feat(share): Implement ODSreader

share/eds/ods.go

@@ -13,8 +13,6 @@ import (
  "github.com/ipld/go-car/util"
 )
 
-var errNilReader = errors.New("ods-reader: can't create ODSReader over nil reader")
-
 // bufferedODSReader will read odsSquareSize amount of leaves from reader into the buffer.
 // It exposes the buffer to be read by io.Reader interface implementation
 type bufferedODSReader struct {
@@ -27,13 +25,13 @@ type bufferedODSReader struct {
 
 // ODSReader reads CARv1 encoded data from io.ReadCloser and limits the reader to the CAR header
 // and first quadrant (ODS)
-func ODSReader(carReader io.ReadCloser) (io.Reader, error) {
+func ODSReader(carReader io.Reader) (io.Reader, error) {
  if carReader == nil {
- return nil, errNilReader
+ return nil, errors.New("eds: can't create ODSReader over nil reader")
  }
 
  odsR := &bufferedODSReader{
- carReader: bufio.NewReaderSize(carReader, 4),
+ carReader: bufio.NewReader(carReader),
  buf: new(bytes.Buffer),
  }
 
@@ -59,12 +57,9 @@ func ODSReader(carReader io.ReadCloser) (io.Reader, error) {
 }
 
 func (r *bufferedODSReader) Read(p []byte) (n int, err error) {
- // provided slice could be fully filled from buffer without extra reads
- if r.buf.Len() > len(p) {
- return r.buf.Read(p)
- }
-
- if r.current < r.odsSquareSize && r.buf.Len() < len(p) {
+ // read leafs to the buffer until it has sufficient data to fill provided container or full eds is
+ // read
+ for r.current < r.odsSquareSize && r.buf.Len() < len(p) {
  if err := r.readLeaf(); err != nil {
  return 0, err
  }
@@ -99,6 +94,5 @@ func (r *bufferedODSReader) readLeaf() error {
  r.buf.Write(buf[:n])
 
  _, err = r.buf.ReadFrom(io.LimitReader(r.carReader, int64(l)))
-
  return err
 }

share/eds/ods_test.go

@@ -60,3 +60,35 @@ func TestODSReader(t *testing.T) {
  _, err = carReader.Next()
  assert.Error(t, io.EOF, err)
 }
+
+// TestODSReaderReconstruction ensures that the reader returned from ODSReader provides sufficient
+// data for EDS reconstruction
+func TestODSReaderReconstruction(t *testing.T) {
+ ctx, cancel := context.WithCancel(context.Background())
+ t.Cleanup(cancel)
+
+ // launch eds store
+ edsStore, err := newStore(t)
+ require.NoError(t, err)
+ err = edsStore.Start(ctx)
+ require.NoError(t, err)
+
+ // generate random eds data and put it into the store
+ eds, dah := randomEDS(t)
+ err = edsStore.Put(ctx, dah, eds)
+ require.NoError(t, err)
+
+ // get CAR reader from store
+ r, err := edsStore.GetCAR(ctx, dah)
+ assert.NoError(t, err)
+
+ // create ODSReader wrapper based on car reader to limit reads to ODS only
+ odsR, err := ODSReader(r)
+ assert.NoError(t, err)
+
+ // reconstruct EDS from ODSReader
+ loaded, err := ReadEDS(ctx, odsR, dah)
+ assert.NoError(t, err)
+ require.Equal(t, eds.RowRoots(), loaded.RowRoots())
+ require.Equal(t, eds.ColRoots(), loaded.ColRoots())
+}