packed, delta: Implement thin packs

1 files changed, 93 insertions, 9 deletions

diff --git a/packed_write_pack.go b/packed_write_pack.go
index 329e2a7f..1d8cbc1e 100644
--- a/packed_write_pack.go
+++ b/packed_write_pack.go
@@ -283,11 +283,39 @@ func packOfsEncode(dist uint64) ([]byte, error) {
 
 // packWrite writes a pack stream for the provided object ids.
 func (repo *Repository) packWrite(w io.Writer, objects []Hash, opts packWriteOptions) (Hash, error) {
+	if opts.EnableThinPack {
+		return Hash{}, errThinPackUnimplemented
+	}
+	return repo.packWriteObjects(w, objects, opts, nil)
+}
+
+// packWriteReachable writes a pack stream for objects reachable from the
+// provided reachability query.
+func (repo *Repository) packWriteReachable(w io.Writer, query ReachabilityQuery, opts packWriteOptions) (Hash, error) {
 	if repo == nil {
 		return Hash{}, ErrInvalidObject
 	}
-	if opts.EnableThinPack {
-		return Hash{}, errThinPackUnimplemented
+	query.Mode = ReachabilityAllObjects
+	walk, err := repo.ReachableObjects(query)
+	if err != nil {
+		return Hash{}, err
+	}
+	var objects []Hash
+	for obj := range walk.Seq() {
+		objects = append(objects, obj.ID)
+	}
+	if err := walk.Err(); err != nil {
+		return Hash{}, err
+	}
+	return repo.packWriteObjects(w, objects, opts, walk)
+}
+
+func (repo *Repository) packWriteObjects(w io.Writer, objects []Hash, opts packWriteOptions, have *ReachabilityWalk) (Hash, error) {
+	if repo == nil {
+		return Hash{}, ErrInvalidObject
+	}
+	if opts.EnableThinPack && have == nil {
+		return Hash{}, ErrInvalidObject
 	}
 	if len(objects) > int(^uint32(0)) {
 		return Hash{}, ErrInvalidObject
@@ -312,15 +340,22 @@ func (repo *Repository) packWrite(w io.Writer, objects []Hash, opts packWriteOpt
 		deltaSeed = binary.LittleEndian.Uint64(seedBytes[:])
 	}
 
+	if opts.EnableDeltas && opts.EnableThinPack {
+		if err := repo.seedDeltaCandidatesFromHaves(&dctx, have.query.Haves); err != nil {
+			return Hash{}, err
+		}
+	}
+
 	for _, id := range objects {
 		ty, body, err := repo.ReadObjectTypeRaw(id)
 		if err != nil {
 			return Hash{}, err
 		}
 		obj := &objectToPack{
-			id:   id,
-			ty:   ty,
-			body: body,
+			id:     id,
+			ty:     ty,
+			body:   body,
+			inPack: true,
 		}
 		startOffset := pw.bytesWritten
 		wroteDelta := false
@@ -328,11 +363,27 @@ func (repo *Repository) packWrite(w io.Writer, objects []Hash, opts packWriteOpt
 		if opts.EnableDeltas && ty == ObjectTypeBlob {
 			base, delta := pickDeltaBase(&dctx, obj, deltaSeed, opts.MinDeltaSavings, opts.MaxDeltaDepth)
 			if base != nil && delta != nil {
-				if err := pw.WriteOfsDelta(base.offset, len(base.body), len(body), delta); err != nil {
-					return Hash{}, err
+				switch {
+				case base.inPack:
+					if err := pw.WriteOfsDelta(base.offset, len(base.body), len(body), delta); err != nil {
+						return Hash{}, err
+					}
+					wroteDelta = true
+					obj.deltaDepth = base.deltaDepth + 1
+				case opts.EnableThinPack:
+					inHave, err := have.HaveContains(base.id)
+					if err != nil {
+						return Hash{}, err
+					}
+					if inHave {
+						if err := pw.WriteRefDelta(base.id, len(base.body), len(body), delta); err != nil {
+							return Hash{}, err
+						}
+						wroteDelta = true
+						obj.deltaDepth = base.deltaDepth + 1
+					}
+				default:
 				}
-				wroteDelta = true
-				obj.deltaDepth = base.deltaDepth + 1
 			}
 		}
 		if !wroteDelta {
@@ -351,6 +402,39 @@ func (repo *Repository) packWrite(w io.Writer, objects []Hash, opts packWriteOpt
 	return pw.Close()
 }
 
+func (repo *Repository) seedDeltaCandidatesFromHaves(ctx *deltaContext, haves []Hash) error {
+	if repo == nil {
+		return ErrInvalidObject
+	}
+	if ctx == nil || ctx.window <= 0 || len(haves) == 0 {
+		return nil
+	}
+	walk, err := repo.ReachableObjects(ReachabilityQuery{
+		Wants: haves,
+		Mode:  ReachabilityAllObjects,
+	})
+	if err != nil {
+		return err
+	}
+	for obj := range walk.Seq() {
+		if obj.Type != ObjectTypeBlob {
+			continue
+		}
+		ty, body, err := repo.ReadObjectTypeRaw(obj.ID)
+		if err != nil {
+			return err
+		}
+		candidate := &objectToPack{
+			id:     obj.ID,
+			ty:     ty,
+			body:   body,
+			inPack: false,
+		}
+		ctx.addCandidate(candidate)
+	}
+	return walk.Err()
+}
+
 type packWriteOptions struct {
 	EnableDeltas    bool
 	EnableThinPack  bool