untangle unmarshal from pb

unmarshal.go

@@ -3,14 +3,16 @@ package dagpb
 import (
 	"io"
 
+	"github.com/ipfs/go-cid"
 	ipld "github.com/ipld/go-ipld-prime"
 	cidlink "github.com/ipld/go-ipld-prime/linking/cid"
-	pb "github.com/rvagg/go-dagpb/pb"
+	"github.com/polydawn/refmt/shared"
+	"golang.org/x/xerrors"
 )
 
-func Unmarshal(na ipld.NodeAssembler, reader io.Reader) error {
-	var curLink ipld.MapAssembler
+var ErrIntOverflow = xerrors.Errorf("protobuf: varint overflow")
 
+func Unmarshal(na ipld.NodeAssembler, in io.Reader) error {
 	ma, err := na.BeginMap(2)
 	if err != nil {
 		return err
@@ -23,9 +25,31 @@ func Unmarshal(na ipld.NodeAssembler, reader io.Reader) error {
 		return err
 	}
 
-	tokenReceiver := func(tok pb.Token) error {
-		switch tok.Type {
-		case pb.TypeData:
+	haveData := false
+	reader := shared.NewReader(in)
+	for {
+		_, err := reader.Readn1()
+		if err == io.EOF {
+			break
+		}
+		reader.Unreadn1()
+
+		fieldNum, wireType, err := decodeKey(reader)
+		if err != nil {
+			return err
+		}
+		if wireType != 2 {
+			return xerrors.Errorf("protobuf: (PBNode) invalid wireType, expected 2, got %d", wireType)
+		}
+
+		if fieldNum == 1 {
+			if haveData {
+				return xerrors.Errorf("protobuf: (PBNode) duplicate Data section")
+			}
+			var chunk []byte
+			if chunk, err = decodeBytes(reader); err != nil {
+				return err
+			}
 			if err := links.Finish(); err != nil {
 				return err
 			}
@@ -33,50 +57,178 @@ func Unmarshal(na ipld.NodeAssembler, reader io.Reader) error {
 			if err := ma.AssembleKey().AssignString("Data"); err != nil {
 				return err
 			}
-			if err := ma.AssembleValue().AssignBytes(tok.Bytes); err != nil {
+			if err := ma.AssembleValue().AssignBytes(chunk); err != nil {
 				return err
 			}
-		case pb.TypeLink:
-		case pb.TypeLinkEnd:
-			if err := curLink.Finish(); err != nil {
+			haveData = true
+		} else if fieldNum == 2 {
+			if haveData {
+				return xerrors.Errorf("protobuf: (PBNode) invalid order, found Data before Links content")
+			}
+
+			bytesLen, err := decodeVarint(reader)
+			if err != nil {
 				return err
 			}
-		case pb.TypeHash:
-			curLink, err = links.AssembleValue().BeginMap(3)
+			curLink, err := links.AssembleValue().BeginMap(3)
 			if err != nil {
 				return err
 			}
-			if err := curLink.AssembleKey().AssignString("Hash"); err != nil {
+			if err = unmarshalLink(reader, int(bytesLen), curLink); err != nil {
 				return err
 			}
-			if err := curLink.AssembleValue().AssignLink(cidlink.Link{*tok.Cid}); err != nil {
+			if err := curLink.Finish(); err != nil {
 				return err
 			}
-		case pb.TypeName:
-			if err := curLink.AssembleKey().AssignString("Name"); err != nil {
+		} else {
+			return xerrors.Errorf("protobuf: (PBNode) invalid fieldNumber, expected 1 or 2, got %d", fieldNum)
+		}
+	}
+
+	if links != nil {
+		if err := links.Finish(); err != nil {
+			return err
+		}
+	}
+	return ma.Finish()
+}
+
+func unmarshalLink(reader shared.SlickReader, length int, ma ipld.MapAssembler) error {
+	haveHash := false
+	haveName := false
+	haveTsize := false
+	startOffset := reader.NumRead()
+	for {
+		readBytes := reader.NumRead() - startOffset
+		if readBytes == length {
+			break
+		} else if readBytes > length {
+			return xerrors.Errorf("protobuf: (PBLink) bad length for link")
+		}
+		fieldNum, wireType, err := decodeKey(reader)
+		if err != nil {
+			return err
+		}
+
+		if fieldNum == 1 {
+			if haveHash {
+				return xerrors.Errorf("protobuf: (PBLink) duplicate Hash section")
+			}
+			if haveName {
+				return xerrors.Errorf("protobuf: (PBLink) invalid order, found Name before Hash")
+			}
+			if haveTsize {
+				return xerrors.Errorf("protobuf: (PBLink) invalid order, found Tsize before Hash")
+			}
+			if wireType != 2 {
+				return xerrors.Errorf("protobuf: (PBLink) wrong wireType (%d) for Hash", wireType)
+			}
+
+			var chunk []byte
+			if chunk, err = decodeBytes(reader); err != nil {
 				return err
 			}
-			if err := curLink.AssembleValue().AssignString(string(tok.Bytes)); err != nil {
+			var c cid.Cid
+			if _, c, err = cid.CidFromBytes(chunk); err != nil {
+				return xerrors.Errorf("invalid Hash field found in link, expected CID (%v)", err)
+			}
+			if err := ma.AssembleKey().AssignString("Hash"); err != nil {
 				return err
 			}
-		case pb.TypeTSize:
-			if err := curLink.AssembleKey().AssignString("Tsize"); err != nil {
+			if err := ma.AssembleValue().AssignLink(cidlink.Link{Cid: c}); err != nil {
 				return err
 			}
-			if err := curLink.AssembleValue().AssignInt(int(tok.Int)); err != nil {
+			haveHash = true
+		} else if fieldNum == 2 {
+			if haveName {
+				return xerrors.Errorf("protobuf: (PBLink) duplicate Name section")
+			}
+			if haveTsize {
+				return xerrors.Errorf("protobuf: (PBLink) invalid order, found Tsize before Name")
+			}
+			if wireType != 2 {
+				return xerrors.Errorf("protobuf: (PBLink) wrong wireType (%d) for Name", wireType)
+			}
+
+			var chunk []byte
+			if chunk, err = decodeBytes(reader); err != nil {
+				return err
+			}
+			if err := ma.AssembleKey().AssignString("Name"); err != nil {
+				return err
+			}
+			if err := ma.AssembleValue().AssignString(string(chunk)); err != nil {
+				return err
+			}
+			haveName = true
+		} else if fieldNum == 3 {
+			if haveTsize {
+				return xerrors.Errorf("protobuf: (PBLink) duplicate Tsize section")
+			}
+			if wireType != 0 {
+				return xerrors.Errorf("protobuf: (PBLink) wrong wireType (%d) for Tsize", wireType)
+			}
+
+			var v uint64
+			if v, err = decodeVarint(reader); err != nil {
+				return err
+			}
+			if err := ma.AssembleKey().AssignString("Tsize"); err != nil {
 				return err
 			}
+			if err := ma.AssembleValue().AssignInt(int(v)); err != nil {
+				return err
+			}
+			haveTsize = true
+		} else {
+			return xerrors.Errorf("protobuf: (PBLink) invalid fieldNumber, expected 1, 2 or 3, got %d", fieldNum)
 		}
-		return nil
 	}
 
-	if err := pb.Unmarshal(reader, tokenReceiver); err != nil {
-		return err
+	if !haveHash {
+		return xerrors.Errorf("invalid Hash field found in link, expected CID")
 	}
-	if links != nil {
-		if err := links.Finish(); err != nil {
-			return err
+
+	return nil
+}
+
+func decodeKey(reader shared.SlickReader) (int, int, error) {
+	var wire uint64
+	var err error
+	if wire, err = decodeVarint(reader); err != nil {
+		return 0, 0, err
+	}
+	fieldNum := int(wire >> 3)
+	wireType := int(wire & 0x7)
+	return fieldNum, wireType, nil
+}
+
+func decodeBytes(reader shared.SlickReader) ([]byte, error) {
+	bytesLen, err := decodeVarint(reader)
+	if err != nil {
+		return nil, err
+	}
+	byts, err := reader.Readn(int(bytesLen))
+	if err != nil {
+		return nil, xerrors.Errorf("protobuf: unexpected read error: %w", err)
+	}
+	return byts, nil
+}
+
+func decodeVarint(reader shared.SlickReader) (uint64, error) {
+	var v uint64
+	for shift := uint(0); ; shift += 7 {
+		if shift >= 64 {
+			return 0, ErrIntOverflow
+		}
+		b, err := reader.Readn1()
+		if err != nil {
+			return 0, xerrors.Errorf("protobuf: unexpected read error: %w", err)
+		}
+		v |= uint64(b&0x7F) << shift
+		if b < 0x80 {
+			break
 		}
 	}
-	return ma.Finish()
+	return v, nil
 }