plugeth/trie/trie.go

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// Copyright 2014 The go-ethereum Authors
// This file is part of the go-ethereum library.
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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
// 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,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// 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 implements Merkle Patricia Tries.
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package trie
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import (
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"bytes"
"errors"
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"fmt"
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"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/core/types"
"github.com/ethereum/go-ethereum/log"
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)
// Trie is a Merkle Patricia Trie. Use New to create a trie that sits on
// top of a database. Whenever trie performs a commit operation, the generated
// nodes will be gathered and returned in a set. Once the trie is committed,
// it's not usable anymore. Callers have to re-create the trie with new root
// based on the updated trie database.
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//
// Trie is not safe for concurrent use.
type Trie struct {
root node
owner common.Hash
// Keep track of the number leaves which have been inserted since the last
// hashing operation. This number will not directly map to the number of
// actually unhashed nodes.
unhashed int
// reader is the handler trie can retrieve nodes from.
reader *trieReader
// tracer is the tool to track the trie changes.
// It will be reset after each commit operation.
tracer *tracer
}
// newFlag returns the cache flag value for a newly created node.
func (t *Trie) newFlag() nodeFlag {
return nodeFlag{dirty: true}
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}
// Copy returns a copy of Trie.
func (t *Trie) Copy() *Trie {
return &Trie{
root: t.root,
owner: t.owner,
unhashed: t.unhashed,
reader: t.reader,
tracer: t.tracer.copy(),
}
}
// New creates the trie instance with provided trie id and the read-only
// database. The state specified by trie id must be available, otherwise
// an error will be returned. The trie root specified by trie id can be
// zero hash or the sha3 hash of an empty string, then trie is initially
// empty, otherwise, the root node must be present in database or returns
// a MissingNodeError if not.
func New(id *ID, db NodeReader) (*Trie, error) {
reader, err := newTrieReader(id.StateRoot, id.Owner, db)
if err != nil {
return nil, err
}
trie := &Trie{
owner: id.Owner,
reader: reader,
//tracer: newTracer(),
}
if id.Root != (common.Hash{}) && id.Root != types.EmptyRootHash {
rootnode, err := trie.resolveAndTrack(id.Root[:], nil)
if err != nil {
return nil, err
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}
trie.root = rootnode
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}
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return trie, nil
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}
// NewEmpty is a shortcut to create empty tree. It's mostly used in tests.
func NewEmpty(db *Database) *Trie {
tr, _ := New(TrieID(common.Hash{}), db)
return tr
}
// NodeIterator returns an iterator that returns nodes of the trie. Iteration starts at
// the key after the given start key.
func (t *Trie) NodeIterator(start []byte) NodeIterator {
return newNodeIterator(t, start)
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}
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// Get returns the value for key stored in the trie.
// The value bytes must not be modified by the caller.
func (t *Trie) Get(key []byte) []byte {
res, err := t.TryGet(key)
if err != nil {
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log.Error("Unhandled trie error in Trie.Get", "err", err)
}
return res
}
// TryGet returns the value for key stored in the trie.
// The value bytes must not be modified by the caller.
// If a node was not found in the database, a MissingNodeError is returned.
func (t *Trie) TryGet(key []byte) ([]byte, error) {
value, newroot, didResolve, err := t.tryGet(t.root, keybytesToHex(key), 0)
if err == nil && didResolve {
t.root = newroot
}
return value, err
}
func (t *Trie) tryGet(origNode node, key []byte, pos int) (value []byte, newnode node, didResolve bool, err error) {
switch n := (origNode).(type) {
case nil:
return nil, nil, false, nil
case valueNode:
return n, n, false, nil
case *shortNode:
if len(key)-pos < len(n.Key) || !bytes.Equal(n.Key, key[pos:pos+len(n.Key)]) {
// key not found in trie
return nil, n, false, nil
}
value, newnode, didResolve, err = t.tryGet(n.Val, key, pos+len(n.Key))
if err == nil && didResolve {
n = n.copy()
n.Val = newnode
}
return value, n, didResolve, err
case *fullNode:
value, newnode, didResolve, err = t.tryGet(n.Children[key[pos]], key, pos+1)
if err == nil && didResolve {
n = n.copy()
n.Children[key[pos]] = newnode
}
return value, n, didResolve, err
case hashNode:
child, err := t.resolveAndTrack(n, key[:pos])
if err != nil {
return nil, n, true, err
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}
value, newnode, _, err := t.tryGet(child, key, pos)
return value, newnode, true, err
default:
panic(fmt.Sprintf("%T: invalid node: %v", origNode, origNode))
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}
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}
// TryGetNode attempts to retrieve a trie node by compact-encoded path. It is not
// possible to use keybyte-encoding as the path might contain odd nibbles.
func (t *Trie) TryGetNode(path []byte) ([]byte, int, error) {
item, newroot, resolved, err := t.tryGetNode(t.root, compactToHex(path), 0)
if err != nil {
return nil, resolved, err
}
if resolved > 0 {
t.root = newroot
}
if item == nil {
return nil, resolved, nil
}
return item, resolved, err
}
func (t *Trie) tryGetNode(origNode node, path []byte, pos int) (item []byte, newnode node, resolved int, err error) {
// If non-existent path requested, abort
if origNode == nil {
return nil, nil, 0, nil
}
// If we reached the requested path, return the current node
if pos >= len(path) {
// Although we most probably have the original node expanded, encoding
// that into consensus form can be nasty (needs to cascade down) and
// time consuming. Instead, just pull the hash up from disk directly.
var hash hashNode
if node, ok := origNode.(hashNode); ok {
hash = node
} else {
hash, _ = origNode.cache()
}
if hash == nil {
return nil, origNode, 0, errors.New("non-consensus node")
}
blob, err := t.reader.nodeBlob(path, common.BytesToHash(hash))
return blob, origNode, 1, err
}
// Path still needs to be traversed, descend into children
switch n := (origNode).(type) {
case valueNode:
// Path prematurely ended, abort
return nil, nil, 0, nil
case *shortNode:
if len(path)-pos < len(n.Key) || !bytes.Equal(n.Key, path[pos:pos+len(n.Key)]) {
// Path branches off from short node
return nil, n, 0, nil
}
item, newnode, resolved, err = t.tryGetNode(n.Val, path, pos+len(n.Key))
if err == nil && resolved > 0 {
n = n.copy()
n.Val = newnode
}
return item, n, resolved, err
case *fullNode:
item, newnode, resolved, err = t.tryGetNode(n.Children[path[pos]], path, pos+1)
if err == nil && resolved > 0 {
n = n.copy()
n.Children[path[pos]] = newnode
}
return item, n, resolved, err
case hashNode:
child, err := t.resolveAndTrack(n, path[:pos])
if err != nil {
return nil, n, 1, err
}
item, newnode, resolved, err := t.tryGetNode(child, path, pos)
return item, newnode, resolved + 1, err
default:
panic(fmt.Sprintf("%T: invalid node: %v", origNode, origNode))
}
}
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// Update associates key with value in the trie. Subsequent calls to
// Get will return value. If value has length zero, any existing value
// is deleted from the trie and calls to Get will return nil.
//
// The value bytes must not be modified by the caller while they are
// stored in the trie.
func (t *Trie) Update(key, value []byte) {
if err := t.TryUpdate(key, value); err != nil {
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log.Error("Unhandled trie error in Trie.Update", "err", err)
}
}
// TryUpdate associates key with value in the trie. Subsequent calls to
// Get will return value. If value has length zero, any existing value
// is deleted from the trie and calls to Get will return nil.
//
// The value bytes must not be modified by the caller while they are
// stored in the trie.
//
// If a node was not found in the database, a MissingNodeError is returned.
func (t *Trie) TryUpdate(key, value []byte) error {
return t.tryUpdate(key, value)
}
// tryUpdate expects an RLP-encoded value and performs the core function
// for TryUpdate and TryUpdateAccount.
func (t *Trie) tryUpdate(key, value []byte) error {
t.unhashed++
k := keybytesToHex(key)
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if len(value) != 0 {
_, n, err := t.insert(t.root, nil, k, valueNode(value))
if err != nil {
return err
}
t.root = n
} else {
_, n, err := t.delete(t.root, nil, k)
if err != nil {
return err
}
t.root = n
}
return nil
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}
func (t *Trie) insert(n node, prefix, key []byte, value node) (bool, node, error) {
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if len(key) == 0 {
if v, ok := n.(valueNode); ok {
return !bytes.Equal(v, value.(valueNode)), value, nil
}
return true, value, nil
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}
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switch n := n.(type) {
case *shortNode:
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matchlen := prefixLen(key, n.Key)
// If the whole key matches, keep this short node as is
// and only update the value.
if matchlen == len(n.Key) {
dirty, nn, err := t.insert(n.Val, append(prefix, key[:matchlen]...), key[matchlen:], value)
if !dirty || err != nil {
return false, n, err
}
return true, &shortNode{n.Key, nn, t.newFlag()}, nil
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}
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// Otherwise branch out at the index where they differ.
branch := &fullNode{flags: t.newFlag()}
var err error
_, branch.Children[n.Key[matchlen]], err = t.insert(nil, append(prefix, n.Key[:matchlen+1]...), n.Key[matchlen+1:], n.Val)
if err != nil {
return false, nil, err
}
_, branch.Children[key[matchlen]], err = t.insert(nil, append(prefix, key[:matchlen+1]...), key[matchlen+1:], value)
if err != nil {
return false, nil, err
}
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// Replace this shortNode with the branch if it occurs at index 0.
if matchlen == 0 {
return true, branch, nil
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}
// New branch node is created as a child of the original short node.
// Track the newly inserted node in the tracer. The node identifier
// passed is the path from the root node.
t.tracer.onInsert(append(prefix, key[:matchlen]...))
// Replace it with a short node leading up to the branch.
return true, &shortNode{key[:matchlen], branch, t.newFlag()}, nil
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case *fullNode:
dirty, nn, err := t.insert(n.Children[key[0]], append(prefix, key[0]), key[1:], value)
if !dirty || err != nil {
return false, n, err
}
n = n.copy()
n.flags = t.newFlag()
n.Children[key[0]] = nn
return true, n, nil
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case nil:
// New short node is created and track it in the tracer. The node identifier
// passed is the path from the root node. Note the valueNode won't be tracked
// since it's always embedded in its parent.
t.tracer.onInsert(prefix)
return true, &shortNode{key, value, t.newFlag()}, nil
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case hashNode:
// We've hit a part of the trie that isn't loaded yet. Load
// the node and insert into it. This leaves all child nodes on
// the path to the value in the trie.
rn, err := t.resolveAndTrack(n, prefix)
if err != nil {
return false, nil, err
}
dirty, nn, err := t.insert(rn, prefix, key, value)
if !dirty || err != nil {
return false, rn, err
}
return true, nn, nil
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default:
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panic(fmt.Sprintf("%T: invalid node: %v", n, n))
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}
}
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// Delete removes any existing value for key from the trie.
func (t *Trie) Delete(key []byte) {
if err := t.TryDelete(key); err != nil {
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log.Error("Unhandled trie error in Trie.Delete", "err", err)
}
}
// TryDelete removes any existing value for key from the trie.
// If a node was not found in the database, a MissingNodeError is returned.
func (t *Trie) TryDelete(key []byte) error {
t.unhashed++
k := keybytesToHex(key)
_, n, err := t.delete(t.root, nil, k)
if err != nil {
return err
}
t.root = n
return nil
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}
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// delete returns the new root of the trie with key deleted.
// It reduces the trie to minimal form by simplifying
// nodes on the way up after deleting recursively.
func (t *Trie) delete(n node, prefix, key []byte) (bool, node, error) {
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switch n := n.(type) {
case *shortNode:
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matchlen := prefixLen(key, n.Key)
if matchlen < len(n.Key) {
return false, n, nil // don't replace n on mismatch
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}
if matchlen == len(key) {
// The matched short node is deleted entirely and track
// it in the deletion set. The same the valueNode doesn't
// need to be tracked at all since it's always embedded.
t.tracer.onDelete(prefix)
return true, nil, nil // remove n entirely for whole matches
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}
// The key is longer than n.Key. Remove the remaining suffix
// from the subtrie. Child can never be nil here since the
// subtrie must contain at least two other values with keys
// longer than n.Key.
dirty, child, err := t.delete(n.Val, append(prefix, key[:len(n.Key)]...), key[len(n.Key):])
if !dirty || err != nil {
return false, n, err
}
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switch child := child.(type) {
case *shortNode:
// The child shortNode is merged into its parent, track
// is deleted as well.
t.tracer.onDelete(append(prefix, n.Key...))
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// Deleting from the subtrie reduced it to another
// short node. Merge the nodes to avoid creating a
// shortNode{..., shortNode{...}}. Use concat (which
// always creates a new slice) instead of append to
// avoid modifying n.Key since it might be shared with
// other nodes.
return true, &shortNode{concat(n.Key, child.Key...), child.Val, t.newFlag()}, nil
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default:
return true, &shortNode{n.Key, child, t.newFlag()}, nil
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}
case *fullNode:
dirty, nn, err := t.delete(n.Children[key[0]], append(prefix, key[0]), key[1:])
if !dirty || err != nil {
return false, n, err
}
n = n.copy()
n.flags = t.newFlag()
n.Children[key[0]] = nn
// Because n is a full node, it must've contained at least two children
// before the delete operation. If the new child value is non-nil, n still
// has at least two children after the deletion, and cannot be reduced to
// a short node.
if nn != nil {
return true, n, nil
}
// Reduction:
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// Check how many non-nil entries are left after deleting and
// reduce the full node to a short node if only one entry is
// left. Since n must've contained at least two children
// before deletion (otherwise it would not be a full node) n
// can never be reduced to nil.
//
// When the loop is done, pos contains the index of the single
// value that is left in n or -2 if n contains at least two
// values.
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pos := -1
for i, cld := range &n.Children {
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if cld != nil {
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if pos == -1 {
pos = i
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} else {
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pos = -2
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break
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}
}
}
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if pos >= 0 {
if pos != 16 {
// If the remaining entry is a short node, it replaces
// n and its key gets the missing nibble tacked to the
// front. This avoids creating an invalid
// shortNode{..., shortNode{...}}. Since the entry
// might not be loaded yet, resolve it just for this
// check.
cnode, err := t.resolve(n.Children[pos], append(prefix, byte(pos)))
if err != nil {
return false, nil, err
}
if cnode, ok := cnode.(*shortNode); ok {
// Replace the entire full node with the short node.
// Mark the original short node as deleted since the
// value is embedded into the parent now.
t.tracer.onDelete(append(prefix, byte(pos)))
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k := append([]byte{byte(pos)}, cnode.Key...)
return true, &shortNode{k, cnode.Val, t.newFlag()}, nil
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}
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}
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// Otherwise, n is replaced by a one-nibble short node
// containing the child.
return true, &shortNode{[]byte{byte(pos)}, n.Children[pos], t.newFlag()}, nil
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}
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// n still contains at least two values and cannot be reduced.
return true, n, nil
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case valueNode:
return true, nil, nil
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case nil:
return false, nil, nil
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case hashNode:
// We've hit a part of the trie that isn't loaded yet. Load
// the node and delete from it. This leaves all child nodes on
// the path to the value in the trie.
rn, err := t.resolveAndTrack(n, prefix)
if err != nil {
return false, nil, err
}
dirty, nn, err := t.delete(rn, prefix, key)
if !dirty || err != nil {
return false, rn, err
}
return true, nn, nil
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default:
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panic(fmt.Sprintf("%T: invalid node: %v (%v)", n, n, key))
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}
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}
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func concat(s1 []byte, s2 ...byte) []byte {
r := make([]byte, len(s1)+len(s2))
copy(r, s1)
copy(r[len(s1):], s2)
return r
}
func (t *Trie) resolve(n node, prefix []byte) (node, error) {
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if n, ok := n.(hashNode); ok {
return t.resolveAndTrack(n, prefix)
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}
return n, nil
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}
// resolveAndTrack loads node from the underlying store with the given node hash
// and path prefix and also tracks the loaded node blob in tracer treated as the
// node's original value. The rlp-encoded blob is preferred to be loaded from
// database because it's easy to decode node while complex to encode node to blob.
func (t *Trie) resolveAndTrack(n hashNode, prefix []byte) (node, error) {
blob, err := t.reader.nodeBlob(prefix, common.BytesToHash(n))
if err != nil {
return nil, err
}
t.tracer.onRead(prefix, blob)
return mustDecodeNode(n, blob), nil
}
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// Hash returns the root hash of the trie. It does not write to the
// database and can be used even if the trie doesn't have one.
func (t *Trie) Hash() common.Hash {
hash, cached, _ := t.hashRoot()
t.root = cached
return common.BytesToHash(hash.(hashNode))
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}
// Commit collects all dirty nodes in the trie and replaces them with the
// corresponding node hash. All collected nodes (including dirty leaves if
// collectLeaf is true) will be encapsulated into a nodeset for return.
// The returned nodeset can be nil if the trie is clean (nothing to commit).
// Once the trie is committed, it's not usable anymore. A new trie must
// be created with new root and updated trie database for following usage
func (t *Trie) Commit(collectLeaf bool) (common.Hash, *NodeSet) {
defer t.tracer.reset()
// Trie is empty and can be classified into two types of situations:
// - The trie was empty and no update happens
// - The trie was non-empty and all nodes are dropped
if t.root == nil {
// Wrap tracked deletions as the return
set := NewNodeSet(t.owner)
t.tracer.markDeletions(set)
return types.EmptyRootHash, set
}
// Derive the hash for all dirty nodes first. We hold the assumption
// in the following procedure that all nodes are hashed.
rootHash := t.Hash()
// Do a quick check if we really need to commit. This can happen e.g.
// if we load a trie for reading storage values, but don't write to it.
if hashedNode, dirty := t.root.cache(); !dirty {
// Replace the root node with the origin hash in order to
// ensure all resolved nodes are dropped after the commit.
t.root = hashedNode
return rootHash, nil
}
h := newCommitter(t.owner, t.tracer, collectLeaf)
newRoot, nodes := h.Commit(t.root)
t.root = newRoot
return rootHash, nodes
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}
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// hashRoot calculates the root hash of the given trie
func (t *Trie) hashRoot() (node, node, error) {
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if t.root == nil {
return hashNode(types.EmptyRootHash.Bytes()), nil, nil
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}
// If the number of changes is below 100, we let one thread handle it
h := newHasher(t.unhashed >= 100)
defer returnHasherToPool(h)
hashed, cached := h.hash(t.root, true)
t.unhashed = 0
return hashed, cached, nil
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}
// Reset drops the referenced root node and cleans all internal state.
func (t *Trie) Reset() {
t.root = nil
t.owner = common.Hash{}
t.unhashed = 0
t.tracer.reset()
}