is now tracked using the 'iteratorEnd' error, which is slightly cleaner and requires less code.
500 lines
14 KiB
Go
500 lines
14 KiB
Go
// Copyright 2014 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package trie
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import (
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"bytes"
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"container/heap"
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"errors"
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"github.com/ethereum/go-ethereum/common"
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)
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var iteratorEnd = errors.New("end of iteration")
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// Iterator is a key-value trie iterator that traverses a Trie.
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type Iterator struct {
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nodeIt NodeIterator
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Key []byte // Current data key on which the iterator is positioned on
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Value []byte // Current data value on which the iterator is positioned on
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}
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// NewIterator creates a new key-value iterator from a node iterator
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func NewIterator(it NodeIterator) *Iterator {
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return &Iterator{
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nodeIt: it,
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}
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}
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// Next moves the iterator forward one key-value entry.
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func (it *Iterator) Next() bool {
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for it.nodeIt.Next(true) {
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if it.nodeIt.Leaf() {
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it.Key = hexToKeybytes(it.nodeIt.Path())
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it.Value = it.nodeIt.LeafBlob()
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return true
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}
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}
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it.Key = nil
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it.Value = nil
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return false
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}
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// NodeIterator is an iterator to traverse the trie pre-order.
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type NodeIterator interface {
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// Hash returns the hash of the current node
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Hash() common.Hash
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// Parent returns the hash of the parent of the current node
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Parent() common.Hash
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// Leaf returns true iff the current node is a leaf node.
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Leaf() bool
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// LeafBlob returns the contents of the node, if it is a leaf.
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// Callers must not retain references to the return value after calling Next()
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LeafBlob() []byte
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// Path returns the hex-encoded path to the current node.
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// Callers must not retain references to the return value after calling Next()
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Path() []byte
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// Next moves the iterator to the next node. If the parameter is false, any child
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// nodes will be skipped.
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Next(bool) bool
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// Error returns the error status of the iterator.
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Error() error
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}
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// nodeIteratorState represents the iteration state at one particular node of the
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// trie, which can be resumed at a later invocation.
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type nodeIteratorState struct {
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hash common.Hash // Hash of the node being iterated (nil if not standalone)
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node node // Trie node being iterated
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parent common.Hash // Hash of the first full ancestor node (nil if current is the root)
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index int // Child to be processed next
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pathlen int // Length of the path to this node
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}
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type nodeIterator struct {
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trie *Trie // Trie being iterated
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stack []*nodeIteratorState // Hierarchy of trie nodes persisting the iteration state
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err error // Failure set in case of an internal error in the iterator
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path []byte // Path to the current node
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}
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func newNodeIterator(trie *Trie, start []byte) NodeIterator {
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if trie.Hash() == emptyState {
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return new(nodeIterator)
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}
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it := &nodeIterator{trie: trie}
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it.seek(start)
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return it
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}
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// Hash returns the hash of the current node
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func (it *nodeIterator) Hash() common.Hash {
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if len(it.stack) == 0 {
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return common.Hash{}
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}
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return it.stack[len(it.stack)-1].hash
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}
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// Parent returns the hash of the parent node
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func (it *nodeIterator) Parent() common.Hash {
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if len(it.stack) == 0 {
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return common.Hash{}
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}
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return it.stack[len(it.stack)-1].parent
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}
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// Leaf returns true if the current node is a leaf
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func (it *nodeIterator) Leaf() bool {
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if len(it.stack) == 0 {
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return false
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}
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_, ok := it.stack[len(it.stack)-1].node.(valueNode)
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return ok
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}
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// LeafBlob returns the data for the current node, if it is a leaf
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func (it *nodeIterator) LeafBlob() []byte {
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if len(it.stack) == 0 {
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return nil
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}
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if node, ok := it.stack[len(it.stack)-1].node.(valueNode); ok {
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return []byte(node)
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}
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return nil
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}
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// Path returns the hex-encoded path to the current node
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func (it *nodeIterator) Path() []byte {
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return it.path
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}
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// Error returns the error set in case of an internal error in the iterator
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func (it *nodeIterator) Error() error {
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if it.err == iteratorEnd {
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return nil
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}
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return it.err
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}
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// Next moves the iterator to the next node, returning whether there are any
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// further nodes. In case of an internal error this method returns false and
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// sets the Error field to the encountered failure. If `descend` is false,
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// skips iterating over any subnodes of the current node.
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func (it *nodeIterator) Next(descend bool) bool {
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if it.err != nil {
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return false
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}
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// Otherwise step forward with the iterator and report any errors
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state, parentIndex, path, err := it.peek(descend)
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if err != nil {
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it.err = err
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return false
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}
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it.push(state, parentIndex, path)
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return true
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}
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func (it *nodeIterator) seek(prefix []byte) {
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// The path we're looking for is the hex encoded key without terminator.
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key := keybytesToHex(prefix)
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key = key[:len(key)-1]
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// Move forward until we're just before the closest match to key.
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for {
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state, parentIndex, path, err := it.peek(bytes.HasPrefix(key, it.path))
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if err != nil || bytes.Compare(path, key) >= 0 {
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it.err = err
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return
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}
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it.push(state, parentIndex, path)
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}
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}
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// peek creates the next state of the iterator.
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func (it *nodeIterator) peek(descend bool) (*nodeIteratorState, *int, []byte, error) {
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if len(it.stack) == 0 {
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// Initialize the iterator if we've just started.
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root := it.trie.Hash()
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state := &nodeIteratorState{node: it.trie.root, index: -1}
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if root != emptyRoot {
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state.hash = root
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}
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return state, nil, nil, nil
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}
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if !descend {
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// If we're skipping children, pop the current node first
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it.pop()
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}
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// Continue iteration to the next child
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for {
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if len(it.stack) == 0 {
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return nil, nil, nil, iteratorEnd
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}
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parent := it.stack[len(it.stack)-1]
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ancestor := parent.hash
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if (ancestor == common.Hash{}) {
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ancestor = parent.parent
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}
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if node, ok := parent.node.(*fullNode); ok {
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// Full node, move to the first non-nil child.
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for i := parent.index + 1; i < len(node.Children); i++ {
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child := node.Children[i]
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if child != nil {
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hash, _ := child.cache()
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state := &nodeIteratorState{
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hash: common.BytesToHash(hash),
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node: child,
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parent: ancestor,
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index: -1,
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pathlen: len(it.path),
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}
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path := append(it.path, byte(i))
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parent.index = i - 1
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return state, &parent.index, path, nil
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}
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}
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} else if node, ok := parent.node.(*shortNode); ok {
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// Short node, return the pointer singleton child
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if parent.index < 0 {
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hash, _ := node.Val.cache()
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state := &nodeIteratorState{
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hash: common.BytesToHash(hash),
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node: node.Val,
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parent: ancestor,
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index: -1,
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pathlen: len(it.path),
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}
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var path []byte
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if hasTerm(node.Key) {
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path = append(it.path, node.Key[:len(node.Key)-1]...)
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} else {
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path = append(it.path, node.Key...)
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}
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return state, &parent.index, path, nil
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}
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} else if hash, ok := parent.node.(hashNode); ok {
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// Hash node, resolve the hash child from the database
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if parent.index < 0 {
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node, err := it.trie.resolveHash(hash, nil, nil)
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if err != nil {
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return it.stack[len(it.stack)-1], &parent.index, it.path, err
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}
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state := &nodeIteratorState{
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hash: common.BytesToHash(hash),
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node: node,
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parent: ancestor,
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index: -1,
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pathlen: len(it.path),
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}
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return state, &parent.index, it.path, nil
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}
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}
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// No more child nodes, move back up.
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it.pop()
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}
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}
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func (it *nodeIterator) push(state *nodeIteratorState, parentIndex *int, path []byte) {
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it.path = path
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it.stack = append(it.stack, state)
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if parentIndex != nil {
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*parentIndex += 1
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}
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}
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func (it *nodeIterator) pop() {
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parent := it.stack[len(it.stack)-1]
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it.path = it.path[:parent.pathlen]
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it.stack = it.stack[:len(it.stack)-1]
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}
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func compareNodes(a, b NodeIterator) int {
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cmp := bytes.Compare(a.Path(), b.Path())
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if cmp != 0 {
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return cmp
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}
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if a.Leaf() && !b.Leaf() {
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return -1
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} else if b.Leaf() && !a.Leaf() {
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return 1
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}
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cmp = bytes.Compare(a.Hash().Bytes(), b.Hash().Bytes())
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if cmp != 0 {
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return cmp
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}
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return bytes.Compare(a.LeafBlob(), b.LeafBlob())
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}
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type differenceIterator struct {
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a, b NodeIterator // Nodes returned are those in b - a.
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eof bool // Indicates a has run out of elements
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count int // Number of nodes scanned on either trie
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}
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// NewDifferenceIterator constructs a NodeIterator that iterates over elements in b that
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// are not in a. Returns the iterator, and a pointer to an integer recording the number
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// of nodes seen.
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func NewDifferenceIterator(a, b NodeIterator) (NodeIterator, *int) {
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a.Next(true)
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it := &differenceIterator{
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a: a,
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b: b,
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}
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return it, &it.count
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}
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func (it *differenceIterator) Hash() common.Hash {
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return it.b.Hash()
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}
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func (it *differenceIterator) Parent() common.Hash {
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return it.b.Parent()
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}
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func (it *differenceIterator) Leaf() bool {
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return it.b.Leaf()
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}
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func (it *differenceIterator) LeafBlob() []byte {
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return it.b.LeafBlob()
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}
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func (it *differenceIterator) Path() []byte {
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return it.b.Path()
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}
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func (it *differenceIterator) Next(bool) bool {
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// Invariants:
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// - We always advance at least one element in b.
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// - At the start of this function, a's path is lexically greater than b's.
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if !it.b.Next(true) {
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return false
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}
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it.count += 1
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if it.eof {
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// a has reached eof, so we just return all elements from b
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return true
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}
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for {
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switch compareNodes(it.a, it.b) {
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case -1:
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// b jumped past a; advance a
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if !it.a.Next(true) {
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it.eof = true
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return true
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}
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it.count += 1
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case 1:
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// b is before a
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return true
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case 0:
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// a and b are identical; skip this whole subtree if the nodes have hashes
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hasHash := it.a.Hash() == common.Hash{}
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if !it.b.Next(hasHash) {
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return false
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}
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it.count += 1
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if !it.a.Next(hasHash) {
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it.eof = true
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return true
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}
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it.count += 1
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}
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}
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}
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func (it *differenceIterator) Error() error {
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if err := it.a.Error(); err != nil {
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return err
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}
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return it.b.Error()
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}
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type nodeIteratorHeap []NodeIterator
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func (h nodeIteratorHeap) Len() int { return len(h) }
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func (h nodeIteratorHeap) Less(i, j int) bool { return compareNodes(h[i], h[j]) < 0 }
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func (h nodeIteratorHeap) Swap(i, j int) { h[i], h[j] = h[j], h[i] }
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func (h *nodeIteratorHeap) Push(x interface{}) { *h = append(*h, x.(NodeIterator)) }
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func (h *nodeIteratorHeap) Pop() interface{} {
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n := len(*h)
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x := (*h)[n-1]
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*h = (*h)[0 : n-1]
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return x
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}
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type unionIterator struct {
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items *nodeIteratorHeap // Nodes returned are the union of the ones in these iterators
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count int // Number of nodes scanned across all tries
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err error // The error, if one has been encountered
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}
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// NewUnionIterator constructs a NodeIterator that iterates over elements in the union
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// of the provided NodeIterators. Returns the iterator, and a pointer to an integer
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// recording the number of nodes visited.
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func NewUnionIterator(iters []NodeIterator) (NodeIterator, *int) {
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h := make(nodeIteratorHeap, len(iters))
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copy(h, iters)
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heap.Init(&h)
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ui := &unionIterator{
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items: &h,
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}
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return ui, &ui.count
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}
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func (it *unionIterator) Hash() common.Hash {
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return (*it.items)[0].Hash()
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}
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func (it *unionIterator) Parent() common.Hash {
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return (*it.items)[0].Parent()
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}
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func (it *unionIterator) Leaf() bool {
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return (*it.items)[0].Leaf()
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}
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func (it *unionIterator) LeafBlob() []byte {
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return (*it.items)[0].LeafBlob()
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}
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func (it *unionIterator) Path() []byte {
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return (*it.items)[0].Path()
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}
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// Next returns the next node in the union of tries being iterated over.
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//
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// It does this by maintaining a heap of iterators, sorted by the iteration
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// order of their next elements, with one entry for each source trie. Each
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// time Next() is called, it takes the least element from the heap to return,
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// advancing any other iterators that also point to that same element. These
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// iterators are called with descend=false, since we know that any nodes under
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// these nodes will also be duplicates, found in the currently selected iterator.
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// Whenever an iterator is advanced, it is pushed back into the heap if it still
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// has elements remaining.
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//
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// In the case that descend=false - eg, we're asked to ignore all subnodes of the
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// current node - we also advance any iterators in the heap that have the current
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// path as a prefix.
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func (it *unionIterator) Next(descend bool) bool {
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if len(*it.items) == 0 {
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return false
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}
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// Get the next key from the union
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least := heap.Pop(it.items).(NodeIterator)
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// Skip over other nodes as long as they're identical, or, if we're not descending, as
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// long as they have the same prefix as the current node.
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for len(*it.items) > 0 && ((!descend && bytes.HasPrefix((*it.items)[0].Path(), least.Path())) || compareNodes(least, (*it.items)[0]) == 0) {
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skipped := heap.Pop(it.items).(NodeIterator)
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// Skip the whole subtree if the nodes have hashes; otherwise just skip this node
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if skipped.Next(skipped.Hash() == common.Hash{}) {
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it.count += 1
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// If there are more elements, push the iterator back on the heap
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heap.Push(it.items, skipped)
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}
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}
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if least.Next(descend) {
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it.count += 1
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heap.Push(it.items, least)
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}
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return len(*it.items) > 0
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}
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func (it *unionIterator) Error() error {
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for i := 0; i < len(*it.items); i++ {
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if err := (*it.items)[i].Error(); err != nil {
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return err
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}
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}
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return nil
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}
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