Use big.Int for bytes sum and int to byte conversion

arbnode/batch_poster.go

@@ -6,7 +6,6 @@ package arbnode
 import (
 	"bytes"
 	"context"
-	"encoding/binary"
 	"encoding/hex"
 	"errors"
 	"fmt"
@@ -343,13 +342,7 @@ func AccessList(opts *AccessListOpts) types.AccessList {
 		{7, opts.SequencerInboxAccs},           // - sequencerInboxAccs.push(...); (keccak256(7, sequencerInboxAccs.length))
 		{6, opts.AfterDelayedMessagesRead - 1}, // - delayedInboxAccs[afterDelayedMessagesRead - 1]; (keccak256(6, afterDelayedMessagesRead - 1))
 	} {
-
-		sia, err := intToBytes(v.val)
-		if err != nil {
-			log.Error("Error converting sequencer inbox accs to bytes", "err", err, "sequencerInboxAccs", opts.SequencerInboxAccs)
-			continue
-		}
-		sb := arbutil.SumBytes(arbutil.PaddedKeccak256([]byte{byte(v.slotIdx)}), sia)
+		sb := arbutil.SumBytes(arbutil.PaddedKeccak256([]byte{byte(v.slotIdx)}), big.NewInt(int64(v.val)).Bytes())
 		l[1].StorageKeys = append(l[1].StorageKeys, common.Hash(sb))
 	}
 
@@ -369,14 +362,6 @@ func AccessList(opts *AccessListOpts) types.AccessList {
 	return l
 }
 
-func intToBytes(val int) ([]byte, error) {
-	buf := new(bytes.Buffer)
-	if err := binary.Write(buf, binary.BigEndian, int64(val)); err != nil {
-		return nil, err
-	}
-	return buf.Bytes(), nil
-}
-
 // checkRevert checks blocks with number in range [from, to] whether they
 // contain reverted batch_poster transaction.
 // It returns true if it finds batch posting needs to halt, which is true if a batch reverts

arbutil/hash.go

@@ -1,6 +1,8 @@
 package arbutil
 
 import (
+	"math/big"
+
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/crypto"
 )
@@ -18,16 +20,7 @@ func PaddedKeccak256(args ...[]byte) []byte {
 // SumBytes sums two byte slices and returns the result.
 // If the sum of bytes are over 32 bytes, it return last 32.
 func SumBytes(a, b []byte) []byte {
-	// Normalize lengths to hash length.
-	a = common.BytesToHash(a).Bytes()
-	b = common.BytesToHash(b).Bytes()
-
-	sum := make([]byte, common.HashLength)
-	c := 0
-	for i := common.HashLength - 1; i >= 0; i-- {
-		tmp := int(a[i]) + int(b[i]) + c
-		sum[i] = byte(tmp & 0xFF)
-		c = tmp >> 8
-	}
-	return sum
+	A := big.NewInt(0).SetBytes(a)
+	B := big.NewInt(0).SetBytes(b)
+	return common.BytesToHash((A.Add(A, B)).Bytes()).Bytes()
 }