Return hdrSize in ListPack

internal/pack/pack.go

@@ -252,21 +252,24 @@ func (e InvalidFileError) Error() string {
 	return e.Message
 }
 
-// List returns the list of entries found in a pack file.
-func List(k *crypto.Key, rd io.ReaderAt, size int64) (entries []restic.Blob, err error) {
+// List returns the list of entries found in a pack file and the length of the
+// header (including header size and crypto overhead)
+func List(k *crypto.Key, rd io.ReaderAt, size int64) (entries []restic.Blob, hdrSize uint32, err error) {
 	buf, err := readHeader(rd, size)
 	if err != nil {
-		return nil, err
+		return nil, 0, err
 	}
 
 	if len(buf) < k.NonceSize()+k.Overhead() {
-		return nil, errors.New("invalid header, too small")
+		return nil, 0, errors.New("invalid header, too small")
 	}
 
+	hdrSize = headerLengthSize + uint32(len(buf))
+
 	nonce, buf := buf[:k.NonceSize()], buf[k.NonceSize():]
 	buf, err = k.Open(buf[:0], nonce, buf, nil)
 	if err != nil {
-		return nil, err
+		return nil, 0, err
 	}
 
 	entries = make([]restic.Blob, 0, uint(len(buf))/entrySize)
@@ -275,7 +278,7 @@ func List(k *crypto.Key, rd io.ReaderAt, size int64) (entries []restic.Blob, err
 	for len(buf) > 0 {
 		entry, err := parseHeaderEntry(buf)
 		if err != nil {
-			return nil, err
+			return nil, 0, err
 		}
 		entry.Offset = pos
 
@@ -284,7 +287,7 @@ func List(k *crypto.Key, rd io.ReaderAt, size int64) (entries []restic.Blob, err
 		buf = buf[entrySize:]
 	}
 
-	return entries, nil
+	return entries, hdrSize, nil
 }
 
 // PackedSizeOfBlob returns the size a blob actually uses when saved in a pack

internal/pack/pack_test.go

@@ -53,19 +53,18 @@ func verifyBlobs(t testing.TB, bufs []Buf, k *crypto.Key, rd io.ReaderAt, packSi
 	for _, buf := range bufs {
 		written += len(buf.data)
 	}
-	// header length
-	written += binary.Size(uint32(0))
-	// header + header crypto
-	headerSize := len(bufs) * (binary.Size(restic.BlobType(0)) + binary.Size(uint32(0)) + len(restic.ID{}))
-	written += restic.CiphertextLength(headerSize)
+	// header length + header + header crypto
+	headerSize := binary.Size(uint32(0)) + restic.CiphertextLength(len(bufs)*int(pack.EntrySize))
+	written += headerSize
 
 	// check length
 	rtest.Equals(t, uint(written), packSize)
 
 	// read and parse it again
-	entries, err := pack.List(k, rd, int64(packSize))
+	entries, hdrSize, err := pack.List(k, rd, int64(packSize))
 	rtest.OK(t, err)
 	rtest.Equals(t, len(entries), len(bufs))
+	rtest.Equals(t, headerSize, int(hdrSize))
 
 	var buf []byte
 	for i, b := range bufs {