mmap_test.go

package cgommap_test

import (
	"bytes"
	"cgommap"
	"github.com/stretchr/testify/require"
	"io"
	"io/ioutil"
	"log"
	"os"
	"testing"
)

func TestMmap(t *testing.T) {
	file, err := ioutil.TempFile(os.TempDir(), "prefix")
	if err != nil {
		log.Fatal(err)
	}
	defer os.Remove(file.Name())
	defer file.Close()

	testText := []byte("Testing the memory mapped file")
	n, err := file.Write(testText)
	require.NoError(t, err)
	require.Equal(t, len(testText), n)
	require.NoError(t, err)

	mmap, err := cgommap.New(int64(len(testText)),0, cgommap.PROT_READWRITE, cgommap.MAP_SHARED, file.Fd())
	require.NoError(t, err)

	defer func() {
		err = mmap.Close()
		require.NoError(t, err)
	}()

	{ // Read Test
		buf := make([]byte, mmap.Size())
		n, err = mmap.Read(buf[0:])
		require.NoError(t, err)
		require.Equal(t, len(testText), len(buf))
		require.True(t, bytes.Equal(testText, buf))

		buf = make([]byte, mmap.Size())
		n, err = mmap.Read(buf[0:])
		require.Error(t, err)
	}


	{ // Seek test
		off, err := mmap.Seek(0, io.SeekStart)
		require.NoError(t, err)
		require.Equal(t, int64(0), off)

		buf := make([]byte, mmap.Size())
		n, err = mmap.Read(buf[0:])
		require.NoError(t, err)
		require.Equal(t, len(testText), len(buf))
		require.True(t, bytes.Equal(testText, buf))

		// Seek to middle of text
		off, err = mmap.Seek(int64(len(testText)/2), io.SeekStart)
		require.NoError(t, err)
		require.Equal(t, int64(len(testText)/2), off)

		buf = make([]byte, len(testText)/2)
		n, err = mmap.Read(buf[0:])
		require.NoError(t, err)
		require.Equal(t, len(testText)/2, len(buf))
		require.True(t, bytes.Equal(testText[len(testText)/2:], buf))
	}

	{ // Write Test
		off, err := mmap.Seek(0, io.SeekStart)
		require.NoError(t, err)
		require.Equal(t, int64(0), off)

		testWriteText := []byte("Writing into the darkest abyss")
		n, err := mmap.Write(testWriteText)
		require.NoError(t, err)
		require.Equal(t, len(testWriteText), n)

		off, err = mmap.Seek(0, io.SeekStart)
		require.NoError(t, err)
		require.Equal(t, int64(0), off)

		buf := make([]byte, mmap.Size())
		n, err = mmap.Read(buf[0:])
		require.NoError(t, err)
		require.Equal(t, len(testWriteText), len(buf))
		require.True(t, bytes.Equal(testWriteText, buf))

		// Try to write again while already seeked to the end of the file
		_, err = mmap.Write(testWriteText)
		require.Error(t, err)
	}
}