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//
// Copyright (c) 2023 ZettaScale Technology
//
// This program and the accompanying materials are made available under the
// terms of the Eclipse Public License 2.0 which is available at
// http://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
// which is available at https://www.apache.org/licenses/LICENSE-2.0.
//
// SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
//
// Contributors:
// Pierre Avital, <pierre.avital@me.com>
//
use core::{marker::PhantomData, ptr::NonNull, sync::atomic::AtomicUsize};
use self::vec::ptr_diff;
#[cfg(feature = "libc")]
/// A libc malloc based implementation of the [`IAlloc`] API
pub mod libc_alloc;
/// A generic allocation error.
#[crate::stabby]
#[derive(Debug, Default, Clone, PartialEq, Eq, Hash)]
pub struct AllocationError();
impl core::fmt::Display for AllocationError {
fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
f.write_str("AllocationError")
}
}
#[cfg(feature = "std")]
impl std::error::Error for AllocationError {}
/// [`alloc::boxed`](https://doc.rust-lang.org/stable/alloc/boxed/), but ABI-stable.
pub mod boxed;
/// A vector that stores a single element on the stack until allocation is necessary.
pub mod single_or_vec;
/// [`alloc::string`](https://doc.rust-lang.org/stable/alloc/string/), but ABI-stable
pub mod string;
/// [`alloc::sync`](https://doc.rust-lang.org/stable/alloc/sync/), but ABI-stable
pub mod sync;
/// [`alloc::vec`](https://doc.rust-lang.org/stable/alloc/vec/), but ABI-stable
pub mod vec;
/// The default allocator: libc malloc based if the libc feature is enabled, or unavailable otherwise.
#[cfg(feature = "libc")]
pub type DefaultAllocator = libc_alloc::LibcAlloc;
#[cfg(not(feature = "libc"))]
pub type DefaultAllocator = core::convert::Infallible;
#[crate::stabby]
#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
/// ABI-stable equivalent of std::mem::Layout
pub struct Layout {
/// The expected size of the allocation.
pub size: usize,
/// The expected alignment of the allocation.
pub align: usize,
}
impl Layout {
/// Returns the [`Layout`] corresponding to `T`
pub const fn of<T: Sized>() -> Self {
Layout {
size: core::mem::size_of::<T>(),
align: core::mem::align_of::<T>(),
}
}
/// Returns the [`Layout`] corresponding to `[T; n]`.
///
/// Note that while this ensures that even if `T`'s size is not a multiple of its alignment,
/// the layout will have sufficient memory to store `n` of `T` in an aligned fashion.
pub const fn array<T: Sized>(n: usize) -> Self {
let Self { mut size, align } = Self::of::<T>();
let sizemodalign = size % align;
if sizemodalign != 0 {
size += align;
size -= sizemodalign;
}
size *= n;
Layout { size, align }
}
/// Concatenates a layout to `self`, ensuring that alignment padding is taken into account.
pub const fn concat(mut self, other: Self) -> Self {
let sizemodalign = self.size % other.align;
if sizemodalign != 0 {
self.size += other.align;
self.size -= sizemodalign;
}
self.size += other.size;
if other.align > self.align {
self.align = other.align;
}
self
}
/// Returns the first pointer where `output >= ptr` such that `output % self.align == 0`.
#[inline]
pub fn next_matching<T>(self, ptr: *mut T) -> *mut T {
fn next_matching(align: usize, ptr: *mut u8) -> *mut u8 {
unsafe { ptr.add(ptr.align_offset(align)) }
}
next_matching(self.align, ptr.cast()).cast()
}
}
/// An interface to an allocator.
///
/// Note that `stabby` often stores allocators inside allocations they made, so allocators that cannot allocate
/// more than their size on stack will systematically fail to construct common stabby types.
///
/// Since the allocator may be moved, it must also be safe to do so, including after it has performed allocations.
pub trait IAlloc: Unpin {
/// Allocates at least as much memory as requested by layout, ensuring the requested alignment is respected.
///
/// If the requested size is 0, or allocation failed, then a null pointer is returned.
fn alloc(&mut self, layout: Layout) -> *mut ();
/// Frees the allocation
///
/// # Safety
/// `ptr` MUST have been allocated through a succesful call to `Self::alloc` or `Self::realloc` with the same instance of `Self`
unsafe fn free(&mut self, ptr: *mut ());
/// Reallocates `ptr`, ensuring that it has enough memory for the newly requested layout.
///
/// If the requested size is 0, or allocation failed, then a null pointer is returned, and `ptr` is not freed.
///
/// # Safety
/// `ptr` MUST have been allocated through a succesful call to `Self::alloc` with the same instance of `Self`
unsafe fn realloc(&mut self, ptr: *mut (), new_layout: Layout) -> *mut () {
let ret = self.alloc(new_layout);
if !ret.is_null() {
unsafe {
core::ptr::copy_nonoverlapping(ptr.cast::<u8>(), ret.cast(), new_layout.size);
self.free(ptr);
}
}
ret
}
}
/// An ABI stable equivalent to [`IAlloc`].
#[crate::stabby]
pub trait IStableAlloc: Unpin {
/// Allocates at least as much memory as requested by layout, ensuring the requested alignment is respected.
///
/// If the requested size is 0, or allocation failed, then a null pointer is returned.
extern "C" fn alloc(&mut self, layout: Layout) -> *mut ();
/// Frees the allocation
///
/// # Safety
/// `ptr` MUST have been allocated through a succesful call to `Self::alloc` or `Self::realloc` with the same instance of `Self`
extern "C" fn free(&mut self, ptr: *mut ());
/// Reallocates `ptr`, ensuring that it has enough memory for the newly requested layout.
///
/// If the requested size is 0, or allocation failed, then a null pointer is returned, and `ptr` is not freed.
///
/// # Safety
/// `ptr` MUST have been allocated through a succesful call to `Self::alloc` with the same instance of `Self`
extern "C" fn realloc(&mut self, ptr: *mut (), new_layout: Layout) -> *mut () {
let ret = self.alloc(new_layout);
if !ret.is_null() {
unsafe {
core::ptr::copy_nonoverlapping(ptr.cast::<u8>(), ret.cast(), new_layout.size);
self.free(ptr);
}
}
ret
}
}
#[allow(clippy::not_unsafe_ptr_arg_deref)]
impl<T: IAlloc> IStableAlloc for T {
extern "C" fn alloc(&mut self, layout: Layout) -> *mut () {
IAlloc::alloc(self, layout)
}
extern "C" fn free(&mut self, ptr: *mut ()) {
unsafe { IAlloc::free(self, ptr) }
}
extern "C" fn realloc(&mut self, ptr: *mut (), layout: Layout) -> *mut () {
unsafe { IAlloc::realloc(self, ptr, layout) }
}
}
impl<T: IStableAllocDynMut<crate::vtable::H> + Unpin> IAlloc for T {
fn alloc(&mut self, layout: Layout) -> *mut () {
IStableAllocDynMut::alloc(self, layout)
}
unsafe fn free(&mut self, ptr: *mut ()) {
IStableAllocDynMut::free(self, ptr)
}
unsafe fn realloc(&mut self, ptr: *mut (), new_layout: Layout) -> *mut () {
IStableAllocDynMut::realloc(self, ptr, new_layout)
}
}
impl IAlloc for core::convert::Infallible {
fn alloc(&mut self, _layout: Layout) -> *mut () {
unreachable!()
}
unsafe fn free(&mut self, _ptr: *mut ()) {
unreachable!()
}
}
/// The prefix common to all allocations in [`stabby::alloc`](crate::alloc).
///
/// This allows reuse of allocations when converting between container types.
#[crate::stabby]
pub struct AllocPrefix<Alloc> {
/// The strong count for reference counted types.
pub strong: core::sync::atomic::AtomicUsize,
/// The weak count for reference counted types.
pub weak: core::sync::atomic::AtomicUsize,
/// A slot to store a vector's capacity when it's turned into a boxed/arced slice.
pub capacity: core::sync::atomic::AtomicUsize,
/// A slot for the allocator.
pub alloc: Alloc,
}
impl<Alloc> AllocPrefix<Alloc> {
/// The offset between the prefix and a field of type `T`.
pub const fn skip_to<T>() -> usize {
let mut size = core::mem::size_of::<Self>();
let align = core::mem::align_of::<T>();
let sizemodalign = size % align;
if sizemodalign != 0 {
size += align;
size -= sizemodalign;
}
size
}
}
/// A non-null pointer guaranteed to be preceded by a valid
/// [`AllocPrefix`] unless the pointer is dangling.
///
/// This means that unless `T` is a ZST, the pointer is guaranteed to be aligned to the maximum of `T`'s alignment and the alignment of the prefix, which itself is ptr-size aligned.
#[crate::stabby]
#[derive(Debug, PartialEq, Eq, PartialOrd, Ord)]
pub struct AllocPtr<T, Alloc> {
/// The pointer to the data.
pub ptr: NonNull<T>,
/// Remember the allocator's type.
pub marker: PhantomData<Alloc>,
}
impl<T, Alloc> Copy for AllocPtr<T, Alloc> {}
impl<T, Alloc> Clone for AllocPtr<T, Alloc> {
fn clone(&self) -> Self {
*self
}
}
impl<T, Alloc> core::ops::Deref for AllocPtr<T, Alloc> {
type Target = NonNull<T>;
fn deref(&self) -> &Self::Target {
&self.ptr
}
}
impl<T, Alloc> core::ops::DerefMut for AllocPtr<T, Alloc> {
fn deref_mut(&mut self) -> &mut Self::Target {
&mut self.ptr
}
}
impl<T, Alloc> AllocPtr<T, Alloc> {
/// Constructs a dangling pointer.
pub const fn dangling() -> Self {
Self {
ptr: NonNull::dangling(),
marker: PhantomData,
}
}
/// Casts an allocated pointer.
pub const fn cast<U>(self) -> AllocPtr<U, Alloc> {
AllocPtr {
ptr: self.ptr.cast(),
marker: PhantomData,
}
}
/// The offset between `self.ptr` and the prefix.
pub const fn prefix_skip() -> usize {
AllocPrefix::<Alloc>::skip_to::<T>()
}
///The pointer to the prefix for this allocation
const fn prefix_ptr(&self) -> NonNull<AllocPrefix<Alloc>> {
unsafe {
NonNull::new_unchecked(
self.ptr
.as_ptr()
.cast::<u8>()
.sub(Self::prefix_skip())
.cast(),
)
}
}
/// A reference to the prefix for this allocation.
/// # Safety
/// `self` must not be dangling, and have been properly allocated, using [`Self::alloc`] or [`Self::realloc`] for example.
#[rustversion::since(1.73)]
pub const unsafe fn prefix(&self) -> &AllocPrefix<Alloc> {
unsafe { self.prefix_ptr().as_ref() }
}
/// A reference to the prefix for this allocation.
/// # Safety
/// `self` must not be dangling, and have been properly allocated, using [`Self::alloc`] or [`Self::realloc`] for example.
#[rustversion::before(1.73)]
pub unsafe fn prefix(&self) -> &AllocPrefix<Alloc> {
unsafe { self.prefix_ptr().as_ref() }
}
/// A mutable reference to the prefix for this allocation.
/// # Safety
/// `self` must not be dangling, and have been properly allocated, using [`Self::alloc`] or [`Self::realloc`] for example.
/// Since this type is [`Copy`], the `&mut self` is not a sufficient guarantee of uniqueness.
pub unsafe fn prefix_mut(&mut self) -> &mut AllocPrefix<Alloc> {
unsafe { self.prefix_ptr().as_mut() }
}
}
impl<T, Alloc: IAlloc> AllocPtr<T, Alloc> {
/// Allocates a pointer to a single element of `T`, prefixed by an [`AllocPrefix`]
pub fn alloc(alloc: &mut Alloc) -> Option<Self> {
let ptr = alloc.alloc(Layout::of::<AllocPrefix<Alloc>>().concat(Layout::of::<T>()));
NonNull::new(ptr).map(|ptr| unsafe {
ptr.cast::<AllocPrefix<Alloc>>().as_mut().capacity = AtomicUsize::new(1);
Self {
ptr: NonNull::new_unchecked(
ptr.as_ptr().cast::<u8>().add(Self::prefix_skip()).cast(),
),
marker: PhantomData,
}
})
}
/// Allocates a pointer to an array of `capacity` `T`, prefixed by an [`AllocPrefix`]
pub fn alloc_array(alloc: &mut Alloc, capacity: usize) -> Option<Self> {
let ptr =
alloc.alloc(Layout::of::<AllocPrefix<Alloc>>().concat(Layout::array::<T>(capacity)));
NonNull::new(ptr).map(|ptr| unsafe {
ptr.cast::<AllocPrefix<Alloc>>().as_mut().capacity = AtomicUsize::new(capacity);
Self {
ptr: NonNull::new_unchecked(
ptr.as_ptr().cast::<u8>().add(Self::prefix_skip()).cast(),
),
marker: PhantomData,
}
})
}
/// Reallocates a pointer to an array of `capacity` `T`, prefixed by an [`AllocPrefix`].
///
/// In case of failure of the allocator, this will return `None` and `self` will not have been freed.
///
/// # Safety
/// `self` must not be dangling
pub unsafe fn realloc(self, alloc: &mut Alloc, capacity: usize) -> Option<Self> {
let ptr = alloc.realloc(
self.prefix() as *const _ as *mut _,
Layout::of::<AllocPrefix<Alloc>>().concat(Layout::array::<T>(capacity)),
);
NonNull::new(ptr).map(|ptr| unsafe {
ptr.cast::<AllocPrefix<Alloc>>().as_mut().capacity = AtomicUsize::new(capacity);
Self {
ptr: NonNull::new_unchecked(
ptr.as_ptr().cast::<u8>().add(Self::prefix_skip()).cast(),
),
marker: PhantomData,
}
})
}
/// Reallocates a pointer to an array of `capacity` `T`, prefixed by an [`AllocPrefix`]
/// # Safety
/// `self` must not be dangling, and is freed after this returns.
pub unsafe fn free(self, alloc: &mut Alloc) {
alloc.free(self.prefix() as *const _ as *mut _)
}
}
/// A helper to work with allocated slices.
#[crate::stabby]
#[derive(Debug, PartialEq, Eq, PartialOrd, Ord)]
pub struct AllocSlice<T, Alloc> {
/// The start of the slice.
pub start: AllocPtr<T, Alloc>,
/// The end of the slice (exclusive).
pub end: NonNull<T>,
}
impl<T, Alloc> AllocSlice<T, Alloc> {
/// Returns the number of elements in the slice.
pub const fn len(&self) -> usize {
ptr_diff(self.end, self.start.ptr)
}
/// Returns `true` if the slice is empty.
pub const fn is_empty(&self) -> bool {
self.len() == 0
}
}
impl<T, Alloc> Copy for AllocSlice<T, Alloc> {}
impl<T, Alloc> Clone for AllocSlice<T, Alloc> {
fn clone(&self) -> Self {
*self
}
}