internal/era: refactor to use slices.Reverse

internal/era/accumulator.go

@@ -20,6 +20,7 @@ import (
 	"errors"
 	"fmt"
 	"math/big"
+	"slices"
 
 	"github.com/ethereum/go-ethereum/common"
 	ssz "github.com/ferranbt/fastssz"
@@ -78,14 +79,6 @@ func (h *headerRecord) HashTreeRootWith(hh ssz.HashWalker) (err error) {
 // bigToBytes32 converts a big.Int into a little-endian 32-byte array.
 func bigToBytes32(n *big.Int) (b [32]byte) {
 	n.FillBytes(b[:])
-	reverseOrder(b[:])
+	slices.Reverse(b[:])
 	return
 }
-
-// reverseOrder reverses the byte order of a slice.
-func reverseOrder(b []byte) []byte {
-	for i := 0; i < 16; i++ {
-		b[i], b[32-i-1] = b[32-i-1], b[i]
-	}
-	return b
-}

internal/era/era.go

@@ -23,6 +23,7 @@ import (
 	"math/big"
 	"os"
 	"path"
+	"slices"
 	"strconv"
 	"strings"
 	"sync"
@@ -244,7 +245,8 @@ func (e *Era) InitialTD() (*big.Int, error) {
 	if err != nil {
 		return nil, err
 	}
-	td := new(big.Int).SetBytes(reverseOrder(rawTd))
+	slices.Reverse(rawTd)
+	td := new(big.Int).SetBytes(rawTd)
 	return td.Sub(td, header.Difficulty), nil
 }
 

internal/era/era_test.go

@@ -22,6 +22,7 @@ import (
 	"io"
 	"math/big"
 	"os"
+	"slices"
 	"testing"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -136,7 +137,8 @@ func TestEra1Builder(t *testing.T) {
 		if err != nil {
 			t.Fatalf("error reading td: %v", err)
 		}
-		td := new(big.Int).SetBytes(reverseOrder(rawTd))
+		slices.Reverse(rawTd)
+		td := new(big.Int).SetBytes(rawTd)
 		if td.Cmp(chain.tds[i]) != 0 {
 			t.Fatalf("mismatched tds: want %s, got %s", chain.tds[i], td)
 		}

internal/era/iterator.go

@@ -20,6 +20,7 @@ import (
 	"errors"
 	"io"
 	"math/big"
+	"slices"
 
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/rlp"
@@ -107,7 +108,8 @@ func (it *Iterator) TotalDifficulty() (*big.Int, error) {
 	if err != nil {
 		return nil, err
 	}
-	return new(big.Int).SetBytes(reverseOrder(td)), nil
+	slices.Reverse(td)
+	return new(big.Int).SetBytes(td), nil
 }
 
 // RawIterator reads an RLP-encode Era1 entries.