neoneo-go/pkg/core/mpt/trie.go
Evgeniy Stratonikov 25428d53f1 mpt: strip branch node in a simple implementation
Signed-off-by: Evgeniy Stratonikov <evgeniy@nspcc.ru>
2021-07-07 15:47:07 +03:00

507 lines
12 KiB
Go

package mpt
import (
"bytes"
"encoding/binary"
"errors"
"fmt"
"github.com/nspcc-dev/neo-go/pkg/core/storage"
"github.com/nspcc-dev/neo-go/pkg/io"
"github.com/nspcc-dev/neo-go/pkg/util"
)
// Trie is an MPT trie storing all key-value pairs.
type Trie struct {
Store *storage.MemCachedStore
root Node
refcountEnabled bool
refcount map[util.Uint256]*cachedNode
}
type cachedNode struct {
bytes []byte
initial int32
refcount int32
}
// ErrNotFound is returned when requested trie item is missing.
var ErrNotFound = errors.New("item not found")
// NewTrie returns new MPT trie. It accepts a MemCachedStore to decouple storage errors from logic errors
// so that all storage errors are processed during `store.Persist()` at the caller.
// This also has the benefit, that every `Put` can be considered an atomic operation.
func NewTrie(root Node, enableRefCount bool, store *storage.MemCachedStore) *Trie {
if root == nil {
root = new(HashNode)
}
return &Trie{
Store: store,
root: root,
refcountEnabled: enableRefCount,
refcount: make(map[util.Uint256]*cachedNode),
}
}
// Get returns value for the provided key in t.
func (t *Trie) Get(key []byte) ([]byte, error) {
path := toNibbles(key)
r, bs, err := t.getWithPath(t.root, path)
if err != nil {
return nil, err
}
t.root = r
return bs, nil
}
// getWithPath returns value the provided path in a subtrie rooting in curr.
// It also returns a current node with all hash nodes along the path
// replaced to their "unhashed" counterparts.
func (t *Trie) getWithPath(curr Node, path []byte) (Node, []byte, error) {
switch n := curr.(type) {
case *LeafNode:
if len(path) == 0 {
return curr, copySlice(n.value), nil
}
case *BranchNode:
i, path := splitPath(path)
r, bs, err := t.getWithPath(n.Children[i], path)
if err != nil {
return nil, nil, err
}
n.Children[i] = r
return n, bs, nil
case *HashNode:
if !n.IsEmpty() {
if r, err := t.getFromStore(n.hash); err == nil {
return t.getWithPath(r, path)
}
}
case *ExtensionNode:
if bytes.HasPrefix(path, n.key) {
r, bs, err := t.getWithPath(n.next, path[len(n.key):])
if err != nil {
return nil, nil, err
}
n.next = r
return curr, bs, err
}
default:
panic("invalid MPT node type")
}
return curr, nil, ErrNotFound
}
// Put puts key-value pair in t.
func (t *Trie) Put(key, value []byte) error {
if len(key) == 0 {
return errors.New("key is empty")
} else if len(key) > MaxKeyLength {
return errors.New("key is too big")
} else if len(value) > MaxValueLength {
return errors.New("value is too big")
}
if len(value) == 0 {
return t.Delete(key)
}
path := toNibbles(key)
n := NewLeafNode(value)
r, err := t.putIntoNode(t.root, path, n)
if err != nil {
return err
}
t.root = r
return nil
}
// putIntoLeaf puts val to trie if current node is a Leaf.
// It returns Node if curr needs to be replaced and error if any.
func (t *Trie) putIntoLeaf(curr *LeafNode, path []byte, val Node) (Node, error) {
v := val.(*LeafNode)
if len(path) == 0 {
t.removeRef(curr.Hash(), curr.bytes)
t.addRef(val.Hash(), val.Bytes())
return v, nil
}
b := NewBranchNode()
b.Children[path[0]] = t.newSubTrie(path[1:], v, true)
b.Children[lastChild] = curr
t.addRef(b.Hash(), b.bytes)
return b, nil
}
// putIntoBranch puts val to trie if current node is a Branch.
// It returns Node if curr needs to be replaced and error if any.
func (t *Trie) putIntoBranch(curr *BranchNode, path []byte, val Node) (Node, error) {
i, path := splitPath(path)
t.removeRef(curr.Hash(), curr.bytes)
r, err := t.putIntoNode(curr.Children[i], path, val)
if err != nil {
return nil, err
}
curr.Children[i] = r
curr.invalidateCache()
t.addRef(curr.Hash(), curr.bytes)
return curr, nil
}
// putIntoExtension puts val to trie if current node is an Extension.
// It returns Node if curr needs to be replaced and error if any.
func (t *Trie) putIntoExtension(curr *ExtensionNode, path []byte, val Node) (Node, error) {
t.removeRef(curr.Hash(), curr.bytes)
if bytes.HasPrefix(path, curr.key) {
r, err := t.putIntoNode(curr.next, path[len(curr.key):], val)
if err != nil {
return nil, err
}
curr.next = r
curr.invalidateCache()
t.addRef(curr.Hash(), curr.bytes)
return curr, nil
}
pref := lcp(curr.key, path)
lp := len(pref)
keyTail := curr.key[lp:]
pathTail := path[lp:]
s1 := t.newSubTrie(keyTail[1:], curr.next, false)
b := NewBranchNode()
b.Children[keyTail[0]] = s1
i, pathTail := splitPath(pathTail)
s2 := t.newSubTrie(pathTail, val, true)
b.Children[i] = s2
t.addRef(b.Hash(), b.bytes)
if lp > 0 {
e := NewExtensionNode(copySlice(pref), b)
t.addRef(e.Hash(), e.bytes)
return e, nil
}
return b, nil
}
// putIntoHash puts val to trie if current node is a HashNode.
// It returns Node if curr needs to be replaced and error if any.
func (t *Trie) putIntoHash(curr *HashNode, path []byte, val Node) (Node, error) {
if curr.IsEmpty() {
hn := t.newSubTrie(path, val, true)
return hn, nil
}
result, err := t.getFromStore(curr.hash)
if err != nil {
return nil, err
}
return t.putIntoNode(result, path, val)
}
// newSubTrie create new trie containing node at provided path.
func (t *Trie) newSubTrie(path []byte, val Node, newVal bool) Node {
if newVal {
t.addRef(val.Hash(), val.Bytes())
}
if len(path) == 0 {
return val
}
e := NewExtensionNode(path, val)
t.addRef(e.Hash(), e.bytes)
return e
}
// putIntoNode puts val with provided path inside curr and returns updated node.
// Reference counters are updated for both curr and returned value.
func (t *Trie) putIntoNode(curr Node, path []byte, val Node) (Node, error) {
switch n := curr.(type) {
case *LeafNode:
return t.putIntoLeaf(n, path, val)
case *BranchNode:
return t.putIntoBranch(n, path, val)
case *ExtensionNode:
return t.putIntoExtension(n, path, val)
case *HashNode:
return t.putIntoHash(n, path, val)
default:
panic("invalid MPT node type")
}
}
// Delete removes key from trie.
// It returns no error on missing key.
func (t *Trie) Delete(key []byte) error {
path := toNibbles(key)
r, err := t.deleteFromNode(t.root, path)
if err != nil {
return err
}
t.root = r
return nil
}
func (t *Trie) deleteFromBranch(b *BranchNode, path []byte) (Node, error) {
i, path := splitPath(path)
h := b.Hash()
bs := b.bytes
r, err := t.deleteFromNode(b.Children[i], path)
if err != nil {
return nil, err
}
t.removeRef(h, bs)
b.Children[i] = r
b.invalidateCache()
var count, index int
for i := range b.Children {
h, ok := b.Children[i].(*HashNode)
if !ok || !h.IsEmpty() {
index = i
count++
}
}
// count is >= 1 because branch node had at least 2 children before deletion.
if count > 1 {
t.addRef(b.Hash(), b.bytes)
return b, nil
}
c := b.Children[index]
if index == lastChild {
return c, nil
}
if h, ok := c.(*HashNode); ok {
c, err = t.getFromStore(h.Hash())
if err != nil {
return nil, err
}
}
if e, ok := c.(*ExtensionNode); ok {
t.removeRef(e.Hash(), e.bytes)
e.key = append([]byte{byte(index)}, e.key...)
e.invalidateCache()
t.addRef(e.Hash(), e.bytes)
return e, nil
}
e := NewExtensionNode([]byte{byte(index)}, c)
t.addRef(e.Hash(), e.bytes)
return e, nil
}
func (t *Trie) deleteFromExtension(n *ExtensionNode, path []byte) (Node, error) {
if !bytes.HasPrefix(path, n.key) {
return n, nil
}
h := n.Hash()
bs := n.bytes
r, err := t.deleteFromNode(n.next, path[len(n.key):])
if err != nil {
return nil, err
}
t.removeRef(h, bs)
switch nxt := r.(type) {
case *ExtensionNode:
t.removeRef(nxt.Hash(), nxt.bytes)
n.key = append(n.key, nxt.key...)
n.next = nxt.next
case *HashNode:
if nxt.IsEmpty() {
return nxt, nil
}
n.next = nxt
default:
n.next = r
}
n.invalidateCache()
t.addRef(n.Hash(), n.bytes)
return n, nil
}
// deleteFromNode removes value with provided path from curr and returns an updated node.
// Reference counters are updated for both curr and returned value.
func (t *Trie) deleteFromNode(curr Node, path []byte) (Node, error) {
switch n := curr.(type) {
case *LeafNode:
if len(path) == 0 {
t.removeRef(curr.Hash(), curr.Bytes())
return new(HashNode), nil
}
return curr, nil
case *BranchNode:
return t.deleteFromBranch(n, path)
case *ExtensionNode:
return t.deleteFromExtension(n, path)
case *HashNode:
if n.IsEmpty() {
return n, nil
}
newNode, err := t.getFromStore(n.Hash())
if err != nil {
return nil, err
}
return t.deleteFromNode(newNode, path)
default:
panic("invalid MPT node type")
}
}
// StateRoot returns root hash of t.
func (t *Trie) StateRoot() util.Uint256 {
if hn, ok := t.root.(*HashNode); ok && hn.IsEmpty() {
return util.Uint256{}
}
return t.root.Hash()
}
func makeStorageKey(mptKey []byte) []byte {
return append([]byte{byte(storage.DataMPT)}, mptKey...)
}
// Flush puts every node in the trie except Hash ones to the storage.
// Because we care only about block-level changes, there is no need to put every
// new node to storage. Normally, flush should be called with every StateRoot persist, i.e.
// after every block.
func (t *Trie) Flush() {
for h, node := range t.refcount {
if node.refcount != 0 {
if node.bytes == nil {
panic("item not in trie")
}
if t.refcountEnabled {
node.initial = t.updateRefCount(h)
if node.initial == 0 {
delete(t.refcount, h)
}
} else if node.refcount > 0 {
_ = t.Store.Put(makeStorageKey(h.BytesBE()), node.bytes)
}
node.refcount = 0
} else {
delete(t.refcount, h)
}
}
}
// updateRefCount should be called only when refcounting is enabled.
func (t *Trie) updateRefCount(h util.Uint256) int32 {
if !t.refcountEnabled {
panic("`updateRefCount` is called, but GC is disabled")
}
var data []byte
key := makeStorageKey(h.BytesBE())
node := t.refcount[h]
cnt := node.initial
if cnt == 0 {
// A newly created item which may be in store.
var err error
data, err = t.Store.Get(key)
if err == nil {
cnt = int32(binary.LittleEndian.Uint32(data[len(data)-4:]))
}
}
if len(data) == 0 {
data = append(node.bytes, 0, 0, 0, 0)
}
cnt += node.refcount
switch {
case cnt < 0:
// BUG: negative reference count
panic(fmt.Sprintf("negative reference count: %s new %d, upd %d", h.StringBE(), cnt, t.refcount[h]))
case cnt == 0:
_ = t.Store.Delete(key)
default:
binary.LittleEndian.PutUint32(data[len(data)-4:], uint32(cnt))
_ = t.Store.Put(key, data)
}
return cnt
}
func (t *Trie) addRef(h util.Uint256, bs []byte) {
node := t.refcount[h]
if node == nil {
t.refcount[h] = &cachedNode{
refcount: 1,
bytes: bs,
}
return
}
node.refcount++
if node.bytes == nil {
node.bytes = bs
}
}
func (t *Trie) removeRef(h util.Uint256, bs []byte) {
node := t.refcount[h]
if node == nil {
t.refcount[h] = &cachedNode{
refcount: -1,
bytes: bs,
}
return
}
node.refcount--
if node.bytes == nil {
node.bytes = bs
}
}
func (t *Trie) getFromStore(h util.Uint256) (Node, error) {
data, err := t.Store.Get(makeStorageKey(h.BytesBE()))
if err != nil {
return nil, err
}
var n NodeObject
r := io.NewBinReaderFromBuf(data)
n.DecodeBinary(r)
if r.Err != nil {
return nil, r.Err
}
if t.refcountEnabled {
data = data[:len(data)-4]
node := t.refcount[h]
if node != nil {
node.bytes = data
node.initial = int32(r.ReadU32LE())
}
}
n.Node.(flushedNode).setCache(data, h)
return n.Node, nil
}
// Collapse compresses all nodes at depth n to the hash nodes.
// Note: this function does not perform any kind of storage flushing so
// `Flush()` should be called explicitly before invoking function.
func (t *Trie) Collapse(depth int) {
if depth < 0 {
panic("negative depth")
}
t.root = collapse(depth, t.root)
t.refcount = make(map[util.Uint256]*cachedNode)
}
func collapse(depth int, node Node) Node {
if _, ok := node.(*HashNode); ok {
return node
} else if depth == 0 {
return NewHashNode(node.Hash())
}
switch n := node.(type) {
case *BranchNode:
for i := range n.Children {
n.Children[i] = collapse(depth-1, n.Children[i])
}
case *ExtensionNode:
n.next = collapse(depth-1, n.next)
case *LeafNode:
case *HashNode:
default:
panic("invalid MPT node type")
}
return node
}