const-field-offset 0.2.0

Derive macro providing const field offsets using core::mem::offset_of!
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125

// Copyright © SixtyFPS GmbH <info@slint.dev>
// SPDX-License-Identifier: MIT OR Apache-2.0

use const_field_offset::*;
use std::mem::offset_of;
use std::sync::atomic::Ordering::SeqCst;

#[derive(FieldOffsets)]
struct MyStruct {
    a: u8,
    b: u16,
    c: u8,
    d: u16,
}

#[derive(FieldOffsets)]
struct MyStruct2 {
    k: core::cell::Cell<isize>,
    xx: MyStruct,
    v: u32,
}

#[derive(FieldOffsets)]
#[allow(unused)]
struct MyStruct3 {
    ms2: MyStruct2,
}

const XX_CONST: usize = MyStruct2::FIELD_OFFSETS.xx().get_byte_offset();
static D_STATIC: usize = MyStruct::FIELD_OFFSETS.d().get_byte_offset();

#[test]
fn test() {
    assert_eq!(offset_of!(MyStruct, a), MyStruct::FIELD_OFFSETS.a().get_byte_offset());
    assert_eq!(offset_of!(MyStruct, b), MyStruct::FIELD_OFFSETS.b().get_byte_offset());
    assert_eq!(offset_of!(MyStruct, c), MyStruct::FIELD_OFFSETS.c().get_byte_offset());
    assert_eq!(offset_of!(MyStruct, d), MyStruct::FIELD_OFFSETS.d().get_byte_offset());
    assert_eq!(offset_of!(MyStruct2, xx), MyStruct2::FIELD_OFFSETS.xx().get_byte_offset());
    assert_eq!(offset_of!(MyStruct2, v), MyStruct2::FIELD_OFFSETS.v().get_byte_offset());
    assert_eq!(offset_of!(MyStruct2, k), MyStruct2::FIELD_OFFSETS.k().get_byte_offset());

    assert_eq!(XX_CONST, offset_of!(MyStruct2, xx));
    assert_eq!(D_STATIC, offset_of!(MyStruct, d));
}

#[derive(FieldOffsets)]
#[pin]
#[allow(dead_code)]
struct MyStructPin {
    phantom: core::marker::PhantomPinned,
    pub a: u8,
    b: u16,
    c: u8,
    d: u16,
}

#[derive(FieldOffsets)]
#[pin]
#[allow(dead_code)]
struct MyStruct2Pin {
    phantom: core::marker::PhantomPinned,
    k: core::cell::Cell<isize>,
    xx: MyStruct,
    v: u32,
}

const XX_CONST_PIN: usize = MyStruct2Pin::FIELD_OFFSETS.xx().get_byte_offset();
static D_STATIC_PIN: usize = MyStructPin::FIELD_OFFSETS.d().get_byte_offset();

#[test]
fn test_pin() {
    assert_eq!(offset_of!(MyStructPin, a), MyStructPin::FIELD_OFFSETS.a().get_byte_offset());
    assert_eq!(offset_of!(MyStructPin, b), MyStructPin::FIELD_OFFSETS.b().get_byte_offset());
    assert_eq!(offset_of!(MyStructPin, c), MyStructPin::FIELD_OFFSETS.c().get_byte_offset());
    assert_eq!(offset_of!(MyStructPin, d), MyStructPin::FIELD_OFFSETS.d().get_byte_offset());
    assert_eq!(offset_of!(MyStruct2Pin, xx), MyStruct2Pin::FIELD_OFFSETS.xx().get_byte_offset());
    assert_eq!(offset_of!(MyStruct2Pin, v), MyStruct2Pin::FIELD_OFFSETS.v().get_byte_offset());
    assert_eq!(offset_of!(MyStruct2Pin, k), MyStruct2Pin::FIELD_OFFSETS.k().get_byte_offset());

    assert_eq!(XX_CONST_PIN, offset_of!(MyStruct2Pin, xx));
    assert_eq!(D_STATIC_PIN, offset_of!(MyStructPin, d));
}

static DROP_CALLED: std::sync::atomic::AtomicBool = std::sync::atomic::AtomicBool::new(false);

#[derive(FieldOffsets)]
#[pin]
#[pin_drop]
#[allow(dead_code)]
struct MyPinnedStructWithDrop {
    x: u32,
}

impl PinnedDrop for MyPinnedStructWithDrop {
    fn drop(self: core::pin::Pin<&mut MyPinnedStructWithDrop>) {
        DROP_CALLED.store(true, SeqCst);
    }
}

#[test]
fn test_pin_drop() {
    DROP_CALLED.store(false, SeqCst);
    {
        let _instance = Box::pin(MyPinnedStructWithDrop { x: 42 });
    }
    assert!(DROP_CALLED.load(SeqCst));
}

mod priv_mod {
    #[derive(const_field_offset::FieldOffsets)]
    #[repr(C)]
    struct PrivStruct {
        pub a: u32,
        pub b: Vec<PrivStruct>,
    }

    #[allow(unused)]
    #[derive(const_field_offset::FieldOffsets)]
    #[repr(C)]
    pub struct PubStruct {
        pub a: u32,
        b: Vec<PrivStruct>,
        pub r#mod: Vec<PubStruct>,
    }
}