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(_: *mut c_void, _: FfiResult, _: u64)
)

Get a size of file opened for read.

Callback parameters: user data, error code, file size