Static memory mapped file in Rust

file_bytes.rs

pub fn file_bytes(filename: &std::path::PathBuf) -> &'static [u8] {
    
    let mut filename = String::from(filename.as_path().to_str().expect("Unexpected file name"));
    filename.push('\0');

    let file = unsafe {
        CreateFileA(
            filename.as_bytes().as_ptr(),
            FILE_GENERIC_READ,
            FILE_SHARE_READ,
            0,
            OPEN_EXISTING,
            FILE_ATTRIBUTE_NORMAL,
            0,
        )
    };

    if file == -1 {
        panic!("Failed to open file `{}`", filename);
    }

    let mut size = 0;
    unsafe { GetFileSizeEx(file, &mut size) };

    if size == 0 {
        return &[];
    }

    unsafe {
    let mapping =
         CreateFileMappingW(file, 0, PAGE_READONLY, 0, 0, 0);

    let data =  MapViewOfFile(mapping, FILE_MAP_READ, 0, 0, 0) as _;
     std::slice::from_raw_parts_mut(data, size as usize) 
    }
}

#[link(name = "KERNEL32")]
extern "system" {
    fn CreateFileA(
        lpfilename: *const u8,
        dwdesiredaccess: u32,
        dwsharemode: u32,
        lpsecurityattributes : isize,
        dwcreationdisposition: u32,
        dwflagsandattributes: u32,
        htemplatefile: isize,
    ) -> isize;
    fn CreateFileMappingW(
        hfile: isize,
        lpfilemappingattributes : isize,
        flprotect: u32,
        dwmaximumsizehigh: u32,
        dwmaximumsizelow: u32,
        lpname: isize,
    ) -> isize;
    fn GetFileSizeEx(
        hfile: isize,
        lpfilesize: *mut i64,
    ) -> i32;
    fn MapViewOfFile(
        hfilemappingobject: isize,
        dwdesiredaccess: u32,
        dwfileoffsethigh: u32,
        dwfileoffsetlow: u32,
        dwnumberofbytestomap: usize,
    ) -> *mut ::std::ffi::c_void;
}

const FILE_ATTRIBUTE_NORMAL: u32 = 128u32;
const FILE_GENERIC_READ: u32 = 1179785u32;
const FILE_SHARE_READ: u32 = 1u32;
const FILE_MAP_READ: u32 = 4u32;
const PAGE_READONLY: u32 = 2u32;
const OPEN_EXISTING: u32 = 3u32;