packed: Write packs with deltas

1 files changed, 110 insertions, 13 deletions

diff --git a/packed_write_pack.go b/packed_write_pack.go
index 435c9edb..0bcaf9ca 100644
--- a/packed_write_pack.go
+++ b/packed_write_pack.go
@@ -115,19 +115,84 @@ func (pw *packWriter) WriteObject(ty ObjectType, body []byte) error {
 }
 
 func (pw *packWriter) WriteOfsDelta(baseOffset uint64, baseSize, resultSize int, delta []byte) error {
-	_ = baseOffset
-	_ = baseSize
-	_ = resultSize
-	_ = delta
-	return errPackDeltaUnimplemented
+	if pw == nil || !pw.wroteHeader {
+		return ErrInvalidObject
+	}
+	if baseSize < 0 || resultSize < 0 {
+		return ErrInvalidObject
+	}
+	if delta == nil {
+		delta = []byte{}
+	}
+	deltaSize := len(delta)
+	if deltaSize <= 0 {
+		return ErrInvalidObject
+	}
+	currentOffset := pw.bytesWritten
+	if baseOffset >= currentOffset {
+		return ErrInvalidObject
+	}
+	dist := currentOffset - baseOffset
+
+	hdr, err := packHeaderEncode(ObjectTypeOfsDelta, deltaSize)
+	if err != nil {
+		return err
+	}
+	if err := pw.writePacked(hdr); err != nil {
+		return err
+	}
+	ofs, err := packOfsEncode(dist)
+	if err != nil {
+		return err
+	}
+	if err := pw.writePacked(ofs); err != nil {
+		return err
+	}
+
+	zw := zlib.NewWriter(&packHashWriter{pw: pw})
+	if _, err := zw.Write(delta); err != nil {
+		_ = zw.Close()
+		return err
+	}
+	return zw.Close()
 }
 
 func (pw *packWriter) WriteRefDelta(base Hash, baseSize, resultSize int, delta []byte) error {
-	_ = base
-	_ = baseSize
-	_ = resultSize
-	_ = delta
-	return errPackDeltaUnimplemented
+	if pw == nil || !pw.wroteHeader {
+		return ErrInvalidObject
+	}
+	if baseSize < 0 || resultSize < 0 {
+		return ErrInvalidObject
+	}
+	if delta == nil {
+		delta = []byte{}
+	}
+	deltaSize := len(delta)
+	if deltaSize <= 0 {
+		return ErrInvalidObject
+	}
+	baseBytes := base.Bytes()
+	if len(baseBytes) == 0 {
+		return ErrInvalidObject
+	}
+
+	hdr, err := packHeaderEncode(ObjectTypeRefDelta, deltaSize)
+	if err != nil {
+		return err
+	}
+	if err := pw.writePacked(hdr); err != nil {
+		return err
+	}
+	if err := pw.writePacked(baseBytes); err != nil {
+		return err
+	}
+
+	zw := zlib.NewWriter(&packHashWriter{pw: pw})
+	if _, err := zw.Write(delta); err != nil {
+		_ = zw.Close()
+		return err
+	}
+	return zw.Close()
 }
 
 func (pw *packWriter) Close() (Hash, error) {
@@ -237,7 +302,7 @@ func (repo *Repository) packWrite(w io.Writer, objects []Hash, opts packWriteOpt
 	if repo == nil {
 		return Hash{}, ErrInvalidObject
 	}
-	if opts.EnableDeltas || opts.EnableThinPack {
+	if opts.EnableThinPack {
 		return Hash{}, errPackDeltaUnimplemented
 	}
 	if len(objects) > int(^uint32(0)) {
@@ -252,13 +317,45 @@ func (repo *Repository) packWrite(w io.Writer, objects []Hash, opts packWriteOpt
 		return Hash{}, err
 	}
 
+	var dctx deltaContext
+	if opts.EnableDeltas {
+		dctx.window = defaultDeltaWindow
+	}
+	deltaSeed := uint32(0)
+
 	for _, id := range objects {
 		ty, body, err := repo.ReadObjectTypeRaw(id)
 		if err != nil {
 			return Hash{}, err
 		}
-		if err := pw.WriteObject(ty, body); err != nil {
-			return Hash{}, err
+		obj := &objectToPack{
+			id:   id,
+			ty:   ty,
+			body: body,
+		}
+		startOffset := pw.bytesWritten
+		wroteDelta := false
+
+		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
+				}
+				wroteDelta = true
+				obj.deltaDepth = base.deltaDepth + 1
+			}
+		}
+		if !wroteDelta {
+			if err := pw.WriteObject(ty, body); err != nil {
+				return Hash{}, err
+			}
+			obj.deltaDepth = 0
+		}
+		obj.offset = startOffset
+
+		if opts.EnableDeltas && ty == ObjectTypeBlob {
+			dctx.addCandidate(obj)
 		}
 	}