1 files changed, 60 insertions, 0 deletions
diff --git a/internal/contentenc/file_header.go b/internal/contentenc/file_header.go
new file mode 100644
index 0000000..8a9dd2c
--- /dev/null
+++ b/internal/contentenc/file_header.go
@@ -0,0 +1,60 @@
+package contentenc
+
+// Per-file header
+//
+// Format: [ "Version" uint16 big endian ] [ "Id" 16 random bytes ]
+
+import (
+	"encoding/binary"
+	"fmt"
+
+	"github.com/rfjakob/gocryptfs/internal/cryptocore"
+)
+
+const (
+	// Current On-Disk-Format version
+	CurrentVersion = 2
+
+	HEADER_VERSION_LEN     = 2                                  // uint16
+	HEADER_ID_LEN          = 16                                 // 128 bit random file id
+	HEADER_LEN             = HEADER_VERSION_LEN + HEADER_ID_LEN // Total header length
+)
+
+type FileHeader struct {
+	Version uint16
+	Id      []byte
+}
+
+// Pack - serialize fileHeader object
+func (h *FileHeader) Pack() []byte {
+	if len(h.Id) != HEADER_ID_LEN || h.Version != CurrentVersion {
+		panic("FileHeader object not properly initialized")
+	}
+	buf := make([]byte, HEADER_LEN)
+	binary.BigEndian.PutUint16(buf[0:HEADER_VERSION_LEN], h.Version)
+	copy(buf[HEADER_VERSION_LEN:], h.Id)
+	return buf
+
+}
+
+// ParseHeader - parse "buf" into fileHeader object
+func ParseHeader(buf []byte) (*FileHeader, error) {
+	if len(buf) != HEADER_LEN {
+		return nil, fmt.Errorf("ParseHeader: invalid length: got %d, want %d", len(buf), HEADER_LEN)
+	}
+	var h FileHeader
+	h.Version = binary.BigEndian.Uint16(buf[0:HEADER_VERSION_LEN])
+	if h.Version != CurrentVersion {
+		return nil, fmt.Errorf("ParseHeader: invalid version: got %d, want %d", h.Version, CurrentVersion)
+	}
+	h.Id = buf[HEADER_VERSION_LEN:]
+	return &h, nil
+}
+
+// RandomHeader - create new fileHeader object with random Id
+func RandomHeader() *FileHeader {
+	var h FileHeader
+	h.Version = CurrentVersion
+	h.Id = cryptocore.RandBytes(HEADER_ID_LEN)
+	return &h
+}