// SPDX-License-Identifier: Apache-2.0 OR MIT #![unstable(feature = "raw_vec_internals", reason = "unstable const warnings", issue = "none")] use core::alloc::LayoutError;use core::cmp;use core::intrinsics;use core::mem::{self, ManuallyDrop, MaybeUninit};use core::ops::Drop;use core::ptr::{self, NonNull, Unique};use core::slice; #[cfg(not(no_global_oom_handling))]use crate::alloc::handle_alloc_error;use crate::alloc::{Allocator, Global, Layout};use crate::boxed::Box;use crate::collections::TryReserveError;use crate::collections::TryReserveErrorKind::*; #[cfg(test)]mod tests; #[cfg(not(no_global_oom_handling))]enum AllocInit { /// The contents of the new memory are uninitialized. Uninitialized, /// The new memory is guaranteed to be zeroed. Zeroed,} /// 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::dangling()` on zero-sized types./// * Produces `Unique::dangling()` on zero-length allocations./// * Avoids freeing `Unique::dangling()`./// * 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(crate) struct RawVec<T, A: Allocator = Global> { ptr: Unique<T>, cap: usize, alloc: A,} impl<T> RawVec<T, Global> { /// HACK(Centril): This exists because stable `const fn` can only call stable `const fn`, so /// they cannot call `Self::new()`. /// /// If you change `RawVec<T>::new` or dependencies, please take care to not introduce anything /// that would truly const-call something unstable. 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. #[must_use] 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 `isize::MAX` bytes. /// /// # Aborts /// /// Aborts on OOM. #[cfg(not(any(no_global_oom_handling, test)))] #[must_use] #[inline] pub fn with_capacity(capacity: usize) -> Self { Self::with_capacity_in(capacity, Global) } /// Like `with_capacity`, but guarantees the buffer is zeroed. #[cfg(not(any(no_global_oom_handling, test)))] #[must_use] #[inline] pub fn with_capacity_zeroed(capacity: usize) -> Self { Self::with_capacity_zeroed_in(capacity, Global) }} impl<T, A: Allocator> RawVec<T, A> { // Tiny Vecs are dumb. Skip to: // - 8 if the element size is 1, because any heap allocators is likely // to round up a request of less than 8 bytes to at least 8 bytes. // - 4 if elements are moderate-sized (<= 1 KiB). // - 1 otherwise, to avoid wasting too much space for very short Vecs. pub(crate) const MIN_NON_ZERO_CAP: usize = if mem::size_of::<T>() == 1 { 8 } else if mem::size_of::<T>() <= 1024 { 4 } else { 1 }; /// 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::dangling(), cap: 0, alloc } } /// Like `with_capacity`, but parameterized over the choice of /// allocator for the returned `RawVec`. #[cfg(not(no_global_oom_handling))] #[inline] pub fn with_capacity_in(capacity: usize, alloc: A) -> Self { Self::allocate_in(capacity, AllocInit::Uninitialized, alloc) } /// Like `with_capacity_zeroed`, but parameterized over the choice /// of allocator for the returned `RawVec`. #[cfg(not(no_global_oom_handling))] #[inline] pub fn with_capacity_zeroed_in(capacity: usize, alloc: A) -> Self { Self::allocate_in(capacity, AllocInit::Zeroed, alloc) } /// 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>], A> { // 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); unsafe { let slice = slice::from_raw_parts_mut(me.ptr() as *mut MaybeUninit<T>, len); Box::from_raw_in(slice, ptr::read(&me.alloc)) } } #[cfg(not(no_global_oom_handling))] fn allocate_in(capacity: usize, init: AllocInit, alloc: A) -> Self { // Don't allocate here because `Drop` will not deallocate when `capacity` is 0. if mem::size_of::<T>() == 0 || capacity == 0 { Self::new_in(alloc) } else { // We avoid `unwrap_or_else` here because it bloats the amount of // LLVM IR generated. let layout = match Layout::array::<T>(capacity) { Ok(layout) => layout, Err(_) => capacity_overflow(), }; match alloc_guard(layout.size()) { Ok(_) => {} Err(_) => capacity_overflow(), } let result = match init { AllocInit::Uninitialized => alloc.allocate(layout), AllocInit::Zeroed => alloc.allocate_zeroed(layout), }; let ptr = match result { Ok(ptr) => ptr, Err(_) => handle_alloc_error(layout), }; // Allocators currently return a `NonNull<[u8]>` whose length // matches the size requested. If that ever changes, the capacity // here should change to `ptr.len() / mem::size_of::<T>()`. Self { ptr: unsafe { Unique::new_unchecked(ptr.cast().as_ptr()) }, cap: capacity, alloc, } } } /// Reconstitutes a `RawVec` from a pointer, capacity, and allocator. /// /// # Safety /// /// The `ptr` must be allocated (via the given allocator `alloc`), 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 `alloc`, then this is /// guaranteed. #[inline] pub unsafe fn from_raw_parts_in(ptr: *mut T, capacity: usize, alloc: A) -> Self { Self { ptr: unsafe { Unique::new_unchecked(ptr) }, cap: capacity, alloc } } /// Gets a raw pointer to the start of the allocation. Note that this is /// `Unique::dangling()` if `capacity == 0` or `T` is zero-sized. In the former case, you must /// be careful. #[inline] 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 allocator(&self) -> &A { &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 layout = Layout::array::<T>(self.cap).unwrap_unchecked(); Some((self.ptr.cast().into(), layout)) } } } /// Ensures that the buffer contains at least enough space to hold `len + /// additional` 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 `len` 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 new capacity exceeds `isize::MAX` bytes. /// /// # Aborts /// /// Aborts on OOM. #[cfg(not(no_global_oom_handling))] #[inline] pub fn reserve(&mut self, len: usize, additional: usize) { // Callers expect this function to be very cheap when there is already sufficient capacity. // Therefore, we move all the resizing and error-handling logic from grow_amortized and // handle_reserve behind a call, while making sure that this function is likely to be // inlined as just a comparison and a call if the comparison fails. #[cold] fn do_reserve_and_handle<T, A: Allocator>( slf: &mut RawVec<T, A>, len: usize, additional: usize, ) { handle_reserve(slf.grow_amortized(len, additional)); } if self.needs_to_grow(len, additional) { do_reserve_and_handle(self, len, additional); } } /// A specialized version of `reserve()` used only by the hot and /// oft-instantiated `Vec::push()`, which does its own capacity check. #[cfg(not(no_global_oom_handling))] #[inline(never)] pub fn reserve_for_push(&mut self, len: usize) { handle_reserve(self.grow_amortized(len, 1)); } /// The same as `reserve`, but returns on errors instead of panicking or aborting. pub fn try_reserve(&mut self, len: usize, additional: usize) -> Result<(), TryReserveError> { if self.needs_to_grow(len, additional) { self.grow_amortized(len, additional) } else { Ok(()) } } /// The same as `reserve_for_push`, but returns on errors instead of panicking or aborting. #[inline(never)] pub fn try_reserve_for_push(&mut self, len: usize) -> Result<(), TryReserveError> { self.grow_amortized(len, 1) } /// Ensures that the buffer contains at least enough space to hold `len + /// additional` 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 `len` 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 new capacity exceeds `isize::MAX` bytes. /// /// # Aborts /// /// Aborts on OOM. #[cfg(not(no_global_oom_handling))] pub fn reserve_exact(&mut self, len: usize, additional: usize) { handle_reserve(self.try_reserve_exact(len, additional)); } /// The same as `reserve_exact`, but returns on errors instead of panicking or aborting. pub fn try_reserve_exact( &mut self, len: usize, additional: usize, ) -> Result<(), TryReserveError> { if self.needs_to_grow(len, additional) { self.grow_exact(len, additional) } else { Ok(()) } } /// Shrinks the buffer down to the specified capacity. 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. #[cfg(not(no_global_oom_handling))] pub fn shrink_to_fit(&mut self, cap: usize) { handle_reserve(self.shrink(cap)); }} impl<T, A: Allocator> 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, len: usize, additional: usize) -> bool { additional > self.capacity().wrapping_sub(len) } fn set_ptr_and_cap(&mut self, ptr: NonNull<[u8]>, cap: usize) { // Allocators currently return a `NonNull<[u8]>` whose length matches // the size requested. If that ever changes, the capacity here should // change to `ptr.len() / mem::size_of::<T>()`. self.ptr = unsafe { Unique::new_unchecked(ptr.cast().as_ptr()) }; self.cap = cap; } // This method is usually instantiated many times. So we want it to be as // small as possible, to improve compile times. But we also want as much of // its contents to be statically computable as possible, to make the // generated code run faster. Therefore, this method is carefully written // so that all of the code that depends on `T` is within it, while as much // of the code that doesn't depend on `T` as possible is in functions that // are non-generic over `T`. fn grow_amortized(&mut self, len: usize, additional: usize) -> Result<(), TryReserveError> { // This is ensured by the calling contexts. debug_assert!(additional > 0); if mem::size_of::<T>() == 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.into()); } // Nothing we can really do about these checks, sadly. let required_cap = len.checked_add(additional).ok_or(CapacityOverflow)?; // This guarantees exponential growth. The doubling cannot overflow // because `cap <= isize::MAX` and the type of `cap` is `usize`. let cap = cmp::max(self.cap * 2, required_cap); let cap = cmp::max(Self::MIN_NON_ZERO_CAP, cap); let new_layout = Layout::array::<T>(cap); // `finish_grow` is non-generic over `T`. let ptr = finish_grow(new_layout, self.current_memory(), &mut self.alloc)?; self.set_ptr_and_cap(ptr, cap); Ok(()) } // The constraints on this method are much the same as those on // `grow_amortized`, but this method is usually instantiated less often so // it's less critical. fn grow_exact(&mut self, len: usize, additional: usize) -> Result<(), TryReserveError> { if mem::size_of::<T>() == 0 { // Since we return a capacity of `usize::MAX` when the type size is // 0, getting to here necessarily means the `RawVec` is overfull. return Err(CapacityOverflow.into()); } let cap = len.checked_add(additional).ok_or(CapacityOverflow)?; let new_layout = Layout::array::<T>(cap); // `finish_grow` is non-generic over `T`. let ptr = finish_grow(new_layout, self.current_memory(), &mut self.alloc)?; self.set_ptr_and_cap(ptr, cap); Ok(()) } #[allow(dead_code)] fn shrink(&mut self, cap: usize) -> Result<(), TryReserveError> { assert!(cap <= self.capacity(), "Tried to shrink to a larger capacity"); let (ptr, layout) = if let Some(mem) = self.current_memory() { mem } else { return Ok(()) }; let ptr = unsafe { // `Layout::array` cannot overflow here because it would have // overflowed earlier when capacity was larger. let new_layout = Layout::array::<T>(cap).unwrap_unchecked(); self.alloc .shrink(ptr, layout, new_layout) .map_err(|_| AllocError { layout: new_layout, non_exhaustive: () })? }; self.set_ptr_and_cap(ptr, cap); Ok(()) }} // This function is outside `RawVec` to minimize compile times. See the comment// above `RawVec::grow_amortized` for details. (The `A` parameter isn't// significant, because the number of different `A` types seen in practice is// much smaller than the number of `T` types.)#[inline(never)]fn finish_grow<A>( new_layout: Result<Layout, LayoutError>, current_memory: Option<(NonNull<u8>, Layout)>, alloc: &mut A,) -> Result<NonNull<[u8]>, TryReserveError>where A: Allocator,{ // Check for the error here to minimize the size of `RawVec::grow_*`. let new_layout = new_layout.map_err(|_| CapacityOverflow)?; alloc_guard(new_layout.size())?; let memory = if let Some((ptr, old_layout)) = current_memory { debug_assert_eq!(old_layout.align(), new_layout.align()); unsafe { // The allocator checks for alignment equality intrinsics::assume(old_layout.align() == new_layout.align()); alloc.grow(ptr, old_layout, new_layout) } } else { alloc.allocate(new_layout) }; memory.map_err(|_| AllocError { layout: new_layout, non_exhaustive: () }.into())} unsafe impl<#[may_dangle] T, A: Allocator> 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.deallocate(ptr, layout) } } }} // Central function for reserve error handling.#[cfg(not(no_global_oom_handling))]#[inline]fn handle_reserve(result: Result<(), TryReserveError>) { match result.map_err(|e| e.kind()) { Err(CapacityOverflow) => capacity_overflow(), Err(AllocError { layout, .. }) => handle_alloc_error(layout), Ok(()) => { /* yay */ } }Lines 1–500 of 527. 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// SPDX-License-Identifier: Apache-2.0 OR MIT #![unstable(feature = "raw_vec_internals", reason = "unstable const warnings", issue = "none")] use core::alloc::LayoutError; use core::cmp; use core::intrinsics; use core::mem::{self, ManuallyDrop, MaybeUninit}; use core::ops::Drop; use core::ptr::{self, NonNull, Unique}; use core::slice; #[cfg(not(no_global_oom_handling))] use crate::alloc::handle_alloc_error; use crate::alloc::{Allocator, Global, Layout}; use crate::boxed::Box; use crate::collections::TryReserveError; use crate::collections::TryReserveErrorKind::*; #[cfg(test)] mod tests; #[cfg(not(no_global_oom_handling))] enum AllocInit { /// The contents of the new memory are uninitialized. Uninitialized, /// The new memory is guaranteed to be zeroed. Zeroed, } /// 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::dangling()` on zero-sized types. /// * Produces `Unique::dangling()` on zero-length allocations. /// * Avoids freeing `Unique::dangling()`. /// * 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(crate) struct RawVec<T, A: Allocator = Global> { ptr: Unique<T>, cap: usize, alloc: A, } impl<T> RawVec<T, Global> { /// HACK(Centril): This exists because stable `const fn` can only call stable `const fn`, so /// they cannot call `Self::new()`. /// /// If you change `RawVec<T>::new` or dependencies, please take care to not introduce anything /// that would truly const-call something unstable. 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. #[must_use] 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 `isize::MAX` bytes. /// /// # Aborts /// /// Aborts on OOM. #[cfg(not(any(no_global_oom_handling, test)))] #[must_use] #[inline] pub fn with_capacity(capacity: usize) -> Self { Self::with_capacity_in(capacity, Global) } /// Like `with_capacity`, but guarantees the buffer is zeroed. #[cfg(not(any(no_global_oom_handling, test)))] #[must_use] #[inline] pub fn with_capacity_zeroed(capacity: usize) -> Self { Self::with_capacity_zeroed_in(capacity, Global) } } impl<T, A: Allocator> RawVec<T, A> { // Tiny Vecs are dumb. Skip to: // - 8 if the element size is 1, because any heap allocators is likely // to round up a request of less than 8 bytes to at least 8 bytes. // - 4 if elements are moderate-sized (<= 1 KiB). // - 1 otherwise, to avoid wasting too much space for very short Vecs. pub(crate) const MIN_NON_ZERO_CAP: usize = if mem::size_of::<T>() == 1 { 8 } else if mem::size_of::<T>() <= 1024 { 4 } else { 1 }; /// 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::dangling(), cap: 0, alloc } } /// Like `with_capacity`, but parameterized over the choice of /// allocator for the returned `RawVec`. #[cfg(not(no_global_oom_handling))] #[inline] pub fn with_capacity_in(capacity: usize, alloc: A) -> Self { Self::allocate_in(capacity, AllocInit::Uninitialized, alloc) } /// Like `with_capacity_zeroed`, but parameterized over the choice /// of allocator for the returned `RawVec`. #[cfg(not(no_global_oom_handling))] #[inline] pub fn with_capacity_zeroed_in(capacity: usize, alloc: A) -> Self { Self::allocate_in(capacity, AllocInit::Zeroed, alloc) } /// 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>], A> { // 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); unsafe { let slice = slice::from_raw_parts_mut(me.ptr() as *mut MaybeUninit<T>, len); Box::from_raw_in(slice, ptr::read(&me.alloc)) } } #[cfg(not(no_global_oom_handling))] fn allocate_in(capacity: usize, init: AllocInit, alloc: A) -> Self { // Don't allocate here because `Drop` will not deallocate when `capacity` is 0. if mem::size_of::<T>() == 0 || capacity == 0 { Self::new_in(alloc) } else { // We avoid `unwrap_or_else` here because it bloats the amount of // LLVM IR generated. let layout = match Layout::array::<T>(capacity) { Ok(layout) => layout, Err(_) => capacity_overflow(), }; match alloc_guard(layout.size()) { Ok(_) => {} Err(_) => capacity_overflow(), } let result = match init { AllocInit::Uninitialized => alloc.allocate(layout), AllocInit::Zeroed => alloc.allocate_zeroed(layout), }; let ptr = match result { Ok(ptr) => ptr, Err(_) => handle_alloc_error(layout), }; // Allocators currently return a `NonNull<[u8]>` whose length // matches the size requested. If that ever changes, the capacity // here should change to `ptr.len() / mem::size_of::<T>()`. Self { ptr: unsafe { Unique::new_unchecked(ptr.cast().as_ptr()) }, cap: capacity, alloc, } } } /// Reconstitutes a `RawVec` from a pointer, capacity, and allocator. /// /// # Safety /// /// The `ptr` must be allocated (via the given allocator `alloc`), 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 `alloc`, then this is /// guaranteed. #[inline] pub unsafe fn from_raw_parts_in(ptr: *mut T, capacity: usize, alloc: A) -> Self { Self { ptr: unsafe { Unique::new_unchecked(ptr) }, cap: capacity, alloc } } /// Gets a raw pointer to the start of the allocation. Note that this is /// `Unique::dangling()` if `capacity == 0` or `T` is zero-sized. In the former case, you must /// be careful. #[inline] 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 allocator(&self) -> &A { &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 layout = Layout::array::<T>(self.cap).unwrap_unchecked(); Some((self.ptr.cast().into(), layout)) } } } /// Ensures that the buffer contains at least enough space to hold `len + /// additional` 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 `len` 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 new capacity exceeds `isize::MAX` bytes. /// /// # Aborts /// /// Aborts on OOM. #[cfg(not(no_global_oom_handling))] #[inline] pub fn reserve(&mut self, len: usize, additional: usize) { // Callers expect this function to be very cheap when there is already sufficient capacity. // Therefore, we move all the resizing and error-handling logic from grow_amortized and // handle_reserve behind a call, while making sure that this function is likely to be // inlined as just a comparison and a call if the comparison fails. #[cold] fn do_reserve_and_handle<T, A: Allocator>( slf: &mut RawVec<T, A>, len: usize, additional: usize, ) { handle_reserve(slf.grow_amortized(len, additional)); } if self.needs_to_grow(len, additional) { do_reserve_and_handle(self, len, additional); } } /// A specialized version of `reserve()` used only by the hot and /// oft-instantiated `Vec::push()`, which does its own capacity check. #[cfg(not(no_global_oom_handling))] #[inline(never)] pub fn reserve_for_push(&mut self, len: usize) { handle_reserve(self.grow_amortized(len, 1)); } /// The same as `reserve`, but returns on errors instead of panicking or aborting. pub fn try_reserve(&mut self, len: usize, additional: usize) -> Result<(), TryReserveError> { if self.needs_to_grow(len, additional) { self.grow_amortized(len, additional) } else { Ok(()) } } /// The same as `reserve_for_push`, but returns on errors instead of panicking or aborting. #[inline(never)] pub fn try_reserve_for_push(&mut self, len: usize) -> Result<(), TryReserveError> { self.grow_amortized(len, 1) } /// Ensures that the buffer contains at least enough space to hold `len + /// additional` 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 `len` 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 new capacity exceeds `isize::MAX` bytes. /// /// # Aborts /// /// Aborts on OOM. #[cfg(not(no_global_oom_handling))] pub fn reserve_exact(&mut self, len: usize, additional: usize) { handle_reserve(self.try_reserve_exact(len, additional)); } /// The same as `reserve_exact`, but returns on errors instead of panicking or aborting. pub fn try_reserve_exact( &mut self, len: usize, additional: usize, ) -> Result<(), TryReserveError> { if self.needs_to_grow(len, additional) { self.grow_exact(len, additional) } else { Ok(()) } } /// Shrinks the buffer down to the specified capacity. 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. #[cfg(not(no_global_oom_handling))] pub fn shrink_to_fit(&mut self, cap: usize) { handle_reserve(self.shrink(cap)); } } impl<T, A: Allocator> 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, len: usize, additional: usize) -> bool { additional > self.capacity().wrapping_sub(len) } fn set_ptr_and_cap(&mut self, ptr: NonNull<[u8]>, cap: usize) { // Allocators currently return a `NonNull<[u8]>` whose length matches // the size requested. If that ever changes, the capacity here should // change to `ptr.len() / mem::size_of::<T>()`. self.ptr = unsafe { Unique::new_unchecked(ptr.cast().as_ptr()) }; self.cap = cap; } // This method is usually instantiated many times. So we want it to be as // small as possible, to improve compile times. But we also want as much of // its contents to be statically computable as possible, to make the // generated code run faster. Therefore, this method is carefully written // so that all of the code that depends on `T` is within it, while as much // of the code that doesn't depend on `T` as possible is in functions that // are non-generic over `T`. fn grow_amortized(&mut self, len: usize, additional: usize) -> Result<(), TryReserveError> { // This is ensured by the calling contexts. debug_assert!(additional > 0); if mem::size_of::<T>() == 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.into()); } // Nothing we can really do about these checks, sadly. let required_cap = len.checked_add(additional).ok_or(CapacityOverflow)?; // This guarantees exponential growth. The doubling cannot overflow // because `cap <= isize::MAX` and the type of `cap` is `usize`. let cap = cmp::max(self.cap * 2, required_cap); let cap = cmp::max(Self::MIN_NON_ZERO_CAP, cap); let new_layout = Layout::array::<T>(cap); // `finish_grow` is non-generic over `T`. let ptr = finish_grow(new_layout, self.current_memory(), &mut self.alloc)?; self.set_ptr_and_cap(ptr, cap); Ok(()) } // The constraints on this method are much the same as those on // `grow_amortized`, but this method is usually instantiated less often so // it's less critical. fn grow_exact(&mut self, len: usize, additional: usize) -> Result<(), TryReserveError> { if mem::size_of::<T>() == 0 { // Since we return a capacity of `usize::MAX` when the type size is // 0, getting to here necessarily means the `RawVec` is overfull. return Err(CapacityOverflow.into()); } let cap = len.checked_add(additional).ok_or(CapacityOverflow)?; let new_layout = Layout::array::<T>(cap); // `finish_grow` is non-generic over `T`. let ptr = finish_grow(new_layout, self.current_memory(), &mut self.alloc)?; self.set_ptr_and_cap(ptr, cap); Ok(()) } #[allow(dead_code)] fn shrink(&mut self, cap: usize) -> Result<(), TryReserveError> { assert!(cap <= self.capacity(), "Tried to shrink to a larger capacity"); let (ptr, layout) = if let Some(mem) = self.current_memory() { mem } else { return Ok(()) }; let ptr = unsafe { // `Layout::array` cannot overflow here because it would have // overflowed earlier when capacity was larger. let new_layout = Layout::array::<T>(cap).unwrap_unchecked(); self.alloc .shrink(ptr, layout, new_layout) .map_err(|_| AllocError { layout: new_layout, non_exhaustive: () })? }; self.set_ptr_and_cap(ptr, cap); Ok(()) } } // This function is outside `RawVec` to minimize compile times. See the comment // above `RawVec::grow_amortized` for details. (The `A` parameter isn't // significant, because the number of different `A` types seen in practice is // much smaller than the number of `T` types.) #[inline(never)] fn finish_grow<A>( new_layout: Result<Layout, LayoutError>, current_memory: Option<(NonNull<u8>, Layout)>, alloc: &mut A, ) -> Result<NonNull<[u8]>, TryReserveError> where A: Allocator, { // Check for the error here to minimize the size of `RawVec::grow_*`. let new_layout = new_layout.map_err(|_| CapacityOverflow)?; alloc_guard(new_layout.size())?; let memory = if let Some((ptr, old_layout)) = current_memory { debug_assert_eq!(old_layout.align(), new_layout.align()); unsafe { // The allocator checks for alignment equality intrinsics::assume(old_layout.align() == new_layout.align()); alloc.grow(ptr, old_layout, new_layout) } } else { alloc.allocate(new_layout) }; memory.map_err(|_| AllocError { layout: new_layout, non_exhaustive: () }.into()) } unsafe impl<#[may_dangle] T, A: Allocator> 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.deallocate(ptr, layout) } } } } // Central function for reserve error handling. #[cfg(not(no_global_oom_handling))] #[inline] fn handle_reserve(result: Result<(), TryReserveError>) { match result.map_err(|e| e.kind()) { Err(CapacityOverflow) => capacity_overflow(), Err(AllocError { layout, .. }) => handle_alloc_error(layout), Ok(()) => { /* yay */ } }