简介
Trie是Merkle Patricia Trie(结合了Merkle Tree默克尔树和Patricia Trie帕特里夏树/前缀树)，对应三独立的树
- 状态树，账户相关，对应块头中的root
- 交易树，对应块头中的TxHash
- 收据树，对应块头中的ReceiptHash
结构
trie.go定义了Trie结构和主要操作，node.go定义了fullNode,shortNode等结点类型，stacktrie.go一种更高效的实现，StateDB.go是对状态 Trie 的高级封装
<<interface>> node Trie fullNode shortNode hashNode valueNode
Trie定义为
go
type Trie struct {
root node
owner common.Hash
// Flag whether the commit operation is already performed. If so the
// trie is not usable(latest states is invisible).
committed bool
// 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
// uncommitted is the number of updates since last commit.
uncommitted int
// reader is the handler trie can retrieve nodes from.
reader *Reader
// Various tracers for capturing the modifications to trie
opTracer *opTracer
prevalueTracer *PrevalueTracer
}node接口定义为
go
type node interface {
cache() (hashNode, bool)
encode(w rlp.EncoderBuffer)
fstring(string) string
}fullNode, shortNode, hashNode, valueNode定义为
go
type (
fullNode struct {
Children [17]node // Actual trie node data to encode/decode (needs custom encoder)
flags nodeFlag
}
shortNode struct {
Key []byte
Val node
flags nodeFlag
}
hashNode []byte
valueNode []byte
)fullNode：0到15对应分支，对应十六进制0到F，第16个对应完整的键值，在查找时，会将key转为十六进制（keybytesToHex）
shortNode:作为路径压缩，即当有公共前缀时
关键操作
获取
- 如果是叶子节点，即valueNode，则直接返回
- 如果是压缩的非叶子节点，并且与压缩节点前缀一致，则从压缩节点对应的Val节点开始查找
- 如果是非压缩非叶子节点，则从对应pos处的子节点开始查找
go
func (t *Trie) get(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 !bytes.HasPrefix(key[pos:], n.Key) {
// key not found in trie
return nil, n, false, nil
}
value, newnode, didResolve, err = t.get(n.Val, key, pos+len(n.Key))
if err == nil && didResolve {
n.Val = newnode
}
return value, n, didResolve, err
case *fullNode:
value, newnode, didResolve, err = t.get(n.Children[key[pos]], key, pos+1)
if err == nil && didResolve {
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
}
value, newnode, _, err := t.get(child, key, pos)
return value, newnode, true, err
default:
panic(fmt.Sprintf("%T: invalid node: %v", origNode, origNode))
}
}添加
go
func (t *Trie) insert(n node, prefix, key []byte, value node) (bool, node, error) {
if len(key) == 0 {
if v, ok := n.(valueNode); ok {
return !bytes.Equal(v, value.(valueNode)), value, nil
}
return true, value, nil
}
switch n := n.(type) {
case *shortNode:
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
}
// 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
}
// Replace this shortNode with the branch if it occurs at index 0.
if matchlen == 0 {
return true, branch, nil
}
// 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.opTracer.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
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.flags = t.newFlag()
n.Children[key[0]] = nn
return true, n, nil
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.opTracer.onInsert(prefix)
return true, &shortNode{key, value, t.newFlag()}, nil
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
default:
panic(fmt.Sprintf("%T: invalid node: %v", n, n))
}
}删除
go
func (t *Trie) delete(n node, prefix, key []byte) (bool, node, error) {
switch n := n.(type) {
case *shortNode:
matchlen := prefixLen(key, n.Key)
if matchlen < len(n.Key) {
return false, n, nil // don't replace n on mismatch
}
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.opTracer.onDelete(prefix)
return true, nil, nil // remove n entirely for whole matches
}
// 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
}
switch child := child.(type) {
case *shortNode:
// The child shortNode is merged into its parent, track
// is deleted as well.
t.opTracer.onDelete(append(prefix, n.Key...))
// 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{slices.Concat(n.Key, child.Key), child.Val, t.newFlag()}, nil
default:
return true, &shortNode{n.Key, child, t.newFlag()}, nil
}
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.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:
// 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.
pos := -1
for i, cld := range &n.Children {
if cld != nil {
if pos == -1 {
pos = i
} else {
pos = -2
break
}
}
}
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.opTracer.onDelete(append(prefix, byte(pos)))
k := append([]byte{byte(pos)}, cnode.Key...)
return true, &shortNode{k, cnode.Val, t.newFlag()}, nil
}
}
// 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
}
// n still contains at least two values and cannot be reduced.
return true, n, nil
case valueNode:
return true, nil, nil
case nil:
return false, nil, nil
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
default:
panic(fmt.Sprintf("%T: invalid node: %v (%v)", n, n, key))
}
}