object/header: Use sentinel errors

1 files changed, 6 insertions, 5 deletions

diff --git a/object/header/parse.go b/object/header/parse.go
index cdefe74e..0958c0dd 100644
--- a/object/header/parse.go
+++ b/object/header/parse.go
@@ -3,6 +3,7 @@ package header
 import (
 	"bytes"
 	"errors"
+	"fmt"
 	"strconv"
 
 	"lindenii.org/go/furgit/object/typ"
@@ -14,29 +15,29 @@ var ErrInvalidHeader = errors.New("object/header: invalid header")
 func Parse(data []byte) (ty typ.Type, size uint64, consumed int, err error) {
 	space := bytes.IndexByte(data, ' ')
 	if space <= 0 {
-		return 0, 0, 0, ErrInvalidHeader
+		return 0, 0, 0, fmt.Errorf("%w: missing ' ' type/size separator", ErrInvalidHeader)
 	}
 
 	nulRel := bytes.IndexByte(data[space+1:], 0)
 	if nulRel < 0 {
-		return 0, 0, 0, ErrInvalidHeader
+		return 0, 0, 0, fmt.Errorf("%w: missing NUL terminator", ErrInvalidHeader)
 	}
 
 	nul := space + 1 + nulRel
 
 	ty, err = typ.Parse(string(data[:space]))
 	if err != nil {
-		return 0, 0, 0, ErrInvalidHeader
+		return 0, 0, 0, fmt.Errorf("%w: type %q: %w", ErrInvalidHeader, data[:space], err)
 	}
 
 	sizeBytes := data[space+1 : nul]
 	if len(sizeBytes) == 0 {
-		return 0, 0, 0, ErrInvalidHeader
+		return 0, 0, 0, fmt.Errorf("%w: empty size field", ErrInvalidHeader)
 	}
 
 	size, err = strconv.ParseUint(string(sizeBytes), 10, 64)
 	if err != nil {
-		return 0, 0, 0, ErrInvalidHeader
+		return 0, 0, 0, fmt.Errorf("%w: size %q: %w", ErrInvalidHeader, sizeBytes, err)
 	}
 
 	return ty, size, nul + 1, nil