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// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// 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,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// 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/>.
package trie
import (
"bytes"
"hash"
"sync"
"github.com/ethereum/go-ethereum/common"
"github.com/ethereum/go-ethereum/crypto/sha3"
"github.com/ethereum/go-ethereum/rlp"
)
type hasher struct {
tmp *bytes.Buffer
sha hash.Hash
}
// hashers live in a global pool.
var hasherPool = sync.Pool{
New: func() interface{} {
return &hasher{tmp: new(bytes.Buffer), sha: sha3.NewKeccak256()}
},
}
func newHasher() *hasher {
return hasherPool.Get().(*hasher)
}
func returnHasherToPool(h *hasher) {
hasherPool.Put(h)
}
// hash collapses a node down into a hash node, also returning a copy of the
// original node initialzied with the computed hash to replace the original one.
func (h *hasher) hash(n node, db DatabaseWriter, force bool) (node, node, error) {
// If we're not storing the node, just hashing, use avaialble cached data
if hash, dirty := n.cache(); hash != nil && (db == nil || !dirty) {
return hash, n, nil
}
// Trie not processed yet or needs storage, walk the children
collapsed, cached, err := h.hashChildren(n, db)
if err != nil {
return hashNode{}, n, err
}
hashed, err := h.store(collapsed, db, force)
if err != nil {
return hashNode{}, n, err
}
// Cache the hash and RLP blob of the ndoe for later reuse
if hash, ok := hashed.(hashNode); ok && !force {
switch cached := cached.(type) {
case shortNode:
cached.hash = hash
if db != nil {
cached.dirty = false
}
return hashed, cached, nil
case fullNode:
cached.hash = hash
if db != nil {
cached.dirty = false
}
return hashed, cached, nil
}
}
return hashed, cached, nil
}
// hashChildren replaces the children of a node with their hashes if the encoded
// size of the child is larger than a hash, returning the collapsed node as well
// as a replacement for the original node with the child hashes cached in.
func (h *hasher) hashChildren(original node, db DatabaseWriter) (node, node, error) {
var err error
switch n := original.(type) {
case shortNode:
// Hash the short node's child, caching the newly hashed subtree
cached := n
cached.Key = common.CopyBytes(cached.Key)
n.Key = compactEncode(n.Key)
if _, ok := n.Val.(valueNode); !ok {
if n.Val, cached.Val, err = h.hash(n.Val, db, false); err != nil {
return n, original, err
}
}
if n.Val == nil {
n.Val = valueNode(nil) // Ensure that nil children are encoded as empty strings.
}
return n, cached, nil
case fullNode:
// Hash the full node's children, caching the newly hashed subtrees
cached := fullNode{dirty: n.dirty}
for i := 0; i < 16; i++ {
if n.Children[i] != nil {
if n.Children[i], cached.Children[i], err = h.hash(n.Children[i], db, false); err != nil {
return n, original, err
}
} else {
n.Children[i] = valueNode(nil) // Ensure that nil children are encoded as empty strings.
}
}
cached.Children[16] = n.Children[16]
if n.Children[16] == nil {
n.Children[16] = valueNode(nil)
}
return n, cached, nil
default:
// Value and hash nodes don't have children so they're left as were
return n, original, nil
}
}
func (h *hasher) store(n node, db DatabaseWriter, force bool) (node, error) {
// Don't store hashes or empty nodes.
if _, isHash := n.(hashNode); n == nil || isHash {
return n, nil
}
// Generate the RLP encoding of the node
h.tmp.Reset()
if err := rlp.Encode(h.tmp, n); err != nil {
panic("encode error: " + err.Error())
}
if h.tmp.Len() < 32 && !force {
return n, nil // Nodes smaller than 32 bytes are stored inside their parent
}
// Larger nodes are replaced by their hash and stored in the database.
hash, _ := n.cache()
if hash == nil {
h.sha.Reset()
h.sha.Write(h.tmp.Bytes())
hash = hashNode(h.sha.Sum(nil))
}
if db != nil {
return hash, db.Put(hash, h.tmp.Bytes())
}
return hash, nil
}
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