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-rw-r--r--vendor/bumpalo/src/lib.rs2019
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+#![doc = include_str!("../README.md")]
+#![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};
+
+pub use alloc::AllocErr;
+
+/// 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(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<AllocErr> for AllocOrInitError<E> {
+ fn from(e: 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 &mdash; 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`]: https://doc.rust-lang.org/std/ops/trait.Drop.html
+/// [`Vec<T>`]: https://doc.rust-lang.org/std/vec/struct.Vec.html
+/// [`std::fs::File`]: https://doc.rust-lang.org/std/fs/struct.File.html
+/// [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/vec/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
+/// [`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 1.54.
+///
+/// ### 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.
+///
+/// [`Result`]: https://doc.rust-lang.org/std/result/enum.Result.html
+/// [`Ok`]: https://doc.rust-lang.org/std/result/enum.Result.html#variant.Ok
+/// [`Err`]: https://doc.rust-lang.org/std/result/enum.Result.html#variant.Err
+///
+/// ### `Bump` Allocation Limits
+///
+/// `bumpalo` supports setting a limit on the maximum bytes of memory that can
+/// be allocated for use in a particular `Bump` arena. This limit can be set and removed with
+/// [`set_allocation_limit`][Bump::set_allocation_limit].
+/// The allocation limit is only enforced when allocating new backing chunks for
+/// a `Bump`. Updating the allocation limit will not affect existing allocations
+/// or any future allocations within the `Bump`'s current chunk.
+///
+/// #### Example
+///
+/// ```
+/// let bump = bumpalo::Bump::new();
+///
+/// assert_eq!(bump.allocation_limit(), None);
+/// bump.set_allocation_limit(Some(0));
+///
+/// assert!(bump.try_alloc(5).is_err());
+///
+/// bump.set_allocation_limit(Some(6));
+///
+/// assert_eq!(bump.allocation_limit(), Some(6));
+///
+/// bump.set_allocation_limit(None);
+///
+/// assert_eq!(bump.allocation_limit(), None);
+/// ```
+///
+/// #### Warning
+///
+/// Because of backwards compatibility, allocations that fail
+/// due to allocation limits will not present differently than
+/// errors due to resource exhaustion.
+
+#[derive(Debug)]
+pub struct Bump {
+ // The current chunk we are bump allocating within.
+ current_chunk_footer: Cell<NonNull<ChunkFooter>>,
+ allocation_limit: Cell<Option<usize>>,
+}
+
+#[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.
+ //
+ // Note that the last node in the `prev` linked list is the canonical empty
+ // chunk, whose `prev` link points to itself.
+ prev: Cell<NonNull<ChunkFooter>>,
+
+ // Bump allocation finger that is always in the range `self.data..=self`.
+ ptr: Cell<NonNull<u8>>,
+
+ // The bytes allocated in all chunks so far, the canonical empty chunk has
+ // a size of 0 and for all other chunks, `allocated_bytes` will be
+ // the allocated_bytes of the current chunk plus the allocated bytes
+ // of the `prev` chunk.
+ allocated_bytes: usize,
+}
+
+/// A wrapper type for the canonical, statically allocated empty chunk.
+///
+/// For the canonical empty chunk to be `static`, its type must be `Sync`, which
+/// is the purpose of this wrapper type. This is safe because the empty chunk is
+/// immutable and never actually modified.
+#[repr(transparent)]
+struct EmptyChunkFooter(ChunkFooter);
+
+unsafe impl Sync for EmptyChunkFooter {}
+
+static EMPTY_CHUNK: EmptyChunkFooter = EmptyChunkFooter(ChunkFooter {
+ // This chunk is empty (except the foot itself).
+ layout: Layout::new::<ChunkFooter>(),
+
+ // The start of the (empty) allocatable region for this chunk is itself.
+ data: unsafe { NonNull::new_unchecked(&EMPTY_CHUNK as *const EmptyChunkFooter as *mut u8) },
+
+ // The end of the (empty) allocatable region for this chunk is also itself.
+ ptr: Cell::new(unsafe {
+ NonNull::new_unchecked(&EMPTY_CHUNK as *const EmptyChunkFooter as *mut u8)
+ }),
+
+ // Invariant: the last chunk footer in all `ChunkFooter::prev` linked lists
+ // is the empty chunk footer, whose `prev` points to itself.
+ prev: Cell::new(unsafe {
+ NonNull::new_unchecked(&EMPTY_CHUNK as *const EmptyChunkFooter as *mut ChunkFooter)
+ }),
+
+ // Empty chunks count as 0 allocated bytes in an arena.
+ allocated_bytes: 0,
+});
+
+impl EmptyChunkFooter {
+ fn get(&'static self) -> NonNull<ChunkFooter> {
+ unsafe { NonNull::new_unchecked(&self.0 as *const ChunkFooter as *mut ChunkFooter) }
+ }
+}
+
+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 *const u8;
+ let ptr = self.ptr.get().as_ptr() as *const u8;
+ debug_assert!(data <= ptr);
+ debug_assert!(ptr <= self as *const ChunkFooter as *const u8);
+ let len = unsafe { (self as *const ChunkFooter as *const u8).offset_from(ptr) as usize };
+ (ptr, len)
+ }
+
+ /// Is this chunk the last empty chunk?
+ fn is_empty(&self) -> bool {
+ ptr::eq(self, EMPTY_CHUNK.get().as_ptr())
+ }
+}
+
+impl Default for Bump {
+ fn default() -> Bump {
+ Bump::new()
+ }
+}
+
+impl Drop for Bump {
+ fn drop(&mut self) {
+ unsafe {
+ dealloc_chunk_list(self.current_chunk_footer.get());
+ }
+ }
+}
+
+#[inline]
+unsafe fn dealloc_chunk_list(mut footer: NonNull<ChunkFooter>) {
+ while !footer.as_ref().is_empty() {
+ let 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))
+}
+
+#[inline]
+pub(crate) fn round_down_to(n: usize, divisor: usize) -> usize {
+ debug_assert!(divisor > 0);
+ debug_assert!(divisor.is_power_of_two());
+ n & !(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;
+
+/// The memory size and alignment details for a potential new chunk
+/// allocation.
+#[derive(Debug, Clone, Copy)]
+struct NewChunkMemoryDetails {
+ new_size_without_footer: usize,
+ align: usize,
+ size: usize,
+}
+
+/// 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")
+}
+
+// This can be migrated to directly use `usize::abs_diff` when the MSRV
+// reaches `1.60`
+fn abs_diff(a: usize, b: usize) -> usize {
+ usize::max(a, b) - usize::min(a, b)
+}
+
+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, 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, AllocErr> {
+ if capacity == 0 {
+ return Ok(Bump {
+ current_chunk_footer: Cell::new(EMPTY_CHUNK.get()),
+ allocation_limit: Cell::new(None),
+ });
+ }
+
+ let layout = unsafe { layout_from_size_align(capacity, 1) };
+
+ let chunk_footer = unsafe {
+ Self::new_chunk(
+ Bump::new_chunk_memory_details(None, layout).ok_or(AllocErr)?,
+ layout,
+ EMPTY_CHUNK.get(),
+ )
+ .ok_or(AllocErr)?
+ };
+
+ Ok(Bump {
+ current_chunk_footer: Cell::new(chunk_footer),
+ allocation_limit: Cell::new(None),
+ })
+ }
+
+ /// The allocation limit for this arena in bytes.
+ ///
+ /// ## Example
+ ///
+ /// ```
+ /// let bump = bumpalo::Bump::with_capacity(0);
+ ///
+ /// assert_eq!(bump.allocation_limit(), None);
+ ///
+ /// bump.set_allocation_limit(Some(6));
+ ///
+ /// assert_eq!(bump.allocation_limit(), Some(6));
+ ///
+ /// bump.set_allocation_limit(None);
+ ///
+ /// assert_eq!(bump.allocation_limit(), None);
+ /// ```
+ pub fn allocation_limit(&self) -> Option<usize> {
+ self.allocation_limit.get()
+ }
+
+ /// Set the allocation limit in bytes for this arena.
+ ///
+ /// The allocation limit is only enforced when allocating new backing chunks for
+ /// a `Bump`. Updating the allocation limit will not affect existing allocations
+ /// or any future allocations within the `Bump`'s current chunk.
+ ///
+ /// ## Example
+ ///
+ /// ```
+ /// let bump = bumpalo::Bump::with_capacity(0);
+ ///
+ /// bump.set_allocation_limit(Some(0));
+ ///
+ /// assert!(bump.try_alloc(5).is_err());
+ /// ```
+ pub fn set_allocation_limit(&self, limit: Option<usize>) {
+ self.allocation_limit.set(limit)
+ }
+
+ /// How much headroom an arena has before it hits its allocation
+ /// limit.
+ fn allocation_limit_remaining(&self) -> Option<usize> {
+ self.allocation_limit.get().and_then(|allocation_limit| {
+ let allocated_bytes = self.allocated_bytes();
+ if allocated_bytes > allocation_limit {
+ None
+ } else {
+ Some(abs_diff(allocation_limit, allocated_bytes))
+ }
+ })
+ }
+
+ /// Whether a request to allocate a new chunk with a given size for a given
+ /// requested layout will fit under the allocation limit set on a `Bump`.
+ fn chunk_fits_under_limit(
+ allocation_limit_remaining: Option<usize>,
+ new_chunk_memory_details: NewChunkMemoryDetails,
+ ) -> bool {
+ allocation_limit_remaining
+ .map(|allocation_limit_left| {
+ allocation_limit_left >= new_chunk_memory_details.new_size_without_footer
+ })
+ .unwrap_or(true)
+ }
+
+ /// Determine the memory details including final size, alignment and
+ /// final size without footer for a new chunk that would be allocated
+ /// to fulfill an allocation request.
+ fn new_chunk_memory_details(
+ new_size_without_footer: Option<usize>,
+ requested_layout: Layout,
+ ) -> Option<NewChunkMemoryDetails> {
+ 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
+ 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);
+
+ Some(NewChunkMemoryDetails {
+ new_size_without_footer,
+ size,
+ align,
+ })
+ }
+
+ /// 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.
+ unsafe fn new_chunk(
+ new_chunk_memory_details: NewChunkMemoryDetails,
+ requested_layout: Layout,
+ prev: NonNull<ChunkFooter>,
+ ) -> Option<NonNull<ChunkFooter>> {
+ let NewChunkMemoryDetails {
+ new_size_without_footer,
+ align,
+ size,
+ } = new_chunk_memory_details;
+
+ let layout = layout_from_size_align(size, align);
+
+ debug_assert!(size >= requested_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().add(new_size_without_footer);
+ debug_assert_eq!((data.as_ptr() as usize) % align, 0);
+ debug_assert_eq!(footer_ptr as usize % 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));
+
+ // The `allocated_bytes` of a new chunk counts the total size
+ // of the chunks, not how much of the chunks are used.
+ let allocated_bytes = prev.as_ref().allocated_bytes + new_size_without_footer;
+
+ ptr::write(
+ footer_ptr,
+ ChunkFooter {
+ data,
+ layout,
+ prev: Cell::new(prev),
+ ptr,
+ allocated_bytes,
+ },
+ );
+
+ 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 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 {
+ if self.current_chunk_footer.get().as_ref().is_empty() {
+ return;
+ }
+
+ let mut cur_chunk = self.current_chunk_footer.get();
+
+ // Deallocate all chunks except the current one
+ let prev_chunk = cur_chunk.as_ref().prev.replace(EMPTY_CHUNK.get());
+ dealloc_chunk_list(prev_chunk);
+
+ // Reset the bump finger to the end of the chunk.
+ cur_chunk.as_ref().ptr.set(cur_chunk.cast());
+
+ // Reset the allocated size of the chunk.
+ cur_chunk.as_mut().allocated_bytes = cur_chunk.as_ref().layout.size();
+
+ debug_assert!(
+ self.current_chunk_footer
+ .get()
+ .as_ref()
+ .prev
+ .get()
+ .as_ref()
+ .is_empty(),
+ "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, 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](#initializer-functions-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](#initializer-functions-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, 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](#initializer-functions-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](#fallible-initialization-the-_try_with-method-suffix).
+ ///
+ /// [`Result`]: https://doc.rust-lang.org/std/result/enum.Result.html
+ /// [`Ok`]: https://doc.rust-lang.org/std/result/enum.Result.html#variant.Ok
+ /// [`Err`]: https://doc.rust-lang.org/std/result/enum.Result.html#variant.Err
+ ///
+ /// ## 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));
+ 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(inner_result_ptr.cast()) {
+ let current_footer_p = self.current_chunk_footer.get();
+ let current_ptr = &current_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](#initializer-functions-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](#fallible-initialization-the-_try_with-method-suffix).
+ ///
+ /// [`Result`]: https://doc.rust-lang.org/std/result/enum.Result.html
+ /// [`Ok`]: https://doc.rust-lang.org/std/result/enum.Result.html#variant.Ok
+ /// [`Err`]: https://doc.rust-lang.org/std/result/enum.Result.html#variant.Err
+ ///
+ /// ## 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)?);
+ 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(inner_result_ptr.cast()) {
+ let current_footer_p = self.current_chunk_footer.get();
+ let current_ptr = &current_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`](#method.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 = [
+ /// 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()`].
+ ///
+ /// [`T::default()`]: https://doc.rust-lang.org/std/default/trait.Default.html#tymethod.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>, AllocErr> {
+ if let Some(p) = self.try_alloc_layout_fast(layout) {
+ Ok(p)
+ } else {
+ self.alloc_layout_slow(layout).ok_or(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();
+ let start = footer.data.as_ptr();
+ debug_assert!(start <= ptr);
+ debug_assert!(ptr as *const u8 <= footer as *const _ as *const u8);
+
+ if (ptr as usize) < layout.size() {
+ return None;
+ }
+
+ let ptr = ptr.wrapping_sub(layout.size());
+ let rem = ptr as usize % layout.align();
+ let aligned_ptr = ptr.wrapping_sub(rem);
+
+ 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();
+ let allocation_limit_remaining = self.allocation_limit_remaining();
+
+ // 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 chunk_memory_details = iter::from_fn(|| {
+ let bypass_min_chunk_size_for_small_limits = match self.allocation_limit() {
+ Some(limit)
+ if layout.size() < limit
+ && base_size >= layout.size()
+ && limit < DEFAULT_CHUNK_SIZE_WITHOUT_FOOTER
+ && self.allocated_bytes() == 0 =>
+ {
+ true
+ }
+ _ => false,
+ };
+
+ if base_size >= min_new_chunk_size || bypass_min_chunk_size_for_small_limits {
+ let size = base_size;
+ base_size = base_size / 2;
+ Bump::new_chunk_memory_details(Some(size), layout)
+ } else {
+ None
+ }
+ });
+
+ let new_footer = chunk_memory_details
+ .filter_map(|chunk_memory_details| {
+ if Bump::chunk_fits_under_limit(
+ allocation_limit_remaining,
+ chunk_memory_details,
+ ) {
+ Bump::new_chunk(chunk_memory_details, layout, current_footer)
+ } else {
+ None
+ }
+ })
+ .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 mut ptr = new_footer.ptr.get().as_ptr().sub(size);
+ // Round the pointer down to the requested alignment.
+ ptr = ptr.sub(ptr as usize % layout.align());
+ debug_assert!(
+ ptr as *const _ <= new_footer,
+ "{:p} <= {:p}",
+ ptr,
+ new_footer
+ );
+ 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[0].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: 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 footer = self.current_chunk_footer.get();
+
+ unsafe { footer.as_ref().allocated_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>,
+ old_layout: Layout,
+ new_layout: Layout,
+ ) -> Result<NonNull<u8>, AllocErr> {
+ let old_size = old_layout.size();
+ let new_size = new_layout.size();
+ let align_is_compatible = old_layout.align() >= new_layout.align();
+
+ if !align_is_compatible {
+ return Err(AllocErr);
+ }
+
+ // This is how much space we would *actually* reclaim while satisfying
+ // the requested alignment.
+ let delta = round_down_to(old_size - new_size, new_layout.align());
+
+ 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.
+ && delta >= old_size / 2
+ {
+ let footer = self.current_chunk_footer.get();
+ let footer = footer.as_ref();
+
+ // NB: new_ptr is aligned, because ptr *has to* be aligned, and we
+ // made sure delta is aligned.
+ let new_ptr = NonNull::new_unchecked(footer.ptr.get().as_ptr().add(delta));
+ footer.ptr.set(new_ptr);
+
+ // 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>,
+ old_layout: Layout,
+ new_layout: Layout,
+ ) -> Result<NonNull<u8>, AllocErr> {
+ let old_size = old_layout.size();
+ let new_size = new_layout.size();
+ let align_is_compatible = old_layout.align() >= new_layout.align();
+
+ if align_is_compatible && 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, old_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_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 are 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: 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.as_ref();
+ if foot.is_empty() {
+ return None;
+ }
+ 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>, 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>, AllocErr> {
+ let old_size = layout.size();
+
+ if old_size == 0 {
+ return self.try_alloc_layout(layout);
+ }
+
+ let new_layout = layout_from_size_align(new_size, layout.align());
+ if new_size <= old_size {
+ self.shrink(ptr, layout, new_layout)
+ } else {
+ self.grow(ptr, layout, new_layout)
+ }
+ }
+}
+
+#[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> {
+ Bump::shrink(self, ptr, old_layout, new_layout)
+ .map(|p| NonNull::slice_from_raw_parts(p, new_layout.size()))
+ .map_err(|_| AllocError)
+ }
+
+ unsafe fn grow(
+ &self,
+ ptr: NonNull<u8>,
+ old_layout: Layout,
+ new_layout: Layout,
+ ) -> Result<NonNull<[u8]>, AllocError> {
+ Bump::grow(self, ptr, old_layout, new_layout)
+ .map(|p| NonNull::slice_from_raw_parts(p, new_layout.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)
+ }
+}
+
+// NB: Only tests which require private types, fields, or methods should be in
+// here. Anything that can just be tested via public API surface should be in
+// `bumpalo/tests/all/*`.
+#[cfg(test)]
+mod tests {
+ use super::*;
+
+ // Uses private type `ChunkFooter`.
+ #[test]
+ fn chunk_footer_is_five_words() {
+ assert_eq!(mem::size_of::<ChunkFooter>(), mem::size_of::<usize>() * 6);
+ }
+
+ // Uses private `alloc` module.
+ #[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();
+ }
+ }
+
+ // Uses our private `alloc` module.
+ #[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();
+ }
+ }
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-08 10:45:17 +0000