Function safe_app::ffi::nfs::file_size

#[no_mangle]
pub unsafe extern "C" fn file_size(
    app: *const App, 
    file_h: FileContextHandle, 
    user_data: *mut c_void, 
    o_cb: extern "C" fn(user_data: *mut c_void, result: *const FfiResult, size: u64)
)

Get a size of file opened for read.