| /*! |
| |
| **A fast bump allocation arena for Rust.** |
| |
| [](https://docs.rs/bumpalo/) |
| [](https://crates.io/crates/bumpalo) |
| [](https://crates.io/crates/bumpalo) |
| [](https://github.com/fitzgen/bumpalo/actions?query=workflow%3ARust) |
| |
|  |
| |
| ## Bump Allocation |
| |
| Bump allocation is a fast, but limited approach to allocation. We have a chunk |
| of memory, and we maintain a pointer within that memory. Whenever we allocate an |
| object, we do a quick test that we have enough capacity left in our chunk to |
| allocate the object and then update the pointer by the object's size. *That's |
| it!* |
| |
| The disadvantage of bump allocation is that there is no general way to |
| deallocate individual objects or reclaim the memory region for a |
| no-longer-in-use object. |
| |
| These trade offs make bump allocation well-suited for *phase-oriented* |
| allocations. That is, a group of objects that will all be allocated during the |
| same program phase, used, and then can all be deallocated together as a group. |
| |
| ## Deallocation en Masse, but No `Drop` |
| |
| To deallocate all the objects in the arena at once, we can simply reset the bump |
| pointer back to the start of the arena's memory chunk. This makes mass |
| deallocation *extremely* fast, but allocated objects' `Drop` implementations are |
| not invoked. |
| |
| > **However:** [`bumpalo::boxed::Box<T>`][crate::boxed::Box] can be used to wrap |
| > `T` values allocated in the `Bump` arena, and calls `T`'s `Drop` |
| > implementation when the `Box<T>` wrapper goes out of scope. This is similar to |
| > how [`std::boxed::Box`] works, except without deallocating its backing memory. |
| |
| [`std::boxed::Box`]: https://doc.rust-lang.org/std/boxed/struct.Box.html |
| |
| ## What happens when the memory chunk is full? |
| |
| This implementation will allocate a new memory chunk from the global allocator |
| and then start bump allocating into this new memory chunk. |
| |
| ## Example |
| |
| ``` |
| use bumpalo::Bump; |
| use std::u64; |
| |
| struct Doggo { |
| cuteness: u64, |
| age: u8, |
| scritches_required: bool, |
| } |
| |
| // Create a new arena to bump allocate into. |
| let bump = Bump::new(); |
| |
| // Allocate values into the arena. |
| let scooter = bump.alloc(Doggo { |
| cuteness: u64::max_value(), |
| age: 8, |
| scritches_required: true, |
| }); |
| |
| // Exclusive, mutable references to the just-allocated value are returned. |
| assert!(scooter.scritches_required); |
| scooter.age += 1; |
| ``` |
| |
| ## Collections |
| |
| When the `"collections"` cargo feature is enabled, a fork of some of the `std` |
| library's collections are available in the `collections` module. These |
| collection types are modified to allocate their space inside `bumpalo::Bump` |
| arenas. |
| |
| ```rust |
| # #[cfg(feature = "collections")] |
| # { |
| use bumpalo::{Bump, collections::Vec}; |
| |
| // Create a new bump arena. |
| let bump = Bump::new(); |
| |
| // Create a vector of integers whose storage is backed by the bump arena. The |
| // vector cannot outlive its backing arena, and this property is enforced with |
| // Rust's lifetime rules. |
| let mut v = Vec::new_in(&bump); |
| |
| // Push a bunch of integers onto `v`! |
| for i in 0..100 { |
| v.push(i); |
| } |
| # } |
| ``` |
| |
| Eventually [all `std` collection types will be parameterized by an |
| allocator](https://github.com/rust-lang/rust/issues/42774) and we can remove |
| this `collections` module and use the `std` versions. |
| |
| For unstable, nightly-only support for custom allocators in `std`, see the |
| `allocator_api` section below. |
| |
| ## `bumpalo::boxed::Box` |
| |
| When the `"boxed"` cargo feature is enabled, a fork of `std::boxed::Box` library |
| is available in the `boxed` module. This `Box` type is modified to allocate its |
| space inside `bumpalo::Bump` arenas. |
| |
| **A `Box<T>` runs `T`'s drop implementation when the `Box<T>` is dropped.** You |
| can use this to work around the fact that `Bump` does not drop values allocated |
| in its space itself. |
| |
| ```rust |
| # #[cfg(feature = "boxed")] |
| # { |
| use bumpalo::{Bump, boxed::Box}; |
| use std::sync::atomic::{AtomicUsize, Ordering}; |
| |
| static NUM_DROPPED: AtomicUsize = AtomicUsize::new(0); |
| |
| struct CountDrops; |
| |
| impl Drop for CountDrops { |
| fn drop(&mut self) { |
| NUM_DROPPED.fetch_add(1, Ordering::SeqCst); |
| } |
| } |
| |
| // Create a new bump arena. |
| let bump = Bump::new(); |
| |
| // Create a `CountDrops` inside the bump arena. |
| let mut c = Box::new_in(CountDrops, &bump); |
| |
| // No `CountDrops` have been dropped yet. |
| assert_eq!(NUM_DROPPED.load(Ordering::SeqCst), 0); |
| |
| // Drop our `Box<CountDrops>`. |
| drop(c); |
| |
| // Its `Drop` implementation was run, and so `NUM_DROPS` has been incremented. |
| assert_eq!(NUM_DROPPED.load(Ordering::SeqCst), 1); |
| # } |
| ``` |
| |
| ## `#![no_std]` Support |
| |
| Bumpalo is a `no_std` crate. It depends only on the `alloc` and `core` crates. |
| |
| ## Thread support |
| |
| The `Bump` is `!Sync`, which makes it hard to use in certain situations around threads ‒ for |
| example in `rayon`. |
| |
| The [`bumpalo-herd`](https://crates.io/crates/bumpalo-herd) crate provides a pool of `Bump` |
| allocators for use in such situations. |
| |
| ## Nightly Rust `feature(allocator_api)` Support |
| |
| The unstable, nightly-only Rust `allocator_api` feature defines an `Allocator` |
| trait and exposes custom allocators for `std` types. Bumpalo has a matching |
| `allocator_api` cargo feature to enable implementing `Allocator` and using |
| `Bump` with `std` collections. Note that, as `feature(allocator_api)` is |
| unstable and only in nightly Rust, Bumpalo's matching `allocator_api` cargo |
| feature should be considered unstable, and will not follow the semver |
| conventions that the rest of the crate does. |
| |
| First, enable the `allocator_api` feature in your `Cargo.toml`: |
| |
| ```toml |
| [dependencies] |
| bumpalo = { version = "3.4.0", features = ["allocator_api"] } |
| ``` |
| |
| Next, enable the `allocator_api` nightly Rust feature in your `src/lib.rs` or `src/main.rs`: |
| |
| ```rust |
| # #[cfg(feature = "allocator_api")] |
| # { |
| #![feature(allocator_api)] |
| # } |
| ``` |
| |
| Finally, use `std` collections with `Bump`, so that their internal heap |
| allocations are made within the given bump arena: |
| |
| ``` |
| # #![cfg_attr(feature = "allocator_api", feature(allocator_api))] |
| # #[cfg(feature = "allocator_api")] |
| # { |
| #![feature(allocator_api)] |
| use bumpalo::Bump; |
| |
| // Create a new bump arena. |
| let bump = Bump::new(); |
| |
| // Create a `Vec` whose elements are allocated within the bump arena. |
| let mut v = Vec::new_in(&bump); |
| v.push(0); |
| v.push(1); |
| v.push(2); |
| # } |
| ``` |
| |
| ### Minimum Supported Rust Version (MSRV) |
| |
| This crate is guaranteed to compile on stable Rust 1.44 and up. It might compile |
| with older versions but that may change in any new patch release. |
| |
| We reserve the right to increment the MSRV on minor releases, however we will strive |
| to only do it deliberately and for good reasons. |
| |
| */ |
| |
| #![deny(missing_debug_implementations)] |
| #![deny(missing_docs)] |
| #![no_std] |
| #![cfg_attr( |
| feature = "allocator_api", |
| feature(allocator_api, nonnull_slice_from_raw_parts) |
| )] |
| |
| #[doc(hidden)] |
| pub extern crate alloc as core_alloc; |
| |
| #[cfg(feature = "boxed")] |
| pub mod boxed; |
| #[cfg(feature = "collections")] |
| pub mod collections; |
| |
| mod alloc; |
| |
| use core::cell::Cell; |
| use core::fmt::Display; |
| use core::iter; |
| use core::marker::PhantomData; |
| use core::mem; |
| use core::ptr::{self, NonNull}; |
| use core::slice; |
| use core::str; |
| use core_alloc::alloc::{alloc, dealloc, Layout}; |
| #[cfg(feature = "allocator_api")] |
| use core_alloc::alloc::{AllocError, Allocator}; |
| |
| /// An error returned from [`Bump::try_alloc_try_with`]. |
| #[derive(Clone, PartialEq, Eq, Debug)] |
| pub enum AllocOrInitError<E> { |
| /// Indicates that the initial allocation failed. |
| Alloc(alloc::AllocErr), |
| /// Indicates that the initializer failed with the contained error after |
| /// allocation. |
| /// |
| /// It is possible but not guaranteed that the allocated memory has been |
| /// released back to the allocator at this point. |
| Init(E), |
| } |
| impl<E> From<alloc::AllocErr> for AllocOrInitError<E> { |
| fn from(e: alloc::AllocErr) -> Self { |
| Self::Alloc(e) |
| } |
| } |
| impl<E: Display> Display for AllocOrInitError<E> { |
| fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result { |
| match self { |
| AllocOrInitError::Alloc(err) => err.fmt(f), |
| AllocOrInitError::Init(err) => write!(f, "initialization failed: {}", err), |
| } |
| } |
| } |
| |
| /// An arena to bump allocate into. |
| /// |
| /// ## No `Drop`s |
| /// |
| /// Objects that are bump-allocated will never have their `Drop` implementation |
| /// called — unless you do it manually yourself. This makes it relatively |
| /// easy to leak memory or other resources. |
| /// |
| /// If you have a type which internally manages |
| /// |
| /// * an allocation from the global heap (e.g. `Vec<T>`), |
| /// * open file descriptors (e.g. `std::fs::File`), or |
| /// * any other resource that must be cleaned up (e.g. an `mmap`) |
| /// |
| /// and relies on its `Drop` implementation to clean up the internal resource, |
| /// then if you allocate that type with a `Bump`, you need to find a new way to |
| /// clean up after it yourself. |
| /// |
| /// Potential solutions are: |
| /// |
| /// * Using [`bumpalo::boxed::Box::new_in`] instead of [`Bump::alloc`], that |
| /// will drop wrapped values similarly to [`std::boxed::Box`]. Note that this |
| /// requires enabling the `"boxed"` Cargo feature for this crate. **This is |
| /// often the easiest solution.** |
| /// |
| /// * Calling [`drop_in_place`][drop_in_place] or using |
| /// [`std::mem::ManuallyDrop`][manuallydrop] to manually drop these types. |
| /// |
| /// * Using [`bumpalo::collections::Vec`] instead of [`std::vec::Vec`]. |
| /// |
| /// * Avoiding allocating these problematic types within a `Bump`. |
| /// |
| /// Note that not calling `Drop` is memory safe! Destructors are never |
| /// guaranteed to run in Rust, you can't rely on them for enforcing memory |
| /// safety. |
| /// |
| /// [drop_in_place]: https://doc.rust-lang.org/std/ptr/fn.drop_in_place.html |
| /// [manuallydrop]: https://doc.rust-lang.org/std/mem/struct.ManuallyDrop.html |
| /// [`bumpalo::collections::Vec`]: ./collections/struct.Vec.html |
| /// [`std::vec::Vec`]: https://doc.rust-lang.org/std/vec/struct.Vec.html |
| /// [`bumpalo::boxed::Box::new_in`]: ./boxed/struct.Box.html#method.new_in |
| /// [`Bump::alloc`]: ./struct.Bump.html#method.alloc |
| /// [`std::boxed::Box`]: https://doc.rust-lang.org/std/boxed/struct.Box.html |
| /// |
| /// ## Example |
| /// |
| /// ``` |
| /// use bumpalo::Bump; |
| /// |
| /// // Create a new bump arena. |
| /// let bump = Bump::new(); |
| /// |
| /// // Allocate values into the arena. |
| /// let forty_two = bump.alloc(42); |
| /// assert_eq!(*forty_two, 42); |
| /// |
| /// // Mutable references are returned from allocation. |
| /// let mut s = bump.alloc("bumpalo"); |
| /// *s = "the bump allocator; and also is a buffalo"; |
| /// ``` |
| /// |
| /// ## Allocation Methods Come in Many Flavors |
| /// |
| /// There are various allocation methods on `Bump`, the simplest being |
| /// [`alloc`][Bump::alloc]. The others exist to satisfy some combination of |
| /// fallible allocation and initialization. The allocation methods are |
| /// summarized in the following table: |
| /// |
| /// <table> |
| /// <thead> |
| /// <tr> |
| /// <th></th> |
| /// <th>Infallible Allocation</th> |
| /// <th>Fallible Allocation</th> |
| /// </tr> |
| /// </thead> |
| /// <tr> |
| /// <th>By Value</th> |
| /// <td><a href="#method.alloc"><code>alloc</code></a></td> |
| /// <td><a href="#method.try_alloc"><code>try_alloc</code></a></td> |
| /// </tr> |
| /// <tr> |
| /// <th>Infallible Initializer Function</th> |
| /// <td><a href="#method.alloc_with"><code>alloc_with</code></a></td> |
| /// <td><a href="#method.try_alloc_with"><code>try_alloc_with</code></a></td> |
| /// </tr> |
| /// <tr> |
| /// <th>Fallible Initializer Function</th> |
| /// <td><a href="#method.alloc_try_with"><code>alloc_try_with</code></a></td> |
| /// <td><a href="#method.try_alloc_try_with"><code>try_alloc_try_with</code></a></td> |
| /// </tr> |
| /// <tbody> |
| /// </tbody> |
| /// </table> |
| /// |
| /// ### Fallible Allocation: The `try_alloc_` Method Prefix |
| /// |
| /// These allocation methods let you recover from out-of-memory (OOM) |
| /// scenarioes, rather than raising a panic on OOM. |
| /// |
| /// ``` |
| /// use bumpalo::Bump; |
| /// |
| /// let bump = Bump::new(); |
| /// |
| /// match bump.try_alloc(MyStruct { |
| /// // ... |
| /// }) { |
| /// Ok(my_struct) => { |
| /// // Allocation succeeded. |
| /// } |
| /// Err(e) => { |
| /// // Out of memory. |
| /// } |
| /// } |
| /// |
| /// struct MyStruct { |
| /// // ... |
| /// } |
| /// ``` |
| /// |
| /// ### Initializer Functions: The `_with` Method Suffix |
| /// |
| /// Calling one of the generic `…alloc(x)` methods is essentially equivalent to |
| /// the matching [`…alloc_with(|| x)`](?search=alloc_with). However if you use |
| /// `…alloc_with`, then the closure will not be invoked until after allocating |
| /// space for storing `x` on the heap. |
| /// |
| /// This can be useful in certain edge-cases related to compiler optimizations. |
| /// When evaluating for example `bump.alloc(x)`, semantically `x` is first put |
| /// on the stack and then moved onto the heap. In some cases, the compiler is |
| /// able to optimize this into constructing `x` directly on the heap, however |
| /// in many cases it does not. |
| /// |
| /// The `*alloc_with` functions try to help the compiler be smarter. In most |
| /// cases doing for example `bump.try_alloc_with(|| x)` on release mode will be |
| /// enough to help the compiler realize that this optimization is valid and |
| /// to construct `x` directly onto the heap. |
| /// |
| /// #### Warning |
| /// |
| /// These functions critically depend on compiler optimizations to achieve their |
| /// desired effect. This means that it is not an effective tool when compiling |
| /// without optimizations on. |
| /// |
| /// Even when optimizations are on, these functions do not **guarantee** that |
| /// the value is constructed on the heap. To the best of our knowledge no such |
| /// guarantee can be made in stable Rust as of 1.44. |
| /// |
| /// ### Fallible Initialization: The `_try_with` Method Suffix |
| /// |
| /// The generic [`…alloc_try_with(|| x)`](?search=_try_with) methods behave |
| /// like the purely `_with` suffixed methods explained above. However, they |
| /// allow for fallible initialization by accepting a closure that returns a |
| /// [`Result`] and will attempt to undo the initial allocation if this closure |
| /// returns [`Err`]. |
| /// |
| /// #### Warning |
| /// |
| /// If the inner closure returns [`Ok`], space for the entire [`Result`] remains |
| /// allocated inside `self`. This can be a problem especially if the [`Err`] |
| /// variant is larger, but even otherwise there may be overhead for the |
| /// [`Result`]'s discriminant. |
| /// |
| /// <p><details><summary>Undoing the allocation in the <code>Err</code> case |
| /// always fails if <code>f</code> successfully made any additional allocations |
| /// in <code>self</code>.</summary> |
| /// |
| /// For example, the following will always leak also space for the [`Result`] |
| /// into this `Bump`, even though the inner reference isn't kept and the [`Err`] |
| /// payload is returned semantically by value: |
| /// |
| /// ```rust |
| /// let bump = bumpalo::Bump::new(); |
| /// |
| /// let r: Result<&mut [u8; 1000], ()> = bump.alloc_try_with(|| { |
| /// let _ = bump.alloc(0_u8); |
| /// Err(()) |
| /// }); |
| /// |
| /// assert!(r.is_err()); |
| /// ``` |
| /// |
| ///</details></p> |
| /// |
| /// Since [`Err`] payloads are first placed on the heap and then moved to the |
| /// stack, `bump.…alloc_try_with(|| x)?` is likely to execute more slowly than |
| /// the matching `bump.…alloc(x?)` in case of initialization failure. If this |
| /// happens frequently, using the plain un-suffixed method may perform better. |
| #[derive(Debug)] |
| pub struct Bump { |
| // The current chunk we are bump allocating within. |
| current_chunk_footer: Cell<NonNull<ChunkFooter>>, |
| } |
| |
| #[repr(C)] |
| #[derive(Debug)] |
| struct ChunkFooter { |
| // Pointer to the start of this chunk allocation. This footer is always at |
| // the end of the chunk. |
| data: NonNull<u8>, |
| |
| // The layout of this chunk's allocation. |
| layout: Layout, |
| |
| // Link to the previous chunk, if any. |
| prev: Cell<Option<NonNull<ChunkFooter>>>, |
| |
| // Bump allocation finger that is always in the range `self.data..=self`. |
| ptr: Cell<NonNull<u8>>, |
| } |
| |
| impl ChunkFooter { |
| // Returns the start and length of the currently allocated region of this |
| // chunk. |
| fn as_raw_parts(&self) -> (*const u8, usize) { |
| let data = self.data.as_ptr() as usize; |
| let ptr = self.ptr.get().as_ptr() as usize; |
| debug_assert!(data <= ptr); |
| debug_assert!(ptr <= self as *const _ as usize); |
| let len = self as *const _ as usize - ptr; |
| (ptr as *const u8, len) |
| } |
| } |
| |
| impl Default for Bump { |
| fn default() -> Bump { |
| Bump::new() |
| } |
| } |
| |
| impl Drop for Bump { |
| fn drop(&mut self) { |
| unsafe { |
| dealloc_chunk_list(Some(self.current_chunk_footer.get())); |
| } |
| } |
| } |
| |
| #[inline] |
| unsafe fn dealloc_chunk_list(mut footer: Option<NonNull<ChunkFooter>>) { |
| while let Some(f) = footer { |
| footer = f.as_ref().prev.get(); |
| dealloc(f.as_ref().data.as_ptr(), f.as_ref().layout); |
| } |
| } |
| |
| // `Bump`s are safe to send between threads because nothing aliases its owned |
| // chunks until you start allocating from it. But by the time you allocate from |
| // it, the returned references to allocations borrow the `Bump` and therefore |
| // prevent sending the `Bump` across threads until the borrows end. |
| unsafe impl Send for Bump {} |
| |
| #[inline] |
| pub(crate) fn round_up_to(n: usize, divisor: usize) -> Option<usize> { |
| debug_assert!(divisor > 0); |
| debug_assert!(divisor.is_power_of_two()); |
| Some(n.checked_add(divisor - 1)? & !(divisor - 1)) |
| } |
| |
| // After this point, we try to hit page boundaries instead of powers of 2 |
| const PAGE_STRATEGY_CUTOFF: usize = 0x1000; |
| |
| // We only support alignments of up to 16 bytes for iter_allocated_chunks. |
| const SUPPORTED_ITER_ALIGNMENT: usize = 16; |
| const CHUNK_ALIGN: usize = SUPPORTED_ITER_ALIGNMENT; |
| const FOOTER_SIZE: usize = mem::size_of::<ChunkFooter>(); |
| |
| // Assert that ChunkFooter is at most the supported alignment. This will give a compile time error if it is not the case |
| const _FOOTER_ALIGN_ASSERTION: bool = mem::align_of::<ChunkFooter>() <= CHUNK_ALIGN; |
| const _: [(); _FOOTER_ALIGN_ASSERTION as usize] = [()]; |
| |
| // Maximum typical overhead per allocation imposed by allocators. |
| const MALLOC_OVERHEAD: usize = 16; |
| |
| // This is the overhead from malloc, footer and alignment. For instance, if |
| // we want to request a chunk of memory that has at least X bytes usable for |
| // allocations (where X is aligned to CHUNK_ALIGN), then we expect that the |
| // after adding a footer, malloc overhead and alignment, the chunk of memory |
| // the allocator actually sets aside for us is X+OVERHEAD rounded up to the |
| // nearest suitable size boundary. |
| const OVERHEAD: usize = (MALLOC_OVERHEAD + FOOTER_SIZE + (CHUNK_ALIGN - 1)) & !(CHUNK_ALIGN - 1); |
| |
| // Choose a relatively small default initial chunk size, since we double chunk |
| // sizes as we grow bump arenas to amortize costs of hitting the global |
| // allocator. |
| const FIRST_ALLOCATION_GOAL: usize = 1 << 9; |
| |
| // The actual size of the first allocation is going to be a bit smaller |
| // than the goal. We need to make room for the footer, and we also need |
| // take the alignment into account. |
| const DEFAULT_CHUNK_SIZE_WITHOUT_FOOTER: usize = FIRST_ALLOCATION_GOAL - OVERHEAD; |
| |
| /// Wrapper around `Layout::from_size_align` that adds debug assertions. |
| #[inline] |
| unsafe fn layout_from_size_align(size: usize, align: usize) -> Layout { |
| if cfg!(debug_assertions) { |
| Layout::from_size_align(size, align).unwrap() |
| } else { |
| Layout::from_size_align_unchecked(size, align) |
| } |
| } |
| |
| #[inline(never)] |
| fn allocation_size_overflow<T>() -> T { |
| panic!("requested allocation size overflowed") |
| } |
| |
| impl Bump { |
| /// Construct a new arena to bump allocate into. |
| /// |
| /// ## Example |
| /// |
| /// ``` |
| /// let bump = bumpalo::Bump::new(); |
| /// # let _ = bump; |
| /// ``` |
| pub fn new() -> Bump { |
| Self::with_capacity(0) |
| } |
| |
| /// Attempt to construct a new arena to bump allocate into. |
| /// |
| /// ## Example |
| /// |
| /// ``` |
| /// let bump = bumpalo::Bump::try_new(); |
| /// # let _ = bump.unwrap(); |
| /// ``` |
| pub fn try_new() -> Result<Bump, alloc::AllocErr> { |
| Bump::try_with_capacity(0) |
| } |
| |
| /// Construct a new arena with the specified byte capacity to bump allocate into. |
| /// |
| /// ## Example |
| /// |
| /// ``` |
| /// let bump = bumpalo::Bump::with_capacity(100); |
| /// # let _ = bump; |
| /// ``` |
| pub fn with_capacity(capacity: usize) -> Bump { |
| Bump::try_with_capacity(capacity).unwrap_or_else(|_| oom()) |
| } |
| |
| /// Attempt to construct a new arena with the specified byte capacity to bump allocate into. |
| /// |
| /// ## Example |
| /// |
| /// ``` |
| /// let bump = bumpalo::Bump::try_with_capacity(100); |
| /// # let _ = bump.unwrap(); |
| /// ``` |
| pub fn try_with_capacity(capacity: usize) -> Result<Self, alloc::AllocErr> { |
| let chunk_footer = Self::new_chunk( |
| None, |
| Some(unsafe { layout_from_size_align(capacity, 1) }), |
| None, |
| ) |
| .ok_or(alloc::AllocErr {})?; |
| |
| Ok(Bump { |
| current_chunk_footer: Cell::new(chunk_footer), |
| }) |
| } |
| |
| /// Allocate a new chunk and return its initialized footer. |
| /// |
| /// If given, `layouts` is a tuple of the current chunk size and the |
| /// layout of the allocation request that triggered us to fall back to |
| /// allocating a new chunk of memory. |
| fn new_chunk( |
| new_size_without_footer: Option<usize>, |
| requested_layout: Option<Layout>, |
| prev: Option<NonNull<ChunkFooter>>, |
| ) -> Option<NonNull<ChunkFooter>> { |
| unsafe { |
| let mut new_size_without_footer = |
| new_size_without_footer.unwrap_or(DEFAULT_CHUNK_SIZE_WITHOUT_FOOTER); |
| |
| // We want to have CHUNK_ALIGN or better alignment |
| let mut align = CHUNK_ALIGN; |
| |
| // If we already know we need to fulfill some request, |
| // make sure we allocate at least enough to satisfy it |
| if let Some(requested_layout) = requested_layout { |
| align = align.max(requested_layout.align()); |
| let requested_size = round_up_to(requested_layout.size(), align) |
| .unwrap_or_else(allocation_size_overflow); |
| new_size_without_footer = new_size_without_footer.max(requested_size); |
| } |
| |
| // We want our allocations to play nice with the memory allocator, |
| // and waste as little memory as possible. |
| // For small allocations, this means that the entire allocation |
| // including the chunk footer and mallocs internal overhead is |
| // as close to a power of two as we can go without going over. |
| // For larger allocations, we only need to get close to a page |
| // boundary without going over. |
| if new_size_without_footer < PAGE_STRATEGY_CUTOFF { |
| new_size_without_footer = |
| (new_size_without_footer + OVERHEAD).next_power_of_two() - OVERHEAD; |
| } else { |
| new_size_without_footer = |
| round_up_to(new_size_without_footer + OVERHEAD, 0x1000)? - OVERHEAD; |
| } |
| |
| debug_assert_eq!(align % CHUNK_ALIGN, 0); |
| debug_assert_eq!(new_size_without_footer % CHUNK_ALIGN, 0); |
| let size = new_size_without_footer |
| .checked_add(FOOTER_SIZE) |
| .unwrap_or_else(allocation_size_overflow); |
| let layout = layout_from_size_align(size, align); |
| |
| debug_assert!(requested_layout.map_or(true, |layout| size >= layout.size())); |
| |
| let data = alloc(layout); |
| let data = NonNull::new(data)?; |
| |
| // The `ChunkFooter` is at the end of the chunk. |
| let footer_ptr = data.as_ptr() as usize + new_size_without_footer; |
| debug_assert_eq!((data.as_ptr() as usize) % align, 0); |
| debug_assert_eq!(footer_ptr % CHUNK_ALIGN, 0); |
| let footer_ptr = footer_ptr as *mut ChunkFooter; |
| |
| // The bump pointer is initialized to the end of the range we will |
| // bump out of. |
| let ptr = Cell::new(NonNull::new_unchecked(footer_ptr as *mut u8)); |
| |
| ptr::write( |
| footer_ptr, |
| ChunkFooter { |
| data, |
| layout, |
| prev: Cell::new(prev), |
| ptr, |
| }, |
| ); |
| |
| Some(NonNull::new_unchecked(footer_ptr)) |
| } |
| } |
| |
| /// Reset this bump allocator. |
| /// |
| /// Performs mass deallocation on everything allocated in this arena by |
| /// resetting the pointer into the underlying chunk of memory to the start |
| /// of the chunk. Does not run any `Drop` implementations on deallocated |
| /// objects; see [the `Bump` type's top-level |
| /// documentation](./struct.Bump.html) for details. |
| /// |
| /// If this arena has allocated multiple chunks to bump allocate into, then |
| /// the excess chunks are returned to the global allocator. |
| /// |
| /// ## Example |
| /// |
| /// ``` |
| /// let mut bump = bumpalo::Bump::new(); |
| /// |
| /// // Allocate a bunch of things. |
| /// { |
| /// for i in 0..100 { |
| /// bump.alloc(i); |
| /// } |
| /// } |
| /// |
| /// // Reset the arena. |
| /// bump.reset(); |
| /// |
| /// // Allocate some new things in the space previously occupied by the |
| /// // original things. |
| /// for j in 200..400 { |
| /// bump.alloc(j); |
| /// } |
| ///``` |
| pub fn reset(&mut self) { |
| // Takes `&mut self` so `self` must be unique and there can't be any |
| // borrows active that would get invalidated by resetting. |
| unsafe { |
| let cur_chunk = self.current_chunk_footer.get(); |
| |
| // Deallocate all chunks except the current one |
| let prev_chunk = cur_chunk.as_ref().prev.replace(None); |
| dealloc_chunk_list(prev_chunk); |
| |
| // Reset the bump finger to the end of the chunk. |
| cur_chunk.as_ref().ptr.set(cur_chunk.cast()); |
| |
| debug_assert!( |
| self.current_chunk_footer |
| .get() |
| .as_ref() |
| .prev |
| .get() |
| .is_none(), |
| "We should only have a single chunk" |
| ); |
| debug_assert_eq!( |
| self.current_chunk_footer.get().as_ref().ptr.get(), |
| self.current_chunk_footer.get().cast(), |
| "Our chunk's bump finger should be reset to the start of its allocation" |
| ); |
| } |
| } |
| |
| /// Allocate an object in this `Bump` and return an exclusive reference to |
| /// it. |
| /// |
| /// ## Panics |
| /// |
| /// Panics if reserving space for `T` fails. |
| /// |
| /// ## Example |
| /// |
| /// ``` |
| /// let bump = bumpalo::Bump::new(); |
| /// let x = bump.alloc("hello"); |
| /// assert_eq!(*x, "hello"); |
| /// ``` |
| #[inline(always)] |
| #[allow(clippy::mut_from_ref)] |
| pub fn alloc<T>(&self, val: T) -> &mut T { |
| self.alloc_with(|| val) |
| } |
| |
| /// Try to allocate an object in this `Bump` and return an exclusive |
| /// reference to it. |
| /// |
| /// ## Errors |
| /// |
| /// Errors if reserving space for `T` fails. |
| /// |
| /// ## Example |
| /// |
| /// ``` |
| /// let bump = bumpalo::Bump::new(); |
| /// let x = bump.try_alloc("hello"); |
| /// assert_eq!(x, Ok(&mut"hello")); |
| /// ``` |
| #[inline(always)] |
| #[allow(clippy::mut_from_ref)] |
| pub fn try_alloc<T>(&self, val: T) -> Result<&mut T, alloc::AllocErr> { |
| self.try_alloc_with(|| val) |
| } |
| |
| /// Pre-allocate space for an object in this `Bump`, initializes it using |
| /// the closure, then returns an exclusive reference to it. |
| /// |
| /// See [The `_with` Method Suffix](#the-_with-method-suffix) for a |
| /// discussion on the differences between the `_with` suffixed methods and |
| /// those methods without it, their performance characteristics, and when |
| /// you might or might not choose a `_with` suffixed method. |
| /// |
| /// ## Panics |
| /// |
| /// Panics if reserving space for `T` fails. |
| /// |
| /// ## Example |
| /// |
| /// ``` |
| /// let bump = bumpalo::Bump::new(); |
| /// let x = bump.alloc_with(|| "hello"); |
| /// assert_eq!(*x, "hello"); |
| /// ``` |
| #[inline(always)] |
| #[allow(clippy::mut_from_ref)] |
| pub fn alloc_with<F, T>(&self, f: F) -> &mut T |
| where |
| F: FnOnce() -> T, |
| { |
| #[inline(always)] |
| unsafe fn inner_writer<T, F>(ptr: *mut T, f: F) |
| where |
| F: FnOnce() -> T, |
| { |
| // This function is translated as: |
| // - allocate space for a T on the stack |
| // - call f() with the return value being put onto this stack space |
| // - memcpy from the stack to the heap |
| // |
| // Ideally we want LLVM to always realize that doing a stack |
| // allocation is unnecessary and optimize the code so it writes |
| // directly into the heap instead. It seems we get it to realize |
| // this most consistently if we put this critical line into it's |
| // own function instead of inlining it into the surrounding code. |
| ptr::write(ptr, f()) |
| } |
| |
| let layout = Layout::new::<T>(); |
| |
| unsafe { |
| let p = self.alloc_layout(layout); |
| let p = p.as_ptr() as *mut T; |
| inner_writer(p, f); |
| &mut *p |
| } |
| } |
| |
| /// Tries to pre-allocate space for an object in this `Bump`, initializes |
| /// it using the closure, then returns an exclusive reference to it. |
| /// |
| /// See [The `_with` Method Suffix](#the-_with-method-suffix) for a |
| /// discussion on the differences between the `_with` suffixed methods and |
| /// those methods without it, their performance characteristics, and when |
| /// you might or might not choose a `_with` suffixed method. |
| /// |
| /// ## Errors |
| /// |
| /// Errors if reserving space for `T` fails. |
| /// |
| /// ## Example |
| /// |
| /// ``` |
| /// let bump = bumpalo::Bump::new(); |
| /// let x = bump.try_alloc_with(|| "hello"); |
| /// assert_eq!(x, Ok(&mut "hello")); |
| /// ``` |
| #[inline(always)] |
| #[allow(clippy::mut_from_ref)] |
| pub fn try_alloc_with<F, T>(&self, f: F) -> Result<&mut T, alloc::AllocErr> |
| where |
| F: FnOnce() -> T, |
| { |
| #[inline(always)] |
| unsafe fn inner_writer<T, F>(ptr: *mut T, f: F) |
| where |
| F: FnOnce() -> T, |
| { |
| // This function is translated as: |
| // - allocate space for a T on the stack |
| // - call f() with the return value being put onto this stack space |
| // - memcpy from the stack to the heap |
| // |
| // Ideally we want LLVM to always realize that doing a stack |
| // allocation is unnecessary and optimize the code so it writes |
| // directly into the heap instead. It seems we get it to realize |
| // this most consistently if we put this critical line into it's |
| // own function instead of inlining it into the surrounding code. |
| ptr::write(ptr, f()) |
| } |
| |
| //SAFETY: Self-contained: |
| // `p` is allocated for `T` and then a `T` is written. |
| let layout = Layout::new::<T>(); |
| let p = self.try_alloc_layout(layout)?; |
| let p = p.as_ptr() as *mut T; |
| |
| unsafe { |
| inner_writer(p, f); |
| Ok(&mut *p) |
| } |
| } |
| |
| /// Pre-allocates space for a [`Result`] in this `Bump`, initializes it using |
| /// the closure, then returns an exclusive reference to its `T` if [`Ok`]. |
| /// |
| /// Iff the allocation fails, the closure is not run. |
| /// |
| /// Iff [`Err`], an allocator rewind is *attempted* and the `E` instance is |
| /// moved out of the allocator to be consumed or dropped as normal. |
| /// |
| /// See [The `_with` Method Suffix](#the-_with-method-suffix) for a |
| /// discussion on the differences between the `_with` suffixed methods and |
| /// those methods without it, their performance characteristics, and when |
| /// you might or might not choose a `_with` suffixed method. |
| /// |
| /// For caveats specific to fallible initialization, see |
| /// [The `_try_with` Method Suffix](#the-_try_with-method-suffix). |
| /// |
| /// ## Errors |
| /// |
| /// Iff the allocation succeeds but `f` fails, that error is forwarded by value. |
| /// |
| /// ## Panics |
| /// |
| /// Panics if reserving space for `Result<T, E>` fails. |
| /// |
| /// ## Example |
| /// |
| /// ``` |
| /// let bump = bumpalo::Bump::new(); |
| /// let x = bump.alloc_try_with(|| Ok("hello"))?; |
| /// assert_eq!(*x, "hello"); |
| /// # Result::<_, ()>::Ok(()) |
| /// ``` |
| #[inline(always)] |
| #[allow(clippy::mut_from_ref)] |
| pub fn alloc_try_with<F, T, E>(&self, f: F) -> Result<&mut T, E> |
| where |
| F: FnOnce() -> Result<T, E>, |
| { |
| let rewind_footer = self.current_chunk_footer.get(); |
| let rewind_ptr = unsafe { rewind_footer.as_ref() }.ptr.get(); |
| let mut inner_result_ptr = NonNull::from(self.alloc_with(f)); |
| let inner_result_address = inner_result_ptr.as_ptr() as usize; |
| match unsafe { inner_result_ptr.as_mut() } { |
| Ok(t) => Ok(unsafe { |
| //SAFETY: |
| // The `&mut Result<T, E>` returned by `alloc_with` may be |
| // lifetime-limited by `E`, but the derived `&mut T` still has |
| // the same validity as in `alloc_with` since the error variant |
| // is already ruled out here. |
| |
| // We could conditionally truncate the allocation here, but |
| // since it grows backwards, it seems unlikely that we'd get |
| // any more than the `Result`'s discriminant this way, if |
| // anything at all. |
| &mut *(t as *mut _) |
| }), |
| Err(e) => unsafe { |
| // If this result was the last allocation in this arena, we can |
| // reclaim its space. In fact, sometimes we can do even better |
| // than simply calling `dealloc` on the result pointer: we can |
| // reclaim any alignment padding we might have added (which |
| // `dealloc` cannot do) if we didn't allocate a new chunk for |
| // this result. |
| if self.is_last_allocation(NonNull::new_unchecked(inner_result_address as *mut _)) { |
| let current_footer_p = self.current_chunk_footer.get(); |
| let current_ptr = ¤t_footer_p.as_ref().ptr; |
| if current_footer_p == rewind_footer { |
| // It's still the same chunk, so reset the bump pointer |
| // to its original value upon entry to this method |
| // (reclaiming any alignment padding we may have |
| // added). |
| current_ptr.set(rewind_ptr); |
| } else { |
| // We allocated a new chunk for this result. |
| // |
| // We know the result is the only allocation in this |
| // chunk: Any additional allocations since the start of |
| // this method could only have happened when running |
| // the initializer function, which is called *after* |
| // reserving space for this result. Therefore, since we |
| // already determined via the check above that this |
| // result was the last allocation, there must not have |
| // been any other allocations, and this result is the |
| // only allocation in this chunk. |
| // |
| // Because this is the only allocation in this chunk, |
| // we can reset the chunk's bump finger to the start of |
| // the chunk. |
| current_ptr.set(current_footer_p.as_ref().data); |
| } |
| } |
| //SAFETY: |
| // As we received `E` semantically by value from `f`, we can |
| // just copy that value here as long as we avoid a double-drop |
| // (which can't happen as any specific references to the `E`'s |
| // data in `self` are destroyed when this function returns). |
| // |
| // The order between this and the deallocation doesn't matter |
| // because `Self: !Sync`. |
| Err(ptr::read(e as *const _)) |
| }, |
| } |
| } |
| |
| /// Tries to pre-allocates space for a [`Result`] in this `Bump`, |
| /// initializes it using the closure, then returns an exclusive reference |
| /// to its `T` if all [`Ok`]. |
| /// |
| /// Iff the allocation fails, the closure is not run. |
| /// |
| /// Iff the closure returns [`Err`], an allocator rewind is *attempted* and |
| /// the `E` instance is moved out of the allocator to be consumed or dropped |
| /// as normal. |
| /// |
| /// See [The `_with` Method Suffix](#the-_with-method-suffix) for a |
| /// discussion on the differences between the `_with` suffixed methods and |
| /// those methods without it, their performance characteristics, and when |
| /// you might or might not choose a `_with` suffixed method. |
| /// |
| /// For caveats specific to fallible initialization, see |
| /// [The `_try_with` Method Suffix](#the-_try_with-method-suffix). |
| /// |
| /// ## Errors |
| /// |
| /// Errors with the [`Alloc`](`AllocOrInitError::Alloc`) variant iff |
| /// reserving space for `Result<T, E>` fails. |
| /// |
| /// Iff the allocation succeeds but `f` fails, that error is forwarded by |
| /// value inside the [`Init`](`AllocOrInitError::Init`) variant. |
| /// |
| /// ## Example |
| /// |
| /// ``` |
| /// let bump = bumpalo::Bump::new(); |
| /// let x = bump.try_alloc_try_with(|| Ok("hello"))?; |
| /// assert_eq!(*x, "hello"); |
| /// # Result::<_, bumpalo::AllocOrInitError<()>>::Ok(()) |
| /// ``` |
| #[inline(always)] |
| #[allow(clippy::mut_from_ref)] |
| pub fn try_alloc_try_with<F, T, E>(&self, f: F) -> Result<&mut T, AllocOrInitError<E>> |
| where |
| F: FnOnce() -> Result<T, E>, |
| { |
| let rewind_footer = self.current_chunk_footer.get(); |
| let rewind_ptr = unsafe { rewind_footer.as_ref() }.ptr.get(); |
| let mut inner_result_ptr = NonNull::from(self.try_alloc_with(f)?); |
| let inner_result_address = inner_result_ptr.as_ptr() as usize; |
| match unsafe { inner_result_ptr.as_mut() } { |
| Ok(t) => Ok(unsafe { |
| //SAFETY: |
| // The `&mut Result<T, E>` returned by `alloc_with` may be |
| // lifetime-limited by `E`, but the derived `&mut T` still has |
| // the same validity as in `alloc_with` since the error variant |
| // is already ruled out here. |
| |
| // We could conditionally truncate the allocation here, but |
| // since it grows backwards, it seems unlikely that we'd get |
| // any more than the `Result`'s discriminant this way, if |
| // anything at all. |
| &mut *(t as *mut _) |
| }), |
| Err(e) => unsafe { |
| // If this result was the last allocation in this arena, we can |
| // reclaim its space. In fact, sometimes we can do even better |
| // than simply calling `dealloc` on the result pointer: we can |
| // reclaim any alignment padding we might have added (which |
| // `dealloc` cannot do) if we didn't allocate a new chunk for |
| // this result. |
| if self.is_last_allocation(NonNull::new_unchecked(inner_result_address as *mut _)) { |
| let current_footer_p = self.current_chunk_footer.get(); |
| let current_ptr = ¤t_footer_p.as_ref().ptr; |
| if current_footer_p == rewind_footer { |
| // It's still the same chunk, so reset the bump pointer |
| // to its original value upon entry to this method |
| // (reclaiming any alignment padding we may have |
| // added). |
| current_ptr.set(rewind_ptr); |
| } else { |
| // We allocated a new chunk for this result. |
| // |
| // We know the result is the only allocation in this |
| // chunk: Any additional allocations since the start of |
| // this method could only have happened when running |
| // the initializer function, which is called *after* |
| // reserving space for this result. Therefore, since we |
| // already determined via the check above that this |
| // result was the last allocation, there must not have |
| // been any other allocations, and this result is the |
| // only allocation in this chunk. |
| // |
| // Because this is the only allocation in this chunk, |
| // we can reset the chunk's bump finger to the start of |
| // the chunk. |
| current_ptr.set(current_footer_p.as_ref().data); |
| } |
| } |
| //SAFETY: |
| // As we received `E` semantically by value from `f`, we can |
| // just copy that value here as long as we avoid a double-drop |
| // (which can't happen as any specific references to the `E`'s |
| // data in `self` are destroyed when this function returns). |
| // |
| // The order between this and the deallocation doesn't matter |
| // because `Self: !Sync`. |
| Err(AllocOrInitError::Init(ptr::read(e as *const _))) |
| }, |
| } |
| } |
| |
| /// `Copy` a slice into this `Bump` and return an exclusive reference to |
| /// the copy. |
| /// |
| /// ## Panics |
| /// |
| /// Panics if reserving space for the slice fails. |
| /// |
| /// ## Example |
| /// |
| /// ``` |
| /// let bump = bumpalo::Bump::new(); |
| /// let x = bump.alloc_slice_copy(&[1, 2, 3]); |
| /// assert_eq!(x, &[1, 2, 3]); |
| /// ``` |
| #[inline(always)] |
| #[allow(clippy::mut_from_ref)] |
| pub fn alloc_slice_copy<T>(&self, src: &[T]) -> &mut [T] |
| where |
| T: Copy, |
| { |
| let layout = Layout::for_value(src); |
| let dst = self.alloc_layout(layout).cast::<T>(); |
| |
| unsafe { |
| ptr::copy_nonoverlapping(src.as_ptr(), dst.as_ptr(), src.len()); |
| slice::from_raw_parts_mut(dst.as_ptr(), src.len()) |
| } |
| } |
| |
| /// `Clone` a slice into this `Bump` and return an exclusive reference to |
| /// the clone. Prefer `alloc_slice_copy` if `T` is `Copy`. |
| /// |
| /// ## Panics |
| /// |
| /// Panics if reserving space for the slice fails. |
| /// |
| /// ## Example |
| /// |
| /// ``` |
| /// #[derive(Clone, Debug, Eq, PartialEq)] |
| /// struct Sheep { |
| /// name: String, |
| /// } |
| /// |
| /// let originals = vec![ |
| /// Sheep { name: "Alice".into() }, |
| /// Sheep { name: "Bob".into() }, |
| /// Sheep { name: "Cathy".into() }, |
| /// ]; |
| /// |
| /// let bump = bumpalo::Bump::new(); |
| /// let clones = bump.alloc_slice_clone(&originals); |
| /// assert_eq!(originals, clones); |
| /// ``` |
| #[inline(always)] |
| #[allow(clippy::mut_from_ref)] |
| pub fn alloc_slice_clone<T>(&self, src: &[T]) -> &mut [T] |
| where |
| T: Clone, |
| { |
| let layout = Layout::for_value(src); |
| let dst = self.alloc_layout(layout).cast::<T>(); |
| |
| unsafe { |
| for (i, val) in src.iter().cloned().enumerate() { |
| ptr::write(dst.as_ptr().add(i), val); |
| } |
| |
| slice::from_raw_parts_mut(dst.as_ptr(), src.len()) |
| } |
| } |
| |
| /// `Copy` a string slice into this `Bump` and return an exclusive reference to it. |
| /// |
| /// ## Panics |
| /// |
| /// Panics if reserving space for the string fails. |
| /// |
| /// ## Example |
| /// |
| /// ``` |
| /// let bump = bumpalo::Bump::new(); |
| /// let hello = bump.alloc_str("hello world"); |
| /// assert_eq!("hello world", hello); |
| /// ``` |
| #[inline(always)] |
| #[allow(clippy::mut_from_ref)] |
| pub fn alloc_str(&self, src: &str) -> &mut str { |
| let buffer = self.alloc_slice_copy(src.as_bytes()); |
| unsafe { |
| // This is OK, because it already came in as str, so it is guaranteed to be utf8 |
| str::from_utf8_unchecked_mut(buffer) |
| } |
| } |
| |
| /// Allocates a new slice of size `len` into this `Bump` and returns an |
| /// exclusive reference to the copy. |
| /// |
| /// The elements of the slice are initialized using the supplied closure. |
| /// The closure argument is the position in the slice. |
| /// |
| /// ## Panics |
| /// |
| /// Panics if reserving space for the slice fails. |
| /// |
| /// ## Example |
| /// |
| /// ``` |
| /// let bump = bumpalo::Bump::new(); |
| /// let x = bump.alloc_slice_fill_with(5, |i| 5*(i+1)); |
| /// assert_eq!(x, &[5, 10, 15, 20, 25]); |
| /// ``` |
| #[inline(always)] |
| #[allow(clippy::mut_from_ref)] |
| pub fn alloc_slice_fill_with<T, F>(&self, len: usize, mut f: F) -> &mut [T] |
| where |
| F: FnMut(usize) -> T, |
| { |
| let layout = Layout::array::<T>(len).unwrap_or_else(|_| oom()); |
| let dst = self.alloc_layout(layout).cast::<T>(); |
| |
| unsafe { |
| for i in 0..len { |
| ptr::write(dst.as_ptr().add(i), f(i)); |
| } |
| |
| let result = slice::from_raw_parts_mut(dst.as_ptr(), len); |
| debug_assert_eq!(Layout::for_value(result), layout); |
| result |
| } |
| } |
| |
| /// Allocates a new slice of size `len` into this `Bump` and returns an |
| /// exclusive reference to the copy. |
| /// |
| /// All elements of the slice are initialized to `value`. |
| /// |
| /// ## Panics |
| /// |
| /// Panics if reserving space for the slice fails. |
| /// |
| /// ## Example |
| /// |
| /// ``` |
| /// let bump = bumpalo::Bump::new(); |
| /// let x = bump.alloc_slice_fill_copy(5, 42); |
| /// assert_eq!(x, &[42, 42, 42, 42, 42]); |
| /// ``` |
| #[inline(always)] |
| #[allow(clippy::mut_from_ref)] |
| pub fn alloc_slice_fill_copy<T: Copy>(&self, len: usize, value: T) -> &mut [T] { |
| self.alloc_slice_fill_with(len, |_| value) |
| } |
| |
| /// Allocates a new slice of size `len` slice into this `Bump` and return an |
| /// exclusive reference to the copy. |
| /// |
| /// All elements of the slice are initialized to `value.clone()`. |
| /// |
| /// ## Panics |
| /// |
| /// Panics if reserving space for the slice fails. |
| /// |
| /// ## Example |
| /// |
| /// ``` |
| /// let bump = bumpalo::Bump::new(); |
| /// let s: String = "Hello Bump!".to_string(); |
| /// let x: &[String] = bump.alloc_slice_fill_clone(2, &s); |
| /// assert_eq!(x.len(), 2); |
| /// assert_eq!(&x[0], &s); |
| /// assert_eq!(&x[1], &s); |
| /// ``` |
| #[inline(always)] |
| #[allow(clippy::mut_from_ref)] |
| pub fn alloc_slice_fill_clone<T: Clone>(&self, len: usize, value: &T) -> &mut [T] { |
| self.alloc_slice_fill_with(len, |_| value.clone()) |
| } |
| |
| /// Allocates a new slice of size `len` slice into this `Bump` and return an |
| /// exclusive reference to the copy. |
| /// |
| /// The elements are initialized using the supplied iterator. |
| /// |
| /// ## Panics |
| /// |
| /// Panics if reserving space for the slice fails, or if the supplied |
| /// iterator returns fewer elements than it promised. |
| /// |
| /// ## Example |
| /// |
| /// ``` |
| /// let bump = bumpalo::Bump::new(); |
| /// let x: &[i32] = bump.alloc_slice_fill_iter([2, 3, 5].iter().cloned().map(|i| i * i)); |
| /// assert_eq!(x, [4, 9, 25]); |
| /// ``` |
| #[inline(always)] |
| #[allow(clippy::mut_from_ref)] |
| pub fn alloc_slice_fill_iter<T, I>(&self, iter: I) -> &mut [T] |
| where |
| I: IntoIterator<Item = T>, |
| I::IntoIter: ExactSizeIterator, |
| { |
| let mut iter = iter.into_iter(); |
| self.alloc_slice_fill_with(iter.len(), |_| { |
| iter.next().expect("Iterator supplied too few elements") |
| }) |
| } |
| |
| /// Allocates a new slice of size `len` slice into this `Bump` and return an |
| /// exclusive reference to the copy. |
| /// |
| /// All elements of the slice are initialized to `T::default()`. |
| /// |
| /// ## Panics |
| /// |
| /// Panics if reserving space for the slice fails. |
| /// |
| /// ## Example |
| /// |
| /// ``` |
| /// let bump = bumpalo::Bump::new(); |
| /// let x = bump.alloc_slice_fill_default::<u32>(5); |
| /// assert_eq!(x, &[0, 0, 0, 0, 0]); |
| /// ``` |
| #[inline(always)] |
| #[allow(clippy::mut_from_ref)] |
| pub fn alloc_slice_fill_default<T: Default>(&self, len: usize) -> &mut [T] { |
| self.alloc_slice_fill_with(len, |_| T::default()) |
| } |
| |
| /// Allocate space for an object with the given `Layout`. |
| /// |
| /// The returned pointer points at uninitialized memory, and should be |
| /// initialized with |
| /// [`std::ptr::write`](https://doc.rust-lang.org/std/ptr/fn.write.html). |
| /// |
| /// # Panics |
| /// |
| /// Panics if reserving space matching `layout` fails. |
| #[inline(always)] |
| pub fn alloc_layout(&self, layout: Layout) -> NonNull<u8> { |
| self.try_alloc_layout(layout).unwrap_or_else(|_| oom()) |
| } |
| |
| /// Attempts to allocate space for an object with the given `Layout` or else returns |
| /// an `Err`. |
| /// |
| /// The returned pointer points at uninitialized memory, and should be |
| /// initialized with |
| /// [`std::ptr::write`](https://doc.rust-lang.org/std/ptr/fn.write.html). |
| /// |
| /// # Errors |
| /// |
| /// Errors if reserving space matching `layout` fails. |
| #[inline(always)] |
| pub fn try_alloc_layout(&self, layout: Layout) -> Result<NonNull<u8>, alloc::AllocErr> { |
| if let Some(p) = self.try_alloc_layout_fast(layout) { |
| Ok(p) |
| } else { |
| self.alloc_layout_slow(layout).ok_or(alloc::AllocErr {}) |
| } |
| } |
| |
| #[inline(always)] |
| fn try_alloc_layout_fast(&self, layout: Layout) -> Option<NonNull<u8>> { |
| // We don't need to check for ZSTs here since they will automatically |
| // be handled properly: the pointer will be bumped by zero bytes, |
| // modulo alignment. This keeps the fast path optimized for non-ZSTs, |
| // which are much more common. |
| unsafe { |
| let footer = self.current_chunk_footer.get(); |
| let footer = footer.as_ref(); |
| let ptr = footer.ptr.get().as_ptr() as usize; |
| let start = footer.data.as_ptr() as usize; |
| debug_assert!(start <= ptr); |
| debug_assert!(ptr <= footer as *const _ as usize); |
| |
| let ptr = ptr.checked_sub(layout.size())?; |
| let aligned_ptr = ptr & !(layout.align() - 1); |
| |
| if aligned_ptr >= start { |
| let aligned_ptr = NonNull::new_unchecked(aligned_ptr as *mut u8); |
| footer.ptr.set(aligned_ptr); |
| Some(aligned_ptr) |
| } else { |
| None |
| } |
| } |
| } |
| |
| /// Gets the remaining capacity in the current chunk (in bytes). |
| /// |
| /// ## Example |
| /// |
| /// ``` |
| /// use bumpalo::Bump; |
| /// |
| /// let bump = Bump::with_capacity(100); |
| /// |
| /// let capacity = bump.chunk_capacity(); |
| /// assert!(capacity >= 100); |
| /// ``` |
| pub fn chunk_capacity(&self) -> usize { |
| let current_footer = self.current_chunk_footer.get(); |
| let current_footer = unsafe { current_footer.as_ref() }; |
| |
| current_footer as *const _ as usize - current_footer.data.as_ptr() as usize |
| } |
| |
| /// Slow path allocation for when we need to allocate a new chunk from the |
| /// parent bump set because there isn't enough room in our current chunk. |
| #[inline(never)] |
| fn alloc_layout_slow(&self, layout: Layout) -> Option<NonNull<u8>> { |
| unsafe { |
| let size = layout.size(); |
| |
| // Get a new chunk from the global allocator. |
| let current_footer = self.current_chunk_footer.get(); |
| let current_layout = current_footer.as_ref().layout; |
| |
| // By default, we want our new chunk to be about twice as big |
| // as the previous chunk. If the global allocator refuses it, |
| // we try to divide it by half until it works or the requested |
| // size is smaller than the default footer size. |
| let min_new_chunk_size = layout.size().max(DEFAULT_CHUNK_SIZE_WITHOUT_FOOTER); |
| let mut base_size = (current_layout.size() - FOOTER_SIZE) |
| .checked_mul(2)? |
| .max(min_new_chunk_size); |
| let sizes = iter::from_fn(|| { |
| if base_size >= min_new_chunk_size { |
| let size = base_size; |
| base_size = base_size / 2; |
| Some(size) |
| } else { |
| None |
| } |
| }); |
| |
| let new_footer = sizes |
| .filter_map(|size| Bump::new_chunk(Some(size), Some(layout), Some(current_footer))) |
| .next()?; |
| |
| debug_assert_eq!( |
| new_footer.as_ref().data.as_ptr() as usize % layout.align(), |
| 0 |
| ); |
| |
| // Set the new chunk as our new current chunk. |
| self.current_chunk_footer.set(new_footer); |
| |
| let new_footer = new_footer.as_ref(); |
| |
| // Move the bump ptr finger down to allocate room for `val`. We know |
| // this can't overflow because we successfully allocated a chunk of |
| // at least the requested size. |
| let ptr = new_footer.ptr.get().as_ptr() as usize - size; |
| // Round the pointer down to the requested alignment. |
| let ptr = ptr & !(layout.align() - 1); |
| debug_assert!( |
| ptr <= new_footer as *const _ as usize, |
| "{:#x} <= {:#x}", |
| ptr, |
| new_footer as *const _ as usize |
| ); |
| let ptr = NonNull::new_unchecked(ptr as *mut u8); |
| new_footer.ptr.set(ptr); |
| |
| // Return a pointer to the freshly allocated region in this chunk. |
| Some(ptr) |
| } |
| } |
| |
| /// Returns an iterator over each chunk of allocated memory that |
| /// this arena has bump allocated into. |
| /// |
| /// The chunks are returned ordered by allocation time, with the most |
| /// recently allocated chunk being returned first, and the least recently |
| /// allocated chunk being returned last. |
| /// |
| /// The values inside each chunk are also ordered by allocation time, with |
| /// the most recent allocation being earlier in the slice, and the least |
| /// recent allocation being towards the end of the slice. |
| /// |
| /// ## Safety |
| /// |
| /// Because this method takes `&mut self`, we know that the bump arena |
| /// reference is unique and therefore there aren't any active references to |
| /// any of the objects we've allocated in it either. This potential aliasing |
| /// of exclusive references is one common footgun for unsafe code that we |
| /// don't need to worry about here. |
| /// |
| /// However, there could be regions of uninitialized memory used as padding |
| /// between allocations, which is why this iterator has items of type |
| /// `[MaybeUninit<u8>]`, instead of simply `[u8]`. |
| /// |
| /// The only way to guarantee that there is no padding between allocations |
| /// or within allocated objects is if all of these properties hold: |
| /// |
| /// 1. Every object allocated in this arena has the same alignment, |
| /// and that alignment is at most 16. |
| /// 2. Every object's size is a multiple of its alignment. |
| /// 3. None of the objects allocated in this arena contain any internal |
| /// padding. |
| /// |
| /// If you want to use this `iter_allocated_chunks` method, it is *your* |
| /// responsibility to ensure that these properties hold before calling |
| /// `MaybeUninit::assume_init` or otherwise reading the returned values. |
| /// |
| /// Finally, you must also ensure that any values allocated into the bump |
| /// arena have not had their `Drop` implementations called on them, |
| /// e.g. after dropping a [`bumpalo::boxed::Box<T>`][crate::boxed::Box]. |
| /// |
| /// ## Example |
| /// |
| /// ``` |
| /// let mut bump = bumpalo::Bump::new(); |
| /// |
| /// // Allocate a bunch of `i32`s in this bump arena, potentially causing |
| /// // additional memory chunks to be reserved. |
| /// for i in 0..10000 { |
| /// bump.alloc(i); |
| /// } |
| /// |
| /// // Iterate over each chunk we've bump allocated into. This is safe |
| /// // because we have only allocated `i32`s in this arena, which fulfills |
| /// // the above requirements. |
| /// for ch in bump.iter_allocated_chunks() { |
| /// println!("Used a chunk that is {} bytes long", ch.len()); |
| /// println!("The first byte is {:?}", unsafe { |
| /// ch.get(0).unwrap().assume_init() |
| /// }); |
| /// } |
| /// |
| /// // Within a chunk, allocations are ordered from most recent to least |
| /// // recent. If we allocated 'a', then 'b', then 'c', when we iterate |
| /// // through the chunk's data, we get them in the order 'c', then 'b', |
| /// // then 'a'. |
| /// |
| /// bump.reset(); |
| /// bump.alloc(b'a'); |
| /// bump.alloc(b'b'); |
| /// bump.alloc(b'c'); |
| /// |
| /// assert_eq!(bump.iter_allocated_chunks().count(), 1); |
| /// let chunk = bump.iter_allocated_chunks().nth(0).unwrap(); |
| /// assert_eq!(chunk.len(), 3); |
| /// |
| /// // Safe because we've only allocated `u8`s in this arena, which |
| /// // fulfills the above requirements. |
| /// unsafe { |
| /// assert_eq!(chunk[0].assume_init(), b'c'); |
| /// assert_eq!(chunk[1].assume_init(), b'b'); |
| /// assert_eq!(chunk[2].assume_init(), b'a'); |
| /// } |
| /// ``` |
| pub fn iter_allocated_chunks(&mut self) -> ChunkIter<'_> { |
| // SAFE: Ensured by mutable borrow of `self`. |
| let raw = unsafe { self.iter_allocated_chunks_raw() }; |
| ChunkIter { |
| raw, |
| bump: PhantomData, |
| } |
| } |
| |
| /// Returns an iterator over raw pointers to chunks of allocated memory that |
| /// this arena has bump allocated into. |
| /// |
| /// This is an unsafe version of [`iter_allocated_chunks()`](Bump::iter_allocated_chunks), |
| /// with the caller responsible for safe usage of the returned pointers as |
| /// well as ensuring that the iterator is not invalidated by new |
| /// allocations. |
| /// |
| /// ## Safety |
| /// |
| /// Allocations from this arena must not be performed while the returned |
| /// iterator is alive. If reading the chunk data (or casting to a reference) |
| /// the caller must ensure that there exist no mutable references to |
| /// previously allocated data. |
| /// |
| /// In addition, all of the caveats when reading the chunk data from |
| /// [`iter_allocated_chunks()`](Bump::iter_allocated_chunks) still apply. |
| pub unsafe fn iter_allocated_chunks_raw(&self) -> ChunkRawIter<'_> { |
| ChunkRawIter { |
| footer: Some(self.current_chunk_footer.get()), |
| bump: PhantomData, |
| } |
| } |
| |
| /// Calculates the number of bytes currently allocated across all chunks in |
| /// this bump arena. |
| /// |
| /// If you allocate types of different alignments or types with |
| /// larger-than-typical alignment in the same arena, some padding |
| /// bytes might get allocated in the bump arena. Note that those padding |
| /// bytes will add to this method's resulting sum, so you cannot rely |
| /// on it only counting the sum of the sizes of the things |
| /// you've allocated in the arena. |
| /// |
| /// ## Example |
| /// |
| /// ``` |
| /// let bump = bumpalo::Bump::new(); |
| /// let _x = bump.alloc_slice_fill_default::<u32>(5); |
| /// let bytes = bump.allocated_bytes(); |
| /// assert!(bytes >= core::mem::size_of::<u32>() * 5); |
| /// ``` |
| pub fn allocated_bytes(&self) -> usize { |
| let mut footer = Some(self.current_chunk_footer.get()); |
| |
| let mut bytes = 0; |
| |
| while let Some(f) = footer { |
| let foot = unsafe { f.as_ref() }; |
| |
| let ptr = foot.ptr.get().as_ptr() as usize; |
| debug_assert!(ptr <= foot as *const _ as usize); |
| |
| bytes += foot as *const _ as usize - ptr; |
| |
| footer = foot.prev.get(); |
| } |
| |
| bytes |
| } |
| |
| #[inline] |
| unsafe fn is_last_allocation(&self, ptr: NonNull<u8>) -> bool { |
| let footer = self.current_chunk_footer.get(); |
| let footer = footer.as_ref(); |
| footer.ptr.get() == ptr |
| } |
| |
| #[inline] |
| unsafe fn dealloc(&self, ptr: NonNull<u8>, layout: Layout) { |
| // If the pointer is the last allocation we made, we can reuse the bytes, |
| // otherwise they are simply leaked -- at least until somebody calls reset(). |
| if self.is_last_allocation(ptr) { |
| let ptr = NonNull::new_unchecked(ptr.as_ptr().add(layout.size())); |
| self.current_chunk_footer.get().as_ref().ptr.set(ptr); |
| } |
| } |
| |
| #[inline] |
| unsafe fn shrink( |
| &self, |
| ptr: NonNull<u8>, |
| layout: Layout, |
| new_size: usize, |
| ) -> Result<NonNull<u8>, alloc::AllocErr> { |
| let old_size = layout.size(); |
| if self.is_last_allocation(ptr) |
| // Only reclaim the excess space (which requires a copy) if it |
| // is worth it: we are actually going to recover "enough" space |
| // and we can do a non-overlapping copy. |
| && new_size <= old_size / 2 |
| { |
| let delta = old_size - new_size; |
| let footer = self.current_chunk_footer.get(); |
| let footer = footer.as_ref(); |
| footer |
| .ptr |
| .set(NonNull::new_unchecked(footer.ptr.get().as_ptr().add(delta))); |
| let new_ptr = footer.ptr.get(); |
| // NB: we know it is non-overlapping because of the size check |
| // in the `if` condition. |
| ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_ptr(), new_size); |
| return Ok(new_ptr); |
| } else { |
| return Ok(ptr); |
| } |
| } |
| |
| #[inline] |
| unsafe fn grow( |
| &self, |
| ptr: NonNull<u8>, |
| layout: Layout, |
| new_size: usize, |
| ) -> Result<NonNull<u8>, alloc::AllocErr> { |
| let old_size = layout.size(); |
| if self.is_last_allocation(ptr) { |
| // Try to allocate the delta size within this same block so we can |
| // reuse the currently allocated space. |
| let delta = new_size - old_size; |
| if let Some(p) = |
| self.try_alloc_layout_fast(layout_from_size_align(delta, layout.align())) |
| { |
| ptr::copy(ptr.as_ptr(), p.as_ptr(), old_size); |
| return Ok(p); |
| } |
| } |
| |
| // Fallback: do a fresh allocation and copy the existing data into it. |
| let new_layout = layout_from_size_align(new_size, layout.align()); |
| let new_ptr = self.try_alloc_layout(new_layout)?; |
| ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_ptr(), old_size); |
| Ok(new_ptr) |
| } |
| } |
| |
| /// An iterator over each chunk of allocated memory that |
| /// an arena has bump allocated into. |
| /// |
| /// The chunks are returned ordered by allocation time, with the most recently |
| /// allocated chunk being returned first. |
| /// |
| /// The values inside each chunk is also ordered by allocation time, with the most |
| /// recent allocation being earlier in the slice. |
| /// |
| /// This struct is created by the [`iter_allocated_chunks`] method on |
| /// [`Bump`]. See that function for a safety description regarding reading from the returned items. |
| /// |
| /// [`Bump`]: ./struct.Bump.html |
| /// [`iter_allocated_chunks`]: ./struct.Bump.html#method.iter_allocated_chunks |
| #[derive(Debug)] |
| pub struct ChunkIter<'a> { |
| raw: ChunkRawIter<'a>, |
| bump: PhantomData<&'a mut Bump>, |
| } |
| |
| impl<'a> Iterator for ChunkIter<'a> { |
| type Item = &'a [mem::MaybeUninit<u8>]; |
| fn next(&mut self) -> Option<&'a [mem::MaybeUninit<u8>]> { |
| unsafe { |
| let (ptr, len) = self.raw.next()?; |
| let slice = slice::from_raw_parts(ptr as *const mem::MaybeUninit<u8>, len); |
| Some(slice) |
| } |
| } |
| } |
| |
| impl<'a> iter::FusedIterator for ChunkIter<'a> {} |
| |
| /// An iterator over raw pointers to chunks of allocated memory that this |
| /// arena has bump allocated into. |
| /// |
| /// See [`ChunkIter`] for details regarding the returned chunks. |
| /// |
| /// This struct is created by the [`iter_allocated_chunks_raw`] method on |
| /// [`Bump`]. See that function for a safety description regarding reading from |
| /// the returned items. |
| /// |
| /// [`Bump`]: ./struct.Bump.html |
| /// [`iter_allocated_chunks_raw`]: ./struct.Bump.html#method.iter_allocated_chunks_raw |
| #[derive(Debug)] |
| pub struct ChunkRawIter<'a> { |
| footer: Option<NonNull<ChunkFooter>>, |
| bump: PhantomData<&'a Bump>, |
| } |
| |
| impl Iterator for ChunkRawIter<'_> { |
| type Item = (*mut u8, usize); |
| fn next(&mut self) -> Option<(*mut u8, usize)> { |
| unsafe { |
| let foot = self.footer?; |
| let foot = foot.as_ref(); |
| let (ptr, len) = foot.as_raw_parts(); |
| self.footer = foot.prev.get(); |
| Some((ptr as *mut u8, len)) |
| } |
| } |
| } |
| |
| impl iter::FusedIterator for ChunkRawIter<'_> {} |
| |
| #[inline(never)] |
| #[cold] |
| fn oom() -> ! { |
| panic!("out of memory") |
| } |
| |
| unsafe impl<'a> alloc::Alloc for &'a Bump { |
| #[inline(always)] |
| unsafe fn alloc(&mut self, layout: Layout) -> Result<NonNull<u8>, alloc::AllocErr> { |
| self.try_alloc_layout(layout) |
| } |
| |
| #[inline] |
| unsafe fn dealloc(&mut self, ptr: NonNull<u8>, layout: Layout) { |
| Bump::dealloc(self, ptr, layout) |
| } |
| |
| #[inline] |
| unsafe fn realloc( |
| &mut self, |
| ptr: NonNull<u8>, |
| layout: Layout, |
| new_size: usize, |
| ) -> Result<NonNull<u8>, alloc::AllocErr> { |
| let old_size = layout.size(); |
| |
| if old_size == 0 { |
| return self.try_alloc_layout(layout); |
| } |
| |
| if new_size <= old_size { |
| self.shrink(ptr, layout, new_size) |
| } else { |
| self.grow(ptr, layout, new_size) |
| } |
| } |
| } |
| |
| #[cfg(feature = "allocator_api")] |
| unsafe impl<'a> Allocator for &'a Bump { |
| fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> { |
| self.try_alloc_layout(layout) |
| .map(|p| NonNull::slice_from_raw_parts(p, layout.size())) |
| .map_err(|_| AllocError) |
| } |
| |
| unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) { |
| Bump::dealloc(self, ptr, layout) |
| } |
| |
| unsafe fn shrink( |
| &self, |
| ptr: NonNull<u8>, |
| old_layout: Layout, |
| new_layout: Layout, |
| ) -> Result<NonNull<[u8]>, AllocError> { |
| let new_size = new_layout.size(); |
| Bump::shrink(self, ptr, old_layout, new_size) |
| .map(|p| NonNull::slice_from_raw_parts(p, new_size)) |
| .map_err(|_| AllocError) |
| } |
| |
| unsafe fn grow( |
| &self, |
| ptr: NonNull<u8>, |
| old_layout: Layout, |
| new_layout: Layout, |
| ) -> Result<NonNull<[u8]>, AllocError> { |
| let new_size = new_layout.size(); |
| Bump::grow(self, ptr, old_layout, new_size) |
| .map(|p| NonNull::slice_from_raw_parts(p, new_size)) |
| .map_err(|_| AllocError) |
| } |
| |
| unsafe fn grow_zeroed( |
| &self, |
| ptr: NonNull<u8>, |
| old_layout: Layout, |
| new_layout: Layout, |
| ) -> Result<NonNull<[u8]>, AllocError> { |
| let mut ptr = self.grow(ptr, old_layout, new_layout)?; |
| ptr.as_mut()[old_layout.size()..].fill(0); |
| Ok(ptr) |
| } |
| } |
| |
| #[cfg(test)] |
| mod tests { |
| use super::*; |
| |
| #[test] |
| fn chunk_footer_is_five_words() { |
| assert_eq!(mem::size_of::<ChunkFooter>(), mem::size_of::<usize>() * 5); |
| } |
| |
| #[test] |
| #[allow(clippy::cognitive_complexity)] |
| fn test_realloc() { |
| use crate::alloc::Alloc; |
| |
| unsafe { |
| const CAPACITY: usize = 1024 - OVERHEAD; |
| let mut b = Bump::with_capacity(CAPACITY); |
| |
| // `realloc` doesn't shrink allocations that aren't "worth it". |
| let layout = Layout::from_size_align(100, 1).unwrap(); |
| let p = b.alloc_layout(layout); |
| let q = (&b).realloc(p, layout, 51).unwrap(); |
| assert_eq!(p, q); |
| b.reset(); |
| |
| // `realloc` will shrink allocations that are "worth it". |
| let layout = Layout::from_size_align(100, 1).unwrap(); |
| let p = b.alloc_layout(layout); |
| let q = (&b).realloc(p, layout, 50).unwrap(); |
| assert!(p != q); |
| b.reset(); |
| |
| // `realloc` will reuse the last allocation when growing. |
| let layout = Layout::from_size_align(10, 1).unwrap(); |
| let p = b.alloc_layout(layout); |
| let q = (&b).realloc(p, layout, 11).unwrap(); |
| assert_eq!(q.as_ptr() as usize, p.as_ptr() as usize - 1); |
| b.reset(); |
| |
| // `realloc` will allocate a new chunk when growing the last |
| // allocation, if need be. |
| let layout = Layout::from_size_align(1, 1).unwrap(); |
| let p = b.alloc_layout(layout); |
| let q = (&b).realloc(p, layout, CAPACITY + 1).unwrap(); |
| assert!(q.as_ptr() as usize != p.as_ptr() as usize - CAPACITY); |
| b = Bump::with_capacity(CAPACITY); |
| |
| // `realloc` will allocate and copy when reallocating anything that |
| // wasn't the last allocation. |
| let layout = Layout::from_size_align(1, 1).unwrap(); |
| let p = b.alloc_layout(layout); |
| let _ = b.alloc_layout(layout); |
| let q = (&b).realloc(p, layout, 2).unwrap(); |
| assert!(q.as_ptr() as usize != p.as_ptr() as usize - 1); |
| b.reset(); |
| } |
| } |
| |
| #[test] |
| fn invalid_read() { |
| use alloc::Alloc; |
| |
| let mut b = &Bump::new(); |
| |
| unsafe { |
| let l1 = Layout::from_size_align(12000, 4).unwrap(); |
| let p1 = Alloc::alloc(&mut b, l1).unwrap(); |
| |
| let l2 = Layout::from_size_align(1000, 4).unwrap(); |
| Alloc::alloc(&mut b, l2).unwrap(); |
| |
| let p1 = b.realloc(p1, l1, 24000).unwrap(); |
| let l3 = Layout::from_size_align(24000, 4).unwrap(); |
| b.realloc(p1, l3, 48000).unwrap(); |
| } |
| } |
| } |
