added mov.Modified

mov.go

@@ -12,14 +12,27 @@ const epochAdjust = 2082844800
 
 // Created attempts to find a created time from the metadata in a .mov file.
 func Created(file io.ReadSeeker) (time.Time, error) {
-	var r time.Time
+	c, _, err := times(file)
+	return c, err
+}
+
+// Modified attempts to find a modification time from the metadata in a .mov
+// file.
+func Modified(file io.ReadSeeker) (time.Time, error) {
+	_, m, err := times(file)
+	return m, err
+}
+
+func times(file io.ReadSeeker) (time.Time, time.Time, error) {
+	var c, m time.Time
+	var i int64
 	var err error
 
 	buf := [8]byte{}
 	for {
 		_, err := file.Read(buf[:])
 		if err != nil {
-			return r, err
+			return c, m, err
 		}
 		if bytes.Equal(buf[4:8], []byte("moov")) {
 			break
@@ -31,26 +44,36 @@ func Created(file io.ReadSeeker) (time.Time, error) {
 
 	_, err = file.Read(buf[:])
 	if err != nil {
-		return r, err
+		return c, m, err
 	}
 
 	s := string(buf[4:8])
 	switch s {
 	case "mvhd":
 		if _, err := file.Seek(4, 1); err != nil {
-			return r, err
+			return c, m, err
 		}
+
 		_, err = file.Read(buf[:4])
 		if err != nil {
-			return r, err
+			return c, m, err
 		}
-		i := int64(binary.BigEndian.Uint32(buf[:4]))
-		c := i - epochAdjust
-		u := time.Unix(c, 0).Local()
-		return u, nil
+
+		i = int64(binary.BigEndian.Uint32(buf[:4]))
+		c := time.Unix(i-epochAdjust, 0).Local()
+
+		_, err = file.Read(buf[:4])
+		if err != nil {
+			return c, m, err
+		}
+
+		i = int64(binary.BigEndian.Uint32(buf[:4]))
+		m := time.Unix(i-epochAdjust, 0).Local()
+
+		return c, m, nil
 	case "cmov":
-		return r, errors.New("moov atom is compressed")
+		return c, m, errors.New("moov atom is compressed")
 	default:
-		return r, errors.New("expected to find 'mvhd' header, didn't")
+		return c, m, errors.New("expected to find 'mvhd' header, didn't")
 	}
 }