Pre-allocate slices (OffchainLabs#11317)

Author: estensen

beacon-chain/cache/depositcache/pending_deposits.go

@@ -55,7 +55,7 @@ func (dc *DepositCache) PendingDeposits(ctx context.Context, untilBlk *big.Int)
 
 	depositCntrs := dc.PendingContainers(ctx, untilBlk)
 
-	var deposits []*ethpb.Deposit
+	deposits := make([]*ethpb.Deposit, 0, len(depositCntrs))
 	for _, dep := range depositCntrs {
 		deposits = append(deposits, dep.Deposit)
 	}
@@ -71,7 +71,7 @@ func (dc *DepositCache) PendingContainers(ctx context.Context, untilBlk *big.Int
 	dc.depositsLock.RLock()
 	defer dc.depositsLock.RUnlock()
 
-	var depositCntrs []*ethpb.DepositContainer
+	depositCntrs := make([]*ethpb.DepositContainer, 0, len(dc.pendingDeposits))
 	for _, ctnr := range dc.pendingDeposits {
 		if untilBlk == nil || untilBlk.Uint64() >= ctnr.Eth1BlockHeight {
 			depositCntrs = append(depositCntrs, ctnr)
@@ -139,7 +139,7 @@ func (dc *DepositCache) PrunePendingDeposits(ctx context.Context, merkleTreeInde
 	dc.depositsLock.Lock()
 	defer dc.depositsLock.Unlock()
 
-	var cleanDeposits []*ethpb.DepositContainer
+	cleanDeposits := make([]*ethpb.DepositContainer, 0, len(dc.pendingDeposits))
 	for _, dp := range dc.pendingDeposits {
 		if dp.Index >= merkleTreeIndex {
 			cleanDeposits = append(cleanDeposits, dp)

beacon-chain/core/helpers/genesis.go

@@ -16,7 +16,7 @@ func UpdateGenesisEth1Data(state state.BeaconState, deposits []*ethpb.Deposit, e
 		return nil, errors.New("no eth1data provided for genesis state")
 	}
 
-	var leaves [][]byte
+	leaves := make([][]byte, 0, len(deposits))
 	for _, deposit := range deposits {
 		if deposit == nil || deposit.Data == nil {
 			return nil, fmt.Errorf("nil deposit or deposit with nil data cannot be processed: %v", deposit)

monitoring/prometheus/service.go

@@ -66,7 +66,7 @@ func (s *Service) healthzHandler(w http.ResponseWriter, r *http.Request) {
 		Err    string `json:"error"`
 	}
 	var hasError bool
-	var statuses []serviceStatus
+	statuses := make([]serviceStatus, 0, len(s.svcRegistry.Statuses()))
 	for k, v := range s.svcRegistry.Statuses() {
 		s := serviceStatus{
 			Name:   k.String(),

runtime/logging/logrus-prefixed-formatter/formatter.go

@@ -167,7 +167,7 @@ func (f *TextFormatter) SetColorScheme(colorScheme *ColorScheme) {
 
 func (f *TextFormatter) Format(entry *logrus.Entry) ([]byte, error) {
 	var b *bytes.Buffer
-	var keys []string = make([]string, 0, len(entry.Data))
+	keys := make([]string, 0, len(entry.Data))
 	for k := range entry.Data {
 		keys = append(keys, k)
 	}
@@ -380,12 +380,12 @@ func (f *TextFormatter) appendValue(b *bytes.Buffer, value interface{}) (err err
 // This is to not silently overwrite `time`, `msg` and `level` fields when
 // dumping it. If this code wasn't there doing:
 //
-//  logrus.WithField("level", 1).Info("hello")
+//	logrus.WithField("level", 1).Info("hello")
 //
 // would just silently drop the user provided level. Instead with this code
 // it'll be logged as:
 //
-//  {"level": "info", "fields.level": 1, "msg": "hello", "time": "..."}
+//	{"level": "info", "fields.level": 1, "msg": "hello", "time": "..."}
 func prefixFieldClashes(data logrus.Fields) {
 	if t, ok := data["time"]; ok {
 		data["fields.time"] = t

testing/assertions/assertions.go

@@ -135,7 +135,7 @@ func isNil(obj interface{}) bool {
 func LogsContain(loggerFn assertionLoggerFn, hook *test.Hook, want string, flag bool, msg ...interface{}) {
 	_, file, line, _ := runtime.Caller(2)
 	entries := hook.AllEntries()
-	var logs []string
+	logs := make([]string, 0, len(entries))
 	match := false
 	for _, e := range entries {
 		msg, err := e.String()

testing/bls/utils/utils.go

@@ -17,8 +17,8 @@ func RetrieveFiles(name string, t *testing.T) ([]string, [][]byte) {
 	testFiles, err := os.ReadDir(filepath)
 	require.NoError(t, err)
 
-	var fileNames []string
-	var fileContent [][]byte
+	fileNames := make([]string, 0, len(testFiles))
+	fileContent := make([][]byte, 0, len(testFiles))
 	require.Equal(t, false, len(testFiles) == 0, "no files exist in directory")
 	for _, f := range testFiles {
 		// Remove .yml suffix

testing/endtoend/components/web3remotesigner.go

@@ -205,7 +205,7 @@ func (w *Web3RemoteSigner) PublicKeys(ctx context.Context) ([]bls.PublicKey, err
 		return nil, errors.New("no keys returned")
 	}
 
-	var pks []bls.PublicKey
+	pks := make([]bls.PublicKey, 0, len(keys))
 	for _, key := range keys {
 		if ctx.Err() != nil {
 			return nil, ctx.Err()

tools/eth1exporter/main.go

@@ -121,7 +121,7 @@ func ToEther(o *big.Int) *big.Float {
 
 // MetricsHTTP - HTTP response handler for /metrics.
 func MetricsHTTP(w http.ResponseWriter, _ *http.Request) {
-	var allOut []string
+	allOut := make([]string, 0, len(allWatching))
 	total := big.NewFloat(0)
 	for _, v := range allWatching {
 		if v.Balance == "" {