Optimize read+write of headers

Author: dirkkul

adapters/repos/db/lsmkv/segmentindex/header.go

@@ -42,20 +42,20 @@ type Header struct {
 }
 
 func (h *Header) WriteTo(w io.Writer) (int64, error) {
-	if err := binary.Write(w, binary.LittleEndian, &h.Level); err != nil {
-		return -1, err
-	}
-	if err := binary.Write(w, binary.LittleEndian, &h.Version); err != nil {
-		return -1, err
-	}
-	if err := binary.Write(w, binary.LittleEndian, &h.SecondaryIndices); err != nil {
-		return -1, err
-	}
-	if err := binary.Write(w, binary.LittleEndian, h.Strategy); err != nil {
-		return -1, err
+	data := make([]byte, HeaderSize)
+	rw := byteops.NewReadWriter(data)
+	rw.WriteUint16(h.Level)
+	rw.WriteUint16(h.Version)
+	rw.WriteUint16(h.SecondaryIndices)
+	rw.WriteUint16(uint16(h.Strategy))
+	rw.WriteUint64(h.IndexStart)
+
+	write, err := w.Write(data)
+	if err != nil {
+		return 0, err
 	}
-	if err := binary.Write(w, binary.LittleEndian, &h.IndexStart); err != nil {
-		return -1, err
+	if write != HeaderSize {
+		return 0, fmt.Errorf("expected to write %d bytes, got %d", HeaderSize, write)
 	}
 
 	return int64(HeaderSize), nil

adapters/repos/db/lsmkv/segmentindex/header_test.go

@@ -1,7 +1,19 @@
+//                           _       _
+// __      _____  __ ___   ___  __ _| |_ ___
+// \ \ /\ / / _ \/ _` \ \ / / |/ _` | __/ _ \
+//  \ V  V /  __/ (_| |\ V /| | (_| | ||  __/
+//   \_/\_/ \___|\__,_| \_/ |_|\__,_|\__\___|
+//
+//  Copyright © 2016 - 2024 Weaviate B.V. All rights reserved.
+//
+//  CONTACT: [email protected]
+//
+
 package segmentindex
 
 import (
 	"bytes"
+	"os"
 	"testing"
 
 	"github.com/stretchr/testify/require"
@@ -16,3 +28,20 @@ func BenchmarkParseHeader(b *testing.B) {
 		require.NoError(b, err)
 	}
 }
+
+func BenchmarkWriteHeader(b *testing.B) {
+	header := Header{
+		Version:          1,
+		Level:            1,
+		SecondaryIndices: 35,
+		Strategy:         StrategyReplace,
+		IndexStart:       234,
+	}
+	path := b.TempDir()
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		f, err := os.Create(path + "/test.tmp")
+		require.NoError(b, err)
+		header.WriteTo(f)
+	}
+}