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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 XL |
13 | use core::ops::Drop; |
14 | use core::ptr::{self, Unique}; | |
92a42be0 | 15 | use core::slice; |
3b2f2976 | 16 | use heap::{Alloc, Layout, Heap}; |
c1a9b12d | 17 | use super::boxed::Box; |
c1a9b12d | 18 | |
5bcae85e | 19 | /// A low-level utility for more ergonomically allocating, reallocating, and deallocating |
c1a9b12d SL |
20 | /// a buffer of memory on the heap without having to worry about all the corner cases |
21 | /// involved. This type is excellent for building your own data structures like Vec and VecDeque. | |
22 | /// In particular: | |
23 | /// | |
7cac9316 XL |
24 | /// * Produces Unique::empty() on zero-sized types |
25 | /// * Produces Unique::empty() on zero-length allocations | |
c1a9b12d SL |
26 | /// * Catches all overflows in capacity computations (promotes them to "capacity overflow" panics) |
27 | /// * Guards against 32-bit systems allocating more than isize::MAX bytes | |
28 | /// * Guards against overflowing your length | |
29 | /// * Aborts on OOM | |
7cac9316 | 30 | /// * Avoids freeing Unique::empty() |
c1a9b12d SL |
31 | /// * Contains a ptr::Unique and thus endows the user with all related benefits |
32 | /// | |
33 | /// This type does not in anyway inspect the memory that it manages. When dropped it *will* | |
34 | /// free its memory, but it *won't* try to Drop its contents. It is up to the user of RawVec | |
35 | /// to handle the actual things *stored* inside of a RawVec. | |
36 | /// | |
37 | /// Note that a RawVec always forces its capacity to be usize::MAX for zero-sized types. | |
38 | /// This enables you to use capacity growing logic catch the overflows in your length | |
39 | /// that might occur with zero-sized types. | |
40 | /// | |
41 | /// However this means that you need to be careful when roundtripping this type | |
42 | /// with a `Box<[T]>`: `cap()` won't yield the len. However `with_capacity`, | |
43 | /// `shrink_to_fit`, and `from_box` will actually set RawVec's private capacity | |
44 | /// field. This allows zero-sized types to not be special-cased by consumers of | |
45 | /// this type. | |
041b39d2 XL |
46 | #[allow(missing_debug_implementations)] |
47 | pub struct RawVec<T, A: Alloc = Heap> { | |
c1a9b12d SL |
48 | ptr: Unique<T>, |
49 | cap: usize, | |
041b39d2 | 50 | a: A, |
c1a9b12d SL |
51 | } |
52 | ||
041b39d2 XL |
53 | impl<T, A: Alloc> RawVec<T, A> { |
54 | /// Like `new` but parameterized over the choice of allocator for | |
55 | /// the returned RawVec. | |
56 | pub fn new_in(a: A) -> Self { | |
7cac9316 XL |
57 | // !0 is usize::MAX. This branch should be stripped at compile time. |
58 | let cap = if mem::size_of::<T>() == 0 { !0 } else { 0 }; | |
c1a9b12d | 59 | |
7cac9316 XL |
60 | // Unique::empty() doubles as "unallocated" and "zero-sized allocation" |
61 | RawVec { | |
62 | ptr: Unique::empty(), | |
3b2f2976 XL |
63 | cap, |
64 | a, | |
c1a9b12d SL |
65 | } |
66 | } | |
67 | ||
041b39d2 XL |
68 | /// Like `with_capacity` but parameterized over the choice of |
69 | /// allocator for the returned RawVec. | |
cc61c64b | 70 | #[inline] |
041b39d2 XL |
71 | pub fn with_capacity_in(cap: usize, a: A) -> Self { |
72 | RawVec::allocate_in(cap, false, a) | |
cc61c64b XL |
73 | } |
74 | ||
041b39d2 XL |
75 | /// Like `with_capacity_zeroed` but parameterized over the choice |
76 | /// of allocator for the returned RawVec. | |
cc61c64b | 77 | #[inline] |
041b39d2 XL |
78 | pub fn with_capacity_zeroed_in(cap: usize, a: A) -> Self { |
79 | RawVec::allocate_in(cap, true, a) | |
cc61c64b XL |
80 | } |
81 | ||
041b39d2 | 82 | fn allocate_in(cap: usize, zeroed: bool, mut a: A) -> Self { |
c1a9b12d SL |
83 | unsafe { |
84 | let elem_size = mem::size_of::<T>(); | |
85 | ||
86 | let alloc_size = cap.checked_mul(elem_size).expect("capacity overflow"); | |
87 | alloc_guard(alloc_size); | |
88 | ||
89 | // handles ZSTs and `cap = 0` alike | |
90 | let ptr = if alloc_size == 0 { | |
7cac9316 | 91 | mem::align_of::<T>() as *mut u8 |
c1a9b12d SL |
92 | } else { |
93 | let align = mem::align_of::<T>(); | |
041b39d2 XL |
94 | let result = if zeroed { |
95 | a.alloc_zeroed(Layout::from_size_align(alloc_size, align).unwrap()) | |
cc61c64b | 96 | } else { |
041b39d2 | 97 | a.alloc(Layout::from_size_align(alloc_size, align).unwrap()) |
cc61c64b | 98 | }; |
041b39d2 XL |
99 | match result { |
100 | Ok(ptr) => ptr, | |
101 | Err(err) => a.oom(err), | |
b039eaaf | 102 | } |
c1a9b12d SL |
103 | }; |
104 | ||
b039eaaf | 105 | RawVec { |
3b2f2976 XL |
106 | ptr: Unique::new_unchecked(ptr as *mut _), |
107 | cap, | |
108 | a, | |
b039eaaf | 109 | } |
c1a9b12d SL |
110 | } |
111 | } | |
041b39d2 XL |
112 | } |
113 | ||
114 | impl<T> RawVec<T, Heap> { | |
115 | /// Creates the biggest possible RawVec (on the system heap) | |
116 | /// without allocating. If T has positive size, then this makes a | |
abe05a73 | 117 | /// RawVec with capacity 0. If T has 0 size, then it makes a |
041b39d2 XL |
118 | /// RawVec with capacity `usize::MAX`. Useful for implementing |
119 | /// delayed allocation. | |
120 | pub fn new() -> Self { | |
121 | Self::new_in(Heap) | |
122 | } | |
123 | ||
124 | /// Creates a RawVec (on the system heap) with exactly the | |
125 | /// capacity and alignment requirements for a `[T; cap]`. This is | |
126 | /// equivalent to calling RawVec::new when `cap` is 0 or T is | |
127 | /// zero-sized. Note that if `T` is zero-sized this means you will | |
128 | /// *not* get a RawVec with the requested capacity! | |
129 | /// | |
130 | /// # Panics | |
131 | /// | |
132 | /// * Panics if the requested capacity exceeds `usize::MAX` bytes. | |
133 | /// * Panics on 32-bit platforms if the requested capacity exceeds | |
134 | /// `isize::MAX` bytes. | |
135 | /// | |
136 | /// # Aborts | |
137 | /// | |
138 | /// Aborts on OOM | |
139 | #[inline] | |
140 | pub fn with_capacity(cap: usize) -> Self { | |
141 | RawVec::allocate_in(cap, false, Heap) | |
142 | } | |
c1a9b12d | 143 | |
041b39d2 XL |
144 | /// Like `with_capacity` but guarantees the buffer is zeroed. |
145 | #[inline] | |
146 | pub fn with_capacity_zeroed(cap: usize) -> Self { | |
147 | RawVec::allocate_in(cap, true, Heap) | |
148 | } | |
149 | } | |
150 | ||
151 | impl<T, A: Alloc> RawVec<T, A> { | |
152 | /// Reconstitutes a RawVec from a pointer, capacity, and allocator. | |
c1a9b12d | 153 | /// |
b039eaaf | 154 | /// # Undefined Behavior |
c1a9b12d | 155 | /// |
041b39d2 XL |
156 | /// The ptr must be allocated (via the given allocator `a`), and with the given capacity. The |
157 | /// capacity cannot exceed `isize::MAX` (only a concern on 32-bit systems). | |
158 | /// If the ptr and capacity come from a RawVec created via `a`, then this is guaranteed. | |
159 | pub unsafe fn from_raw_parts_in(ptr: *mut T, cap: usize, a: A) -> Self { | |
160 | RawVec { | |
3b2f2976 XL |
161 | ptr: Unique::new_unchecked(ptr), |
162 | cap, | |
163 | a, | |
041b39d2 XL |
164 | } |
165 | } | |
166 | } | |
167 | ||
168 | impl<T> RawVec<T, Heap> { | |
169 | /// Reconstitutes a RawVec from a pointer, capacity. | |
170 | /// | |
171 | /// # Undefined Behavior | |
172 | /// | |
173 | /// The ptr must be allocated (on the system heap), and with the given capacity. The | |
c1a9b12d SL |
174 | /// capacity cannot exceed `isize::MAX` (only a concern on 32-bit systems). |
175 | /// If the ptr and capacity come from a RawVec, then this is guaranteed. | |
176 | pub unsafe fn from_raw_parts(ptr: *mut T, cap: usize) -> Self { | |
b039eaaf | 177 | RawVec { |
3b2f2976 XL |
178 | ptr: Unique::new_unchecked(ptr), |
179 | cap, | |
041b39d2 | 180 | a: Heap, |
b039eaaf | 181 | } |
c1a9b12d SL |
182 | } |
183 | ||
184 | /// Converts a `Box<[T]>` into a `RawVec<T>`. | |
185 | pub fn from_box(mut slice: Box<[T]>) -> Self { | |
186 | unsafe { | |
187 | let result = RawVec::from_raw_parts(slice.as_mut_ptr(), slice.len()); | |
188 | mem::forget(slice); | |
189 | result | |
190 | } | |
191 | } | |
192 | } | |
193 | ||
041b39d2 | 194 | impl<T, A: Alloc> RawVec<T, A> { |
c1a9b12d | 195 | /// Gets a raw pointer to the start of the allocation. Note that this is |
7cac9316 | 196 | /// Unique::empty() if `cap = 0` or T is zero-sized. In the former case, you must |
c1a9b12d SL |
197 | /// be careful. |
198 | pub fn ptr(&self) -> *mut T { | |
7cac9316 | 199 | self.ptr.as_ptr() |
c1a9b12d SL |
200 | } |
201 | ||
202 | /// Gets the capacity of the allocation. | |
203 | /// | |
204 | /// This will always be `usize::MAX` if `T` is zero-sized. | |
a7813a04 | 205 | #[inline(always)] |
c1a9b12d | 206 | pub fn cap(&self) -> usize { |
b039eaaf SL |
207 | if mem::size_of::<T>() == 0 { |
208 | !0 | |
209 | } else { | |
210 | self.cap | |
211 | } | |
c1a9b12d SL |
212 | } |
213 | ||
041b39d2 XL |
214 | /// Returns a shared reference to the allocator backing this RawVec. |
215 | pub fn alloc(&self) -> &A { | |
216 | &self.a | |
217 | } | |
218 | ||
219 | /// Returns a mutable reference to the allocator backing this RawVec. | |
220 | pub fn alloc_mut(&mut self) -> &mut A { | |
221 | &mut self.a | |
222 | } | |
223 | ||
3b2f2976 XL |
224 | fn current_layout(&self) -> Option<Layout> { |
225 | if self.cap == 0 { | |
226 | None | |
227 | } else { | |
228 | // We have an allocated chunk of memory, so we can bypass runtime | |
229 | // checks to get our current layout. | |
230 | unsafe { | |
231 | let align = mem::align_of::<T>(); | |
232 | let size = mem::size_of::<T>() * self.cap; | |
233 | Some(Layout::from_size_align_unchecked(size, align)) | |
234 | } | |
235 | } | |
236 | } | |
237 | ||
c1a9b12d SL |
238 | /// Doubles the size of the type's backing allocation. This is common enough |
239 | /// to want to do that it's easiest to just have a dedicated method. Slightly | |
240 | /// more efficient logic can be provided for this than the general case. | |
241 | /// | |
242 | /// This function is ideal for when pushing elements one-at-a-time because | |
243 | /// you don't need to incur the costs of the more general computations | |
244 | /// reserve needs to do to guard against overflow. You do however need to | |
245 | /// manually check if your `len == cap`. | |
246 | /// | |
247 | /// # Panics | |
248 | /// | |
249 | /// * Panics if T is zero-sized on the assumption that you managed to exhaust | |
250 | /// all `usize::MAX` slots in your imaginary buffer. | |
251 | /// * Panics on 32-bit platforms if the requested capacity exceeds | |
252 | /// `isize::MAX` bytes. | |
253 | /// | |
254 | /// # Aborts | |
255 | /// | |
256 | /// Aborts on OOM | |
257 | /// | |
258 | /// # Examples | |
259 | /// | |
041b39d2 XL |
260 | /// ``` |
261 | /// # #![feature(alloc)] | |
262 | /// # extern crate alloc; | |
263 | /// # use std::ptr; | |
264 | /// # use alloc::raw_vec::RawVec; | |
c1a9b12d SL |
265 | /// struct MyVec<T> { |
266 | /// buf: RawVec<T>, | |
267 | /// len: usize, | |
268 | /// } | |
269 | /// | |
270 | /// impl<T> MyVec<T> { | |
271 | /// pub fn push(&mut self, elem: T) { | |
272 | /// if self.len == self.buf.cap() { self.buf.double(); } | |
273 | /// // double would have aborted or panicked if the len exceeded | |
274 | /// // `isize::MAX` so this is safe to do unchecked now. | |
275 | /// unsafe { | |
276 | /// ptr::write(self.buf.ptr().offset(self.len as isize), elem); | |
277 | /// } | |
278 | /// self.len += 1; | |
279 | /// } | |
280 | /// } | |
041b39d2 XL |
281 | /// # fn main() { |
282 | /// # let mut vec = MyVec { buf: RawVec::new(), len: 0 }; | |
283 | /// # vec.push(1); | |
284 | /// # } | |
c1a9b12d SL |
285 | /// ``` |
286 | #[inline(never)] | |
287 | #[cold] | |
288 | pub fn double(&mut self) { | |
289 | unsafe { | |
290 | let elem_size = mem::size_of::<T>(); | |
291 | ||
292 | // since we set the capacity to usize::MAX when elem_size is | |
293 | // 0, getting to here necessarily means the RawVec is overfull. | |
294 | assert!(elem_size != 0, "capacity overflow"); | |
295 | ||
3b2f2976 XL |
296 | let (new_cap, uniq) = match self.current_layout() { |
297 | Some(cur) => { | |
298 | // Since we guarantee that we never allocate more than | |
299 | // isize::MAX bytes, `elem_size * self.cap <= isize::MAX` as | |
300 | // a precondition, so this can't overflow. Additionally the | |
301 | // alignment will never be too large as to "not be | |
302 | // satisfiable", so `Layout::from_size_align` will always | |
303 | // return `Some`. | |
304 | // | |
305 | // tl;dr; we bypass runtime checks due to dynamic assertions | |
306 | // in this module, allowing us to use | |
307 | // `from_size_align_unchecked`. | |
308 | let new_cap = 2 * self.cap; | |
309 | let new_size = new_cap * elem_size; | |
310 | let new_layout = Layout::from_size_align_unchecked(new_size, cur.align()); | |
311 | alloc_guard(new_size); | |
312 | let ptr_res = self.a.realloc(self.ptr.as_ptr() as *mut u8, | |
313 | cur, | |
314 | new_layout); | |
315 | match ptr_res { | |
316 | Ok(ptr) => (new_cap, Unique::new_unchecked(ptr as *mut T)), | |
317 | Err(e) => self.a.oom(e), | |
318 | } | |
319 | } | |
320 | None => { | |
321 | // skip to 4 because tiny Vec's are dumb; but not if that | |
322 | // would cause overflow | |
323 | let new_cap = if elem_size > (!0) / 8 { 1 } else { 4 }; | |
324 | match self.a.alloc_array::<T>(new_cap) { | |
325 | Ok(ptr) => (new_cap, ptr), | |
326 | Err(e) => self.a.oom(e), | |
327 | } | |
328 | } | |
041b39d2 | 329 | }; |
041b39d2 | 330 | self.ptr = uniq; |
c1a9b12d SL |
331 | self.cap = new_cap; |
332 | } | |
333 | } | |
334 | ||
9cc50fc6 SL |
335 | /// Attempts to double the size of the type's backing allocation in place. This is common |
336 | /// enough to want to do that it's easiest to just have a dedicated method. Slightly | |
337 | /// more efficient logic can be provided for this than the general case. | |
338 | /// | |
339 | /// Returns true if the reallocation attempt has succeeded, or false otherwise. | |
340 | /// | |
341 | /// # Panics | |
342 | /// | |
343 | /// * Panics if T is zero-sized on the assumption that you managed to exhaust | |
344 | /// all `usize::MAX` slots in your imaginary buffer. | |
345 | /// * Panics on 32-bit platforms if the requested capacity exceeds | |
346 | /// `isize::MAX` bytes. | |
347 | #[inline(never)] | |
348 | #[cold] | |
349 | pub fn double_in_place(&mut self) -> bool { | |
350 | unsafe { | |
351 | let elem_size = mem::size_of::<T>(); | |
3b2f2976 XL |
352 | let old_layout = match self.current_layout() { |
353 | Some(layout) => layout, | |
354 | None => return false, // nothing to double | |
355 | }; | |
9cc50fc6 SL |
356 | |
357 | // since we set the capacity to usize::MAX when elem_size is | |
358 | // 0, getting to here necessarily means the RawVec is overfull. | |
359 | assert!(elem_size != 0, "capacity overflow"); | |
360 | ||
3b2f2976 XL |
361 | // Since we guarantee that we never allocate more than isize::MAX |
362 | // bytes, `elem_size * self.cap <= isize::MAX` as a precondition, so | |
363 | // this can't overflow. | |
364 | // | |
365 | // Similarly like with `double` above we can go straight to | |
366 | // `Layout::from_size_align_unchecked` as we know this won't | |
367 | // overflow and the alignment is sufficiently small. | |
9cc50fc6 | 368 | let new_cap = 2 * self.cap; |
3b2f2976 XL |
369 | let new_size = new_cap * elem_size; |
370 | alloc_guard(new_size); | |
041b39d2 | 371 | let ptr = self.ptr() as *mut _; |
3b2f2976 | 372 | let new_layout = Layout::from_size_align_unchecked(new_size, old_layout.align()); |
041b39d2 XL |
373 | match self.a.grow_in_place(ptr, old_layout, new_layout) { |
374 | Ok(_) => { | |
375 | // We can't directly divide `size`. | |
376 | self.cap = new_cap; | |
377 | true | |
378 | } | |
379 | Err(_) => { | |
380 | false | |
381 | } | |
9cc50fc6 | 382 | } |
9cc50fc6 SL |
383 | } |
384 | } | |
385 | ||
c1a9b12d SL |
386 | /// Ensures that the buffer contains at least enough space to hold |
387 | /// `used_cap + needed_extra_cap` elements. If it doesn't already, | |
388 | /// will reallocate the minimum possible amount of memory necessary. | |
389 | /// Generally this will be exactly the amount of memory necessary, | |
390 | /// but in principle the allocator is free to give back more than | |
391 | /// we asked for. | |
392 | /// | |
393 | /// If `used_cap` exceeds `self.cap()`, this may fail to actually allocate | |
394 | /// the requested space. This is not really unsafe, but the unsafe | |
b039eaaf | 395 | /// code *you* write that relies on the behavior of this function may break. |
c1a9b12d SL |
396 | /// |
397 | /// # Panics | |
398 | /// | |
399 | /// * Panics if the requested capacity exceeds `usize::MAX` bytes. | |
400 | /// * Panics on 32-bit platforms if the requested capacity exceeds | |
401 | /// `isize::MAX` bytes. | |
402 | /// | |
403 | /// # Aborts | |
404 | /// | |
405 | /// Aborts on OOM | |
406 | pub fn reserve_exact(&mut self, used_cap: usize, needed_extra_cap: usize) { | |
407 | unsafe { | |
c1a9b12d SL |
408 | // NOTE: we don't early branch on ZSTs here because we want this |
409 | // to actually catch "asking for more than usize::MAX" in that case. | |
410 | // If we make it past the first branch then we are guaranteed to | |
411 | // panic. | |
412 | ||
413 | // Don't actually need any more capacity. | |
414 | // Wrapping in case they gave a bad `used_cap`. | |
b039eaaf SL |
415 | if self.cap().wrapping_sub(used_cap) >= needed_extra_cap { |
416 | return; | |
417 | } | |
c1a9b12d SL |
418 | |
419 | // Nothing we can really do about these checks :( | |
420 | let new_cap = used_cap.checked_add(needed_extra_cap).expect("capacity overflow"); | |
3b2f2976 XL |
421 | let new_layout = match Layout::array::<T>(new_cap) { |
422 | Some(layout) => layout, | |
423 | None => panic!("capacity overflow"), | |
c1a9b12d | 424 | }; |
3b2f2976 XL |
425 | alloc_guard(new_layout.size()); |
426 | let res = match self.current_layout() { | |
427 | Some(layout) => { | |
428 | let old_ptr = self.ptr.as_ptr() as *mut u8; | |
429 | self.a.realloc(old_ptr, layout, new_layout) | |
430 | } | |
431 | None => self.a.alloc(new_layout), | |
432 | }; | |
433 | let uniq = match res { | |
434 | Ok(ptr) => Unique::new_unchecked(ptr as *mut T), | |
435 | Err(e) => self.a.oom(e), | |
041b39d2 | 436 | }; |
041b39d2 | 437 | self.ptr = uniq; |
c1a9b12d SL |
438 | self.cap = new_cap; |
439 | } | |
440 | } | |
441 | ||
9cc50fc6 SL |
442 | /// Calculates the buffer's new size given that it'll hold `used_cap + |
443 | /// needed_extra_cap` elements. This logic is used in amortized reserve methods. | |
444 | /// Returns `(new_capacity, new_alloc_size)`. | |
3b2f2976 | 445 | fn amortized_new_size(&self, used_cap: usize, needed_extra_cap: usize) -> usize { |
9cc50fc6 SL |
446 | // Nothing we can really do about these checks :( |
447 | let required_cap = used_cap.checked_add(needed_extra_cap) | |
c30ab7b3 | 448 | .expect("capacity overflow"); |
9cc50fc6 SL |
449 | // Cannot overflow, because `cap <= isize::MAX`, and type of `cap` is `usize`. |
450 | let double_cap = self.cap * 2; | |
451 | // `double_cap` guarantees exponential growth. | |
3b2f2976 | 452 | cmp::max(double_cap, required_cap) |
9cc50fc6 SL |
453 | } |
454 | ||
c1a9b12d SL |
455 | /// Ensures that the buffer contains at least enough space to hold |
456 | /// `used_cap + needed_extra_cap` elements. If it doesn't already have | |
457 | /// enough capacity, will reallocate enough space plus comfortable slack | |
b039eaaf | 458 | /// space to get amortized `O(1)` behavior. Will limit this behavior |
c1a9b12d SL |
459 | /// if it would needlessly cause itself to panic. |
460 | /// | |
461 | /// If `used_cap` exceeds `self.cap()`, this may fail to actually allocate | |
462 | /// the requested space. This is not really unsafe, but the unsafe | |
b039eaaf | 463 | /// code *you* write that relies on the behavior of this function may break. |
c1a9b12d SL |
464 | /// |
465 | /// This is ideal for implementing a bulk-push operation like `extend`. | |
466 | /// | |
467 | /// # Panics | |
468 | /// | |
469 | /// * Panics if the requested capacity exceeds `usize::MAX` bytes. | |
470 | /// * Panics on 32-bit platforms if the requested capacity exceeds | |
471 | /// `isize::MAX` bytes. | |
472 | /// | |
473 | /// # Aborts | |
474 | /// | |
475 | /// Aborts on OOM | |
476 | /// | |
477 | /// # Examples | |
478 | /// | |
041b39d2 XL |
479 | /// ``` |
480 | /// # #![feature(alloc)] | |
481 | /// # extern crate alloc; | |
482 | /// # use std::ptr; | |
483 | /// # use alloc::raw_vec::RawVec; | |
c1a9b12d SL |
484 | /// struct MyVec<T> { |
485 | /// buf: RawVec<T>, | |
486 | /// len: usize, | |
487 | /// } | |
488 | /// | |
041b39d2 | 489 | /// impl<T: Clone> MyVec<T> { |
c1a9b12d SL |
490 | /// pub fn push_all(&mut self, elems: &[T]) { |
491 | /// self.buf.reserve(self.len, elems.len()); | |
492 | /// // reserve would have aborted or panicked if the len exceeded | |
493 | /// // `isize::MAX` so this is safe to do unchecked now. | |
494 | /// for x in elems { | |
495 | /// unsafe { | |
496 | /// ptr::write(self.buf.ptr().offset(self.len as isize), x.clone()); | |
497 | /// } | |
498 | /// self.len += 1; | |
499 | /// } | |
500 | /// } | |
501 | /// } | |
041b39d2 XL |
502 | /// # fn main() { |
503 | /// # let mut vector = MyVec { buf: RawVec::new(), len: 0 }; | |
504 | /// # vector.push_all(&[1, 3, 5, 7, 9]); | |
505 | /// # } | |
c1a9b12d SL |
506 | /// ``` |
507 | pub fn reserve(&mut self, used_cap: usize, needed_extra_cap: usize) { | |
508 | unsafe { | |
c1a9b12d SL |
509 | // NOTE: we don't early branch on ZSTs here because we want this |
510 | // to actually catch "asking for more than usize::MAX" in that case. | |
511 | // If we make it past the first branch then we are guaranteed to | |
512 | // panic. | |
513 | ||
514 | // Don't actually need any more capacity. | |
92a42be0 | 515 | // Wrapping in case they give a bad `used_cap` |
b039eaaf SL |
516 | if self.cap().wrapping_sub(used_cap) >= needed_extra_cap { |
517 | return; | |
518 | } | |
c1a9b12d | 519 | |
3b2f2976 | 520 | let new_cap = self.amortized_new_size(used_cap, needed_extra_cap); |
c1a9b12d | 521 | |
3b2f2976 XL |
522 | let new_layout = match Layout::array::<T>(new_cap) { |
523 | Some(layout) => layout, | |
524 | None => panic!("capacity overflow"), | |
c1a9b12d | 525 | }; |
3b2f2976 XL |
526 | // FIXME: may crash and burn on over-reserve |
527 | alloc_guard(new_layout.size()); | |
528 | let res = match self.current_layout() { | |
529 | Some(layout) => { | |
530 | let old_ptr = self.ptr.as_ptr() as *mut u8; | |
531 | self.a.realloc(old_ptr, layout, new_layout) | |
532 | } | |
533 | None => self.a.alloc(new_layout), | |
534 | }; | |
535 | let uniq = match res { | |
536 | Ok(ptr) => Unique::new_unchecked(ptr as *mut T), | |
537 | Err(e) => self.a.oom(e), | |
041b39d2 | 538 | }; |
041b39d2 | 539 | self.ptr = uniq; |
c1a9b12d SL |
540 | self.cap = new_cap; |
541 | } | |
542 | } | |
543 | ||
9cc50fc6 SL |
544 | /// Attempts to ensure that the buffer contains at least enough space to hold |
545 | /// `used_cap + needed_extra_cap` elements. If it doesn't already have | |
546 | /// enough capacity, will reallocate in place enough space plus comfortable slack | |
3b2f2976 | 547 | /// space to get amortized `O(1)` behavior. Will limit this behaviour |
9cc50fc6 SL |
548 | /// if it would needlessly cause itself to panic. |
549 | /// | |
550 | /// If `used_cap` exceeds `self.cap()`, this may fail to actually allocate | |
551 | /// the requested space. This is not really unsafe, but the unsafe | |
3b2f2976 | 552 | /// code *you* write that relies on the behavior of this function may break. |
9cc50fc6 SL |
553 | /// |
554 | /// Returns true if the reallocation attempt has succeeded, or false otherwise. | |
555 | /// | |
556 | /// # Panics | |
557 | /// | |
558 | /// * Panics if the requested capacity exceeds `usize::MAX` bytes. | |
559 | /// * Panics on 32-bit platforms if the requested capacity exceeds | |
560 | /// `isize::MAX` bytes. | |
561 | pub fn reserve_in_place(&mut self, used_cap: usize, needed_extra_cap: usize) -> bool { | |
562 | unsafe { | |
9cc50fc6 SL |
563 | // NOTE: we don't early branch on ZSTs here because we want this |
564 | // to actually catch "asking for more than usize::MAX" in that case. | |
565 | // If we make it past the first branch then we are guaranteed to | |
566 | // panic. | |
567 | ||
568 | // Don't actually need any more capacity. If the current `cap` is 0, we can't | |
569 | // reallocate in place. | |
570 | // Wrapping in case they give a bad `used_cap` | |
3b2f2976 XL |
571 | let old_layout = match self.current_layout() { |
572 | Some(layout) => layout, | |
573 | None => return false, | |
574 | }; | |
575 | if self.cap().wrapping_sub(used_cap) >= needed_extra_cap { | |
9cc50fc6 SL |
576 | return false; |
577 | } | |
578 | ||
3b2f2976 | 579 | let new_cap = self.amortized_new_size(used_cap, needed_extra_cap); |
9cc50fc6 | 580 | |
041b39d2 XL |
581 | // Here, `cap < used_cap + needed_extra_cap <= new_cap` |
582 | // (regardless of whether `self.cap - used_cap` wrapped). | |
583 | // Therefore we can safely call grow_in_place. | |
584 | ||
585 | let ptr = self.ptr() as *mut _; | |
041b39d2 | 586 | let new_layout = Layout::new::<T>().repeat(new_cap).unwrap().0; |
3b2f2976 XL |
587 | // FIXME: may crash and burn on over-reserve |
588 | alloc_guard(new_layout.size()); | |
041b39d2 XL |
589 | match self.a.grow_in_place(ptr, old_layout, new_layout) { |
590 | Ok(_) => { | |
591 | self.cap = new_cap; | |
592 | true | |
593 | } | |
594 | Err(_) => { | |
595 | false | |
596 | } | |
9cc50fc6 | 597 | } |
9cc50fc6 SL |
598 | } |
599 | } | |
600 | ||
c1a9b12d SL |
601 | /// Shrinks the allocation down to the specified amount. If the given amount |
602 | /// is 0, actually completely deallocates. | |
603 | /// | |
604 | /// # Panics | |
605 | /// | |
606 | /// Panics if the given amount is *larger* than the current capacity. | |
607 | /// | |
608 | /// # Aborts | |
609 | /// | |
610 | /// Aborts on OOM. | |
611 | pub fn shrink_to_fit(&mut self, amount: usize) { | |
612 | let elem_size = mem::size_of::<T>(); | |
c1a9b12d SL |
613 | |
614 | // Set the `cap` because they might be about to promote to a `Box<[T]>` | |
615 | if elem_size == 0 { | |
616 | self.cap = amount; | |
617 | return; | |
618 | } | |
619 | ||
620 | // This check is my waterloo; it's the only thing Vec wouldn't have to do. | |
621 | assert!(self.cap >= amount, "Tried to shrink to a larger capacity"); | |
622 | ||
623 | if amount == 0 { | |
041b39d2 XL |
624 | // We want to create a new zero-length vector within the |
625 | // same allocator. We use ptr::write to avoid an | |
626 | // erroneous attempt to drop the contents, and we use | |
627 | // ptr::read to sidestep condition against destructuring | |
628 | // types that implement Drop. | |
629 | ||
630 | unsafe { | |
631 | let a = ptr::read(&self.a as *const A); | |
632 | self.dealloc_buffer(); | |
633 | ptr::write(self, RawVec::new_in(a)); | |
634 | } | |
c1a9b12d SL |
635 | } else if self.cap != amount { |
636 | unsafe { | |
3b2f2976 XL |
637 | // We know here that our `amount` is greater than zero. This |
638 | // implies, via the assert above, that capacity is also greater | |
639 | // than zero, which means that we've got a current layout that | |
640 | // "fits" | |
641 | // | |
642 | // We also know that `self.cap` is greater than `amount`, and | |
643 | // consequently we don't need runtime checks for creating either | |
644 | // layout | |
645 | let old_size = elem_size * self.cap; | |
646 | let new_size = elem_size * amount; | |
647 | let align = mem::align_of::<T>(); | |
648 | let old_layout = Layout::from_size_align_unchecked(old_size, align); | |
649 | let new_layout = Layout::from_size_align_unchecked(new_size, align); | |
650 | match self.a.realloc(self.ptr.as_ptr() as *mut u8, | |
651 | old_layout, | |
652 | new_layout) { | |
653 | Ok(p) => self.ptr = Unique::new_unchecked(p as *mut T), | |
041b39d2 | 654 | Err(err) => self.a.oom(err), |
b039eaaf | 655 | } |
c1a9b12d SL |
656 | } |
657 | self.cap = amount; | |
658 | } | |
659 | } | |
041b39d2 | 660 | } |
c1a9b12d | 661 | |
041b39d2 | 662 | impl<T> RawVec<T, Heap> { |
c1a9b12d SL |
663 | /// Converts the entire buffer into `Box<[T]>`. |
664 | /// | |
b039eaaf | 665 | /// While it is not *strictly* Undefined Behavior to call |
5bcae85e SL |
666 | /// this procedure while some of the RawVec is uninitialized, |
667 | /// it certainly makes it trivial to trigger it. | |
c1a9b12d SL |
668 | /// |
669 | /// Note that this will correctly reconstitute any `cap` changes | |
670 | /// that may have been performed. (see description of type for details) | |
671 | pub unsafe fn into_box(self) -> Box<[T]> { | |
672 | // NOTE: not calling `cap()` here, actually using the real `cap` field! | |
673 | let slice = slice::from_raw_parts_mut(self.ptr(), self.cap); | |
674 | let output: Box<[T]> = Box::from_raw(slice); | |
675 | mem::forget(self); | |
676 | output | |
677 | } | |
c1a9b12d SL |
678 | } |
679 | ||
041b39d2 | 680 | impl<T, A: Alloc> RawVec<T, A> { |
c1a9b12d | 681 | /// Frees the memory owned by the RawVec *without* trying to Drop its contents. |
041b39d2 | 682 | pub unsafe fn dealloc_buffer(&mut self) { |
c1a9b12d | 683 | let elem_size = mem::size_of::<T>(); |
3b2f2976 XL |
684 | if elem_size != 0 { |
685 | if let Some(layout) = self.current_layout() { | |
686 | let ptr = self.ptr() as *mut u8; | |
687 | self.a.dealloc(ptr, layout); | |
688 | } | |
c1a9b12d SL |
689 | } |
690 | } | |
691 | } | |
692 | ||
041b39d2 XL |
693 | unsafe impl<#[may_dangle] T, A: Alloc> Drop for RawVec<T, A> { |
694 | /// Frees the memory owned by the RawVec *without* trying to Drop its contents. | |
695 | fn drop(&mut self) { | |
696 | unsafe { self.dealloc_buffer(); } | |
697 | } | |
698 | } | |
699 | ||
c1a9b12d SL |
700 | |
701 | ||
702 | // We need to guarantee the following: | |
703 | // * We don't ever allocate `> isize::MAX` byte-size objects | |
704 | // * We don't overflow `usize::MAX` and actually allocate too little | |
705 | // | |
706 | // On 64-bit we just need to check for overflow since trying to allocate | |
3157f602 XL |
707 | // `> isize::MAX` bytes will surely fail. On 32-bit and 16-bit we need to add |
708 | // an extra guard for this in case we're running on a platform which can use | |
709 | // all 4GB in user-space. e.g. PAE or x32 | |
c1a9b12d SL |
710 | |
711 | #[inline] | |
c1a9b12d | 712 | fn alloc_guard(alloc_size: usize) { |
9cc50fc6 | 713 | if mem::size_of::<usize>() < 8 { |
b039eaaf SL |
714 | assert!(alloc_size <= ::core::isize::MAX as usize, |
715 | "capacity overflow"); | |
e9174d1e | 716 | } |
c1a9b12d | 717 | } |
92a42be0 SL |
718 | |
719 | ||
720 | #[cfg(test)] | |
721 | mod tests { | |
722 | use super::*; | |
723 | ||
041b39d2 XL |
724 | #[test] |
725 | fn allocator_param() { | |
726 | use allocator::{Alloc, AllocErr}; | |
727 | ||
728 | // Writing a test of integration between third-party | |
729 | // allocators and RawVec is a little tricky because the RawVec | |
730 | // API does not expose fallible allocation methods, so we | |
731 | // cannot check what happens when allocator is exhausted | |
732 | // (beyond detecting a panic). | |
733 | // | |
734 | // Instead, this just checks that the RawVec methods do at | |
735 | // least go through the Allocator API when it reserves | |
736 | // storage. | |
737 | ||
738 | // A dumb allocator that consumes a fixed amount of fuel | |
739 | // before allocation attempts start failing. | |
740 | struct BoundedAlloc { fuel: usize } | |
741 | unsafe impl Alloc for BoundedAlloc { | |
742 | unsafe fn alloc(&mut self, layout: Layout) -> Result<*mut u8, AllocErr> { | |
743 | let size = layout.size(); | |
744 | if size > self.fuel { | |
745 | return Err(AllocErr::Unsupported { details: "fuel exhausted" }); | |
746 | } | |
747 | match Heap.alloc(layout) { | |
748 | ok @ Ok(_) => { self.fuel -= size; ok } | |
749 | err @ Err(_) => err, | |
750 | } | |
751 | } | |
752 | unsafe fn dealloc(&mut self, ptr: *mut u8, layout: Layout) { | |
753 | Heap.dealloc(ptr, layout) | |
754 | } | |
755 | } | |
756 | ||
757 | let a = BoundedAlloc { fuel: 500 }; | |
758 | let mut v: RawVec<u8, _> = RawVec::with_capacity_in(50, a); | |
759 | assert_eq!(v.a.fuel, 450); | |
760 | v.reserve(50, 150); // (causes a realloc, thus using 50 + 150 = 200 units of fuel) | |
761 | assert_eq!(v.a.fuel, 250); | |
762 | } | |
763 | ||
92a42be0 SL |
764 | #[test] |
765 | fn reserve_does_not_overallocate() { | |
766 | { | |
767 | let mut v: RawVec<u32> = RawVec::new(); | |
768 | // First `reserve` allocates like `reserve_exact` | |
769 | v.reserve(0, 9); | |
770 | assert_eq!(9, v.cap()); | |
771 | } | |
772 | ||
773 | { | |
774 | let mut v: RawVec<u32> = RawVec::new(); | |
775 | v.reserve(0, 7); | |
776 | assert_eq!(7, v.cap()); | |
777 | // 97 if more than double of 7, so `reserve` should work | |
778 | // like `reserve_exact`. | |
779 | v.reserve(7, 90); | |
780 | assert_eq!(97, v.cap()); | |
781 | } | |
782 | ||
783 | { | |
784 | let mut v: RawVec<u32> = RawVec::new(); | |
785 | v.reserve(0, 12); | |
786 | assert_eq!(12, v.cap()); | |
787 | v.reserve(12, 3); | |
788 | // 3 is less than half of 12, so `reserve` must grow | |
789 | // exponentially. At the time of writing this test grow | |
790 | // factor is 2, so new capacity is 24, however, grow factor | |
791 | // of 1.5 is OK too. Hence `>= 18` in assert. | |
792 | assert!(v.cap() >= 12 + 12 / 2); | |
793 | } | |
794 | } | |
795 | ||
041b39d2 | 796 | |
92a42be0 | 797 | } |