boc_sys/
vsizeof.rs

1use core::mem;
2
3// Only used for size calculations.
4#[allow(dead_code)]
5#[repr(C)]
6#[cfg_attr(target_pointer_width = "64", repr(align(16)))]
7struct ObjectHeader {
8    f1: *mut (),
9    f2: *mut (),
10    #[cfg(feature = "systematic_testing")]
11    f3: *mut (),
12}
13
14const SIZEOF_OBJECT_HEADER: usize = mem::size_of::<ObjectHeader>();
15const OBJECT_ALIGNMENT: usize = mem::align_of::<ObjectHeader>();
16
17/// Returns the size required for a Verona object to embed the rust object T.
18///
19// The runtime stores an object header below the returned pointer, but we still
20// need space for it in the allocation.
21pub const fn vsizeof<T>() -> usize {
22    // port of vsizeof from rt/object/object.h
23    align_up(mem::size_of::<T>() + SIZEOF_OBJECT_HEADER, OBJECT_ALIGNMENT)
24}
25
26const fn align_up(value: usize, alignment: usize) -> usize {
27    // port of align_up from snmalloc/ds_core/bits.h
28    assert!(alignment.is_power_of_two());
29    let align_1 = alignment - 1;
30    (value + align_1) & !align_1
31}
32
33#[cfg(test)]
34mod tests {
35    use super::*;
36
37    extern "C" {
38        fn boxcar_vsizeof_info(sizeof_object_header: &mut usize, object_alignment: &mut usize);
39        fn boxcar_vsizeof_examples(
40            bool: &mut usize,
41            i32: &mut usize,
42            voidstar: &mut usize,
43            charx17: &mut usize,
44        );
45    }
46
47    #[test]
48    fn metadata() {
49        let mut sizeof_object_header = 0;
50        let mut object_alignment = 0;
51
52        unsafe {
53            boxcar_vsizeof_info(&mut sizeof_object_header, &mut object_alignment);
54        }
55
56        assert_eq!(sizeof_object_header, SIZEOF_OBJECT_HEADER);
57        assert_eq!(object_alignment, OBJECT_ALIGNMENT)
58    }
59
60    #[test]
61    fn examples() {
62        let mut bool_ = 0;
63        let mut i32_ = 0;
64        let mut voidstar = 0;
65        let mut charx17_ = 0;
66
67        unsafe { boxcar_vsizeof_examples(&mut bool_, &mut i32_, &mut voidstar, &mut charx17_) }
68
69        assert_eq!(bool_, vsizeof::<bool>());
70        assert_eq!(i32_, vsizeof::<i32>());
71        assert_eq!(voidstar, vsizeof::<*mut ()>());
72        assert_eq!(charx17_, vsizeof::<[u8; 17]>());
73    }
74}
boc_sys/vsizeof.rs

boc_sys/
vsizeof.rs
