Update index format

doc/Design.md

@@ -164,7 +164,7 @@ Data and Tree Blobs, so the outer structure is `IV || Ciphertext || MAC` again.
 The plaintext consists of a JSON document like the following:
 
     {
-      "obsolete": [
+      "supersedes": [
         "ed54ae36197f4745ebc4b54d10e0f623eaaaedd03013eb7ae90df881b7781452"
       ],
       "packs": [
@@ -197,10 +197,9 @@ This JSON document lists Packs and the blobs contained therein. In this
 example, the Pack `73d04e61` contains two data Blobs and one Tree blob, the
 plaintext hashes are listed afterwards.
 
-The field `obsolete` lists the storage IDs of index files that have been
+The field `supersedes` lists the storage IDs of index files that have been
 replaced with the current index file. This happens when index files are
-repacked, this happens for example when old snapshots are removed and Packs are
+repacked, for example when old snapshots are removed and Packs are recombined.
-recombined.
 
 There may be an arbitrary number of index files, containing information on
 non-disjoint sets of Packs. The number of packs described in a single file is

repository/index.go

@@ -256,8 +256,15 @@ func (idx *Index) generatePackList(selectFn func(indexEntry) bool) ([]*packJSON,
 	return list, nil
 }
 
+type jsonIndex struct {
+	Supersedes []backend.ID `json:"supersedes,omitempty"`
+	Packs      []*packJSON  `json:"packs"`
+}
+
+type jsonOldIndex []*packJSON
+
 // encode writes the JSON serialization of the index filtered by selectFn to enc.
-func (idx *Index) encode(w io.Writer, selectFn func(indexEntry) bool) error {
+func (idx *Index) encode(w io.Writer, supersedes []backend.ID, selectFn func(indexEntry) bool) error {
 	list, err := idx.generatePackList(func(entry indexEntry) bool {
 		return !entry.old
 	})
@@ -268,7 +275,11 @@ func (idx *Index) encode(w io.Writer, selectFn func(indexEntry) bool) error {
 	debug.Log("Index.Encode", "done")
 
 	enc := json.NewEncoder(w)
-	return enc.Encode(list)
+	idxJSON := jsonIndex{
+		Supersedes: supersedes,
+		Packs:      list,
+	}
+	return enc.Encode(idxJSON)
 }
 
 // Encode writes the JSON serialization of the index to the writer w. This
@@ -279,7 +290,7 @@ func (idx *Index) Encode(w io.Writer) error {
 	idx.m.Lock()
 	defer idx.m.Unlock()
 
-	return idx.encode(w, func(e indexEntry) bool { return !e.old })
+	return idx.encode(w, nil, func(e indexEntry) bool { return !e.old })
 }
 
 // Dump writes the pretty-printed JSON representation of the index to w.
@@ -309,14 +320,38 @@ func (idx *Index) Dump(w io.Writer) error {
 }
 
 // DecodeIndex loads and unserializes an index from rd.
-func DecodeIndex(rd io.Reader) (*Index, error) {
+func DecodeIndex(rd io.Reader) (*Index, backend.IDs, error) {
 	debug.Log("Index.DecodeIndex", "Start decoding index")
+	idxJSON := jsonIndex{}
+
+	dec := json.NewDecoder(rd)
+	err := dec.Decode(&idxJSON)
+	if err != nil {
+		debug.Log("Index.DecodeIndex", "Error %#v", err)
+		return nil, nil, err
+	}
+
+	idx := NewIndex()
+	for _, pack := range idxJSON.Packs {
+		for _, blob := range pack.Blobs {
+			idx.store(blob.Type, blob.ID, &pack.ID, blob.Offset, blob.Length, true)
+		}
+	}
+
+	debug.Log("Index.DecodeIndex", "done")
+	return idx, idxJSON.Supersedes, err
+}
+
+// DecodeOldIndex loads and unserializes an index in the old format from rd.
+func DecodeOldIndex(rd io.Reader) (*Index, backend.IDs, error) {
+	debug.Log("Index.DecodeOldIndex", "Start decoding old index")
 	list := []*packJSON{}
 
 	dec := json.NewDecoder(rd)
 	err := dec.Decode(&list)
 	if err != nil {
-		return nil, err
+		debug.Log("Index.DecodeOldIndex", "Error %#v", err)
+		return nil, nil, err
 	}
 
 	idx := NewIndex()
@@ -326,6 +361,6 @@ func DecodeIndex(rd io.Reader) (*Index, error) {
 		}
 	}
 
-	debug.Log("Index.DecodeIndex", "done")
+	debug.Log("Index.DecodeOldIndex", "done")
-	return idx, err
+	return idx, backend.IDs{}, err
 }

repository/index_test.go

@@ -58,7 +58,7 @@ func TestIndexSerialize(t *testing.T) {
 	err := idx.Encode(wr)
 	OK(t, err)
 
-	idx2, err := repository.DecodeIndex(wr)
+	idx2, _, err := repository.DecodeIndex(wr)
 	OK(t, err)
 	Assert(t, idx2 != nil,
 		"nil returned for decoded index")
@@ -113,7 +113,7 @@ func TestIndexSerialize(t *testing.T) {
 	err = idx2.Encode(wr3)
 	OK(t, err)
 
-	idx3, err := repository.DecodeIndex(wr3)
+	idx3, _, err := repository.DecodeIndex(wr3)
 	OK(t, err)
 	Assert(t, idx3 != nil,
 		"nil returned for decoded index")
@@ -165,6 +165,38 @@ func TestIndexSize(t *testing.T) {
 
 // example index serialization from doc/Design.md
 var docExample = []byte(`
+{
+  "supersedes": [
+	"ed54ae36197f4745ebc4b54d10e0f623eaaaedd03013eb7ae90df881b7781452"
+  ],
+  "packs": [
+	{
+	  "id": "73d04e6125cf3c28a299cc2f3cca3b78ceac396e4fcf9575e34536b26782413c",
+	  "blobs": [
+		{
+		  "id": "3ec79977ef0cf5de7b08cd12b874cd0f62bbaf7f07f3497a5b1bbcc8cb39b1ce",
+		  "type": "data",
+		  "offset": 0,
+		  "length": 25
+		},{
+		  "id": "9ccb846e60d90d4eb915848add7aa7ea1e4bbabfc60e573db9f7bfb2789afbae",
+		  "type": "tree",
+		  "offset": 38,
+		  "length": 100
+		},
+		{
+		  "id": "d3dc577b4ffd38cc4b32122cabf8655a0223ed22edfd93b353dc0c3f2b0fdf66",
+		  "type": "data",
+		  "offset": 150,
+		  "length": 123
+		}
+	  ]
+	}
+  ]
+}
+`)
+
+var docOldExample = []byte(`
 [ {
   "id": "73d04e6125cf3c28a299cc2f3cca3b78ceac396e4fcf9575e34536b26782413c",
   "blobs": [
@@ -210,7 +242,9 @@ var exampleTests = []struct {
 }
 
 func TestIndexUnserialize(t *testing.T) {
-	idx, err := repository.DecodeIndex(bytes.NewReader(docExample))
+	oldIdx := backend.IDs{ParseID("ed54ae36197f4745ebc4b54d10e0f623eaaaedd03013eb7ae90df881b7781452")}
+
+	idx, supersedes, err := repository.DecodeIndex(bytes.NewReader(docExample))
 	OK(t, err)
 
 	for _, test := range exampleTests {
@@ -222,6 +256,26 @@ func TestIndexUnserialize(t *testing.T) {
 		Equals(t, test.offset, offset)
 		Equals(t, test.length, length)
 	}
+
+	Equals(t, oldIdx, supersedes)
+}
+
+func TestIndexUnserializeOld(t *testing.T) {
+	idx, supersedes, err := repository.DecodeOldIndex(bytes.NewReader(docOldExample))
+	OK(t, err)
+
+	for _, test := range exampleTests {
+		packID, tpe, offset, length, err := idx.Lookup(test.id)
+		OK(t, err)
+
+		Equals(t, test.packID, *packID)
+		Equals(t, test.tpe, tpe)
+		Equals(t, test.offset, offset)
+		Equals(t, test.length, length)
+	}
+
+	Assert(t, len(supersedes) == 0,
+		"expected %v supersedes, got %v", 0, len(supersedes))
 }
 
 func TestStoreOverwritesPreliminaryEntry(t *testing.T) {

repository/repository.go

@@ -555,7 +555,7 @@ func LoadIndex(repo *Repository, id string) (*Index, error) {
 		return nil, err
 	}
 
-	idx, err := DecodeIndex(decryptRd)
+	idx, _, err := DecodeIndex(decryptRd)
 	if err != nil {
 		debug.Log("LoadIndex", "error while decoding index %v: %v", id, err)
 		return nil, err