github.com/scottcagno/storage@v1.8.0/pkg/lsmtree/readwrite_test.go

package lsmtree

import (
	"fmt"
	"io"
	"os"
	"testing"
)

func makeData(prefix string, i int) []byte {
	return []byte(fmt.Sprintf("%s-%06d", prefix, i))
}

func TestReadWriteEntries(t *testing.T) {

	readAndWriteEntriesFunc := func(file *os.File) {

		// offsets for read at later on
		var offsets []int64
		var err error

		fmt.Println("writing entries...")
		// write entries
		for i := 0; i < 500; i++ {
			// make entry
			e := &Entry{
				Key:   makeData("key", i),
				Value: makeData("value", i),
			}
			// add checksum
			e.CRC = checksum(append(e.Key, e.Value...))

			// get current offset for later
			offset, err := file.Seek(0, io.SeekCurrent)
			if err != nil {
				t.Errorf("seek current offset: %v\n", err)
			}
			offsets = append(offsets, offset)

			// write entry
			_, err = writeEntry(file, e)
			if err != nil {
				t.Errorf("writing entry: %v\n", err)
			}
		}

		// rewind
		_, err = file.Seek(0, io.SeekStart)
		if err != nil {
			t.Errorf("rewind: %v\n", err)
		}

		fmt.Println("reading entries...")
		// read entries
		i := 0
		for {
			// read entry
			e, err := readEntry(file)
			if err != nil {
				if err == io.EOF || err == io.ErrUnexpectedEOF {
					break
				}
				t.Errorf("reading entry: %v\n", err)
			}
			if i%25 == 0 {
				fmt.Printf("%s\n", e)
			}
			i++
		}

		fmt.Println("reading entries at...")
		// read entries at
		for i := 500 - 1; i > 0; i -= 25 {
			e, err := readEntryAt(file, offsets[i])
			if err != nil {
				t.Errorf("reading entry at (%d): %v\n", err, offsets[i])
			}
			fmt.Printf("offset: %d, %s\n", offsets[i], e)
		}

	}

	GetTempFileForTesting(t, readAndWriteEntriesFunc)

}