core/state: make statedb/stateobjects reuse a hasher

core/state/state_object.go

@@ -325,6 +325,7 @@ func (s *stateObject) updateTrie(db Database) Trie {
 	var storage map[common.Hash][]byte
 	// Insert all the pending updates into the trie
 	tr := s.getTrie(db)
+	hasher := s.db.hasher
 	for key, value := range s.pendingStorage {
 		// Skip noop changes, persist actual changes
 		if value == s.originStorage[key] {
@@ -349,7 +350,7 @@ func (s *stateObject) updateTrie(db Database) Trie {
 					s.db.snapStorage[s.addrHash] = storage
 				}
 			}
-			storage[crypto.Keccak256Hash(key[:])] = v // v will be nil if value is 0x00
+			storage[crypto.HashData(hasher, key[:])] = v // v will be nil if value is 0x00
 		}
 	}
 	if len(s.pendingStorage) > 0 {

core/state/statedb.go

@@ -64,8 +64,9 @@ func (n *proofList) Delete(key []byte) error {
 // * Contracts
 // * Accounts
 type StateDB struct {
-	db   Database
-	trie Trie
+	db     Database
+	trie   Trie
+	hasher crypto.KeccakHasher
 
 	snaps         *snapshot.Tree
 	snap          snapshot.Snapshot
@@ -131,6 +132,7 @@ func New(root common.Hash, db Database, snaps *snapshot.Tree) (*StateDB, error)
 		logs:                make(map[common.Hash][]*types.Log),
 		preimages:           make(map[common.Hash][]byte),
 		journal:             newJournal(),
+		hasher:              crypto.NewKeccakHasher(),
 	}
 	if sdb.snaps != nil {
 		if sdb.snap = sdb.snaps.Snapshot(root); sdb.snap != nil {
@@ -516,7 +518,7 @@ func (s *StateDB) getDeletedStateObject(addr common.Address) *stateObject {
 			defer func(start time.Time) { s.SnapshotAccountReads += time.Since(start) }(time.Now())
 		}
 		var acc *snapshot.Account
-		if acc, err = s.snap.Account(crypto.Keccak256Hash(addr[:])); err == nil {
+		if acc, err = s.snap.Account(crypto.HashData(s.hasher, addr[:])); err == nil {
 			if acc == nil {
 				return nil
 			}
@@ -648,6 +650,7 @@ func (s *StateDB) Copy() *StateDB {
 		logSize:             s.logSize,
 		preimages:           make(map[common.Hash][]byte, len(s.preimages)),
 		journal:             newJournal(),
+		hasher:              crypto.NewKeccakHasher(),
 	}
 	// Copy the dirty states, logs, and preimages
 	for addr := range s.journal.dirties {

crypto/crypto.go

@@ -24,6 +24,7 @@ import (
 	"encoding/hex"
 	"errors"
 	"fmt"
+	"hash"
 	"io"
 	"io/ioutil"
 	"math/big"
@@ -51,6 +52,27 @@ var (
 
 var errInvalidPubkey = errors.New("invalid secp256k1 public key")
 
+// KeccakHasher wraps sha3.state. In addition to the usual hash methods, it also supports
+// Read to get a variable amount of data from the hash state. Read is faster than Sum
+// because it doesn't copy the internal state, but also modifies the internal state.
+type KeccakHasher interface {
+	hash.Hash
+	Read([]byte) (int, error)
+}
+
+func NewKeccakHasher() KeccakHasher {
+	return sha3.NewLegacyKeccak256().(KeccakHasher)
+}
+
+// hashData hashes the provided data and returns a 32 byte hash
+// This method is not threadsafe
+func HashData(kh KeccakHasher, data []byte) (h common.Hash) {
+	kh.Reset()
+	kh.Write(data)
+	kh.Read(h[:])
+	return h
+}
+
 // Keccak256 calculates and returns the Keccak256 hash of the input data.
 func Keccak256(data ...[]byte) []byte {
 	d := sha3.NewLegacyKeccak256()

crypto/crypto_test.go

@@ -42,6 +42,13 @@ func TestKeccak256Hash(t *testing.T) {
 	checkhash(t, "Sha3-256-array", func(in []byte) []byte { h := Keccak256Hash(in); return h[:] }, msg, exp)
 }
 
+func TestKeccak256Hasher(t *testing.T) {
+	msg := []byte("abc")
+	exp, _ := hex.DecodeString("4e03657aea45a94fc7d47ba826c8d667c0d1e6e33a64a036ec44f58fa12d6c45")
+	hasher := NewKeccakHasher()
+	checkhash(t, "Sha3-256-array", func(in []byte) []byte { h := HashData(hasher, in); return h[:] }, msg, exp)
+}
+
 func TestToECDSAErrors(t *testing.T) {
 	if _, err := HexToECDSA("0000000000000000000000000000000000000000000000000000000000000000"); err == nil {
 		t.Fatal("HexToECDSA should've returned error")