gimli/read/
util.rs

1#[cfg(feature = "read")]
2use alloc::boxed::Box;
3#[cfg(feature = "read")]
4use alloc::vec::Vec;
5use core::fmt;
6use core::mem::MaybeUninit;
7use core::ops;
8use core::ptr;
9use core::slice;
10
11mod sealed {
12    /// # Safety
13    /// Implementer must not modify the content in storage.
14    pub unsafe trait Sealed {
15        type Storage;
16
17        fn new_storage() -> Self::Storage;
18
19        fn grow(_storage: &mut Self::Storage, _additional: usize) -> Result<(), CapacityFull> {
20            Err(CapacityFull)
21        }
22    }
23
24    #[derive(Clone, Copy, Debug)]
25    pub struct CapacityFull;
26}
27
28use sealed::*;
29
30/// Marker trait for types that can be used as backing storage when a growable array type is needed.
31///
32/// This trait is sealed and cannot be implemented for types outside this crate.
33pub trait ArrayLike: Sealed {
34    /// Type of the elements being stored.
35    type Item;
36
37    #[doc(hidden)]
38    fn as_slice(storage: &Self::Storage) -> &[MaybeUninit<Self::Item>];
39
40    #[doc(hidden)]
41    fn as_mut_slice(storage: &mut Self::Storage) -> &mut [MaybeUninit<Self::Item>];
42}
43
44// Use macro since const generics can't be used due to MSRV.
45macro_rules! impl_array {
46    () => {};
47    ($n:literal $($rest:tt)*) => {
48        // SAFETY: does not modify the content in storage.
49        unsafe impl<T> Sealed for [T; $n] {
50            type Storage = [MaybeUninit<T>; $n];
51
52            fn new_storage() -> Self::Storage {
53                // SAFETY: An uninitialized `[MaybeUninit<_>; _]` is valid.
54                unsafe { MaybeUninit::uninit().assume_init() }
55            }
56        }
57
58        impl<T> ArrayLike for [T; $n] {
59            type Item = T;
60
61            fn as_slice(storage: &Self::Storage) -> &[MaybeUninit<T>] {
62                storage
63            }
64
65            fn as_mut_slice(storage: &mut Self::Storage) -> &mut [MaybeUninit<T>] {
66                storage
67            }
68        }
69
70        impl_array!($($rest)*);
71    }
72}
73
74#[cfg(feature = "read")]
75macro_rules! impl_box {
76    () => {};
77    ($n:literal $($rest:tt)*) => {
78        // SAFETY: does not modify the content in storage.
79        unsafe impl<T> Sealed for Box<[T; $n]> {
80            type Storage = Box<[MaybeUninit<T>; $n]>;
81
82            fn new_storage() -> Self::Storage {
83                // SAFETY: An uninitialized `[MaybeUninit<_>; _]` is valid.
84                Box::new(unsafe { MaybeUninit::uninit().assume_init() })
85            }
86        }
87
88        impl<T> ArrayLike for Box<[T; $n]> {
89            type Item = T;
90
91            fn as_slice(storage: &Self::Storage) -> &[MaybeUninit<T>] {
92                &storage[..]
93            }
94
95            fn as_mut_slice(storage: &mut Self::Storage) -> &mut [MaybeUninit<T>] {
96                &mut storage[..]
97            }
98        }
99
100        impl_box!($($rest)*);
101    }
102}
103
104impl_array!(0 1 2 3 4 8 16 32 64 128 192);
105#[cfg(feature = "read")]
106impl_box!(0 1 2 3 4 8 16 32 64 128 192);
107
108#[cfg(feature = "read")]
109unsafe impl<T> Sealed for Vec<T> {
110    type Storage = Box<[MaybeUninit<T>]>;
111
112    fn new_storage() -> Self::Storage {
113        Box::new([])
114    }
115
116    fn grow(storage: &mut Self::Storage, additional: usize) -> Result<(), CapacityFull> {
117        let mut vec: Vec<_> = core::mem::replace(storage, Box::new([])).into();
118        vec.reserve(additional);
119        // SAFETY: This is a `Vec` of `MaybeUninit`.
120        unsafe { vec.set_len(vec.capacity()) };
121        *storage = vec.into_boxed_slice();
122        Ok(())
123    }
124}
125
126#[cfg(feature = "read")]
127impl<T> ArrayLike for Vec<T> {
128    type Item = T;
129
130    fn as_slice(storage: &Self::Storage) -> &[MaybeUninit<T>] {
131        storage
132    }
133
134    fn as_mut_slice(storage: &mut Self::Storage) -> &mut [MaybeUninit<T>] {
135        storage
136    }
137}
138
139pub(crate) struct ArrayVec<A: ArrayLike> {
140    storage: A::Storage,
141    len: usize,
142}
143
144impl<A: ArrayLike> ArrayVec<A> {
145    pub fn new() -> Self {
146        Self {
147            storage: A::new_storage(),
148            len: 0,
149        }
150    }
151
152    pub fn clear(&mut self) {
153        let ptr: *mut [A::Item] = &mut **self;
154        // Set length first so the type invariant is upheld even if `drop_in_place` panicks.
155        self.len = 0;
156        // SAFETY: `ptr` contains valid elements only and we "forget" them by setting the length.
157        unsafe { ptr::drop_in_place(ptr) };
158    }
159
160    pub fn try_push(&mut self, value: A::Item) -> Result<(), CapacityFull> {
161        let mut storage = A::as_mut_slice(&mut self.storage);
162        if self.len >= storage.len() {
163            A::grow(&mut self.storage, 1)?;
164            storage = A::as_mut_slice(&mut self.storage);
165        }
166
167        storage[self.len] = MaybeUninit::new(value);
168        self.len += 1;
169        Ok(())
170    }
171
172    pub fn try_insert(&mut self, index: usize, element: A::Item) -> Result<(), CapacityFull> {
173        assert!(index <= self.len);
174
175        let mut storage = A::as_mut_slice(&mut self.storage);
176        if self.len >= storage.len() {
177            A::grow(&mut self.storage, 1)?;
178            storage = A::as_mut_slice(&mut self.storage);
179        }
180
181        // SAFETY: storage[index] is filled later.
182        unsafe {
183            let p = storage.as_mut_ptr().add(index);
184            core::ptr::copy(p as *const _, p.add(1), self.len - index);
185        }
186        storage[index] = MaybeUninit::new(element);
187        self.len += 1;
188        Ok(())
189    }
190
191    pub fn pop(&mut self) -> Option<A::Item> {
192        if self.len == 0 {
193            None
194        } else {
195            self.len -= 1;
196            // SAFETY: this element is valid and we "forget" it by setting the length.
197            Some(unsafe { A::as_slice(&self.storage)[self.len].as_ptr().read() })
198        }
199    }
200
201    pub fn swap_remove(&mut self, index: usize) -> A::Item {
202        assert!(self.len > 0);
203        A::as_mut_slice(&mut self.storage).swap(index, self.len - 1);
204        self.pop().unwrap()
205    }
206}
207
208#[cfg(feature = "read")]
209impl<T> ArrayVec<Vec<T>> {
210    pub fn into_vec(mut self) -> Vec<T> {
211        let len = core::mem::replace(&mut self.len, 0);
212        let storage = core::mem::replace(&mut self.storage, Box::new([]));
213        let slice = Box::leak(storage);
214        debug_assert!(len <= slice.len());
215        // SAFETY: valid elements.
216        unsafe { Vec::from_raw_parts(slice.as_mut_ptr() as *mut T, len, slice.len()) }
217    }
218}
219
220impl<A: ArrayLike> Drop for ArrayVec<A> {
221    fn drop(&mut self) {
222        self.clear();
223    }
224}
225
226impl<A: ArrayLike> Default for ArrayVec<A> {
227    fn default() -> Self {
228        Self::new()
229    }
230}
231
232impl<A: ArrayLike> ops::Deref for ArrayVec<A> {
233    type Target = [A::Item];
234
235    fn deref(&self) -> &[A::Item] {
236        let slice = &A::as_slice(&self.storage);
237        debug_assert!(self.len <= slice.len());
238        // SAFETY: valid elements.
239        unsafe { slice::from_raw_parts(slice.as_ptr() as _, self.len) }
240    }
241}
242
243impl<A: ArrayLike> ops::DerefMut for ArrayVec<A> {
244    fn deref_mut(&mut self) -> &mut [A::Item] {
245        let slice = &mut A::as_mut_slice(&mut self.storage);
246        debug_assert!(self.len <= slice.len());
247        // SAFETY: valid elements.
248        unsafe { slice::from_raw_parts_mut(slice.as_mut_ptr() as _, self.len) }
249    }
250}
251
252impl<A: ArrayLike> Clone for ArrayVec<A>
253where
254    A::Item: Clone,
255{
256    fn clone(&self) -> Self {
257        let mut new = Self::default();
258        for value in &**self {
259            new.try_push(value.clone()).unwrap();
260        }
261        new
262    }
263}
264
265impl<A: ArrayLike> PartialEq for ArrayVec<A>
266where
267    A::Item: PartialEq,
268{
269    fn eq(&self, other: &Self) -> bool {
270        **self == **other
271    }
272}
273
274impl<A: ArrayLike> Eq for ArrayVec<A> where A::Item: Eq {}
275
276impl<A: ArrayLike> fmt::Debug for ArrayVec<A>
277where
278    A::Item: fmt::Debug,
279{
280    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
281        fmt::Debug::fmt(&**self, f)
282    }
283}
gimli/read/util.rs

gimli/read/
util.rs
