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-rw-r--r--trie/hasher.go157
1 files changed, 157 insertions, 0 deletions
diff --git a/trie/hasher.go b/trie/hasher.go
new file mode 100644
index 000000000..87e02fb85
--- /dev/null
+++ b/trie/hasher.go
@@ -0,0 +1,157 @@
+// 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
+}