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Commit | Line | Data |
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dfeec247 | 1 | #![unstable(feature = "raw_vec_internals", reason = "implementation detail", issue = "none")] |
8faf50e0 XL |
2 | #![doc(hidden)] |
3 | ||
3dfed10e | 4 | use core::alloc::LayoutErr; |
3b2f2976 | 5 | use core::cmp; |
1b1a35ee | 6 | use core::intrinsics; |
ba9703b0 | 7 | use core::mem::{self, ManuallyDrop, MaybeUninit}; |
3b2f2976 | 8 | use core::ops::Drop; |
ba9703b0 | 9 | use core::ptr::{NonNull, Unique}; |
92a42be0 | 10 | use core::slice; |
83c7162d | 11 | |
3dfed10e | 12 | use crate::alloc::{handle_alloc_error, AllocRef, Global, Layout}; |
9fa01778 | 13 | use crate::boxed::Box; |
dfeec247 | 14 | use crate::collections::TryReserveError::{self, *}; |
c1a9b12d | 15 | |
416331ca XL |
16 | #[cfg(test)] |
17 | mod tests; | |
18 | ||
3dfed10e XL |
19 | enum AllocInit { |
20 | /// The contents of the new memory are uninitialized. | |
21 | Uninitialized, | |
22 | /// The new memory is guaranteed to be zeroed. | |
23 | Zeroed, | |
24 | } | |
25 | ||
5bcae85e | 26 | /// A low-level utility for more ergonomically allocating, reallocating, and deallocating |
c1a9b12d SL |
27 | /// a buffer of memory on the heap without having to worry about all the corner cases |
28 | /// involved. This type is excellent for building your own data structures like Vec and VecDeque. | |
29 | /// In particular: | |
30 | /// | |
f9f354fc XL |
31 | /// * Produces `Unique::dangling()` on zero-sized types. |
32 | /// * Produces `Unique::dangling()` on zero-length allocations. | |
33 | /// * Avoids freeing `Unique::dangling()`. | |
e1599b0c XL |
34 | /// * Catches all overflows in capacity computations (promotes them to "capacity overflow" panics). |
35 | /// * Guards against 32-bit systems allocating more than isize::MAX bytes. | |
36 | /// * Guards against overflowing your length. | |
ba9703b0 | 37 | /// * Calls `handle_alloc_error` for fallible allocations. |
e1599b0c | 38 | /// * Contains a `ptr::Unique` and thus endows the user with all related benefits. |
ba9703b0 | 39 | /// * Uses the excess returned from the allocator to use the largest available capacity. |
c1a9b12d SL |
40 | /// |
41 | /// This type does not in anyway inspect the memory that it manages. When dropped it *will* | |
e1599b0c XL |
42 | /// free its memory, but it *won't* try to drop its contents. It is up to the user of `RawVec` |
43 | /// to handle the actual things *stored* inside of a `RawVec`. | |
c1a9b12d | 44 | /// |
ba9703b0 XL |
45 | /// Note that the excess of a zero-sized types is always infinite, so `capacity()` always returns |
46 | /// `usize::MAX`. This means that you need to be careful when round-tripping this type with a | |
47 | /// `Box<[T]>`, since `capacity()` won't yield the length. | |
041b39d2 | 48 | #[allow(missing_debug_implementations)] |
74b04a01 | 49 | pub struct RawVec<T, A: AllocRef = Global> { |
c1a9b12d SL |
50 | ptr: Unique<T>, |
51 | cap: usize, | |
ba9703b0 | 52 | alloc: A, |
041b39d2 XL |
53 | } |
54 | ||
83c7162d | 55 | impl<T> RawVec<T, Global> { |
e1599b0c XL |
56 | /// HACK(Centril): This exists because `#[unstable]` `const fn`s needn't conform |
57 | /// to `min_const_fn` and so they cannot be called in `min_const_fn`s either. | |
58 | /// | |
59 | /// If you change `RawVec<T>::new` or dependencies, please take care to not | |
60 | /// introduce anything that would truly violate `min_const_fn`. | |
61 | /// | |
62 | /// NOTE: We could avoid this hack and check conformance with some | |
63 | /// `#[rustc_force_min_const_fn]` attribute which requires conformance | |
64 | /// with `min_const_fn` but does not necessarily allow calling it in | |
65 | /// `stable(...) const fn` / user code not enabling `foo` when | |
f035d41b | 66 | /// `#[rustc_const_unstable(feature = "foo", issue = "01234")]` is present. |
e1599b0c XL |
67 | pub const NEW: Self = Self::new(); |
68 | ||
69 | /// Creates the biggest possible `RawVec` (on the system heap) | |
70 | /// without allocating. If `T` has positive size, then this makes a | |
71 | /// `RawVec` with capacity `0`. If `T` is zero-sized, then it makes a | |
72 | /// `RawVec` with capacity `usize::MAX`. Useful for implementing | |
041b39d2 | 73 | /// delayed allocation. |
83c7162d | 74 | pub const fn new() -> Self { |
dfeec247 | 75 | Self::new_in(Global) |
041b39d2 XL |
76 | } |
77 | ||
e1599b0c | 78 | /// Creates a `RawVec` (on the system heap) with exactly the |
416331ca | 79 | /// capacity and alignment requirements for a `[T; capacity]`. This is |
e1599b0c | 80 | /// equivalent to calling `RawVec::new` when `capacity` is `0` or `T` is |
041b39d2 | 81 | /// zero-sized. Note that if `T` is zero-sized this means you will |
e1599b0c | 82 | /// *not* get a `RawVec` with the requested capacity. |
041b39d2 XL |
83 | /// |
84 | /// # Panics | |
85 | /// | |
f035d41b | 86 | /// Panics if the requested capacity exceeds `isize::MAX` bytes. |
041b39d2 XL |
87 | /// |
88 | /// # Aborts | |
89 | /// | |
e1599b0c | 90 | /// Aborts on OOM. |
041b39d2 | 91 | #[inline] |
416331ca | 92 | pub fn with_capacity(capacity: usize) -> Self { |
ba9703b0 | 93 | Self::with_capacity_in(capacity, Global) |
041b39d2 | 94 | } |
c1a9b12d | 95 | |
e1599b0c | 96 | /// Like `with_capacity`, but guarantees the buffer is zeroed. |
041b39d2 | 97 | #[inline] |
416331ca | 98 | pub fn with_capacity_zeroed(capacity: usize) -> Self { |
ba9703b0 | 99 | Self::with_capacity_zeroed_in(capacity, Global) |
041b39d2 | 100 | } |
041b39d2 | 101 | |
e1599b0c | 102 | /// Reconstitutes a `RawVec` from a pointer and capacity. |
041b39d2 | 103 | /// |
ba9703b0 | 104 | /// # Safety |
041b39d2 | 105 | /// |
e1599b0c | 106 | /// The `ptr` must be allocated (on the system heap), and with the given `capacity`. |
ba9703b0 XL |
107 | /// The `capacity` cannot exceed `isize::MAX` for sized types. (only a concern on 32-bit |
108 | /// systems). ZST vectors may have a capacity up to `usize::MAX`. | |
e1599b0c | 109 | /// If the `ptr` and `capacity` come from a `RawVec`, then this is guaranteed. |
ba9703b0 | 110 | #[inline] |
416331ca | 111 | pub unsafe fn from_raw_parts(ptr: *mut T, capacity: usize) -> Self { |
f035d41b | 112 | unsafe { Self::from_raw_parts_in(ptr, capacity, Global) } |
c1a9b12d SL |
113 | } |
114 | ||
115 | /// Converts a `Box<[T]>` into a `RawVec<T>`. | |
ba9703b0 | 116 | pub fn from_box(slice: Box<[T]>) -> Self { |
c1a9b12d | 117 | unsafe { |
ba9703b0 XL |
118 | let mut slice = ManuallyDrop::new(slice); |
119 | RawVec::from_raw_parts(slice.as_mut_ptr(), slice.len()) | |
c1a9b12d SL |
120 | } |
121 | } | |
f035d41b XL |
122 | |
123 | /// Converts the entire buffer into `Box<[MaybeUninit<T>]>` with the specified `len`. | |
124 | /// | |
125 | /// Note that this will correctly reconstitute any `cap` changes | |
126 | /// that may have been performed. (See description of type for details.) | |
127 | /// | |
128 | /// # Safety | |
129 | /// | |
130 | /// * `len` must be greater than or equal to the most recently requested capacity, and | |
131 | /// * `len` must be less than or equal to `self.capacity()`. | |
132 | /// | |
133 | /// Note, that the requested capacity and `self.capacity()` could differ, as | |
134 | /// an allocator could overallocate and return a greater memory block than requested. | |
135 | pub unsafe fn into_box(self, len: usize) -> Box<[MaybeUninit<T>]> { | |
136 | // Sanity-check one half of the safety requirement (we cannot check the other half). | |
137 | debug_assert!( | |
138 | len <= self.capacity(), | |
139 | "`len` must be smaller than or equal to `self.capacity()`" | |
140 | ); | |
141 | ||
142 | let me = ManuallyDrop::new(self); | |
143 | unsafe { | |
144 | let slice = slice::from_raw_parts_mut(me.ptr() as *mut MaybeUninit<T>, len); | |
145 | Box::from_raw(slice) | |
146 | } | |
147 | } | |
c1a9b12d SL |
148 | } |
149 | ||
74b04a01 | 150 | impl<T, A: AllocRef> RawVec<T, A> { |
ba9703b0 XL |
151 | /// Like `new`, but parameterized over the choice of allocator for |
152 | /// the returned `RawVec`. | |
1b1a35ee | 153 | #[allow_internal_unstable(const_fn)] |
ba9703b0 XL |
154 | pub const fn new_in(alloc: A) -> Self { |
155 | // `cap: 0` means "unallocated". zero-sized types are ignored. | |
f9f354fc | 156 | Self { ptr: Unique::dangling(), cap: 0, alloc } |
ba9703b0 XL |
157 | } |
158 | ||
159 | /// Like `with_capacity`, but parameterized over the choice of | |
160 | /// allocator for the returned `RawVec`. | |
161 | #[inline] | |
162 | pub fn with_capacity_in(capacity: usize, alloc: A) -> Self { | |
3dfed10e | 163 | Self::allocate_in(capacity, AllocInit::Uninitialized, alloc) |
ba9703b0 XL |
164 | } |
165 | ||
166 | /// Like `with_capacity_zeroed`, but parameterized over the choice | |
167 | /// of allocator for the returned `RawVec`. | |
168 | #[inline] | |
169 | pub fn with_capacity_zeroed_in(capacity: usize, alloc: A) -> Self { | |
3dfed10e | 170 | Self::allocate_in(capacity, AllocInit::Zeroed, alloc) |
ba9703b0 XL |
171 | } |
172 | ||
1b1a35ee | 173 | fn allocate_in(capacity: usize, init: AllocInit, alloc: A) -> Self { |
ba9703b0 XL |
174 | if mem::size_of::<T>() == 0 { |
175 | Self::new_in(alloc) | |
176 | } else { | |
f035d41b XL |
177 | // We avoid `unwrap_or_else` here because it bloats the amount of |
178 | // LLVM IR generated. | |
179 | let layout = match Layout::array::<T>(capacity) { | |
180 | Ok(layout) => layout, | |
181 | Err(_) => capacity_overflow(), | |
182 | }; | |
183 | match alloc_guard(layout.size()) { | |
184 | Ok(_) => {} | |
185 | Err(_) => capacity_overflow(), | |
186 | } | |
3dfed10e XL |
187 | let result = match init { |
188 | AllocInit::Uninitialized => alloc.alloc(layout), | |
189 | AllocInit::Zeroed => alloc.alloc_zeroed(layout), | |
190 | }; | |
191 | let ptr = match result { | |
192 | Ok(ptr) => ptr, | |
f035d41b XL |
193 | Err(_) => handle_alloc_error(layout), |
194 | }; | |
ba9703b0 | 195 | |
ba9703b0 | 196 | Self { |
3dfed10e XL |
197 | ptr: unsafe { Unique::new_unchecked(ptr.cast().as_ptr()) }, |
198 | cap: Self::capacity_from_bytes(ptr.len()), | |
ba9703b0 XL |
199 | alloc, |
200 | } | |
201 | } | |
202 | } | |
203 | ||
204 | /// Reconstitutes a `RawVec` from a pointer, capacity, and allocator. | |
205 | /// | |
206 | /// # Safety | |
207 | /// | |
3dfed10e XL |
208 | /// The `ptr` must be allocated (via the given allocator `alloc`), and with the given |
209 | /// `capacity`. | |
ba9703b0 XL |
210 | /// The `capacity` cannot exceed `isize::MAX` for sized types. (only a concern on 32-bit |
211 | /// systems). ZST vectors may have a capacity up to `usize::MAX`. | |
3dfed10e XL |
212 | /// If the `ptr` and `capacity` come from a `RawVec` created via `alloc`, then this is |
213 | /// guaranteed. | |
ba9703b0 | 214 | #[inline] |
3dfed10e XL |
215 | pub unsafe fn from_raw_parts_in(ptr: *mut T, capacity: usize, alloc: A) -> Self { |
216 | Self { ptr: unsafe { Unique::new_unchecked(ptr) }, cap: capacity, alloc } | |
ba9703b0 XL |
217 | } |
218 | ||
c1a9b12d | 219 | /// Gets a raw pointer to the start of the allocation. Note that this is |
f9f354fc | 220 | /// `Unique::dangling()` if `capacity == 0` or `T` is zero-sized. In the former case, you must |
c1a9b12d SL |
221 | /// be careful. |
222 | pub fn ptr(&self) -> *mut T { | |
7cac9316 | 223 | self.ptr.as_ptr() |
c1a9b12d SL |
224 | } |
225 | ||
226 | /// Gets the capacity of the allocation. | |
227 | /// | |
228 | /// This will always be `usize::MAX` if `T` is zero-sized. | |
a7813a04 | 229 | #[inline(always)] |
416331ca | 230 | pub fn capacity(&self) -> usize { |
ba9703b0 | 231 | if mem::size_of::<T>() == 0 { usize::MAX } else { self.cap } |
c1a9b12d SL |
232 | } |
233 | ||
e1599b0c | 234 | /// Returns a shared reference to the allocator backing this `RawVec`. |
041b39d2 | 235 | pub fn alloc(&self) -> &A { |
ba9703b0 | 236 | &self.alloc |
041b39d2 XL |
237 | } |
238 | ||
e1599b0c | 239 | /// Returns a mutable reference to the allocator backing this `RawVec`. |
041b39d2 | 240 | pub fn alloc_mut(&mut self) -> &mut A { |
ba9703b0 | 241 | &mut self.alloc |
041b39d2 XL |
242 | } |
243 | ||
ba9703b0 XL |
244 | fn current_memory(&self) -> Option<(NonNull<u8>, Layout)> { |
245 | if mem::size_of::<T>() == 0 || self.cap == 0 { | |
3b2f2976 XL |
246 | None |
247 | } else { | |
248 | // We have an allocated chunk of memory, so we can bypass runtime | |
249 | // checks to get our current layout. | |
250 | unsafe { | |
251 | let align = mem::align_of::<T>(); | |
252 | let size = mem::size_of::<T>() * self.cap; | |
ba9703b0 XL |
253 | let layout = Layout::from_size_align_unchecked(size, align); |
254 | Some((self.ptr.cast().into(), layout)) | |
3b2f2976 XL |
255 | } |
256 | } | |
257 | } | |
258 | ||
f035d41b XL |
259 | /// Ensures that the buffer contains at least enough space to hold `len + |
260 | /// additional` elements. If it doesn't already have enough capacity, will | |
261 | /// reallocate enough space plus comfortable slack space to get amortized | |
262 | /// `O(1)` behavior. Will limit this behavior if it would needlessly cause | |
263 | /// itself to panic. | |
c1a9b12d | 264 | /// |
f035d41b | 265 | /// If `len` exceeds `self.capacity()`, this may fail to actually allocate |
c1a9b12d | 266 | /// the requested space. This is not really unsafe, but the unsafe |
b039eaaf | 267 | /// code *you* write that relies on the behavior of this function may break. |
c1a9b12d SL |
268 | /// |
269 | /// This is ideal for implementing a bulk-push operation like `extend`. | |
270 | /// | |
271 | /// # Panics | |
272 | /// | |
f035d41b | 273 | /// Panics if the new capacity exceeds `isize::MAX` bytes. |
c1a9b12d SL |
274 | /// |
275 | /// # Aborts | |
276 | /// | |
e1599b0c | 277 | /// Aborts on OOM. |
c1a9b12d SL |
278 | /// |
279 | /// # Examples | |
280 | /// | |
041b39d2 | 281 | /// ``` |
48663c56 | 282 | /// # #![feature(raw_vec_internals)] |
041b39d2 XL |
283 | /// # extern crate alloc; |
284 | /// # use std::ptr; | |
285 | /// # use alloc::raw_vec::RawVec; | |
c1a9b12d SL |
286 | /// struct MyVec<T> { |
287 | /// buf: RawVec<T>, | |
288 | /// len: usize, | |
289 | /// } | |
290 | /// | |
041b39d2 | 291 | /// impl<T: Clone> MyVec<T> { |
c1a9b12d SL |
292 | /// pub fn push_all(&mut self, elems: &[T]) { |
293 | /// self.buf.reserve(self.len, elems.len()); | |
294 | /// // reserve would have aborted or panicked if the len exceeded | |
295 | /// // `isize::MAX` so this is safe to do unchecked now. | |
296 | /// for x in elems { | |
297 | /// unsafe { | |
b7449926 | 298 | /// ptr::write(self.buf.ptr().add(self.len), x.clone()); |
c1a9b12d SL |
299 | /// } |
300 | /// self.len += 1; | |
301 | /// } | |
302 | /// } | |
303 | /// } | |
041b39d2 XL |
304 | /// # fn main() { |
305 | /// # let mut vector = MyVec { buf: RawVec::new(), len: 0 }; | |
306 | /// # vector.push_all(&[1, 3, 5, 7, 9]); | |
307 | /// # } | |
c1a9b12d | 308 | /// ``` |
f035d41b | 309 | pub fn reserve(&mut self, len: usize, additional: usize) { |
1b1a35ee | 310 | handle_reserve(self.try_reserve(len, additional)); |
94b46f34 | 311 | } |
ba9703b0 XL |
312 | |
313 | /// The same as `reserve`, but returns on errors instead of panicking or aborting. | |
f035d41b XL |
314 | pub fn try_reserve(&mut self, len: usize, additional: usize) -> Result<(), TryReserveError> { |
315 | if self.needs_to_grow(len, additional) { | |
316 | self.grow_amortized(len, additional) | |
ba9703b0 XL |
317 | } else { |
318 | Ok(()) | |
319 | } | |
320 | } | |
321 | ||
f035d41b XL |
322 | /// Ensures that the buffer contains at least enough space to hold `len + |
323 | /// additional` elements. If it doesn't already, will reallocate the | |
324 | /// minimum possible amount of memory necessary. Generally this will be | |
325 | /// exactly the amount of memory necessary, but in principle the allocator | |
326 | /// is free to give back more than we asked for. | |
9cc50fc6 | 327 | /// |
f035d41b XL |
328 | /// If `len` exceeds `self.capacity()`, this may fail to actually allocate |
329 | /// the requested space. This is not really unsafe, but the unsafe code | |
330 | /// *you* write that relies on the behavior of this function may break. | |
9cc50fc6 SL |
331 | /// |
332 | /// # Panics | |
333 | /// | |
f035d41b | 334 | /// Panics if the new capacity exceeds `isize::MAX` bytes. |
ba9703b0 XL |
335 | /// |
336 | /// # Aborts | |
337 | /// | |
338 | /// Aborts on OOM. | |
f035d41b | 339 | pub fn reserve_exact(&mut self, len: usize, additional: usize) { |
1b1a35ee | 340 | handle_reserve(self.try_reserve_exact(len, additional)); |
ba9703b0 XL |
341 | } |
342 | ||
343 | /// The same as `reserve_exact`, but returns on errors instead of panicking or aborting. | |
344 | pub fn try_reserve_exact( | |
345 | &mut self, | |
f035d41b XL |
346 | len: usize, |
347 | additional: usize, | |
ba9703b0 | 348 | ) -> Result<(), TryReserveError> { |
f035d41b | 349 | if self.needs_to_grow(len, additional) { self.grow_exact(len, additional) } else { Ok(()) } |
9cc50fc6 SL |
350 | } |
351 | ||
c1a9b12d SL |
352 | /// Shrinks the allocation down to the specified amount. If the given amount |
353 | /// is 0, actually completely deallocates. | |
354 | /// | |
355 | /// # Panics | |
356 | /// | |
357 | /// Panics if the given amount is *larger* than the current capacity. | |
358 | /// | |
359 | /// # Aborts | |
360 | /// | |
361 | /// Aborts on OOM. | |
362 | pub fn shrink_to_fit(&mut self, amount: usize) { | |
1b1a35ee | 363 | handle_reserve(self.shrink(amount)); |
c1a9b12d | 364 | } |
041b39d2 | 365 | } |
c1a9b12d | 366 | |
ba9703b0 XL |
367 | impl<T, A: AllocRef> RawVec<T, A> { |
368 | /// Returns if the buffer needs to grow to fulfill the needed extra capacity. | |
369 | /// Mainly used to make inlining reserve-calls possible without inlining `grow`. | |
f035d41b XL |
370 | fn needs_to_grow(&self, len: usize, additional: usize) -> bool { |
371 | additional > self.capacity().wrapping_sub(len) | |
ba9703b0 | 372 | } |
94b46f34 | 373 | |
ba9703b0 XL |
374 | fn capacity_from_bytes(excess: usize) -> usize { |
375 | debug_assert_ne!(mem::size_of::<T>(), 0); | |
376 | excess / mem::size_of::<T>() | |
377 | } | |
94b46f34 | 378 | |
3dfed10e XL |
379 | fn set_ptr(&mut self, ptr: NonNull<[u8]>) { |
380 | self.ptr = unsafe { Unique::new_unchecked(ptr.cast().as_ptr()) }; | |
381 | self.cap = Self::capacity_from_bytes(ptr.len()); | |
ba9703b0 | 382 | } |
94b46f34 | 383 | |
f9f354fc XL |
384 | // This method is usually instantiated many times. So we want it to be as |
385 | // small as possible, to improve compile times. But we also want as much of | |
386 | // its contents to be statically computable as possible, to make the | |
387 | // generated code run faster. Therefore, this method is carefully written | |
388 | // so that all of the code that depends on `T` is within it, while as much | |
389 | // of the code that doesn't depend on `T` as possible is in functions that | |
390 | // are non-generic over `T`. | |
f035d41b | 391 | fn grow_amortized(&mut self, len: usize, additional: usize) -> Result<(), TryReserveError> { |
f9f354fc | 392 | // This is ensured by the calling contexts. |
f035d41b | 393 | debug_assert!(additional > 0); |
f9f354fc XL |
394 | |
395 | if mem::size_of::<T>() == 0 { | |
ba9703b0 XL |
396 | // Since we return a capacity of `usize::MAX` when `elem_size` is |
397 | // 0, getting to here necessarily means the `RawVec` is overfull. | |
398 | return Err(CapacityOverflow); | |
399 | } | |
74b04a01 | 400 | |
f9f354fc | 401 | // Nothing we can really do about these checks, sadly. |
f035d41b | 402 | let required_cap = len.checked_add(additional).ok_or(CapacityOverflow)?; |
f9f354fc XL |
403 | |
404 | // This guarantees exponential growth. The doubling cannot overflow | |
405 | // because `cap <= isize::MAX` and the type of `cap` is `usize`. | |
406 | let cap = cmp::max(self.cap * 2, required_cap); | |
407 | ||
408 | // Tiny Vecs are dumb. Skip to: | |
409 | // - 8 if the element size is 1, because any heap allocators is likely | |
410 | // to round up a request of less than 8 bytes to at least 8 bytes. | |
411 | // - 4 if elements are moderate-sized (<= 1 KiB). | |
412 | // - 1 otherwise, to avoid wasting too much space for very short Vecs. | |
413 | // Note that `min_non_zero_cap` is computed statically. | |
414 | let elem_size = mem::size_of::<T>(); | |
415 | let min_non_zero_cap = if elem_size == 1 { | |
416 | 8 | |
417 | } else if elem_size <= 1024 { | |
418 | 4 | |
ba9703b0 | 419 | } else { |
f9f354fc | 420 | 1 |
ba9703b0 | 421 | }; |
f9f354fc XL |
422 | let cap = cmp::max(min_non_zero_cap, cap); |
423 | ||
424 | let new_layout = Layout::array::<T>(cap); | |
425 | ||
426 | // `finish_grow` is non-generic over `T`. | |
3dfed10e XL |
427 | let ptr = finish_grow(new_layout, self.current_memory(), &mut self.alloc)?; |
428 | self.set_ptr(ptr); | |
f9f354fc XL |
429 | Ok(()) |
430 | } | |
431 | ||
432 | // The constraints on this method are much the same as those on | |
433 | // `grow_amortized`, but this method is usually instantiated less often so | |
434 | // it's less critical. | |
f035d41b | 435 | fn grow_exact(&mut self, len: usize, additional: usize) -> Result<(), TryReserveError> { |
f9f354fc XL |
436 | if mem::size_of::<T>() == 0 { |
437 | // Since we return a capacity of `usize::MAX` when the type size is | |
438 | // 0, getting to here necessarily means the `RawVec` is overfull. | |
439 | return Err(CapacityOverflow); | |
440 | } | |
441 | ||
f035d41b | 442 | let cap = len.checked_add(additional).ok_or(CapacityOverflow)?; |
f9f354fc XL |
443 | let new_layout = Layout::array::<T>(cap); |
444 | ||
445 | // `finish_grow` is non-generic over `T`. | |
3dfed10e XL |
446 | let ptr = finish_grow(new_layout, self.current_memory(), &mut self.alloc)?; |
447 | self.set_ptr(ptr); | |
ba9703b0 XL |
448 | Ok(()) |
449 | } | |
94b46f34 | 450 | |
3dfed10e | 451 | fn shrink(&mut self, amount: usize) -> Result<(), TryReserveError> { |
ba9703b0 | 452 | assert!(amount <= self.capacity(), "Tried to shrink to a larger capacity"); |
94b46f34 | 453 | |
ba9703b0 XL |
454 | let (ptr, layout) = if let Some(mem) = self.current_memory() { mem } else { return Ok(()) }; |
455 | let new_size = amount * mem::size_of::<T>(); | |
94b46f34 | 456 | |
3dfed10e | 457 | let ptr = unsafe { |
1b1a35ee XL |
458 | let new_layout = Layout::from_size_align_unchecked(new_size, layout.align()); |
459 | self.alloc.shrink(ptr, layout, new_layout).map_err(|_| TryReserveError::AllocError { | |
460 | layout: new_layout, | |
3dfed10e | 461 | non_exhaustive: (), |
ba9703b0 XL |
462 | })? |
463 | }; | |
3dfed10e | 464 | self.set_ptr(ptr); |
ba9703b0 | 465 | Ok(()) |
94b46f34 | 466 | } |
94b46f34 XL |
467 | } |
468 | ||
f9f354fc XL |
469 | // This function is outside `RawVec` to minimize compile times. See the comment |
470 | // above `RawVec::grow_amortized` for details. (The `A` parameter isn't | |
471 | // significant, because the number of different `A` types seen in practice is | |
472 | // much smaller than the number of `T` types.) | |
473 | fn finish_grow<A>( | |
474 | new_layout: Result<Layout, LayoutErr>, | |
f9f354fc XL |
475 | current_memory: Option<(NonNull<u8>, Layout)>, |
476 | alloc: &mut A, | |
3dfed10e | 477 | ) -> Result<NonNull<[u8]>, TryReserveError> |
f9f354fc XL |
478 | where |
479 | A: AllocRef, | |
480 | { | |
481 | // Check for the error here to minimize the size of `RawVec::grow_*`. | |
482 | let new_layout = new_layout.map_err(|_| CapacityOverflow)?; | |
483 | ||
484 | alloc_guard(new_layout.size())?; | |
485 | ||
486 | let memory = if let Some((ptr, old_layout)) = current_memory { | |
487 | debug_assert_eq!(old_layout.align(), new_layout.align()); | |
1b1a35ee XL |
488 | unsafe { |
489 | // The allocator checks for alignment equality | |
490 | intrinsics::assume(old_layout.align() == new_layout.align()); | |
491 | alloc.grow(ptr, old_layout, new_layout) | |
492 | } | |
f9f354fc | 493 | } else { |
3dfed10e | 494 | alloc.alloc(new_layout) |
1b1a35ee | 495 | }; |
f9f354fc | 496 | |
1b1a35ee | 497 | memory.map_err(|_| AllocError { layout: new_layout, non_exhaustive: () }) |
f9f354fc XL |
498 | } |
499 | ||
74b04a01 | 500 | unsafe impl<#[may_dangle] T, A: AllocRef> Drop for RawVec<T, A> { |
e1599b0c | 501 | /// Frees the memory owned by the `RawVec` *without* trying to drop its contents. |
041b39d2 | 502 | fn drop(&mut self) { |
ba9703b0 XL |
503 | if let Some((ptr, layout)) = self.current_memory() { |
504 | unsafe { self.alloc.dealloc(ptr, layout) } | |
dfeec247 | 505 | } |
041b39d2 XL |
506 | } |
507 | } | |
508 | ||
1b1a35ee XL |
509 | // Central function for reserve error handling. |
510 | #[inline] | |
511 | fn handle_reserve(result: Result<(), TryReserveError>) { | |
512 | match result { | |
513 | Err(CapacityOverflow) => capacity_overflow(), | |
514 | Err(AllocError { layout, .. }) => handle_alloc_error(layout), | |
515 | Ok(()) => { /* yay */ } | |
516 | } | |
517 | } | |
518 | ||
c1a9b12d | 519 | // We need to guarantee the following: |
e1599b0c XL |
520 | // * We don't ever allocate `> isize::MAX` byte-size objects. |
521 | // * We don't overflow `usize::MAX` and actually allocate too little. | |
c1a9b12d SL |
522 | // |
523 | // On 64-bit we just need to check for overflow since trying to allocate | |
3157f602 XL |
524 | // `> isize::MAX` bytes will surely fail. On 32-bit and 16-bit we need to add |
525 | // an extra guard for this in case we're running on a platform which can use | |
e1599b0c | 526 | // all 4GB in user-space, e.g., PAE or x32. |
c1a9b12d SL |
527 | |
528 | #[inline] | |
e1599b0c | 529 | fn alloc_guard(alloc_size: usize) -> Result<(), TryReserveError> { |
1b1a35ee | 530 | if usize::BITS < 64 && alloc_size > isize::MAX as usize { |
0531ce1d XL |
531 | Err(CapacityOverflow) |
532 | } else { | |
533 | Ok(()) | |
e9174d1e | 534 | } |
c1a9b12d | 535 | } |
92a42be0 | 536 | |
83c7162d XL |
537 | // One central function responsible for reporting capacity overflows. This'll |
538 | // ensure that the code generation related to these panics is minimal as there's | |
539 | // only one location which panics rather than a bunch throughout the module. | |
540 | fn capacity_overflow() -> ! { | |
e1599b0c | 541 | panic!("capacity overflow"); |
83c7162d | 542 | } |