You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: lib.rs
    path of file: ./repos/phaser/phaser/vendor/jemallocator/src
    
    the code of the file until where you have to start completion: // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
// file at the top-
    
    unsafe fn alloc_excess(&mut self, layout: Layout) -> Result<Excess, AllocErr> {
        let flags = layout_to_flags(layout.align(), layout.size());
        let ptr = ffi::mallocx(layout.size(), flags);
        if let Some(nonnull) = NonNull::new(ptr as *mut u8) {
            let excess = ffi::nallocx(layout.size(), flags);
            Ok(Excess(nonnull, excess))
        } else {
            Err(AllocErr)
        }
    }