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1 | // Copyright 2015 The Rust Project Developers. See the COPYRIGHT |
2 | // file at the top-level directory of this distribution and at | |
3 | // http://rust-lang.org/COPYRIGHT. | |
4 | // | |
5 | // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or | |
6 | // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license | |
7 | // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your | |
8 | // option. This file may not be copied, modified, or distributed | |
9 | // except according to those terms. | |
10 | ||
3b2f2976 | 11 | use core::cmp; |
c1a9b12d | 12 | use core::mem; |
3b2f2976 | 13 | use core::ops::Drop; |
83c7162d | 14 | use core::ptr::{self, NonNull, Unique}; |
92a42be0 | 15 | use core::slice; |
83c7162d XL |
16 | |
17 | use alloc::{Alloc, Layout, Global, oom}; | |
18 | use alloc::CollectionAllocErr; | |
19 | use alloc::CollectionAllocErr::*; | |
20 | use boxed::Box; | |
c1a9b12d | 21 | |
5bcae85e | 22 | /// A low-level utility for more ergonomically allocating, reallocating, and deallocating |
c1a9b12d SL |
23 | /// a buffer of memory on the heap without having to worry about all the corner cases |
24 | /// involved. This type is excellent for building your own data structures like Vec and VecDeque. | |
25 | /// In particular: | |
26 | /// | |
7cac9316 XL |
27 | /// * Produces Unique::empty() on zero-sized types |
28 | /// * Produces Unique::empty() on zero-length allocations | |
c1a9b12d SL |
29 | /// * Catches all overflows in capacity computations (promotes them to "capacity overflow" panics) |
30 | /// * Guards against 32-bit systems allocating more than isize::MAX bytes | |
31 | /// * Guards against overflowing your length | |
32 | /// * Aborts on OOM | |
7cac9316 | 33 | /// * Avoids freeing Unique::empty() |
c1a9b12d SL |
34 | /// * Contains a ptr::Unique and thus endows the user with all related benefits |
35 | /// | |
36 | /// This type does not in anyway inspect the memory that it manages. When dropped it *will* | |
37 | /// free its memory, but it *won't* try to Drop its contents. It is up to the user of RawVec | |
38 | /// to handle the actual things *stored* inside of a RawVec. | |
39 | /// | |
40 | /// Note that a RawVec always forces its capacity to be usize::MAX for zero-sized types. | |
41 | /// This enables you to use capacity growing logic catch the overflows in your length | |
42 | /// that might occur with zero-sized types. | |
43 | /// | |
44 | /// However this means that you need to be careful when roundtripping this type | |
45 | /// with a `Box<[T]>`: `cap()` won't yield the len. However `with_capacity`, | |
46 | /// `shrink_to_fit`, and `from_box` will actually set RawVec's private capacity | |
47 | /// field. This allows zero-sized types to not be special-cased by consumers of | |
48 | /// this type. | |
041b39d2 | 49 | #[allow(missing_debug_implementations)] |
83c7162d | 50 | pub struct RawVec<T, A: Alloc = Global> { |
c1a9b12d SL |
51 | ptr: Unique<T>, |
52 | cap: usize, | |
041b39d2 | 53 | a: A, |
c1a9b12d SL |
54 | } |
55 | ||
041b39d2 XL |
56 | impl<T, A: Alloc> RawVec<T, A> { |
57 | /// Like `new` but parameterized over the choice of allocator for | |
58 | /// the returned RawVec. | |
83c7162d | 59 | pub const fn new_in(a: A) -> Self { |
7cac9316 | 60 | // !0 is usize::MAX. This branch should be stripped at compile time. |
83c7162d XL |
61 | // FIXME(mark-i-m): use this line when `if`s are allowed in `const` |
62 | //let cap = if mem::size_of::<T>() == 0 { !0 } else { 0 }; | |
c1a9b12d | 63 | |
7cac9316 XL |
64 | // Unique::empty() doubles as "unallocated" and "zero-sized allocation" |
65 | RawVec { | |
66 | ptr: Unique::empty(), | |
83c7162d XL |
67 | // FIXME(mark-i-m): use `cap` when ifs are allowed in const |
68 | cap: [0, !0][(mem::size_of::<T>() == 0) as usize], | |
3b2f2976 | 69 | a, |
c1a9b12d SL |
70 | } |
71 | } | |
72 | ||
041b39d2 XL |
73 | /// Like `with_capacity` but parameterized over the choice of |
74 | /// allocator for the returned RawVec. | |
cc61c64b | 75 | #[inline] |
041b39d2 XL |
76 | pub fn with_capacity_in(cap: usize, a: A) -> Self { |
77 | RawVec::allocate_in(cap, false, a) | |
cc61c64b XL |
78 | } |
79 | ||
041b39d2 XL |
80 | /// Like `with_capacity_zeroed` but parameterized over the choice |
81 | /// of allocator for the returned RawVec. | |
cc61c64b | 82 | #[inline] |
041b39d2 XL |
83 | pub fn with_capacity_zeroed_in(cap: usize, a: A) -> Self { |
84 | RawVec::allocate_in(cap, true, a) | |
cc61c64b XL |
85 | } |
86 | ||
041b39d2 | 87 | fn allocate_in(cap: usize, zeroed: bool, mut a: A) -> Self { |
c1a9b12d SL |
88 | unsafe { |
89 | let elem_size = mem::size_of::<T>(); | |
90 | ||
83c7162d XL |
91 | let alloc_size = cap.checked_mul(elem_size).unwrap_or_else(|| capacity_overflow()); |
92 | alloc_guard(alloc_size).unwrap_or_else(|_| capacity_overflow()); | |
c1a9b12d SL |
93 | |
94 | // handles ZSTs and `cap = 0` alike | |
95 | let ptr = if alloc_size == 0 { | |
83c7162d | 96 | NonNull::<T>::dangling().as_opaque() |
c1a9b12d SL |
97 | } else { |
98 | let align = mem::align_of::<T>(); | |
041b39d2 XL |
99 | let result = if zeroed { |
100 | a.alloc_zeroed(Layout::from_size_align(alloc_size, align).unwrap()) | |
cc61c64b | 101 | } else { |
041b39d2 | 102 | a.alloc(Layout::from_size_align(alloc_size, align).unwrap()) |
cc61c64b | 103 | }; |
041b39d2 XL |
104 | match result { |
105 | Ok(ptr) => ptr, | |
83c7162d | 106 | Err(_) => oom(), |
b039eaaf | 107 | } |
c1a9b12d SL |
108 | }; |
109 | ||
b039eaaf | 110 | RawVec { |
83c7162d | 111 | ptr: ptr.cast().into(), |
3b2f2976 XL |
112 | cap, |
113 | a, | |
b039eaaf | 114 | } |
c1a9b12d SL |
115 | } |
116 | } | |
041b39d2 XL |
117 | } |
118 | ||
83c7162d | 119 | impl<T> RawVec<T, Global> { |
041b39d2 XL |
120 | /// Creates the biggest possible RawVec (on the system heap) |
121 | /// without allocating. If T has positive size, then this makes a | |
abe05a73 | 122 | /// RawVec with capacity 0. If T has 0 size, then it makes a |
041b39d2 XL |
123 | /// RawVec with capacity `usize::MAX`. Useful for implementing |
124 | /// delayed allocation. | |
83c7162d XL |
125 | pub const fn new() -> Self { |
126 | Self::new_in(Global) | |
041b39d2 XL |
127 | } |
128 | ||
129 | /// Creates a RawVec (on the system heap) with exactly the | |
130 | /// capacity and alignment requirements for a `[T; cap]`. This is | |
131 | /// equivalent to calling RawVec::new when `cap` is 0 or T is | |
132 | /// zero-sized. Note that if `T` is zero-sized this means you will | |
133 | /// *not* get a RawVec with the requested capacity! | |
134 | /// | |
135 | /// # Panics | |
136 | /// | |
137 | /// * Panics if the requested capacity exceeds `usize::MAX` bytes. | |
138 | /// * Panics on 32-bit platforms if the requested capacity exceeds | |
139 | /// `isize::MAX` bytes. | |
140 | /// | |
141 | /// # Aborts | |
142 | /// | |
143 | /// Aborts on OOM | |
144 | #[inline] | |
145 | pub fn with_capacity(cap: usize) -> Self { | |
83c7162d | 146 | RawVec::allocate_in(cap, false, Global) |
041b39d2 | 147 | } |
c1a9b12d | 148 | |
041b39d2 XL |
149 | /// Like `with_capacity` but guarantees the buffer is zeroed. |
150 | #[inline] | |
151 | pub fn with_capacity_zeroed(cap: usize) -> Self { | |
83c7162d | 152 | RawVec::allocate_in(cap, true, Global) |
041b39d2 XL |
153 | } |
154 | } | |
155 | ||
156 | impl<T, A: Alloc> RawVec<T, A> { | |
157 | /// Reconstitutes a RawVec from a pointer, capacity, and allocator. | |
c1a9b12d | 158 | /// |
b039eaaf | 159 | /// # Undefined Behavior |
c1a9b12d | 160 | /// |
041b39d2 XL |
161 | /// The ptr must be allocated (via the given allocator `a`), and with the given capacity. The |
162 | /// capacity cannot exceed `isize::MAX` (only a concern on 32-bit systems). | |
163 | /// If the ptr and capacity come from a RawVec created via `a`, then this is guaranteed. | |
164 | pub unsafe fn from_raw_parts_in(ptr: *mut T, cap: usize, a: A) -> Self { | |
165 | RawVec { | |
3b2f2976 XL |
166 | ptr: Unique::new_unchecked(ptr), |
167 | cap, | |
168 | a, | |
041b39d2 XL |
169 | } |
170 | } | |
171 | } | |
172 | ||
83c7162d | 173 | impl<T> RawVec<T, Global> { |
041b39d2 XL |
174 | /// Reconstitutes a RawVec from a pointer, capacity. |
175 | /// | |
176 | /// # Undefined Behavior | |
177 | /// | |
178 | /// The ptr must be allocated (on the system heap), and with the given capacity. The | |
c1a9b12d SL |
179 | /// capacity cannot exceed `isize::MAX` (only a concern on 32-bit systems). |
180 | /// If the ptr and capacity come from a RawVec, then this is guaranteed. | |
181 | pub unsafe fn from_raw_parts(ptr: *mut T, cap: usize) -> Self { | |
b039eaaf | 182 | RawVec { |
3b2f2976 XL |
183 | ptr: Unique::new_unchecked(ptr), |
184 | cap, | |
83c7162d | 185 | a: Global, |
b039eaaf | 186 | } |
c1a9b12d SL |
187 | } |
188 | ||
189 | /// Converts a `Box<[T]>` into a `RawVec<T>`. | |
190 | pub fn from_box(mut slice: Box<[T]>) -> Self { | |
191 | unsafe { | |
192 | let result = RawVec::from_raw_parts(slice.as_mut_ptr(), slice.len()); | |
193 | mem::forget(slice); | |
194 | result | |
195 | } | |
196 | } | |
197 | } | |
198 | ||
041b39d2 | 199 | impl<T, A: Alloc> RawVec<T, A> { |
c1a9b12d | 200 | /// Gets a raw pointer to the start of the allocation. Note that this is |
7cac9316 | 201 | /// Unique::empty() if `cap = 0` or T is zero-sized. In the former case, you must |
c1a9b12d SL |
202 | /// be careful. |
203 | pub fn ptr(&self) -> *mut T { | |
7cac9316 | 204 | self.ptr.as_ptr() |
c1a9b12d SL |
205 | } |
206 | ||
207 | /// Gets the capacity of the allocation. | |
208 | /// | |
209 | /// This will always be `usize::MAX` if `T` is zero-sized. | |
a7813a04 | 210 | #[inline(always)] |
c1a9b12d | 211 | pub fn cap(&self) -> usize { |
b039eaaf SL |
212 | if mem::size_of::<T>() == 0 { |
213 | !0 | |
214 | } else { | |
215 | self.cap | |
216 | } | |
c1a9b12d SL |
217 | } |
218 | ||
041b39d2 XL |
219 | /// Returns a shared reference to the allocator backing this RawVec. |
220 | pub fn alloc(&self) -> &A { | |
221 | &self.a | |
222 | } | |
223 | ||
224 | /// Returns a mutable reference to the allocator backing this RawVec. | |
225 | pub fn alloc_mut(&mut self) -> &mut A { | |
226 | &mut self.a | |
227 | } | |
228 | ||
3b2f2976 XL |
229 | fn current_layout(&self) -> Option<Layout> { |
230 | if self.cap == 0 { | |
231 | None | |
232 | } else { | |
233 | // We have an allocated chunk of memory, so we can bypass runtime | |
234 | // checks to get our current layout. | |
235 | unsafe { | |
236 | let align = mem::align_of::<T>(); | |
237 | let size = mem::size_of::<T>() * self.cap; | |
238 | Some(Layout::from_size_align_unchecked(size, align)) | |
239 | } | |
240 | } | |
241 | } | |
242 | ||
c1a9b12d SL |
243 | /// Doubles the size of the type's backing allocation. This is common enough |
244 | /// to want to do that it's easiest to just have a dedicated method. Slightly | |
245 | /// more efficient logic can be provided for this than the general case. | |
246 | /// | |
247 | /// This function is ideal for when pushing elements one-at-a-time because | |
248 | /// you don't need to incur the costs of the more general computations | |
249 | /// reserve needs to do to guard against overflow. You do however need to | |
250 | /// manually check if your `len == cap`. | |
251 | /// | |
252 | /// # Panics | |
253 | /// | |
254 | /// * Panics if T is zero-sized on the assumption that you managed to exhaust | |
255 | /// all `usize::MAX` slots in your imaginary buffer. | |
256 | /// * Panics on 32-bit platforms if the requested capacity exceeds | |
257 | /// `isize::MAX` bytes. | |
258 | /// | |
259 | /// # Aborts | |
260 | /// | |
261 | /// Aborts on OOM | |
262 | /// | |
263 | /// # Examples | |
264 | /// | |
041b39d2 XL |
265 | /// ``` |
266 | /// # #![feature(alloc)] | |
267 | /// # extern crate alloc; | |
268 | /// # use std::ptr; | |
269 | /// # use alloc::raw_vec::RawVec; | |
c1a9b12d SL |
270 | /// struct MyVec<T> { |
271 | /// buf: RawVec<T>, | |
272 | /// len: usize, | |
273 | /// } | |
274 | /// | |
275 | /// impl<T> MyVec<T> { | |
276 | /// pub fn push(&mut self, elem: T) { | |
277 | /// if self.len == self.buf.cap() { self.buf.double(); } | |
278 | /// // double would have aborted or panicked if the len exceeded | |
279 | /// // `isize::MAX` so this is safe to do unchecked now. | |
280 | /// unsafe { | |
281 | /// ptr::write(self.buf.ptr().offset(self.len as isize), elem); | |
282 | /// } | |
283 | /// self.len += 1; | |
284 | /// } | |
285 | /// } | |
041b39d2 XL |
286 | /// # fn main() { |
287 | /// # let mut vec = MyVec { buf: RawVec::new(), len: 0 }; | |
288 | /// # vec.push(1); | |
289 | /// # } | |
c1a9b12d SL |
290 | /// ``` |
291 | #[inline(never)] | |
292 | #[cold] | |
293 | pub fn double(&mut self) { | |
294 | unsafe { | |
295 | let elem_size = mem::size_of::<T>(); | |
296 | ||
297 | // since we set the capacity to usize::MAX when elem_size is | |
298 | // 0, getting to here necessarily means the RawVec is overfull. | |
299 | assert!(elem_size != 0, "capacity overflow"); | |
300 | ||
3b2f2976 XL |
301 | let (new_cap, uniq) = match self.current_layout() { |
302 | Some(cur) => { | |
303 | // Since we guarantee that we never allocate more than | |
304 | // isize::MAX bytes, `elem_size * self.cap <= isize::MAX` as | |
305 | // a precondition, so this can't overflow. Additionally the | |
306 | // alignment will never be too large as to "not be | |
307 | // satisfiable", so `Layout::from_size_align` will always | |
308 | // return `Some`. | |
309 | // | |
310 | // tl;dr; we bypass runtime checks due to dynamic assertions | |
311 | // in this module, allowing us to use | |
312 | // `from_size_align_unchecked`. | |
313 | let new_cap = 2 * self.cap; | |
314 | let new_size = new_cap * elem_size; | |
83c7162d XL |
315 | alloc_guard(new_size).unwrap_or_else(|_| capacity_overflow()); |
316 | let ptr_res = self.a.realloc(NonNull::from(self.ptr).as_opaque(), | |
3b2f2976 | 317 | cur, |
83c7162d | 318 | new_size); |
3b2f2976 | 319 | match ptr_res { |
83c7162d XL |
320 | Ok(ptr) => (new_cap, ptr.cast().into()), |
321 | Err(_) => oom(), | |
3b2f2976 XL |
322 | } |
323 | } | |
324 | None => { | |
325 | // skip to 4 because tiny Vec's are dumb; but not if that | |
326 | // would cause overflow | |
327 | let new_cap = if elem_size > (!0) / 8 { 1 } else { 4 }; | |
328 | match self.a.alloc_array::<T>(new_cap) { | |
2c00a5a8 | 329 | Ok(ptr) => (new_cap, ptr.into()), |
83c7162d | 330 | Err(_) => oom(), |
3b2f2976 XL |
331 | } |
332 | } | |
041b39d2 | 333 | }; |
041b39d2 | 334 | self.ptr = uniq; |
c1a9b12d SL |
335 | self.cap = new_cap; |
336 | } | |
337 | } | |
338 | ||
9cc50fc6 SL |
339 | /// Attempts to double the size of the type's backing allocation in place. This is common |
340 | /// enough to want to do that it's easiest to just have a dedicated method. Slightly | |
341 | /// more efficient logic can be provided for this than the general case. | |
342 | /// | |
343 | /// Returns true if the reallocation attempt has succeeded, or false otherwise. | |
344 | /// | |
345 | /// # Panics | |
346 | /// | |
347 | /// * Panics if T is zero-sized on the assumption that you managed to exhaust | |
348 | /// all `usize::MAX` slots in your imaginary buffer. | |
349 | /// * Panics on 32-bit platforms if the requested capacity exceeds | |
350 | /// `isize::MAX` bytes. | |
351 | #[inline(never)] | |
352 | #[cold] | |
353 | pub fn double_in_place(&mut self) -> bool { | |
354 | unsafe { | |
355 | let elem_size = mem::size_of::<T>(); | |
3b2f2976 XL |
356 | let old_layout = match self.current_layout() { |
357 | Some(layout) => layout, | |
358 | None => return false, // nothing to double | |
359 | }; | |
9cc50fc6 SL |
360 | |
361 | // since we set the capacity to usize::MAX when elem_size is | |
362 | // 0, getting to here necessarily means the RawVec is overfull. | |
363 | assert!(elem_size != 0, "capacity overflow"); | |
364 | ||
3b2f2976 XL |
365 | // Since we guarantee that we never allocate more than isize::MAX |
366 | // bytes, `elem_size * self.cap <= isize::MAX` as a precondition, so | |
367 | // this can't overflow. | |
368 | // | |
369 | // Similarly like with `double` above we can go straight to | |
370 | // `Layout::from_size_align_unchecked` as we know this won't | |
371 | // overflow and the alignment is sufficiently small. | |
9cc50fc6 | 372 | let new_cap = 2 * self.cap; |
3b2f2976 | 373 | let new_size = new_cap * elem_size; |
83c7162d XL |
374 | alloc_guard(new_size).unwrap_or_else(|_| capacity_overflow()); |
375 | match self.a.grow_in_place(NonNull::from(self.ptr).as_opaque(), old_layout, new_size) { | |
041b39d2 XL |
376 | Ok(_) => { |
377 | // We can't directly divide `size`. | |
378 | self.cap = new_cap; | |
379 | true | |
380 | } | |
381 | Err(_) => { | |
382 | false | |
383 | } | |
9cc50fc6 | 384 | } |
9cc50fc6 SL |
385 | } |
386 | } | |
387 | ||
c1a9b12d SL |
388 | /// Ensures that the buffer contains at least enough space to hold |
389 | /// `used_cap + needed_extra_cap` elements. If it doesn't already, | |
390 | /// will reallocate the minimum possible amount of memory necessary. | |
391 | /// Generally this will be exactly the amount of memory necessary, | |
392 | /// but in principle the allocator is free to give back more than | |
393 | /// we asked for. | |
394 | /// | |
395 | /// If `used_cap` exceeds `self.cap()`, this may fail to actually allocate | |
396 | /// the requested space. This is not really unsafe, but the unsafe | |
b039eaaf | 397 | /// code *you* write that relies on the behavior of this function may break. |
c1a9b12d SL |
398 | /// |
399 | /// # Panics | |
400 | /// | |
401 | /// * Panics if the requested capacity exceeds `usize::MAX` bytes. | |
402 | /// * Panics on 32-bit platforms if the requested capacity exceeds | |
403 | /// `isize::MAX` bytes. | |
404 | /// | |
405 | /// # Aborts | |
406 | /// | |
407 | /// Aborts on OOM | |
0531ce1d XL |
408 | pub fn try_reserve_exact(&mut self, used_cap: usize, needed_extra_cap: usize) |
409 | -> Result<(), CollectionAllocErr> { | |
410 | ||
c1a9b12d | 411 | unsafe { |
c1a9b12d SL |
412 | // NOTE: we don't early branch on ZSTs here because we want this |
413 | // to actually catch "asking for more than usize::MAX" in that case. | |
414 | // If we make it past the first branch then we are guaranteed to | |
415 | // panic. | |
416 | ||
417 | // Don't actually need any more capacity. | |
418 | // Wrapping in case they gave a bad `used_cap`. | |
b039eaaf | 419 | if self.cap().wrapping_sub(used_cap) >= needed_extra_cap { |
0531ce1d | 420 | return Ok(()); |
b039eaaf | 421 | } |
c1a9b12d SL |
422 | |
423 | // Nothing we can really do about these checks :( | |
0531ce1d | 424 | let new_cap = used_cap.checked_add(needed_extra_cap).ok_or(CapacityOverflow)?; |
83c7162d | 425 | let new_layout = Layout::array::<T>(new_cap).map_err(|_| CapacityOverflow)?; |
0531ce1d XL |
426 | |
427 | alloc_guard(new_layout.size())?; | |
428 | ||
3b2f2976 XL |
429 | let res = match self.current_layout() { |
430 | Some(layout) => { | |
83c7162d XL |
431 | debug_assert!(new_layout.align() == layout.align()); |
432 | self.a.realloc(NonNull::from(self.ptr).as_opaque(), layout, new_layout.size()) | |
3b2f2976 XL |
433 | } |
434 | None => self.a.alloc(new_layout), | |
435 | }; | |
0531ce1d | 436 | |
83c7162d | 437 | self.ptr = res?.cast().into(); |
c1a9b12d | 438 | self.cap = new_cap; |
0531ce1d XL |
439 | |
440 | Ok(()) | |
c1a9b12d SL |
441 | } |
442 | } | |
443 | ||
0531ce1d XL |
444 | pub fn reserve_exact(&mut self, used_cap: usize, needed_extra_cap: usize) { |
445 | match self.try_reserve_exact(used_cap, needed_extra_cap) { | |
83c7162d XL |
446 | Err(CapacityOverflow) => capacity_overflow(), |
447 | Err(AllocErr) => oom(), | |
0531ce1d XL |
448 | Ok(()) => { /* yay */ } |
449 | } | |
450 | } | |
451 | ||
9cc50fc6 SL |
452 | /// Calculates the buffer's new size given that it'll hold `used_cap + |
453 | /// needed_extra_cap` elements. This logic is used in amortized reserve methods. | |
454 | /// Returns `(new_capacity, new_alloc_size)`. | |
0531ce1d XL |
455 | fn amortized_new_size(&self, used_cap: usize, needed_extra_cap: usize) |
456 | -> Result<usize, CollectionAllocErr> { | |
457 | ||
9cc50fc6 | 458 | // Nothing we can really do about these checks :( |
0531ce1d | 459 | let required_cap = used_cap.checked_add(needed_extra_cap).ok_or(CapacityOverflow)?; |
9cc50fc6 SL |
460 | // Cannot overflow, because `cap <= isize::MAX`, and type of `cap` is `usize`. |
461 | let double_cap = self.cap * 2; | |
462 | // `double_cap` guarantees exponential growth. | |
0531ce1d | 463 | Ok(cmp::max(double_cap, required_cap)) |
9cc50fc6 SL |
464 | } |
465 | ||
c1a9b12d SL |
466 | /// Ensures that the buffer contains at least enough space to hold |
467 | /// `used_cap + needed_extra_cap` elements. If it doesn't already have | |
468 | /// enough capacity, will reallocate enough space plus comfortable slack | |
b039eaaf | 469 | /// space to get amortized `O(1)` behavior. Will limit this behavior |
c1a9b12d SL |
470 | /// if it would needlessly cause itself to panic. |
471 | /// | |
472 | /// If `used_cap` exceeds `self.cap()`, this may fail to actually allocate | |
473 | /// the requested space. This is not really unsafe, but the unsafe | |
b039eaaf | 474 | /// code *you* write that relies on the behavior of this function may break. |
c1a9b12d SL |
475 | /// |
476 | /// This is ideal for implementing a bulk-push operation like `extend`. | |
477 | /// | |
478 | /// # Panics | |
479 | /// | |
480 | /// * Panics if the requested capacity exceeds `usize::MAX` bytes. | |
481 | /// * Panics on 32-bit platforms if the requested capacity exceeds | |
482 | /// `isize::MAX` bytes. | |
483 | /// | |
484 | /// # Aborts | |
485 | /// | |
486 | /// Aborts on OOM | |
487 | /// | |
488 | /// # Examples | |
489 | /// | |
041b39d2 XL |
490 | /// ``` |
491 | /// # #![feature(alloc)] | |
492 | /// # extern crate alloc; | |
493 | /// # use std::ptr; | |
494 | /// # use alloc::raw_vec::RawVec; | |
c1a9b12d SL |
495 | /// struct MyVec<T> { |
496 | /// buf: RawVec<T>, | |
497 | /// len: usize, | |
498 | /// } | |
499 | /// | |
041b39d2 | 500 | /// impl<T: Clone> MyVec<T> { |
c1a9b12d SL |
501 | /// pub fn push_all(&mut self, elems: &[T]) { |
502 | /// self.buf.reserve(self.len, elems.len()); | |
503 | /// // reserve would have aborted or panicked if the len exceeded | |
504 | /// // `isize::MAX` so this is safe to do unchecked now. | |
505 | /// for x in elems { | |
506 | /// unsafe { | |
507 | /// ptr::write(self.buf.ptr().offset(self.len as isize), x.clone()); | |
508 | /// } | |
509 | /// self.len += 1; | |
510 | /// } | |
511 | /// } | |
512 | /// } | |
041b39d2 XL |
513 | /// # fn main() { |
514 | /// # let mut vector = MyVec { buf: RawVec::new(), len: 0 }; | |
515 | /// # vector.push_all(&[1, 3, 5, 7, 9]); | |
516 | /// # } | |
c1a9b12d | 517 | /// ``` |
0531ce1d XL |
518 | pub fn try_reserve(&mut self, used_cap: usize, needed_extra_cap: usize) |
519 | -> Result<(), CollectionAllocErr> { | |
520 | unsafe { | |
c1a9b12d SL |
521 | // NOTE: we don't early branch on ZSTs here because we want this |
522 | // to actually catch "asking for more than usize::MAX" in that case. | |
523 | // If we make it past the first branch then we are guaranteed to | |
524 | // panic. | |
525 | ||
526 | // Don't actually need any more capacity. | |
92a42be0 | 527 | // Wrapping in case they give a bad `used_cap` |
b039eaaf | 528 | if self.cap().wrapping_sub(used_cap) >= needed_extra_cap { |
0531ce1d | 529 | return Ok(()); |
b039eaaf | 530 | } |
c1a9b12d | 531 | |
0531ce1d | 532 | let new_cap = self.amortized_new_size(used_cap, needed_extra_cap)?; |
83c7162d | 533 | let new_layout = Layout::array::<T>(new_cap).map_err(|_| CapacityOverflow)?; |
0531ce1d XL |
534 | |
535 | // FIXME: may crash and burn on over-reserve | |
536 | alloc_guard(new_layout.size())?; | |
c1a9b12d | 537 | |
3b2f2976 XL |
538 | let res = match self.current_layout() { |
539 | Some(layout) => { | |
83c7162d XL |
540 | debug_assert!(new_layout.align() == layout.align()); |
541 | self.a.realloc(NonNull::from(self.ptr).as_opaque(), layout, new_layout.size()) | |
3b2f2976 XL |
542 | } |
543 | None => self.a.alloc(new_layout), | |
544 | }; | |
0531ce1d | 545 | |
83c7162d | 546 | self.ptr = res?.cast().into(); |
c1a9b12d | 547 | self.cap = new_cap; |
0531ce1d XL |
548 | |
549 | Ok(()) | |
c1a9b12d SL |
550 | } |
551 | } | |
552 | ||
0531ce1d XL |
553 | /// The same as try_reserve, but errors are lowered to a call to oom(). |
554 | pub fn reserve(&mut self, used_cap: usize, needed_extra_cap: usize) { | |
555 | match self.try_reserve(used_cap, needed_extra_cap) { | |
83c7162d XL |
556 | Err(CapacityOverflow) => capacity_overflow(), |
557 | Err(AllocErr) => oom(), | |
0531ce1d XL |
558 | Ok(()) => { /* yay */ } |
559 | } | |
560 | } | |
9cc50fc6 SL |
561 | /// Attempts to ensure that the buffer contains at least enough space to hold |
562 | /// `used_cap + needed_extra_cap` elements. If it doesn't already have | |
563 | /// enough capacity, will reallocate in place enough space plus comfortable slack | |
3b2f2976 | 564 | /// space to get amortized `O(1)` behavior. Will limit this behaviour |
9cc50fc6 SL |
565 | /// if it would needlessly cause itself to panic. |
566 | /// | |
567 | /// If `used_cap` exceeds `self.cap()`, this may fail to actually allocate | |
568 | /// the requested space. This is not really unsafe, but the unsafe | |
3b2f2976 | 569 | /// code *you* write that relies on the behavior of this function may break. |
9cc50fc6 SL |
570 | /// |
571 | /// Returns true if the reallocation attempt has succeeded, or false otherwise. | |
572 | /// | |
573 | /// # Panics | |
574 | /// | |
575 | /// * Panics if the requested capacity exceeds `usize::MAX` bytes. | |
576 | /// * Panics on 32-bit platforms if the requested capacity exceeds | |
577 | /// `isize::MAX` bytes. | |
578 | pub fn reserve_in_place(&mut self, used_cap: usize, needed_extra_cap: usize) -> bool { | |
579 | unsafe { | |
9cc50fc6 SL |
580 | // NOTE: we don't early branch on ZSTs here because we want this |
581 | // to actually catch "asking for more than usize::MAX" in that case. | |
582 | // If we make it past the first branch then we are guaranteed to | |
583 | // panic. | |
584 | ||
585 | // Don't actually need any more capacity. If the current `cap` is 0, we can't | |
586 | // reallocate in place. | |
587 | // Wrapping in case they give a bad `used_cap` | |
3b2f2976 XL |
588 | let old_layout = match self.current_layout() { |
589 | Some(layout) => layout, | |
590 | None => return false, | |
591 | }; | |
592 | if self.cap().wrapping_sub(used_cap) >= needed_extra_cap { | |
9cc50fc6 SL |
593 | return false; |
594 | } | |
595 | ||
0531ce1d | 596 | let new_cap = self.amortized_new_size(used_cap, needed_extra_cap) |
83c7162d | 597 | .unwrap_or_else(|_| capacity_overflow()); |
9cc50fc6 | 598 | |
041b39d2 XL |
599 | // Here, `cap < used_cap + needed_extra_cap <= new_cap` |
600 | // (regardless of whether `self.cap - used_cap` wrapped). | |
601 | // Therefore we can safely call grow_in_place. | |
602 | ||
041b39d2 | 603 | let new_layout = Layout::new::<T>().repeat(new_cap).unwrap().0; |
3b2f2976 | 604 | // FIXME: may crash and burn on over-reserve |
83c7162d XL |
605 | alloc_guard(new_layout.size()).unwrap_or_else(|_| capacity_overflow()); |
606 | match self.a.grow_in_place( | |
607 | NonNull::from(self.ptr).as_opaque(), old_layout, new_layout.size(), | |
608 | ) { | |
041b39d2 XL |
609 | Ok(_) => { |
610 | self.cap = new_cap; | |
611 | true | |
612 | } | |
613 | Err(_) => { | |
614 | false | |
615 | } | |
9cc50fc6 | 616 | } |
9cc50fc6 SL |
617 | } |
618 | } | |
619 | ||
c1a9b12d SL |
620 | /// Shrinks the allocation down to the specified amount. If the given amount |
621 | /// is 0, actually completely deallocates. | |
622 | /// | |
623 | /// # Panics | |
624 | /// | |
625 | /// Panics if the given amount is *larger* than the current capacity. | |
626 | /// | |
627 | /// # Aborts | |
628 | /// | |
629 | /// Aborts on OOM. | |
630 | pub fn shrink_to_fit(&mut self, amount: usize) { | |
631 | let elem_size = mem::size_of::<T>(); | |
c1a9b12d SL |
632 | |
633 | // Set the `cap` because they might be about to promote to a `Box<[T]>` | |
634 | if elem_size == 0 { | |
635 | self.cap = amount; | |
636 | return; | |
637 | } | |
638 | ||
639 | // This check is my waterloo; it's the only thing Vec wouldn't have to do. | |
640 | assert!(self.cap >= amount, "Tried to shrink to a larger capacity"); | |
641 | ||
642 | if amount == 0 { | |
041b39d2 XL |
643 | // We want to create a new zero-length vector within the |
644 | // same allocator. We use ptr::write to avoid an | |
645 | // erroneous attempt to drop the contents, and we use | |
646 | // ptr::read to sidestep condition against destructuring | |
647 | // types that implement Drop. | |
648 | ||
649 | unsafe { | |
650 | let a = ptr::read(&self.a as *const A); | |
651 | self.dealloc_buffer(); | |
652 | ptr::write(self, RawVec::new_in(a)); | |
653 | } | |
c1a9b12d SL |
654 | } else if self.cap != amount { |
655 | unsafe { | |
3b2f2976 XL |
656 | // We know here that our `amount` is greater than zero. This |
657 | // implies, via the assert above, that capacity is also greater | |
658 | // than zero, which means that we've got a current layout that | |
659 | // "fits" | |
660 | // | |
661 | // We also know that `self.cap` is greater than `amount`, and | |
662 | // consequently we don't need runtime checks for creating either | |
663 | // layout | |
664 | let old_size = elem_size * self.cap; | |
665 | let new_size = elem_size * amount; | |
666 | let align = mem::align_of::<T>(); | |
667 | let old_layout = Layout::from_size_align_unchecked(old_size, align); | |
83c7162d | 668 | match self.a.realloc(NonNull::from(self.ptr).as_opaque(), |
3b2f2976 | 669 | old_layout, |
83c7162d XL |
670 | new_size) { |
671 | Ok(p) => self.ptr = p.cast().into(), | |
672 | Err(_) => oom(), | |
b039eaaf | 673 | } |
c1a9b12d SL |
674 | } |
675 | self.cap = amount; | |
676 | } | |
677 | } | |
041b39d2 | 678 | } |
c1a9b12d | 679 | |
83c7162d | 680 | impl<T> RawVec<T, Global> { |
c1a9b12d SL |
681 | /// Converts the entire buffer into `Box<[T]>`. |
682 | /// | |
b039eaaf | 683 | /// While it is not *strictly* Undefined Behavior to call |
5bcae85e SL |
684 | /// this procedure while some of the RawVec is uninitialized, |
685 | /// it certainly makes it trivial to trigger it. | |
c1a9b12d SL |
686 | /// |
687 | /// Note that this will correctly reconstitute any `cap` changes | |
688 | /// that may have been performed. (see description of type for details) | |
689 | pub unsafe fn into_box(self) -> Box<[T]> { | |
690 | // NOTE: not calling `cap()` here, actually using the real `cap` field! | |
691 | let slice = slice::from_raw_parts_mut(self.ptr(), self.cap); | |
692 | let output: Box<[T]> = Box::from_raw(slice); | |
693 | mem::forget(self); | |
694 | output | |
695 | } | |
c1a9b12d SL |
696 | } |
697 | ||
041b39d2 | 698 | impl<T, A: Alloc> RawVec<T, A> { |
c1a9b12d | 699 | /// Frees the memory owned by the RawVec *without* trying to Drop its contents. |
041b39d2 | 700 | pub unsafe fn dealloc_buffer(&mut self) { |
c1a9b12d | 701 | let elem_size = mem::size_of::<T>(); |
3b2f2976 XL |
702 | if elem_size != 0 { |
703 | if let Some(layout) = self.current_layout() { | |
83c7162d | 704 | self.a.dealloc(NonNull::from(self.ptr).as_opaque(), layout); |
3b2f2976 | 705 | } |
c1a9b12d SL |
706 | } |
707 | } | |
708 | } | |
709 | ||
041b39d2 XL |
710 | unsafe impl<#[may_dangle] T, A: Alloc> Drop for RawVec<T, A> { |
711 | /// Frees the memory owned by the RawVec *without* trying to Drop its contents. | |
712 | fn drop(&mut self) { | |
713 | unsafe { self.dealloc_buffer(); } | |
714 | } | |
715 | } | |
716 | ||
c1a9b12d SL |
717 | |
718 | ||
719 | // We need to guarantee the following: | |
720 | // * We don't ever allocate `> isize::MAX` byte-size objects | |
721 | // * We don't overflow `usize::MAX` and actually allocate too little | |
722 | // | |
723 | // On 64-bit we just need to check for overflow since trying to allocate | |
3157f602 XL |
724 | // `> isize::MAX` bytes will surely fail. On 32-bit and 16-bit we need to add |
725 | // an extra guard for this in case we're running on a platform which can use | |
726 | // all 4GB in user-space. e.g. PAE or x32 | |
c1a9b12d SL |
727 | |
728 | #[inline] | |
0531ce1d XL |
729 | fn alloc_guard(alloc_size: usize) -> Result<(), CollectionAllocErr> { |
730 | if mem::size_of::<usize>() < 8 && alloc_size > ::core::isize::MAX as usize { | |
731 | Err(CapacityOverflow) | |
732 | } else { | |
733 | Ok(()) | |
e9174d1e | 734 | } |
c1a9b12d | 735 | } |
92a42be0 | 736 | |
83c7162d XL |
737 | // One central function responsible for reporting capacity overflows. This'll |
738 | // ensure that the code generation related to these panics is minimal as there's | |
739 | // only one location which panics rather than a bunch throughout the module. | |
740 | fn capacity_overflow() -> ! { | |
741 | panic!("capacity overflow") | |
742 | } | |
743 | ||
92a42be0 SL |
744 | #[cfg(test)] |
745 | mod tests { | |
746 | use super::*; | |
83c7162d | 747 | use alloc::Opaque; |
92a42be0 | 748 | |
041b39d2 XL |
749 | #[test] |
750 | fn allocator_param() { | |
751 | use allocator::{Alloc, AllocErr}; | |
752 | ||
753 | // Writing a test of integration between third-party | |
754 | // allocators and RawVec is a little tricky because the RawVec | |
755 | // API does not expose fallible allocation methods, so we | |
756 | // cannot check what happens when allocator is exhausted | |
757 | // (beyond detecting a panic). | |
758 | // | |
759 | // Instead, this just checks that the RawVec methods do at | |
760 | // least go through the Allocator API when it reserves | |
761 | // storage. | |
762 | ||
763 | // A dumb allocator that consumes a fixed amount of fuel | |
764 | // before allocation attempts start failing. | |
765 | struct BoundedAlloc { fuel: usize } | |
766 | unsafe impl Alloc for BoundedAlloc { | |
83c7162d | 767 | unsafe fn alloc(&mut self, layout: Layout) -> Result<NonNull<Opaque>, AllocErr> { |
041b39d2 XL |
768 | let size = layout.size(); |
769 | if size > self.fuel { | |
83c7162d | 770 | return Err(AllocErr); |
041b39d2 | 771 | } |
83c7162d | 772 | match Global.alloc(layout) { |
041b39d2 XL |
773 | ok @ Ok(_) => { self.fuel -= size; ok } |
774 | err @ Err(_) => err, | |
775 | } | |
776 | } | |
83c7162d XL |
777 | unsafe fn dealloc(&mut self, ptr: NonNull<Opaque>, layout: Layout) { |
778 | Global.dealloc(ptr, layout) | |
041b39d2 XL |
779 | } |
780 | } | |
781 | ||
782 | let a = BoundedAlloc { fuel: 500 }; | |
783 | let mut v: RawVec<u8, _> = RawVec::with_capacity_in(50, a); | |
784 | assert_eq!(v.a.fuel, 450); | |
785 | v.reserve(50, 150); // (causes a realloc, thus using 50 + 150 = 200 units of fuel) | |
786 | assert_eq!(v.a.fuel, 250); | |
787 | } | |
788 | ||
92a42be0 SL |
789 | #[test] |
790 | fn reserve_does_not_overallocate() { | |
791 | { | |
792 | let mut v: RawVec<u32> = RawVec::new(); | |
793 | // First `reserve` allocates like `reserve_exact` | |
794 | v.reserve(0, 9); | |
795 | assert_eq!(9, v.cap()); | |
796 | } | |
797 | ||
798 | { | |
799 | let mut v: RawVec<u32> = RawVec::new(); | |
800 | v.reserve(0, 7); | |
801 | assert_eq!(7, v.cap()); | |
802 | // 97 if more than double of 7, so `reserve` should work | |
803 | // like `reserve_exact`. | |
804 | v.reserve(7, 90); | |
805 | assert_eq!(97, v.cap()); | |
806 | } | |
807 | ||
808 | { | |
809 | let mut v: RawVec<u32> = RawVec::new(); | |
810 | v.reserve(0, 12); | |
811 | assert_eq!(12, v.cap()); | |
812 | v.reserve(12, 3); | |
813 | // 3 is less than half of 12, so `reserve` must grow | |
814 | // exponentially. At the time of writing this test grow | |
815 | // factor is 2, so new capacity is 24, however, grow factor | |
816 | // of 1.5 is OK too. Hence `>= 18` in assert. | |
817 | assert!(v.cap() >= 12 + 12 / 2); | |
818 | } | |
819 | } | |
820 | ||
041b39d2 | 821 | |
92a42be0 | 822 | } |