61 lines
1.5 KiB
Rust
61 lines
1.5 KiB
Rust
#![allow(clippy::disallowed_names)]
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use bytemuck::{offset_of, Zeroable};
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#[test]
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fn test_offset_of_vertex() {
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#[repr(C)]
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struct Vertex {
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pos: [f32; 2],
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uv: [u16; 2],
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color: [u8; 4],
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}
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unsafe impl Zeroable for Vertex {}
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let pos = offset_of!(Zeroable::zeroed(), Vertex, pos);
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let uv = offset_of!(Zeroable::zeroed(), Vertex, uv);
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let color = offset_of!(Zeroable::zeroed(), Vertex, color);
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assert_eq!(pos, 0);
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assert_eq!(uv, 8);
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assert_eq!(color, 12);
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}
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#[test]
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fn test_offset_of_foo() {
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#[derive(Default)]
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struct Foo {
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a: u8,
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b: &'static str,
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c: i32,
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}
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let a_offset = offset_of!(Default::default(), Foo, a);
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let b_offset = offset_of!(Default::default(), Foo, b);
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let c_offset = offset_of!(Default::default(), Foo, c);
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assert_ne!(a_offset, b_offset);
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assert_ne!(b_offset, c_offset);
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// We can't check against hardcoded values for a repr(Rust) type,
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// but prove to ourself this way.
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let foo = Foo::default();
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// Note: offsets are in bytes.
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let as_bytes = &foo as *const _ as *const u8;
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// we're using wrapping_offset here because it's not worth
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// the unsafe block, but it would be valid to use `add` instead,
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// as it cannot overflow.
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assert_eq!(
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&foo.a as *const _ as usize,
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as_bytes.wrapping_add(a_offset) as usize
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);
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assert_eq!(
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&foo.b as *const _ as usize,
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as_bytes.wrapping_add(b_offset) as usize
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);
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assert_eq!(
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&foo.c as *const _ as usize,
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as_bytes.wrapping_add(c_offset) as usize
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);
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}
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