projecture 0.0.4

Easy arbitrary type projections without proc macros
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
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162

use crate::{
    CustomWrapper, DerefProjectable, FinalizeProjection, Helper, Marker, Owned, Projectable,
    ProjectableMarker, SupportsPacked,
};
use core::marker::PhantomData;
use core::mem::transmute_copy;
use core::ptr::null_mut;

unsafe impl<T> CustomWrapper for Option<T> {
    type Output = Option<Owned<T>>;
}
unsafe impl<'a, T> CustomWrapper for &Option<&'a T> {
    type Output = Option<Helper<&'a T>>;
}
unsafe impl<'a, T> CustomWrapper for &Option<&'a mut T> {
    type Output = Option<Helper<&'a mut T>>;
}
unsafe impl<T: CustomWrapper> CustomWrapper for &&Option<T> {
    type Output = Option<T::Output>;
}
unsafe impl<T> Projectable for Option<Owned<T>> {
    type Target = T;
    type Marker = OptionMarker<<Owned<T> as Projectable>::Marker>;

    fn get_raw(&self) -> (*mut Self::Target, Self::Marker) {
        (
            unsafe { core::mem::transmute(self.as_ref()) },
            self.as_ref().map(|_| Marker::new()).into(),
        )
    }
}

// unsafe impl<'a, T> Projectable for &Option<T>
// where
//     Helper<T>: Projectable,
// {
//     type Target = <Helper<T> as Projectable>::Target;
//     type Marker = Option<<Helper<T> as Projectable>::Marker>;
//
//     fn get_raw(&self) -> (*mut Self::Target, Self::Marker) {
//         if let Some(x) = self {
//             let (raw, marker) = unsafe { &*(x as *const T as *const Helper<T>) }.get_raw();
//             (raw as _, Some(marker))
//         } else {
//             (null_mut(), None)
//         }
//     }
// }
#[repr(transparent)]
pub struct OptionMarker<T>(Option<T>);
impl<T> OptionMarker<T> {
    pub fn check(&self) {}
}
impl<T> From<Option<T>> for OptionMarker<T> {
    fn from(from: Option<T>) -> Self {
        OptionMarker(from)
    }
}

unsafe impl<T> Projectable for &&Option<T>
where
    T: Projectable,
{
    type Target = T::Target;
    type Marker = OptionMarker<T::Marker>;

    fn get_raw(&self) -> (*mut Self::Target, Self::Marker) {
        if let Some(x) = self {
            let (raw, marker) = x.get_raw();
            (raw as _, Some(marker).into())
        } else {
            (null_mut(), None.into())
        }
    }
}
unsafe impl<'a, T> Projectable for &&&'a Option<T>
where
    &'a T: Projectable,
{
    type Target = <&'a T as Projectable>::Target;
    type Marker = OptionMarker<<&'a T as Projectable>::Marker>;

    fn get_raw(&self) -> (*mut Self::Target, Self::Marker) {
        if let Some(x) = self {
            let (raw, marker) = x.get_raw();
            (raw as _, Some(marker).into())
        } else {
            (null_mut(), None.into())
        }
    }
}

impl<T, M: ProjectableMarker<T>> ProjectableMarker<T> for OptionMarker<M> {
    type Output = Option<M::Output>;

    unsafe fn from_raw(&self, raw: *mut T) -> Self::Output {
        self.0.as_ref().map(|m| m.from_raw(raw))
    }
}

impl<T: FinalizeProjection> FinalizeProjection for Option<T> {
    type Output = Option<T::Output>;

    unsafe fn finalize(&self) -> Self::Output {
        self.as_ref().map(|x| x.finalize())
    }
}

// todo make more general Option flattening
impl<T> FinalizeProjection for &Option<Option<T>> {
    type Output = Option<T>;

    unsafe fn finalize(&self) -> Self::Output {
        if let Some(Some(x)) = self {
            Some(transmute_copy(x))
        } else {
            None
        }
    }
}

unsafe impl<T: DerefProjectable> DerefProjectable for Option<T>
where
    // temporary limitation
    T::Target: Sized,
{
    type Target = T::Target;
    type Marker = OptionMarker<T::Marker>;

    fn deref_raw(&self) -> (*mut Self::Target, Self::Marker) {
        if let Some(x) = self {
            let (raw, marker) = x.deref_raw();
            (raw, Some(marker).into())
        } else {
            (null_mut(), None.into())
        }
    }
}
unsafe impl<'a, T, Target, Marker> DerefProjectable for &'a Option<T>
where
    &'a T: DerefProjectable<Target = Target, Marker = Marker>,
{
    type Target = Target;
    type Marker = OptionMarker<Marker>;

    fn deref_raw(&self) -> (*mut Self::Target, Self::Marker) {
        if let Some(x) = self {
            let (raw, marker) = x.deref_raw();
            (raw, Some(marker).into())
        } else {
            (null_mut(), None.into())
        }
    }
}

unsafe impl<'a, 'b, ToCheck, NotPacked, M> SupportsPacked
    for &'a (*mut ToCheck, &'b OptionMarker<M>, PhantomData<NotPacked>)
where
    &'a (*mut ToCheck, &'b M, PhantomData<NotPacked>): SupportsPacked<Result = NotPacked>,
{
    type Result = NotPacked;
}