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 use std::mem;
  12
  13 #[repr(packed)]
  14 struct S4 {
  15     a: u8,
  16     b: [u8; 3],
  17 }
  18
  19 #[repr(packed)]
  20 struct S5 {
  21     a: u8,
  22     b: u32
  23 }
  24
  25 pub fn main() {
  26     unsafe {
  27         let s4 = S4 { a: 1, b: [2,3,4] };
  28         let transd : [u8; 4] = mem::transmute(s4);
  29         assert!(transd == [1, 2, 3, 4]);
  30
  31         let s5 = S5 { a: 1, b: 0xff_00_00_ff };
  32         let transd : [u8; 5] = mem::transmute(s5);
  33         // Don't worry about endianness, the u32 is palindromic.
  34         assert!(transd == [1, 0xff, 0, 0, 0xff]);
  35     }
  36 }