| #![unstable(feature = "raw_vec_internals", reason = "implementation detail", issue = "none")] |
| #![doc(hidden)] |
| |
| use core::alloc::MemoryBlock; |
| use core::cmp; |
| use core::mem::{self, ManuallyDrop, MaybeUninit}; |
| use core::ops::Drop; |
| use core::ptr::{NonNull, Unique}; |
| use core::slice; |
| |
| use crate::alloc::{ |
| handle_alloc_error, AllocErr, |
| AllocInit::{self, *}, |
| AllocRef, Global, Layout, |
| ReallocPlacement::{self, *}, |
| }; |
| use crate::boxed::Box; |
| use crate::collections::TryReserveError::{self, *}; |
| |
| #[cfg(test)] |
| mod tests; |
| |
| /// A low-level utility for more ergonomically allocating, reallocating, and deallocating |
| /// a buffer of memory on the heap without having to worry about all the corner cases |
| /// involved. This type is excellent for building your own data structures like Vec and VecDeque. |
| /// In particular: |
| /// |
| /// * Produces `Unique::empty()` on zero-sized types. |
| /// * Produces `Unique::empty()` on zero-length allocations. |
| /// * Avoids freeing `Unique::empty()`. |
| /// * Catches all overflows in capacity computations (promotes them to "capacity overflow" panics). |
| /// * Guards against 32-bit systems allocating more than isize::MAX bytes. |
| /// * Guards against overflowing your length. |
| /// * Calls `handle_alloc_error` for fallible allocations. |
| /// * Contains a `ptr::Unique` and thus endows the user with all related benefits. |
| /// * Uses the excess returned from the allocator to use the largest available capacity. |
| /// |
| /// This type does not in anyway inspect the memory that it manages. When dropped it *will* |
| /// free its memory, but it *won't* try to drop its contents. It is up to the user of `RawVec` |
| /// to handle the actual things *stored* inside of a `RawVec`. |
| /// |
| /// Note that the excess of a zero-sized types is always infinite, so `capacity()` always returns |
| /// `usize::MAX`. This means that you need to be careful when round-tripping this type with a |
| /// `Box<[T]>`, since `capacity()` won't yield the length. |
| #[allow(missing_debug_implementations)] |
| pub struct RawVec<T, A: AllocRef = Global> { |
| ptr: Unique<T>, |
| cap: usize, |
| alloc: A, |
| } |
| |
| impl<T> RawVec<T, Global> { |
| /// HACK(Centril): This exists because `#[unstable]` `const fn`s needn't conform |
| /// to `min_const_fn` and so they cannot be called in `min_const_fn`s either. |
| /// |
| /// If you change `RawVec<T>::new` or dependencies, please take care to not |
| /// introduce anything that would truly violate `min_const_fn`. |
| /// |
| /// NOTE: We could avoid this hack and check conformance with some |
| /// `#[rustc_force_min_const_fn]` attribute which requires conformance |
| /// with `min_const_fn` but does not necessarily allow calling it in |
| /// `stable(...) const fn` / user code not enabling `foo` when |
| /// `#[rustc_const_unstable(feature = "foo", ..)]` is present. |
| pub const NEW: Self = Self::new(); |
| |
| /// Creates the biggest possible `RawVec` (on the system heap) |
| /// without allocating. If `T` has positive size, then this makes a |
| /// `RawVec` with capacity `0`. If `T` is zero-sized, then it makes a |
| /// `RawVec` with capacity `usize::MAX`. Useful for implementing |
| /// delayed allocation. |
| pub const fn new() -> Self { |
| Self::new_in(Global) |
| } |
| |
| /// Creates a `RawVec` (on the system heap) with exactly the |
| /// capacity and alignment requirements for a `[T; capacity]`. This is |
| /// equivalent to calling `RawVec::new` when `capacity` is `0` or `T` is |
| /// zero-sized. Note that if `T` is zero-sized this means you will |
| /// *not* get a `RawVec` with the requested capacity. |
| /// |
| /// # Panics |
| /// |
| /// * Panics if the requested capacity exceeds `usize::MAX` bytes. |
| /// * Panics on 32-bit platforms if the requested capacity exceeds |
| /// `isize::MAX` bytes. |
| /// |
| /// # Aborts |
| /// |
| /// Aborts on OOM. |
| #[inline] |
| pub fn with_capacity(capacity: usize) -> Self { |
| Self::with_capacity_in(capacity, Global) |
| } |
| |
| /// Like `with_capacity`, but guarantees the buffer is zeroed. |
| #[inline] |
| pub fn with_capacity_zeroed(capacity: usize) -> Self { |
| Self::with_capacity_zeroed_in(capacity, Global) |
| } |
| |
| /// Reconstitutes a `RawVec` from a pointer and capacity. |
| /// |
| /// # Safety |
| /// |
| /// The `ptr` must be allocated (on the system heap), and with the given `capacity`. |
| /// The `capacity` cannot exceed `isize::MAX` for sized types. (only a concern on 32-bit |
| /// systems). ZST vectors may have a capacity up to `usize::MAX`. |
| /// If the `ptr` and `capacity` come from a `RawVec`, then this is guaranteed. |
| #[inline] |
| pub unsafe fn from_raw_parts(ptr: *mut T, capacity: usize) -> Self { |
| Self::from_raw_parts_in(ptr, capacity, Global) |
| } |
| |
| /// Converts a `Box<[T]>` into a `RawVec<T>`. |
| pub fn from_box(slice: Box<[T]>) -> Self { |
| unsafe { |
| let mut slice = ManuallyDrop::new(slice); |
| RawVec::from_raw_parts(slice.as_mut_ptr(), slice.len()) |
| } |
| } |
| } |
| |
| impl<T, A: AllocRef> RawVec<T, A> { |
| /// Like `new`, but parameterized over the choice of allocator for |
| /// the returned `RawVec`. |
| pub const fn new_in(alloc: A) -> Self { |
| // `cap: 0` means "unallocated". zero-sized types are ignored. |
| Self { ptr: Unique::empty(), cap: 0, alloc } |
| } |
| |
| /// Like `with_capacity`, but parameterized over the choice of |
| /// allocator for the returned `RawVec`. |
| #[inline] |
| pub fn with_capacity_in(capacity: usize, alloc: A) -> Self { |
| Self::allocate_in(capacity, Uninitialized, alloc) |
| } |
| |
| /// Like `with_capacity_zeroed`, but parameterized over the choice |
| /// of allocator for the returned `RawVec`. |
| #[inline] |
| pub fn with_capacity_zeroed_in(capacity: usize, alloc: A) -> Self { |
| Self::allocate_in(capacity, Zeroed, alloc) |
| } |
| |
| fn allocate_in(capacity: usize, init: AllocInit, mut alloc: A) -> Self { |
| if mem::size_of::<T>() == 0 { |
| Self::new_in(alloc) |
| } else { |
| let layout = Layout::array::<T>(capacity).unwrap_or_else(|_| capacity_overflow()); |
| alloc_guard(layout.size()).unwrap_or_else(|_| capacity_overflow()); |
| |
| let memory = alloc.alloc(layout, init).unwrap_or_else(|_| handle_alloc_error(layout)); |
| Self { |
| ptr: memory.ptr.cast().into(), |
| cap: Self::capacity_from_bytes(memory.size), |
| alloc, |
| } |
| } |
| } |
| |
| /// Reconstitutes a `RawVec` from a pointer, capacity, and allocator. |
| /// |
| /// # Safety |
| /// |
| /// The `ptr` must be allocated (via the given allocator `a`), and with the given `capacity`. |
| /// The `capacity` cannot exceed `isize::MAX` for sized types. (only a concern on 32-bit |
| /// systems). ZST vectors may have a capacity up to `usize::MAX`. |
| /// If the `ptr` and `capacity` come from a `RawVec` created via `a`, then this is guaranteed. |
| #[inline] |
| pub unsafe fn from_raw_parts_in(ptr: *mut T, capacity: usize, a: A) -> Self { |
| Self { ptr: Unique::new_unchecked(ptr), cap: capacity, alloc: a } |
| } |
| |
| /// Gets a raw pointer to the start of the allocation. Note that this is |
| /// `Unique::empty()` if `capacity == 0` or `T` is zero-sized. In the former case, you must |
| /// be careful. |
| pub fn ptr(&self) -> *mut T { |
| self.ptr.as_ptr() |
| } |
| |
| /// Gets the capacity of the allocation. |
| /// |
| /// This will always be `usize::MAX` if `T` is zero-sized. |
| #[inline(always)] |
| pub fn capacity(&self) -> usize { |
| if mem::size_of::<T>() == 0 { usize::MAX } else { self.cap } |
| } |
| |
| /// Returns a shared reference to the allocator backing this `RawVec`. |
| pub fn alloc(&self) -> &A { |
| &self.alloc |
| } |
| |
| /// Returns a mutable reference to the allocator backing this `RawVec`. |
| pub fn alloc_mut(&mut self) -> &mut A { |
| &mut self.alloc |
| } |
| |
| fn current_memory(&self) -> Option<(NonNull<u8>, Layout)> { |
| if mem::size_of::<T>() == 0 || self.cap == 0 { |
| None |
| } else { |
| // We have an allocated chunk of memory, so we can bypass runtime |
| // checks to get our current layout. |
| unsafe { |
| let align = mem::align_of::<T>(); |
| let size = mem::size_of::<T>() * self.cap; |
| let layout = Layout::from_size_align_unchecked(size, align); |
| Some((self.ptr.cast().into(), layout)) |
| } |
| } |
| } |
| |
| /// Doubles the size of the type's backing allocation. This is common enough |
| /// to want to do that it's easiest to just have a dedicated method. Slightly |
| /// more efficient logic can be provided for this than the general case. |
| /// |
| /// This function is ideal for when pushing elements one-at-a-time because |
| /// you don't need to incur the costs of the more general computations |
| /// reserve needs to do to guard against overflow. You do however need to |
| /// manually check if your `len == capacity`. |
| /// |
| /// # Panics |
| /// |
| /// * Panics if `T` is zero-sized on the assumption that you managed to exhaust |
| /// all `usize::MAX` slots in your imaginary buffer. |
| /// * Panics on 32-bit platforms if the requested capacity exceeds |
| /// `isize::MAX` bytes. |
| /// |
| /// # Aborts |
| /// |
| /// Aborts on OOM |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// # #![feature(raw_vec_internals)] |
| /// # extern crate alloc; |
| /// # use std::ptr; |
| /// # use alloc::raw_vec::RawVec; |
| /// struct MyVec<T> { |
| /// buf: RawVec<T>, |
| /// len: usize, |
| /// } |
| /// |
| /// impl<T> MyVec<T> { |
| /// pub fn push(&mut self, elem: T) { |
| /// if self.len == self.buf.capacity() { self.buf.double(); } |
| /// // double would have aborted or panicked if the len exceeded |
| /// // `isize::MAX` so this is safe to do unchecked now. |
| /// unsafe { |
| /// ptr::write(self.buf.ptr().add(self.len), elem); |
| /// } |
| /// self.len += 1; |
| /// } |
| /// } |
| /// # fn main() { |
| /// # let mut vec = MyVec { buf: RawVec::new(), len: 0 }; |
| /// # vec.push(1); |
| /// # } |
| /// ``` |
| #[inline(never)] |
| #[cold] |
| pub fn double(&mut self) { |
| match self.grow(Double, MayMove, Uninitialized) { |
| Err(CapacityOverflow) => capacity_overflow(), |
| Err(AllocError { layout, .. }) => handle_alloc_error(layout), |
| Ok(()) => { /* yay */ } |
| } |
| } |
| |
| /// Attempts to double the size of the type's backing allocation in place. This is common |
| /// enough to want to do that it's easiest to just have a dedicated method. Slightly |
| /// more efficient logic can be provided for this than the general case. |
| /// |
| /// Returns `true` if the reallocation attempt has succeeded. |
| /// |
| /// # Panics |
| /// |
| /// * Panics if `T` is zero-sized on the assumption that you managed to exhaust |
| /// all `usize::MAX` slots in your imaginary buffer. |
| /// * Panics on 32-bit platforms if the requested capacity exceeds |
| /// `isize::MAX` bytes. |
| #[inline(never)] |
| #[cold] |
| pub fn double_in_place(&mut self) -> bool { |
| self.grow(Double, InPlace, Uninitialized).is_ok() |
| } |
| |
| /// Ensures that the buffer contains at least enough space to hold |
| /// `used_capacity + needed_extra_capacity` elements. If it doesn't already have |
| /// enough capacity, will reallocate enough space plus comfortable slack |
| /// space to get amortized `O(1)` behavior. Will limit this behavior |
| /// if it would needlessly cause itself to panic. |
| /// |
| /// If `used_capacity` exceeds `self.capacity()`, this may fail to actually allocate |
| /// the requested space. This is not really unsafe, but the unsafe |
| /// code *you* write that relies on the behavior of this function may break. |
| /// |
| /// This is ideal for implementing a bulk-push operation like `extend`. |
| /// |
| /// # Panics |
| /// |
| /// * Panics if the requested capacity exceeds `usize::MAX` bytes. |
| /// * Panics on 32-bit platforms if the requested capacity exceeds |
| /// `isize::MAX` bytes. |
| /// |
| /// # Aborts |
| /// |
| /// Aborts on OOM. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// # #![feature(raw_vec_internals)] |
| /// # extern crate alloc; |
| /// # use std::ptr; |
| /// # use alloc::raw_vec::RawVec; |
| /// struct MyVec<T> { |
| /// buf: RawVec<T>, |
| /// len: usize, |
| /// } |
| /// |
| /// impl<T: Clone> MyVec<T> { |
| /// pub fn push_all(&mut self, elems: &[T]) { |
| /// self.buf.reserve(self.len, elems.len()); |
| /// // reserve would have aborted or panicked if the len exceeded |
| /// // `isize::MAX` so this is safe to do unchecked now. |
| /// for x in elems { |
| /// unsafe { |
| /// ptr::write(self.buf.ptr().add(self.len), x.clone()); |
| /// } |
| /// self.len += 1; |
| /// } |
| /// } |
| /// } |
| /// # fn main() { |
| /// # let mut vector = MyVec { buf: RawVec::new(), len: 0 }; |
| /// # vector.push_all(&[1, 3, 5, 7, 9]); |
| /// # } |
| /// ``` |
| pub fn reserve(&mut self, used_capacity: usize, needed_extra_capacity: usize) { |
| match self.try_reserve(used_capacity, needed_extra_capacity) { |
| Err(CapacityOverflow) => capacity_overflow(), |
| Err(AllocError { layout, .. }) => handle_alloc_error(layout), |
| Ok(()) => { /* yay */ } |
| } |
| } |
| |
| /// The same as `reserve`, but returns on errors instead of panicking or aborting. |
| pub fn try_reserve( |
| &mut self, |
| used_capacity: usize, |
| needed_extra_capacity: usize, |
| ) -> Result<(), TryReserveError> { |
| if self.needs_to_grow(used_capacity, needed_extra_capacity) { |
| self.grow(Amortized { used_capacity, needed_extra_capacity }, MayMove, Uninitialized) |
| } else { |
| Ok(()) |
| } |
| } |
| |
| /// Attempts to ensure that the buffer contains at least enough space to hold |
| /// `used_capacity + needed_extra_capacity` elements. If it doesn't already have |
| /// enough capacity, will reallocate in place enough space plus comfortable slack |
| /// space to get amortized `O(1)` behavior. Will limit this behaviour |
| /// if it would needlessly cause itself to panic. |
| /// |
| /// If `used_capacity` exceeds `self.capacity()`, this may fail to actually allocate |
| /// the requested space. This is not really unsafe, but the unsafe |
| /// code *you* write that relies on the behavior of this function may break. |
| /// |
| /// Returns `true` if the reallocation attempt has succeeded. |
| /// |
| /// # Panics |
| /// |
| /// * Panics if the requested capacity exceeds `usize::MAX` bytes. |
| /// * Panics on 32-bit platforms if the requested capacity exceeds |
| /// `isize::MAX` bytes. |
| pub fn reserve_in_place(&mut self, used_capacity: usize, needed_extra_capacity: usize) -> bool { |
| // This is more readable than putting this in one line: |
| // `!self.needs_to_grow(...) || self.grow(...).is_ok()` |
| if self.needs_to_grow(used_capacity, needed_extra_capacity) { |
| self.grow(Amortized { used_capacity, needed_extra_capacity }, InPlace, Uninitialized) |
| .is_ok() |
| } else { |
| true |
| } |
| } |
| |
| /// Ensures that the buffer contains at least enough space to hold |
| /// `used_capacity + needed_extra_capacity` elements. If it doesn't already, |
| /// will reallocate the minimum possible amount of memory necessary. |
| /// Generally this will be exactly the amount of memory necessary, |
| /// but in principle the allocator is free to give back more than |
| /// we asked for. |
| /// |
| /// If `used_capacity` exceeds `self.capacity()`, this may fail to actually allocate |
| /// the requested space. This is not really unsafe, but the unsafe |
| /// code *you* write that relies on the behavior of this function may break. |
| /// |
| /// # Panics |
| /// |
| /// * Panics if the requested capacity exceeds `usize::MAX` bytes. |
| /// * Panics on 32-bit platforms if the requested capacity exceeds |
| /// `isize::MAX` bytes. |
| /// |
| /// # Aborts |
| /// |
| /// Aborts on OOM. |
| pub fn reserve_exact(&mut self, used_capacity: usize, needed_extra_capacity: usize) { |
| match self.try_reserve_exact(used_capacity, needed_extra_capacity) { |
| Err(CapacityOverflow) => capacity_overflow(), |
| Err(AllocError { layout, .. }) => handle_alloc_error(layout), |
| Ok(()) => { /* yay */ } |
| } |
| } |
| |
| /// The same as `reserve_exact`, but returns on errors instead of panicking or aborting. |
| pub fn try_reserve_exact( |
| &mut self, |
| used_capacity: usize, |
| needed_extra_capacity: usize, |
| ) -> Result<(), TryReserveError> { |
| if self.needs_to_grow(used_capacity, needed_extra_capacity) { |
| self.grow(Exact { used_capacity, needed_extra_capacity }, MayMove, Uninitialized) |
| } else { |
| Ok(()) |
| } |
| } |
| |
| /// Shrinks the allocation down to the specified amount. If the given amount |
| /// is 0, actually completely deallocates. |
| /// |
| /// # Panics |
| /// |
| /// Panics if the given amount is *larger* than the current capacity. |
| /// |
| /// # Aborts |
| /// |
| /// Aborts on OOM. |
| pub fn shrink_to_fit(&mut self, amount: usize) { |
| match self.shrink(amount, MayMove) { |
| Err(CapacityOverflow) => capacity_overflow(), |
| Err(AllocError { layout, .. }) => handle_alloc_error(layout), |
| Ok(()) => { /* yay */ } |
| } |
| } |
| } |
| |
| #[derive(Copy, Clone)] |
| enum Strategy { |
| Double, |
| Amortized { used_capacity: usize, needed_extra_capacity: usize }, |
| Exact { used_capacity: usize, needed_extra_capacity: usize }, |
| } |
| use Strategy::*; |
| |
| impl<T, A: AllocRef> RawVec<T, A> { |
| /// Returns if the buffer needs to grow to fulfill the needed extra capacity. |
| /// Mainly used to make inlining reserve-calls possible without inlining `grow`. |
| fn needs_to_grow(&self, used_capacity: usize, needed_extra_capacity: usize) -> bool { |
| needed_extra_capacity > self.capacity().wrapping_sub(used_capacity) |
| } |
| |
| fn capacity_from_bytes(excess: usize) -> usize { |
| debug_assert_ne!(mem::size_of::<T>(), 0); |
| excess / mem::size_of::<T>() |
| } |
| |
| fn set_memory(&mut self, memory: MemoryBlock) { |
| self.ptr = memory.ptr.cast().into(); |
| self.cap = Self::capacity_from_bytes(memory.size); |
| } |
| |
| /// Single method to handle all possibilities of growing the buffer. |
| fn grow( |
| &mut self, |
| strategy: Strategy, |
| placement: ReallocPlacement, |
| init: AllocInit, |
| ) -> Result<(), TryReserveError> { |
| let elem_size = mem::size_of::<T>(); |
| if elem_size == 0 { |
| // Since we return a capacity of `usize::MAX` when `elem_size` is |
| // 0, getting to here necessarily means the `RawVec` is overfull. |
| return Err(CapacityOverflow); |
| } |
| let new_layout = match strategy { |
| Double => unsafe { |
| // Since we guarantee that we never allocate more than `isize::MAX` bytes, |
| // `elem_size * self.cap <= isize::MAX` as a precondition, so this can't overflow. |
| // Additionally the alignment will never be too large as to "not be satisfiable", |
| // so `Layout::from_size_align` will always return `Some`. |
| // |
| // TL;DR, we bypass runtime checks due to dynamic assertions in this module, |
| // allowing us to use `from_size_align_unchecked`. |
| let cap = if self.cap == 0 { |
| // Skip to 4 because tiny `Vec`'s are dumb; but not if that would cause overflow. |
| if elem_size > usize::MAX / 8 { 1 } else { 4 } |
| } else { |
| self.cap * 2 |
| }; |
| Layout::from_size_align_unchecked(cap * elem_size, mem::align_of::<T>()) |
| }, |
| Amortized { used_capacity, needed_extra_capacity } => { |
| // Nothing we can really do about these checks, sadly. |
| let required_cap = |
| used_capacity.checked_add(needed_extra_capacity).ok_or(CapacityOverflow)?; |
| // Cannot overflow, because `cap <= isize::MAX`, and type of `cap` is `usize`. |
| let double_cap = self.cap * 2; |
| // `double_cap` guarantees exponential growth. |
| let cap = cmp::max(double_cap, required_cap); |
| Layout::array::<T>(cap).map_err(|_| CapacityOverflow)? |
| } |
| Exact { used_capacity, needed_extra_capacity } => { |
| let cap = |
| used_capacity.checked_add(needed_extra_capacity).ok_or(CapacityOverflow)?; |
| Layout::array::<T>(cap).map_err(|_| CapacityOverflow)? |
| } |
| }; |
| alloc_guard(new_layout.size())?; |
| |
| let memory = if let Some((ptr, old_layout)) = self.current_memory() { |
| debug_assert_eq!(old_layout.align(), new_layout.align()); |
| unsafe { |
| self.alloc |
| .grow(ptr, old_layout, new_layout.size(), placement, init) |
| .map_err(|_| AllocError { layout: new_layout, non_exhaustive: () })? |
| } |
| } else { |
| match placement { |
| MayMove => self.alloc.alloc(new_layout, init), |
| InPlace => Err(AllocErr), |
| } |
| .map_err(|_| AllocError { layout: new_layout, non_exhaustive: () })? |
| }; |
| self.set_memory(memory); |
| Ok(()) |
| } |
| |
| fn shrink( |
| &mut self, |
| amount: usize, |
| placement: ReallocPlacement, |
| ) -> Result<(), TryReserveError> { |
| assert!(amount <= self.capacity(), "Tried to shrink to a larger capacity"); |
| |
| let (ptr, layout) = if let Some(mem) = self.current_memory() { mem } else { return Ok(()) }; |
| let new_size = amount * mem::size_of::<T>(); |
| |
| let memory = unsafe { |
| self.alloc.shrink(ptr, layout, new_size, placement).map_err(|_| { |
| TryReserveError::AllocError { |
| layout: Layout::from_size_align_unchecked(new_size, layout.align()), |
| non_exhaustive: (), |
| } |
| })? |
| }; |
| self.set_memory(memory); |
| Ok(()) |
| } |
| } |
| |
| impl<T> RawVec<T, Global> { |
| /// Converts the entire buffer into `Box<[MaybeUninit<T>]>` with the specified `len`. |
| /// |
| /// Note that this will correctly reconstitute any `cap` changes |
| /// that may have been performed. (See description of type for details.) |
| /// |
| /// # Safety |
| /// |
| /// * `len` must be greater than or equal to the most recently requested capacity, and |
| /// * `len` must be less than or equal to `self.capacity()`. |
| /// |
| /// Note, that the requested capacity and `self.capacity()` could differ, as |
| /// an allocator could overallocate and return a greater memory block than requested. |
| pub unsafe fn into_box(self, len: usize) -> Box<[MaybeUninit<T>]> { |
| // Sanity-check one half of the safety requirement (we cannot check the other half). |
| debug_assert!( |
| len <= self.capacity(), |
| "`len` must be smaller than or equal to `self.capacity()`" |
| ); |
| |
| let me = ManuallyDrop::new(self); |
| let slice = slice::from_raw_parts_mut(me.ptr() as *mut MaybeUninit<T>, len); |
| Box::from_raw(slice) |
| } |
| } |
| |
| unsafe impl<#[may_dangle] T, A: AllocRef> Drop for RawVec<T, A> { |
| /// Frees the memory owned by the `RawVec` *without* trying to drop its contents. |
| fn drop(&mut self) { |
| if let Some((ptr, layout)) = self.current_memory() { |
| unsafe { self.alloc.dealloc(ptr, layout) } |
| } |
| } |
| } |
| |
| // We need to guarantee the following: |
| // * We don't ever allocate `> isize::MAX` byte-size objects. |
| // * We don't overflow `usize::MAX` and actually allocate too little. |
| // |
| // On 64-bit we just need to check for overflow since trying to allocate |
| // `> isize::MAX` bytes will surely fail. On 32-bit and 16-bit we need to add |
| // an extra guard for this in case we're running on a platform which can use |
| // all 4GB in user-space, e.g., PAE or x32. |
| |
| #[inline] |
| fn alloc_guard(alloc_size: usize) -> Result<(), TryReserveError> { |
| if mem::size_of::<usize>() < 8 && alloc_size > core::isize::MAX as usize { |
| Err(CapacityOverflow) |
| } else { |
| Ok(()) |
| } |
| } |
| |
| // One central function responsible for reporting capacity overflows. This'll |
| // ensure that the code generation related to these panics is minimal as there's |
| // only one location which panics rather than a bunch throughout the module. |
| fn capacity_overflow() -> ! { |
| panic!("capacity overflow"); |
| } |