(@ file-format bytes +-
    ('// bytes >
        [IS_PNG] / FILE_PNG
    >
        [IS_JPEG] / FILE_JPG
    >
        [IS_GIF87] / FILE_GIF
    >
        [IS_GIF89A] / FILE_GIF
    >
        [IS_PM_ICON] / FILE_ICO
    >
        [IS_PM_BITMAP] / FILE_BMP
    >
        (exit ERR_FILE_FORMAT)
    )
+
    {array : integer : 2^8} bytes
)
