gimli/read/
util.rs

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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// SAFETY: does not modify the content in storage.
45unsafe impl<T, const N: usize> Sealed for [T; N] {
46    type Storage = [MaybeUninit<T>; N];
47
48    fn new_storage() -> Self::Storage {
49        // SAFETY: An uninitialized `[MaybeUninit<_>; _]` is valid.
50        unsafe { MaybeUninit::uninit().assume_init() }
51    }
52}
53
54impl<T, const N: usize> ArrayLike for [T; N] {
55    type Item = T;
56
57    fn as_slice(storage: &Self::Storage) -> &[MaybeUninit<T>] {
58        storage
59    }
60
61    fn as_mut_slice(storage: &mut Self::Storage) -> &mut [MaybeUninit<T>] {
62        storage
63    }
64}
65
66// SAFETY: does not modify the content in storage.
67#[cfg(feature = "read")]
68unsafe impl<T, const N: usize> Sealed for Box<[T; N]> {
69    type Storage = Box<[MaybeUninit<T>; N]>;
70
71    fn new_storage() -> Self::Storage {
72        // SAFETY: An uninitialized `[MaybeUninit<_>; _]` is valid.
73        Box::new(unsafe { MaybeUninit::uninit().assume_init() })
74    }
75}
76
77#[cfg(feature = "read")]
78impl<T, const N: usize> ArrayLike for Box<[T; N]> {
79    type Item = T;
80
81    fn as_slice(storage: &Self::Storage) -> &[MaybeUninit<T>] {
82        &storage[..]
83    }
84
85    fn as_mut_slice(storage: &mut Self::Storage) -> &mut [MaybeUninit<T>] {
86        &mut storage[..]
87    }
88}
89
90#[cfg(feature = "read")]
91unsafe impl<T> Sealed for Vec<T> {
92    type Storage = Box<[MaybeUninit<T>]>;
93
94    fn new_storage() -> Self::Storage {
95        Box::new([])
96    }
97
98    fn grow(storage: &mut Self::Storage, additional: usize) -> Result<(), CapacityFull> {
99        let mut vec: Vec<_> = core::mem::replace(storage, Box::new([])).into();
100        vec.reserve(additional);
101        // SAFETY: This is a `Vec` of `MaybeUninit`.
102        unsafe { vec.set_len(vec.capacity()) };
103        *storage = vec.into_boxed_slice();
104        Ok(())
105    }
106}
107
108#[cfg(feature = "read")]
109impl<T> ArrayLike for Vec<T> {
110    type Item = T;
111
112    fn as_slice(storage: &Self::Storage) -> &[MaybeUninit<T>] {
113        storage
114    }
115
116    fn as_mut_slice(storage: &mut Self::Storage) -> &mut [MaybeUninit<T>] {
117        storage
118    }
119}
120
121pub(crate) struct ArrayVec<A: ArrayLike> {
122    storage: A::Storage,
123    len: usize,
124}
125
126impl<A: ArrayLike> ArrayVec<A> {
127    pub fn new() -> Self {
128        Self {
129            storage: A::new_storage(),
130            len: 0,
131        }
132    }
133
134    pub fn clear(&mut self) {
135        let ptr: *mut [A::Item] = &mut **self;
136        // Set length first so the type invariant is upheld even if `drop_in_place` panicks.
137        self.len = 0;
138        // SAFETY: `ptr` contains valid elements only and we "forget" them by setting the length.
139        unsafe { ptr::drop_in_place(ptr) };
140    }
141
142    pub fn try_push(&mut self, value: A::Item) -> Result<(), CapacityFull> {
143        let mut storage = A::as_mut_slice(&mut self.storage);
144        if self.len >= storage.len() {
145            A::grow(&mut self.storage, 1)?;
146            storage = A::as_mut_slice(&mut self.storage);
147        }
148
149        storage[self.len] = MaybeUninit::new(value);
150        self.len += 1;
151        Ok(())
152    }
153
154    pub fn try_insert(&mut self, index: usize, element: A::Item) -> Result<(), CapacityFull> {
155        assert!(index <= self.len);
156
157        let mut storage = A::as_mut_slice(&mut self.storage);
158        if self.len >= storage.len() {
159            A::grow(&mut self.storage, 1)?;
160            storage = A::as_mut_slice(&mut self.storage);
161        }
162
163        // SAFETY: storage[index] is filled later.
164        unsafe {
165            let p = storage.as_mut_ptr().add(index);
166            core::ptr::copy(p as *const _, p.add(1), self.len - index);
167        }
168        storage[index] = MaybeUninit::new(element);
169        self.len += 1;
170        Ok(())
171    }
172
173    pub fn pop(&mut self) -> Option<A::Item> {
174        if self.len == 0 {
175            None
176        } else {
177            self.len -= 1;
178            // SAFETY: this element is valid and we "forget" it by setting the length.
179            Some(unsafe { A::as_slice(&self.storage)[self.len].as_ptr().read() })
180        }
181    }
182
183    pub fn swap_remove(&mut self, index: usize) -> A::Item {
184        assert!(self.len > 0);
185        A::as_mut_slice(&mut self.storage).swap(index, self.len - 1);
186        self.pop().unwrap()
187    }
188}
189
190#[cfg(feature = "read")]
191impl<T> ArrayVec<Vec<T>> {
192    pub fn into_vec(mut self) -> Vec<T> {
193        let len = core::mem::replace(&mut self.len, 0);
194        let storage = core::mem::replace(&mut self.storage, Box::new([]));
195        let slice = Box::leak(storage);
196        debug_assert!(len <= slice.len());
197        // SAFETY: valid elements.
198        unsafe { Vec::from_raw_parts(slice.as_mut_ptr() as *mut T, len, slice.len()) }
199    }
200}
201
202impl<A: ArrayLike> Drop for ArrayVec<A> {
203    fn drop(&mut self) {
204        self.clear();
205    }
206}
207
208impl<A: ArrayLike> Default for ArrayVec<A> {
209    fn default() -> Self {
210        Self::new()
211    }
212}
213
214impl<A: ArrayLike> ops::Deref for ArrayVec<A> {
215    type Target = [A::Item];
216
217    fn deref(&self) -> &[A::Item] {
218        let slice = &A::as_slice(&self.storage);
219        debug_assert!(self.len <= slice.len());
220        // SAFETY: valid elements.
221        unsafe { slice::from_raw_parts(slice.as_ptr() as _, self.len) }
222    }
223}
224
225impl<A: ArrayLike> ops::DerefMut for ArrayVec<A> {
226    fn deref_mut(&mut self) -> &mut [A::Item] {
227        let slice = &mut A::as_mut_slice(&mut self.storage);
228        debug_assert!(self.len <= slice.len());
229        // SAFETY: valid elements.
230        unsafe { slice::from_raw_parts_mut(slice.as_mut_ptr() as _, self.len) }
231    }
232}
233
234impl<A: ArrayLike> Clone for ArrayVec<A>
235where
236    A::Item: Clone,
237{
238    fn clone(&self) -> Self {
239        let mut new = Self::default();
240        for value in &**self {
241            new.try_push(value.clone()).unwrap();
242        }
243        new
244    }
245}
246
247impl<A: ArrayLike> PartialEq for ArrayVec<A>
248where
249    A::Item: PartialEq,
250{
251    fn eq(&self, other: &Self) -> bool {
252        **self == **other
253    }
254}
255
256impl<A: ArrayLike> Eq for ArrayVec<A> where A::Item: Eq {}
257
258impl<A: ArrayLike> fmt::Debug for ArrayVec<A>
259where
260    A::Item: fmt::Debug,
261{
262    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
263        fmt::Debug::fmt(&**self, f)
264    }
265}
gimli/read/util.rs

gimli/read/
util.rs
