Function libheif_sys::heif_image_handle_get_number_of_metadata_blocks

pub unsafe extern "C" fn heif_image_handle_get_number_of_metadata_blocks(
    handle: *const heif_image_handle,
    type_filter: *const c_char
) -> c_int

How many metadata blocks are attached to an image. If you only want to get EXIF data, set the type_filter to “Exif”. Otherwise, set the type_filter to NULL.