mmap.rs

fn main() {
    let buf = unsafe { mmap_stdin() };
}

#[link(name = "c")]
extern {
    fn mmap(addr: *mut u8, len: usize, prot: i32, flags: i32, fd: i32, offset: i64) -> *mut u8;
    fn __errno_location() -> *const i32;
    fn lseek(fd: i32, offset: i64, whence: i32) -> i64;
    fn open(path: *const u8, oflag: i32) -> i32;
}

#[allow(dead_code)]
unsafe fn mmap_stdin<'a>() -> &'a [u8] {
    mmap_fd(0)
}

#[allow(dead_code)]
unsafe fn mmap_path<'a>(path: &str) -> &'a [u8] {
    let mut path2 = vec![];
    path2.extend_from_slice(path.as_bytes());
    path2.push(0);
    let fd = open(path2.as_ptr(), 0);
    if fd == -1 {
        panic!("open failed, errno {}", *__errno_location());
    }
    mmap_fd(fd)
}

unsafe fn mmap_fd<'a>(fd: i32) -> &'a [u8] {
    let seek_end = 2;
    let size = lseek(fd, 0, seek_end);
    if size == -1 {
        panic!("lseek failed, errno {}", *__errno_location());
    }
    let prot_read = 0x01;
    let map_private = 0x02;
    let map_populate = 0x08000;
    let ptr = mmap(0 as _, size as usize, prot_read, map_private | map_populate, fd, 0);
    if ptr as isize == -1 {
        panic!("mmap failed, errno {}", *__errno_location());
    }
    std::slice::from_raw_parts(ptr, size as usize)
}