Add HTTPFS implementation (#93)

iio/reader.go

@@ -7,3 +7,8 @@ type Reader interface {
 	io.Closer
 	io.Reader
 }
+
+type ReaderSeeker interface {
+	Reader
+	io.Seeker
+}

iio/wrapper.go

@@ -38,3 +38,42 @@ func (rw *readAtWrapper) Close() error {
 
 	return c.Close()
 }
+
+type seekerWrapper struct {
+	mu   sync.Mutex
+	pos  int64
+	size int64
+
+	io.Seeker
+	Reader
+}
+
+func NewSeekerWrapper(r Reader, size int64) *seekerWrapper {
+	return &seekerWrapper{Reader: r}
+}
+
+func (r *seekerWrapper) Seek(offset int64, whence int) (int64, error) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	switch whence {
+	case io.SeekStart:
+		r.pos = offset
+	case io.SeekCurrent:
+		r.pos = r.pos + offset
+	case io.SeekEnd:
+		r.pos = r.size + offset
+	}
+
+	return r.pos, nil
+}
+
+func (r *seekerWrapper) Read(p []byte) (int, error) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	n, err := r.ReadAt(p, r.pos)
+	r.pos += int64(n)
+
+	return n, err
+}

iio/wrapper_test.go

@@ -0,0 +1,56 @@
+package iio_test
+
+import (
+	"bytes"
+	"io"
+	"testing"
+
+	"github.com/distribyted/distribyted/fs"
+	"github.com/distribyted/distribyted/iio"
+	"github.com/stretchr/testify/require"
+)
+
+var testData []byte = []byte("Hello World")
+
+func TestReadAtWrapper(t *testing.T) {
+	t.Parallel()
+
+	require := require.New(t)
+
+	br := bytes.NewReader(testData)
+
+	r := iio.NewReadAtWrapper(br)
+	defer r.Close()
+
+	toRead := make([]byte, 5)
+	n, err := r.ReadAt(toRead, 6)
+	require.NoError(err)
+	require.Equal(5, n)
+	require.Equal("World", string(toRead))
+
+	n, err = r.ReadAt(toRead, 0)
+	require.NoError(err)
+	require.Equal(5, n)
+	require.Equal("Hello", string(toRead))
+}
+
+func TestSeekerWrapper(t *testing.T) {
+	t.Parallel()
+
+	require := require.New(t)
+
+	mf := fs.NewMemoryFile(testData)
+
+	r := iio.NewSeekerWrapper(mf, mf.Size())
+	defer r.Close()
+
+	n, err := r.Seek(6, io.SeekStart)
+	require.NoError(err)
+	require.Equal(int64(6), n)
+
+	toRead := make([]byte, 5)
+	nn, err := r.Read(toRead)
+	require.NoError(err)
+	require.Equal(5, nn)
+	require.Equal("World", string(toRead))
+}