diplomat_runtime/
result.rs

1use core::fmt;
2use core::mem::ManuallyDrop;
3
4#[repr(C)]
5union DiplomatResultValue<T, E> {
6    ok: ManuallyDrop<T>,
7    err: ManuallyDrop<E>,
8}
9
10/// A [`Result`]-like type that can be passed across the FFI boundary
11/// as a value. Used internally to return [`Result`]s and [`Option`]s
12/// from functions.
13#[repr(C)]
14pub struct DiplomatResult<T, E> {
15    value: DiplomatResultValue<T, E>,
16    pub is_ok: bool,
17}
18
19/// A type to represent Option<T> over FFI.
20///
21/// Used internally to handle `Option<T>` arguments and return types, and needs to be
22/// used explicitly for optional struct fields.
23pub type DiplomatOption<T> = DiplomatResult<T, ()>;
24
25impl<T, E> DiplomatResult<T, E> {
26    pub fn as_ref(&self) -> Result<&T, &E> {
27        // Safety: we're only accessing the union variants when the flag is correct
28        unsafe {
29            if self.is_ok {
30                Ok(&self.value.ok)
31            } else {
32                Err(&self.value.err)
33            }
34        }
35    }
36}
37
38impl<T> DiplomatOption<T> {
39    /// Helper for converting into an Option to avoid trait ambiguity errors with Into
40    #[inline]
41    pub fn into_option(self) -> Option<T> {
42        self.into()
43    }
44
45    /// Helper for converting into an Option with the inner type converted
46    #[inline]
47    pub fn into_converted_option<U: From<T>>(self) -> Option<U> {
48        self.into_option().map(Into::into)
49    }
50}
51
52impl<T: Clone, E: Clone> Clone for DiplomatResult<T, E> {
53    fn clone(&self) -> Self {
54        unsafe {
55            if self.is_ok {
56                Ok((*self.value.ok).clone()).into()
57            } else {
58                Err((*self.value.err).clone()).into()
59            }
60        }
61    }
62}
63
64impl<T, E> Drop for DiplomatResult<T, E> {
65    fn drop(&mut self) {
66        unsafe {
67            if self.is_ok {
68                let _ = ManuallyDrop::take(&mut self.value.ok);
69            } else {
70                let _ = ManuallyDrop::take(&mut self.value.err);
71            }
72        }
73    }
74}
75
76impl<T, E> From<Result<T, E>> for DiplomatResult<T, E> {
77    fn from(result: Result<T, E>) -> Self {
78        match result {
79            Result::Ok(ok) => DiplomatResult {
80                value: DiplomatResultValue {
81                    ok: ManuallyDrop::new(ok),
82                },
83                is_ok: true,
84            },
85
86            Result::Err(err) => DiplomatResult {
87                value: DiplomatResultValue {
88                    err: ManuallyDrop::new(err),
89                },
90                is_ok: false,
91            },
92        }
93    }
94}
95
96impl<T> From<Option<T>> for DiplomatOption<T> {
97    fn from(option: Option<T>) -> Self {
98        option.ok_or(()).into()
99    }
100}
101
102impl<T> From<DiplomatOption<T>> for Option<T> {
103    fn from(result: DiplomatOption<T>) -> Self {
104        Result::<T, ()>::from(result).ok()
105    }
106}
107
108impl<T, E> From<DiplomatResult<T, E>> for Result<T, E> {
109    fn from(mut result: DiplomatResult<T, E>) -> Result<T, E> {
110        unsafe {
111            if result.is_ok {
112                Ok(ManuallyDrop::take(&mut result.value.ok))
113            } else {
114                Err(ManuallyDrop::take(&mut result.value.err))
115            }
116        }
117    }
118}
119
120impl<T: fmt::Debug, E: fmt::Debug> fmt::Debug for DiplomatResult<T, E> {
121    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
122        self.as_ref().fmt(f)
123    }
124}
diplomat_runtime/result.rs

diplomat_runtime/
result.rs
