73 lines
1.6 KiB
Rust
73 lines
1.6 KiB
Rust
#![feature(untagged_unions)]
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#[repr(C)]
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#[derive(Clone, Copy)]
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struct Pair<T, U>(T, U);
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#[repr(C)]
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#[derive(Clone, Copy)]
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struct Triple<T>(T, T, T);
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#[repr(C)]
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union U<A: Copy, B: Copy> {
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a: Pair<A, A>,
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b: B,
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}
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#[repr(C)]
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union W<A: Copy, B: Copy> {
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a: A,
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b: B,
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}
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#[cfg(target_endian = "little")]
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unsafe fn check() {
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let mut u = U::<u8, u16> { b: 0xDE_DE };
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u.a.0 = 0xBE;
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assert_eq!(u.b, 0xDE_BE);
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let mut u = U::<u16, u32> { b: 0xDEAD_DEAD };
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u.a.0 = 0xBEEF;
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assert_eq!(u.b, 0xDEAD_BEEF);
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let mut u = U::<u32, u64> { b: 0xDEADBEEF_DEADBEEF };
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u.a.0 = 0xBAADF00D;
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assert_eq!(u.b, 0xDEADBEEF_BAADF00D);
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let mut w = W::<Pair<Triple<u8>, u8>, u32> { b: 0xDEAD_DEAD };
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w.a.0 = Triple(0, 0, 0);
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assert_eq!(w.b, 0xDE00_0000);
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let mut w = W::<Pair<u8, Triple<u8>>, u32> { b: 0xDEAD_DEAD };
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w.a.1 = Triple(0, 0, 0);
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assert_eq!(w.b, 0x0000_00AD);
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}
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#[cfg(target_endian = "big")]
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unsafe fn check() {
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let mut u = U::<u8, u16> { b: 0xDE_DE };
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u.a.0 = 0xBE;
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assert_eq!(u.b, 0xBE_DE);
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let mut u = U::<u16, u32> { b: 0xDEAD_DEAD };
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u.a.0 = 0xBEEF;
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assert_eq!(u.b, 0xBEEF_DEAD);
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let mut u = U::<u32, u64> { b: 0xDEADBEEF_DEADBEEF };
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u.a.0 = 0xBAADF00D;
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assert_eq!(u.b, 0xBAADF00D_DEADBEEF);
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let mut w = W::<Pair<Triple<u8>, u8>, u32> { b: 0xDEAD_DEAD };
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w.a.0 = Triple(0, 0, 0);
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assert_eq!(w.b, 0x0000_00AD);
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let mut w = W::<Pair<u8, Triple<u8>>, u32> { b: 0xDEAD_DEAD };
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w.a.1 = Triple(0, 0, 0);
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assert_eq!(w.b, 0xDE00_0000);
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}
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fn main() {
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unsafe {
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check();
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}
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}
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