src/test/run-pass/packed-struct-layout.rs

   1 // Copyright 2013 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11
  12 use std::mem;
  13
  14 #[repr(packed)]
  15 struct S4 {
  16     a: u8,
  17     b: [u8; 3],
  18 }
  19
  20 #[repr(packed)]
  21 struct S5 {
  22     a: u8,
  23     b: u32
  24 }
  25
  26 pub fn main() {
  27     unsafe {
  28         let s4 = S4 { a: 1, b: [2,3,4] };
  29         let transd : [u8; 4] = mem::transmute(s4);
  30         assert_eq!(transd, [1, 2, 3, 4]);
  31
  32         let s5 = S5 { a: 1, b: 0xff_00_00_ff };
  33         let transd : [u8; 5] = mem::transmute(s5);
  34         // Don't worry about endianness, the u32 is palindromic.
  35         assert_eq!(transd, [1, 0xff, 0, 0, 0xff]);
  36     }
  37 }