musli/context/
capture.rs

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1use core::cell::UnsafeCell;
2use core::error::Error;
3use core::fmt;
4use core::marker::PhantomData;
5
6use crate::alloc::{self, Allocator, String};
7#[cfg(feature = "alloc")]
8use crate::alloc::{System, SYSTEM};
9use crate::Context;
10
11use super::{ContextError, ErrorMarker};
12
13/// A simple non-diagnostical capturing context.
14pub struct Capture<M, E, A>
15where
16    E: ContextError,
17{
18    alloc: A,
19    error: UnsafeCell<Option<E>>,
20    _marker: PhantomData<M>,
21}
22
23#[cfg(feature = "alloc")]
24#[cfg_attr(doc_cfg, doc(cfg(feature = "alloc")))]
25impl<M, E> Capture<M, E, &'static System>
26where
27    E: ContextError,
28{
29    /// Construct a new capturing context using the [`System`] allocator.
30    pub fn new() -> Self {
31        Self::with_alloc(&SYSTEM)
32    }
33}
34
35impl<M, E, A> Capture<M, E, A>
36where
37    E: ContextError,
38{
39    /// Construct a new capturing allocator.
40    pub fn with_alloc(alloc: A) -> Self {
41        Self {
42            alloc,
43            error: UnsafeCell::new(None),
44            _marker: PhantomData,
45        }
46    }
47
48    /// Construct an error or panic.
49    pub fn unwrap(self) -> E {
50        let Some(error) = self.error.into_inner() else {
51            return E::message("no error captured");
52        };
53
54        error
55    }
56}
57
58impl<M, E, A> Context for Capture<M, E, A>
59where
60    M: 'static,
61    E: ContextError,
62    A: Allocator,
63{
64    type Mode = M;
65    type Error = ErrorMarker;
66    type Mark = ();
67    type Allocator = A;
68    type String<'this> = String<'this, A> where Self: 'this;
69
70    #[inline]
71    fn clear(&self) {
72        // SAFETY: We're restricting access to the context, so that this is
73        // safe.
74        unsafe {
75            (*self.error.get()) = None;
76        }
77    }
78
79    #[inline]
80    fn alloc(&self) -> &Self::Allocator {
81        &self.alloc
82    }
83
84    #[inline]
85    fn collect_string<T>(&self, value: &T) -> Result<Self::String<'_>, Self::Error>
86    where
87        T: ?Sized + fmt::Display,
88    {
89        alloc::collect_string(self, value)
90    }
91
92    #[inline]
93    fn custom<T>(&self, error: T) -> ErrorMarker
94    where
95        T: 'static + Send + Sync + Error,
96    {
97        // SAFETY: We're restricting access to the context, so that this is
98        // safe.
99        unsafe {
100            self.error.get().replace(Some(E::custom(error)));
101        }
102
103        ErrorMarker
104    }
105
106    #[inline]
107    fn message<T>(&self, message: T) -> ErrorMarker
108    where
109        T: fmt::Display,
110    {
111        // SAFETY: We're restricting access to the context, so that this is
112        // safe.
113        unsafe {
114            self.error.get().replace(Some(E::message(message)));
115        }
116
117        ErrorMarker
118    }
119}
120
121#[cfg(feature = "alloc")]
122#[cfg_attr(doc_cfg, doc(cfg(feature = "alloc")))]
123impl<M, E> Default for Capture<M, E, &'static System>
124where
125    E: ContextError,
126{
127    #[inline]
128    fn default() -> Self {
129        Self::new()
130    }
131}
musli/context/capture.rs

musli/context/
capture.rs
