eth/protocols/snap: speed up hash checks (#22023)

* eth/protocols/snap: speed up hash checks

* eth/protocols/snap: nit fix

Co-authored-by: Péter Szilágyi <peterke@gmail.com>

eth/protocols/snap/sync.go

@@ -2112,14 +2112,15 @@ func (s *Syncer) onByteCodes(peer *Peer, id uint64, bytecodes [][]byte) error {
 
 	// Cross reference the requested bytecodes with the response to find gaps
 	// that the serving node is missing
-	hasher := sha3.NewLegacyKeccak256()
+	hasher := sha3.NewLegacyKeccak256().(crypto.KeccakState)
+	hash := make([]byte, 32)
 
 	codes := make([][]byte, len(req.hashes))
 	for i, j := 0, 0; i < len(bytecodes); i++ {
 		// Find the next hash that we've been served, leaving misses with nils
 		hasher.Reset()
 		hasher.Write(bytecodes[i])
-		hash := hasher.Sum(nil)
+		hasher.Read(hash)
 
 		for j < len(req.hashes) && !bytes.Equal(hash, req.hashes[j][:]) {
 			j++
@@ -2350,14 +2351,15 @@ func (s *Syncer) OnTrieNodes(peer *Peer, id uint64, trienodes [][]byte) error {
 
 	// Cross reference the requested trienodes with the response to find gaps
 	// that the serving node is missing
-	hasher := sha3.NewLegacyKeccak256()
+	hasher := sha3.NewLegacyKeccak256().(crypto.KeccakState)
+	hash := make([]byte, 32)
 
 	nodes := make([][]byte, len(req.hashes))
 	for i, j := 0, 0; i < len(trienodes); i++ {
 		// Find the next hash that we've been served, leaving misses with nils
 		hasher.Reset()
 		hasher.Write(trienodes[i])
-		hash := hasher.Sum(nil)
+		hasher.Read(hash)
 
 		for j < len(req.hashes) && !bytes.Equal(hash, req.hashes[j][:]) {
 			j++
@@ -2437,14 +2439,15 @@ func (s *Syncer) onHealByteCodes(peer *Peer, id uint64, bytecodes [][]byte) erro
 
 	// Cross reference the requested bytecodes with the response to find gaps
 	// that the serving node is missing
-	hasher := sha3.NewLegacyKeccak256()
+	hasher := sha3.NewLegacyKeccak256().(crypto.KeccakState)
+	hash := make([]byte, 32)
 
 	codes := make([][]byte, len(req.hashes))
 	for i, j := 0, 0; i < len(bytecodes); i++ {
 		// Find the next hash that we've been served, leaving misses with nils
 		hasher.Reset()
 		hasher.Write(bytecodes[i])
-		hash := hasher.Sum(nil)
+		hasher.Read(hash)
 
 		for j < len(req.hashes) && !bytes.Equal(hash, req.hashes[j][:]) {
 			j++

eth/protocols/snap/sync_test.go

@@ -0,0 +1,98 @@
+// Copyright 2020 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 snap
+
+import (
+	"crypto/rand"
+	"fmt"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/crypto"
+	"golang.org/x/crypto/sha3"
+)
+
+func TestHashing(t *testing.T) {
+	var bytecodes = make([][]byte, 10)
+	for i := 0; i < len(bytecodes); i++ {
+		buf := make([]byte, 100)
+		rand.Read(buf)
+		bytecodes[i] = buf
+	}
+	var want, got string
+	var old = func() {
+		hasher := sha3.NewLegacyKeccak256()
+		for i := 0; i < len(bytecodes); i++ {
+			hasher.Reset()
+			hasher.Write(bytecodes[i])
+			hash := hasher.Sum(nil)
+			got = fmt.Sprintf("%v\n%v", got, hash)
+		}
+	}
+	var new = func() {
+		hasher := sha3.NewLegacyKeccak256().(crypto.KeccakState)
+		var hash = make([]byte, 32)
+		for i := 0; i < len(bytecodes); i++ {
+			hasher.Reset()
+			hasher.Write(bytecodes[i])
+			hasher.Read(hash)
+			want = fmt.Sprintf("%v\n%v", want, hash)
+		}
+	}
+	old()
+	new()
+	if want != got {
+		t.Errorf("want\n%v\ngot\n%v\n", want, got)
+	}
+}
+
+func BenchmarkHashing(b *testing.B) {
+	var bytecodes = make([][]byte, 10000)
+	for i := 0; i < len(bytecodes); i++ {
+		buf := make([]byte, 100)
+		rand.Read(buf)
+		bytecodes[i] = buf
+	}
+	var old = func() {
+		hasher := sha3.NewLegacyKeccak256()
+		for i := 0; i < len(bytecodes); i++ {
+			hasher.Reset()
+			hasher.Write(bytecodes[i])
+			hasher.Sum(nil)
+		}
+	}
+	var new = func() {
+		hasher := sha3.NewLegacyKeccak256().(crypto.KeccakState)
+		var hash = make([]byte, 32)
+		for i := 0; i < len(bytecodes); i++ {
+			hasher.Reset()
+			hasher.Write(bytecodes[i])
+			hasher.Read(hash)
+		}
+	}
+	b.Run("old", func(b *testing.B) {
+		b.ReportAllocs()
+		for i := 0; i < b.N; i++ {
+			old()
+		}
+	})
+	b.Run("new", func(b *testing.B) {
+		b.ReportAllocs()
+		for i := 0; i < b.N; i++ {
+			new()
+		}
+	})
+}