blockstore: give a direct access to the index for read operations

This commit was moved from ipld/go-car@2f59674

ipld/car/v2/blockstore/readonly.go

@@ -179,6 +179,12 @@ func OpenReadOnly(path string, opts ...carv2.Option) (*ReadOnly, error) {
 	return robs, nil
 }
 
+// Index gives direct access to the index.
+// You should never add records on your own there.
+func (b *ReadOnly) Index() index.Index {
+	return b.idx
+}
+
 // DeleteBlock is unsupported and always errors.
 func (b *ReadOnly) DeleteBlock(_ context.Context, _ cid.Cid) error {
 	return errReadOnly

ipld/car/v2/blockstore/readonly_test.go

@@ -12,10 +12,14 @@ import (
 	format "github.com/ipfs/go-ipld-format"
 	blocks "github.com/ipfs/go-libipfs/blocks"
 	"github.com/ipfs/go-merkledag"
-	carv2 "github.com/ipld/go-car/v2"
-	"github.com/ipld/go-car/v2/internal/carv1"
 	"github.com/multiformats/go-multicodec"
+	"github.com/multiformats/go-multihash"
 	"github.com/stretchr/testify/require"
+
+	carv2 "github.com/ipld/go-car/v2"
+	"github.com/ipld/go-car/v2/index"
+	"github.com/ipld/go-car/v2/internal/carv1"
+	"github.com/ipld/go-car/v2/internal/store"
 )
 
 func TestReadOnlyGetReturnsBlockstoreNotFoundWhenCidDoesNotExist(t *testing.T) {
@@ -331,3 +335,62 @@ func TestNewReadOnly_CarV1WithoutIndexWorksAsExpected(t *testing.T) {
 	require.NoError(t, err)
 	require.Equal(t, wantBlock, gotBlock)
 }
+
+func TestReadOnlyIndex(t *testing.T) {
+	tests := []struct {
+		name     string
+		path     string
+		wantCIDs []cid.Cid
+	}{
+		{
+			"IndexCarV1",
+			"../testdata/sample-v1.car",
+			listCids(t, newV1ReaderFromV1File(t, "../testdata/sample-v1.car", false)),
+		},
+		{
+			"IndexCarV2",
+			"../testdata/sample-wrapped-v2.car",
+			listCids(t, newV1ReaderFromV2File(t, "../testdata/sample-wrapped-v2.car", false)),
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			subject, err := OpenReadOnly(tt.path, UseWholeCIDs(true))
+			require.NoError(t, err)
+
+			idx := subject.Index()
+
+			for _, c := range tt.wantCIDs {
+				_, isIdentity, err := store.IsIdentity(c)
+				require.NoError(t, err)
+				if isIdentity {
+					// the index doesn't hold identity CIDs
+					continue
+				}
+				_, err = index.GetFirst(idx, c)
+				require.NoError(t, err)
+			}
+
+			if idx, ok := idx.(index.IterableIndex); ok {
+				expected := make([]multihash.Multihash, 0, len(tt.wantCIDs))
+				for _, c := range tt.wantCIDs {
+					_, isIdentity, err := store.IsIdentity(c)
+					require.NoError(t, err)
+					if isIdentity {
+						// the index doesn't hold identity CIDs
+						continue
+					}
+					expected = append(expected, c.Hash())
+				}
+
+				var got []multihash.Multihash
+				err = idx.ForEach(func(m multihash.Multihash, u uint64) error {
+					got = append(got, m)
+					return nil
+				})
+				require.NoError(t, err)
+				require.ElementsMatch(t, expected, got)
+			}
+		})
+	}
+}

ipld/car/v2/blockstore/readwrite.go

@@ -10,6 +10,7 @@ import (
 	blocks "github.com/ipfs/go-libipfs/blocks"
 
 	carv2 "github.com/ipld/go-car/v2"
+	"github.com/ipld/go-car/v2/index"
 	"github.com/ipld/go-car/v2/internal/carv1"
 	"github.com/ipld/go-car/v2/internal/carv1/util"
 	internalio "github.com/ipld/go-car/v2/internal/io"
@@ -178,6 +179,12 @@ func (b *ReadWrite) initWithRoots(v2 bool, roots []cid.Cid) error {
 	return carv1.WriteHeader(&carv1.CarHeader{Roots: roots, Version: 1}, b.dataWriter)
 }
 
+// Index gives direct access to the index.
+// You should never add records on your own there.
+func (b *ReadWrite) Index() index.Index {
+	return b.idx
+}
+
 // Put puts a given block to the underlying datastore
 func (b *ReadWrite) Put(ctx context.Context, blk blocks.Block) error {
 	// PutMany already checks b.ronly.closed.

ipld/car/v2/blockstore/readwrite_test.go

@@ -18,14 +18,15 @@ import (
 	format "github.com/ipfs/go-ipld-format"
 	blocks "github.com/ipfs/go-libipfs/blocks"
 	"github.com/ipfs/go-merkledag"
-	carv2 "github.com/ipld/go-car/v2"
-	"github.com/ipld/go-car/v2/blockstore"
-	"github.com/ipld/go-car/v2/index"
-	"github.com/ipld/go-car/v2/internal/carv1"
 	"github.com/multiformats/go-multicodec"
 	"github.com/multiformats/go-multihash"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+
+	carv2 "github.com/ipld/go-car/v2"
+	"github.com/ipld/go-car/v2/blockstore"
+	"github.com/ipld/go-car/v2/index"
+	"github.com/ipld/go-car/v2/internal/carv1"
 )
 
 var (
@@ -1135,3 +1136,42 @@ func TestWholeCID(t *testing.T) {
 		})
 	}
 }
+
+func TestReadWriteIndex(t *testing.T) {
+	tmpPath := requireTmpCopy(t, "../testdata/sample-wrapped-v2.car")
+
+	root := cid.MustParse("bafy2bzaced4ueelaegfs5fqu4tzsh6ywbbpfk3cxppupmxfdhbpbhzawfw5oy")
+	subject, err := blockstore.OpenReadWrite(tmpPath, []cid.Cid{root})
+	require.NoError(t, err)
+
+	defer func() {
+		err = subject.Finalize()
+		require.NoError(t, err)
+	}()
+
+	var wantCids []cid.Cid
+	var wantMh []multihash.Multihash
+	ch, err := subject.AllKeysChan(context.Background())
+	require.NoError(t, err)
+	for c := range ch {
+		wantCids = append(wantCids, c)
+		wantMh = append(wantMh, c.Hash())
+	}
+
+	idx := subject.Index()
+
+	for _, c := range wantCids {
+		_, err = index.GetFirst(idx, c)
+		require.NoError(t, err)
+	}
+
+	if idx, ok := idx.(index.IterableIndex); ok {
+		var got []multihash.Multihash
+		err = idx.ForEach(func(m multihash.Multihash, u uint64) error {
+			got = append(got, m)
+			return nil
+		})
+		require.NoError(t, err)
+		require.ElementsMatch(t, wantMh, got)
+	}
+}

ipld/car/v2/index/index.go

@@ -134,7 +134,7 @@ func WriteTo(idx Index, w io.Writer) (uint64, error) {
 // Returns error if the encoding is not known.
 //
 // Attempting to read index data from untrusted sources is not recommended.
-// Instead the index should be regenerated from the CARv2 data payload.
+// Instead, the index should be regenerated from the CARv2 data payload.
 func ReadFrom(r io.Reader) (Index, error) {
 	codec, err := ReadCodec(r)
 	if err != nil {