434 lines
13 KiB
Go
434 lines
13 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 implements Merkle Patricia Tries.
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package trie
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import (
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"bytes"
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"fmt"
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"github.com/ethereum/go-ethereum/common"
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"github.com/ethereum/go-ethereum/crypto"
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"github.com/ethereum/go-ethereum/log"
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)
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var (
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// emptyRoot is the known root hash of an empty trie.
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emptyRoot = common.HexToHash("56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421")
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// emptyState is the known hash of an empty state trie entry.
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emptyState = crypto.Keccak256Hash(nil)
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)
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// LeafCallback is a callback type invoked when a trie operation reaches a leaf
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// node. It's used by state sync and commit to allow handling external references
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// between account and storage tries.
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type LeafCallback func(leaf []byte, parent common.Hash) error
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// Trie is a Merkle Patricia Trie.
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// The zero value is an empty trie with no database.
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// Use New to create a trie that sits on top of a database.
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//
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// Trie is not safe for concurrent use.
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type Trie struct {
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db *Database
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root node
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}
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// newFlag returns the cache flag value for a newly created node.
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func (t *Trie) newFlag() nodeFlag {
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return nodeFlag{dirty: true}
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}
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// New creates a trie with an existing root node from db.
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//
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// If root is the zero hash or the sha3 hash of an empty string, the
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// trie is initially empty and does not require a database. Otherwise,
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// New will panic if db is nil and returns a MissingNodeError if root does
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// not exist in the database. Accessing the trie loads nodes from db on demand.
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func New(root common.Hash, db *Database) (*Trie, error) {
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if db == nil {
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panic("trie.New called without a database")
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}
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trie := &Trie{
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db: db,
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}
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if root != (common.Hash{}) && root != emptyRoot {
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rootnode, err := trie.resolveHash(root[:], nil)
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if err != nil {
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return nil, err
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}
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trie.root = rootnode
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}
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return trie, nil
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}
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// NodeIterator returns an iterator that returns nodes of the trie. Iteration starts at
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// the key after the given start key.
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func (t *Trie) NodeIterator(start []byte) NodeIterator {
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return newNodeIterator(t, start)
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}
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// Get returns the value for key stored in the trie.
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// The value bytes must not be modified by the caller.
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func (t *Trie) Get(key []byte) []byte {
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res, err := t.TryGet(key)
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if err != nil {
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log.Error(fmt.Sprintf("Unhandled trie error: %v", err))
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}
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return res
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}
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// TryGet returns the value for key stored in the trie.
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// The value bytes must not be modified by the caller.
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// If a node was not found in the database, a MissingNodeError is returned.
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func (t *Trie) TryGet(key []byte) ([]byte, error) {
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key = keybytesToHex(key)
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value, newroot, didResolve, err := t.tryGet(t.root, key, 0)
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if err == nil && didResolve {
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t.root = newroot
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}
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return value, err
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}
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func (t *Trie) tryGet(origNode node, key []byte, pos int) (value []byte, newnode node, didResolve bool, err error) {
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switch n := (origNode).(type) {
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case nil:
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return nil, nil, false, nil
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case valueNode:
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return n, n, false, nil
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case *shortNode:
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if len(key)-pos < len(n.Key) || !bytes.Equal(n.Key, key[pos:pos+len(n.Key)]) {
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// key not found in trie
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return nil, n, false, nil
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}
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value, newnode, didResolve, err = t.tryGet(n.Val, key, pos+len(n.Key))
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if err == nil && didResolve {
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n = n.copy()
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n.Val = newnode
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}
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return value, n, didResolve, err
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case *fullNode:
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value, newnode, didResolve, err = t.tryGet(n.Children[key[pos]], key, pos+1)
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if err == nil && didResolve {
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n = n.copy()
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n.Children[key[pos]] = newnode
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}
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return value, n, didResolve, err
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case hashNode:
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child, err := t.resolveHash(n, key[:pos])
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if err != nil {
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return nil, n, true, err
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}
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value, newnode, _, err := t.tryGet(child, key, pos)
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return value, newnode, true, err
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default:
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panic(fmt.Sprintf("%T: invalid node: %v", origNode, origNode))
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}
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}
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// Update associates key with value in the trie. Subsequent calls to
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// Get will return value. If value has length zero, any existing value
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// is deleted from the trie and calls to Get will return nil.
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//
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// The value bytes must not be modified by the caller while they are
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// stored in the trie.
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func (t *Trie) Update(key, value []byte) {
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if err := t.TryUpdate(key, value); err != nil {
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log.Error(fmt.Sprintf("Unhandled trie error: %v", err))
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}
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}
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// TryUpdate associates key with value in the trie. Subsequent calls to
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// Get will return value. If value has length zero, any existing value
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// is deleted from the trie and calls to Get will return nil.
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//
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// The value bytes must not be modified by the caller while they are
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// stored in the trie.
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//
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// If a node was not found in the database, a MissingNodeError is returned.
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func (t *Trie) TryUpdate(key, value []byte) error {
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k := keybytesToHex(key)
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if len(value) != 0 {
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_, n, err := t.insert(t.root, nil, k, valueNode(value))
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if err != nil {
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return err
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}
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t.root = n
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} else {
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_, n, err := t.delete(t.root, nil, k)
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if err != nil {
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return err
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}
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t.root = n
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}
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return nil
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}
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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 {
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if v, ok := n.(valueNode); ok {
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return !bytes.Equal(v, value.(valueNode)), value, nil
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}
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return true, value, nil
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}
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switch n := n.(type) {
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case *shortNode:
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matchlen := prefixLen(key, n.Key)
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// If the whole key matches, keep this short node as is
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// and only update the value.
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if matchlen == len(n.Key) {
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dirty, nn, err := t.insert(n.Val, append(prefix, key[:matchlen]...), key[matchlen:], value)
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if !dirty || err != nil {
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return false, n, err
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}
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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.
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branch := &fullNode{flags: t.newFlag()}
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var err error
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_, branch.Children[n.Key[matchlen]], err = t.insert(nil, append(prefix, n.Key[:matchlen+1]...), n.Key[matchlen+1:], n.Val)
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if err != nil {
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return false, nil, err
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}
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_, branch.Children[key[matchlen]], err = t.insert(nil, append(prefix, key[:matchlen+1]...), key[matchlen+1:], value)
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if err != nil {
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return false, nil, err
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}
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// Replace this shortNode with the branch if it occurs at index 0.
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if matchlen == 0 {
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return true, branch, nil
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}
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// Otherwise, replace it with a short node leading up to the branch.
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return true, &shortNode{key[:matchlen], branch, t.newFlag()}, nil
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case *fullNode:
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dirty, nn, err := t.insert(n.Children[key[0]], append(prefix, key[0]), key[1:], value)
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if !dirty || err != nil {
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return false, n, err
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}
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n = n.copy()
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n.flags = t.newFlag()
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n.Children[key[0]] = nn
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return true, n, nil
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case nil:
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return true, &shortNode{key, value, t.newFlag()}, nil
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case hashNode:
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// We've hit a part of the trie that isn't loaded yet. Load
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// the node and insert into it. This leaves all child nodes on
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// the path to the value in the trie.
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rn, err := t.resolveHash(n, prefix)
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if err != nil {
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return false, nil, err
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}
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dirty, nn, err := t.insert(rn, prefix, key, value)
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if !dirty || err != nil {
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return false, rn, err
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}
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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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}
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// Delete removes any existing value for key from the trie.
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func (t *Trie) Delete(key []byte) {
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if err := t.TryDelete(key); err != nil {
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log.Error(fmt.Sprintf("Unhandled trie error: %v", err))
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}
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}
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// TryDelete removes any existing value for key from the trie.
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// If a node was not found in the database, a MissingNodeError is returned.
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func (t *Trie) TryDelete(key []byte) error {
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k := keybytesToHex(key)
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_, n, err := t.delete(t.root, nil, k)
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if err != nil {
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return err
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}
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t.root = n
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return nil
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}
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// delete returns the new root of the trie with key deleted.
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// It reduces the trie to minimal form by simplifying
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// nodes on the way up after deleting recursively.
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func (t *Trie) delete(n node, prefix, key []byte) (bool, node, error) {
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switch n := n.(type) {
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case *shortNode:
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matchlen := prefixLen(key, n.Key)
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if matchlen < len(n.Key) {
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return false, n, nil // don't replace n on mismatch
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}
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if matchlen == len(key) {
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return true, nil, nil // remove n entirely for whole matches
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}
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// The key is longer than n.Key. Remove the remaining suffix
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// from the subtrie. Child can never be nil here since the
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// subtrie must contain at least two other values with keys
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// longer than n.Key.
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dirty, child, err := t.delete(n.Val, append(prefix, key[:len(n.Key)]...), key[len(n.Key):])
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if !dirty || err != nil {
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return false, n, err
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}
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switch child := child.(type) {
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case *shortNode:
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// Deleting from the subtrie reduced it to another
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// short node. Merge the nodes to avoid creating a
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// shortNode{..., shortNode{...}}. Use concat (which
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// always creates a new slice) instead of append to
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// avoid modifying n.Key since it might be shared with
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// other nodes.
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return true, &shortNode{concat(n.Key, child.Key...), child.Val, t.newFlag()}, nil
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default:
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return true, &shortNode{n.Key, child, t.newFlag()}, nil
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}
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case *fullNode:
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dirty, nn, err := t.delete(n.Children[key[0]], append(prefix, key[0]), key[1:])
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if !dirty || err != nil {
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return false, n, err
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}
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n = n.copy()
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n.flags = t.newFlag()
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n.Children[key[0]] = nn
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// Check how many non-nil entries are left after deleting and
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// reduce the full node to a short node if only one entry is
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// left. Since n must've contained at least two children
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// before deletion (otherwise it would not be a full node) n
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// can never be reduced to nil.
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//
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// When the loop is done, pos contains the index of the single
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// value that is left in n or -2 if n contains at least two
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// values.
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pos := -1
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for i, cld := range &n.Children {
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if cld != nil {
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if pos == -1 {
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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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}
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}
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if pos >= 0 {
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if pos != 16 {
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// If the remaining entry is a short node, it replaces
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// n and its key gets the missing nibble tacked to the
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// front. This avoids creating an invalid
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// shortNode{..., shortNode{...}}. Since the entry
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// might not be loaded yet, resolve it just for this
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// check.
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cnode, err := t.resolve(n.Children[pos], prefix)
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if err != nil {
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return false, nil, err
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}
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if cnode, ok := cnode.(*shortNode); ok {
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k := append([]byte{byte(pos)}, cnode.Key...)
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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
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// containing the child.
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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.
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return true, n, nil
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case valueNode:
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return true, nil, nil
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case nil:
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return false, nil, nil
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case hashNode:
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// We've hit a part of the trie that isn't loaded yet. Load
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// the node and delete from it. This leaves all child nodes on
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// the path to the value in the trie.
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rn, err := t.resolveHash(n, prefix)
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if err != nil {
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return false, nil, err
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}
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dirty, nn, err := t.delete(rn, prefix, key)
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if !dirty || err != nil {
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return false, rn, err
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}
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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 {
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r := make([]byte, len(s1)+len(s2))
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copy(r, s1)
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copy(r[len(s1):], s2)
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return r
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}
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func (t *Trie) resolve(n node, prefix []byte) (node, error) {
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if n, ok := n.(hashNode); ok {
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return t.resolveHash(n, prefix)
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}
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return n, nil
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}
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func (t *Trie) resolveHash(n hashNode, prefix []byte) (node, error) {
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hash := common.BytesToHash(n)
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if node := t.db.node(hash); node != nil {
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return node, nil
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}
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return nil, &MissingNodeError{NodeHash: hash, Path: prefix}
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}
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// Hash returns the root hash of the trie. It does not write to the
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// database and can be used even if the trie doesn't have one.
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func (t *Trie) Hash() common.Hash {
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hash, cached, _ := t.hashRoot(nil, nil)
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t.root = cached
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return common.BytesToHash(hash.(hashNode))
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}
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// Commit writes all nodes to the trie's memory database, tracking the internal
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// and external (for account tries) references.
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func (t *Trie) Commit(onleaf LeafCallback) (root common.Hash, err error) {
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if t.db == nil {
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panic("commit called on trie with nil database")
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}
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hash, cached, err := t.hashRoot(t.db, onleaf)
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if err != nil {
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return common.Hash{}, err
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}
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t.root = cached
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return common.BytesToHash(hash.(hashNode)), nil
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}
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func (t *Trie) hashRoot(db *Database, onleaf LeafCallback) (node, node, error) {
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if t.root == nil {
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return hashNode(emptyRoot.Bytes()), nil, nil
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}
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h := newHasher(onleaf)
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defer returnHasherToPool(h)
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return h.hash(t.root, db, true)
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}
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