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diff --git a/vendor/smallvec/src/lib.rs b/vendor/smallvec/src/lib.rs new file mode 100644 index 0000000..f9a6c8a --- /dev/null +++ b/vendor/smallvec/src/lib.rs @@ -0,0 +1,2457 @@ +// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or +// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license +// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +//! Small vectors in various sizes. These store a certain number of elements inline, and fall back +//! to the heap for larger allocations. This can be a useful optimization for improving cache +//! locality and reducing allocator traffic for workloads that fit within the inline buffer. +//! +//! ## `no_std` support +//! +//! By default, `smallvec` does not depend on `std`. However, the optional +//! `write` feature implements the `std::io::Write` trait for vectors of `u8`. +//! When this feature is enabled, `smallvec` depends on `std`. +//! +//! ## Optional features +//! +//! ### `serde` +//! +//! When this optional dependency is enabled, `SmallVec` implements the `serde::Serialize` and +//! `serde::Deserialize` traits. +//! +//! ### `write` +//! +//! When this feature is enabled, `SmallVec<[u8; _]>` implements the `std::io::Write` trait. +//! This feature is not compatible with `#![no_std]` programs. +//! +//! ### `union` +//! +//! **This feature requires Rust 1.49.** +//! +//! When the `union` feature is enabled `smallvec` will track its state (inline or spilled) +//! without the use of an enum tag, reducing the size of the `smallvec` by one machine word. +//! This means that there is potentially no space overhead compared to `Vec`. +//! Note that `smallvec` can still be larger than `Vec` if the inline buffer is larger than two +//! machine words. +//! +//! To use this feature add `features = ["union"]` in the `smallvec` section of Cargo.toml. +//! Note that this feature requires Rust 1.49. +//! +//! Tracking issue: [rust-lang/rust#55149](https://github.com/rust-lang/rust/issues/55149) +//! +//! ### `const_generics` +//! +//! **This feature requires Rust 1.51.** +//! +//! When this feature is enabled, `SmallVec` works with any arrays of any size, not just a fixed +//! list of sizes. +//! +//! ### `const_new` +//! +//! **This feature requires Rust 1.51.** +//! +//! This feature exposes the functions [`SmallVec::new_const`], [`SmallVec::from_const`], and [`smallvec_inline`] which enables the `SmallVec` to be initialized from a const context. +//! For details, see the +//! [Rust Reference](https://doc.rust-lang.org/reference/const_eval.html#const-functions). +//! +//! ### `drain_filter` +//! +//! **This feature is unstable.** It may change to match the unstable `drain_filter` method in libstd. +//! +//! Enables the `drain_filter` method, which produces an iterator that calls a user-provided +//! closure to determine which elements of the vector to remove and yield from the iterator. +//! +//! ### `drain_keep_rest` +//! +//! **This feature is unstable.** It may change to match the unstable `drain_keep_rest` method in libstd. +//! +//! Enables the `DrainFilter::keep_rest` method. +//! +//! ### `specialization` +//! +//! **This feature is unstable and requires a nightly build of the Rust toolchain.** +//! +//! When this feature is enabled, `SmallVec::from(slice)` has improved performance for slices +//! of `Copy` types. (Without this feature, you can use `SmallVec::from_slice` to get optimal +//! performance for `Copy` types.) +//! +//! Tracking issue: [rust-lang/rust#31844](https://github.com/rust-lang/rust/issues/31844) +//! +//! ### `may_dangle` +//! +//! **This feature is unstable and requires a nightly build of the Rust toolchain.** +//! +//! This feature makes the Rust compiler less strict about use of vectors that contain borrowed +//! references. For details, see the +//! [Rustonomicon](https://doc.rust-lang.org/1.42.0/nomicon/dropck.html#an-escape-hatch). +//! +//! Tracking issue: [rust-lang/rust#34761](https://github.com/rust-lang/rust/issues/34761) + +#![no_std] +#![cfg_attr(docsrs, feature(doc_cfg))] +#![cfg_attr(feature = "specialization", allow(incomplete_features))] +#![cfg_attr(feature = "specialization", feature(specialization))] +#![cfg_attr(feature = "may_dangle", feature(dropck_eyepatch))] +#![cfg_attr( + feature = "debugger_visualizer", + feature(debugger_visualizer), + debugger_visualizer(natvis_file = "../debug_metadata/smallvec.natvis") +)] +#![deny(missing_docs)] + +#[doc(hidden)] +pub extern crate alloc; + +#[cfg(any(test, feature = "write"))] +extern crate std; + +#[cfg(test)] +mod tests; + +#[allow(deprecated)] +use alloc::alloc::{Layout, LayoutErr}; +use alloc::boxed::Box; +use alloc::{vec, vec::Vec}; +use core::borrow::{Borrow, BorrowMut}; +use core::cmp; +use core::fmt; +use core::hash::{Hash, Hasher}; +use core::hint::unreachable_unchecked; +use core::iter::{repeat, FromIterator, FusedIterator, IntoIterator}; +use core::mem; +use core::mem::MaybeUninit; +use core::ops::{self, Range, RangeBounds}; +use core::ptr::{self, NonNull}; +use core::slice::{self, SliceIndex}; + +#[cfg(feature = "serde")] +use serde::{ + de::{Deserialize, Deserializer, SeqAccess, Visitor}, + ser::{Serialize, SerializeSeq, Serializer}, +}; + +#[cfg(feature = "serde")] +use core::marker::PhantomData; + +#[cfg(feature = "write")] +use std::io; + +#[cfg(feature = "drain_keep_rest")] +use core::mem::ManuallyDrop; + +/// Creates a [`SmallVec`] containing the arguments. +/// +/// `smallvec!` allows `SmallVec`s to be defined with the same syntax as array expressions. +/// There are two forms of this macro: +/// +/// - Create a [`SmallVec`] containing a given list of elements: +/// +/// ``` +/// # use smallvec::{smallvec, SmallVec}; +/// # fn main() { +/// let v: SmallVec<[_; 128]> = smallvec![1, 2, 3]; +/// assert_eq!(v[0], 1); +/// assert_eq!(v[1], 2); +/// assert_eq!(v[2], 3); +/// # } +/// ``` +/// +/// - Create a [`SmallVec`] from a given element and size: +/// +/// ``` +/// # use smallvec::{smallvec, SmallVec}; +/// # fn main() { +/// let v: SmallVec<[_; 0x8000]> = smallvec![1; 3]; +/// assert_eq!(v, SmallVec::from_buf([1, 1, 1])); +/// # } +/// ``` +/// +/// Note that unlike array expressions this syntax supports all elements +/// which implement [`Clone`] and the number of elements doesn't have to be +/// a constant. +/// +/// This will use `clone` to duplicate an expression, so one should be careful +/// using this with types having a nonstandard `Clone` implementation. For +/// example, `smallvec![Rc::new(1); 5]` will create a vector of five references +/// to the same boxed integer value, not five references pointing to independently +/// boxed integers. + +#[macro_export] +macro_rules! smallvec { + // count helper: transform any expression into 1 + (@one $x:expr) => (1usize); + ($elem:expr; $n:expr) => ({ + $crate::SmallVec::from_elem($elem, $n) + }); + ($($x:expr),*$(,)*) => ({ + let count = 0usize $(+ $crate::smallvec!(@one $x))*; + #[allow(unused_mut)] + let mut vec = $crate::SmallVec::new(); + if count <= vec.inline_size() { + $(vec.push($x);)* + vec + } else { + $crate::SmallVec::from_vec($crate::alloc::vec![$($x,)*]) + } + }); +} + +/// Creates an inline [`SmallVec`] containing the arguments. This macro is enabled by the feature `const_new`. +/// +/// `smallvec_inline!` allows `SmallVec`s to be defined with the same syntax as array expressions in `const` contexts. +/// The inline storage `A` will always be an array of the size specified by the arguments. +/// There are two forms of this macro: +/// +/// - Create a [`SmallVec`] containing a given list of elements: +/// +/// ``` +/// # use smallvec::{smallvec_inline, SmallVec}; +/// # fn main() { +/// const V: SmallVec<[i32; 3]> = smallvec_inline![1, 2, 3]; +/// assert_eq!(V[0], 1); +/// assert_eq!(V[1], 2); +/// assert_eq!(V[2], 3); +/// # } +/// ``` +/// +/// - Create a [`SmallVec`] from a given element and size: +/// +/// ``` +/// # use smallvec::{smallvec_inline, SmallVec}; +/// # fn main() { +/// const V: SmallVec<[i32; 3]> = smallvec_inline![1; 3]; +/// assert_eq!(V, SmallVec::from_buf([1, 1, 1])); +/// # } +/// ``` +/// +/// Note that the behavior mimics that of array expressions, in contrast to [`smallvec`]. +#[cfg(feature = "const_new")] +#[cfg_attr(docsrs, doc(cfg(feature = "const_new")))] +#[macro_export] +macro_rules! smallvec_inline { + // count helper: transform any expression into 1 + (@one $x:expr) => (1usize); + ($elem:expr; $n:expr) => ({ + $crate::SmallVec::<[_; $n]>::from_const([$elem; $n]) + }); + ($($x:expr),+ $(,)?) => ({ + const N: usize = 0usize $(+ $crate::smallvec_inline!(@one $x))*; + $crate::SmallVec::<[_; N]>::from_const([$($x,)*]) + }); +} + +/// `panic!()` in debug builds, optimization hint in release. +#[cfg(not(feature = "union"))] +macro_rules! debug_unreachable { + () => { + debug_unreachable!("entered unreachable code") + }; + ($e:expr) => { + if cfg!(debug_assertions) { + panic!($e); + } else { + unreachable_unchecked(); + } + }; +} + +/// Trait to be implemented by a collection that can be extended from a slice +/// +/// ## Example +/// +/// ```rust +/// use smallvec::{ExtendFromSlice, SmallVec}; +/// +/// fn initialize<V: ExtendFromSlice<u8>>(v: &mut V) { +/// v.extend_from_slice(b"Test!"); +/// } +/// +/// let mut vec = Vec::new(); +/// initialize(&mut vec); +/// assert_eq!(&vec, b"Test!"); +/// +/// let mut small_vec = SmallVec::<[u8; 8]>::new(); +/// initialize(&mut small_vec); +/// assert_eq!(&small_vec as &[_], b"Test!"); +/// ``` +#[doc(hidden)] +#[deprecated] +pub trait ExtendFromSlice<T> { + /// Extends a collection from a slice of its element type + fn extend_from_slice(&mut self, other: &[T]); +} + +#[allow(deprecated)] +impl<T: Clone> ExtendFromSlice<T> for Vec<T> { + fn extend_from_slice(&mut self, other: &[T]) { + Vec::extend_from_slice(self, other) + } +} + +/// Error type for APIs with fallible heap allocation +#[derive(Debug)] +pub enum CollectionAllocErr { + /// Overflow `usize::MAX` or other error during size computation + CapacityOverflow, + /// The allocator return an error + AllocErr { + /// The layout that was passed to the allocator + layout: Layout, + }, +} + +impl fmt::Display for CollectionAllocErr { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + write!(f, "Allocation error: {:?}", self) + } +} + +#[allow(deprecated)] +impl From<LayoutErr> for CollectionAllocErr { + fn from(_: LayoutErr) -> Self { + CollectionAllocErr::CapacityOverflow + } +} + +fn infallible<T>(result: Result<T, CollectionAllocErr>) -> T { + match result { + Ok(x) => x, + Err(CollectionAllocErr::CapacityOverflow) => panic!("capacity overflow"), + Err(CollectionAllocErr::AllocErr { layout }) => alloc::alloc::handle_alloc_error(layout), + } +} + +/// FIXME: use `Layout::array` when we require a Rust version where it’s stable +/// <https://github.com/rust-lang/rust/issues/55724> +fn layout_array<T>(n: usize) -> Result<Layout, CollectionAllocErr> { + let size = mem::size_of::<T>() + .checked_mul(n) + .ok_or(CollectionAllocErr::CapacityOverflow)?; + let align = mem::align_of::<T>(); + Layout::from_size_align(size, align).map_err(|_| CollectionAllocErr::CapacityOverflow) +} + +unsafe fn deallocate<T>(ptr: NonNull<T>, capacity: usize) { + // This unwrap should succeed since the same did when allocating. + let layout = layout_array::<T>(capacity).unwrap(); + alloc::alloc::dealloc(ptr.as_ptr() as *mut u8, layout) +} + +/// An iterator that removes the items from a `SmallVec` and yields them by value. +/// +/// Returned from [`SmallVec::drain`][1]. +/// +/// [1]: struct.SmallVec.html#method.drain +pub struct Drain<'a, T: 'a + Array> { + tail_start: usize, + tail_len: usize, + iter: slice::Iter<'a, T::Item>, + vec: NonNull<SmallVec<T>>, +} + +impl<'a, T: 'a + Array> fmt::Debug for Drain<'a, T> +where + T::Item: fmt::Debug, +{ + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_tuple("Drain").field(&self.iter.as_slice()).finish() + } +} + +unsafe impl<'a, T: Sync + Array> Sync for Drain<'a, T> {} +unsafe impl<'a, T: Send + Array> Send for Drain<'a, T> {} + +impl<'a, T: 'a + Array> Iterator for Drain<'a, T> { + type Item = T::Item; + + #[inline] + fn next(&mut self) -> Option<T::Item> { + self.iter + .next() + .map(|reference| unsafe { ptr::read(reference) }) + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + self.iter.size_hint() + } +} + +impl<'a, T: 'a + Array> DoubleEndedIterator for Drain<'a, T> { + #[inline] + fn next_back(&mut self) -> Option<T::Item> { + self.iter + .next_back() + .map(|reference| unsafe { ptr::read(reference) }) + } +} + +impl<'a, T: Array> ExactSizeIterator for Drain<'a, T> { + #[inline] + fn len(&self) -> usize { + self.iter.len() + } +} + +impl<'a, T: Array> FusedIterator for Drain<'a, T> {} + +impl<'a, T: 'a + Array> Drop for Drain<'a, T> { + fn drop(&mut self) { + self.for_each(drop); + + if self.tail_len > 0 { + unsafe { + let source_vec = self.vec.as_mut(); + + // memmove back untouched tail, update to new length + let start = source_vec.len(); + let tail = self.tail_start; + if tail != start { + // as_mut_ptr creates a &mut, invalidating other pointers. + // This pattern avoids calling it with a pointer already present. + let ptr = source_vec.as_mut_ptr(); + let src = ptr.add(tail); + let dst = ptr.add(start); + ptr::copy(src, dst, self.tail_len); + } + source_vec.set_len(start + self.tail_len); + } + } + } +} + +#[cfg(feature = "drain_filter")] +/// An iterator which uses a closure to determine if an element should be removed. +/// +/// Returned from [`SmallVec::drain_filter`][1]. +/// +/// [1]: struct.SmallVec.html#method.drain_filter +pub struct DrainFilter<'a, T, F> +where + F: FnMut(&mut T::Item) -> bool, + T: Array, +{ + vec: &'a mut SmallVec<T>, + /// The index of the item that will be inspected by the next call to `next`. + idx: usize, + /// The number of items that have been drained (removed) thus far. + del: usize, + /// The original length of `vec` prior to draining. + old_len: usize, + /// The filter test predicate. + pred: F, + /// A flag that indicates a panic has occurred in the filter test predicate. + /// This is used as a hint in the drop implementation to prevent consumption + /// of the remainder of the `DrainFilter`. Any unprocessed items will be + /// backshifted in the `vec`, but no further items will be dropped or + /// tested by the filter predicate. + panic_flag: bool, +} + +#[cfg(feature = "drain_filter")] +impl <T, F> fmt::Debug for DrainFilter<'_, T, F> +where + F: FnMut(&mut T::Item) -> bool, + T: Array, + T::Item: fmt::Debug, +{ + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_tuple("DrainFilter").field(&self.vec.as_slice()).finish() + } +} + +#[cfg(feature = "drain_filter")] +impl <T, F> Iterator for DrainFilter<'_, T, F> +where + F: FnMut(&mut T::Item) -> bool, + T: Array, +{ + type Item = T::Item; + + fn next(&mut self) -> Option<T::Item> + { + unsafe { + while self.idx < self.old_len { + let i = self.idx; + let v = slice::from_raw_parts_mut(self.vec.as_mut_ptr(), self.old_len); + self.panic_flag = true; + let drained = (self.pred)(&mut v[i]); + self.panic_flag = false; + // Update the index *after* the predicate is called. If the index + // is updated prior and the predicate panics, the element at this + // index would be leaked. + self.idx += 1; + if drained { + self.del += 1; + return Some(ptr::read(&v[i])); + } else if self.del > 0 { + let del = self.del; + let src: *const Self::Item = &v[i]; + let dst: *mut Self::Item = &mut v[i - del]; + ptr::copy_nonoverlapping(src, dst, 1); + } + } + None + } + } + + fn size_hint(&self) -> (usize, Option<usize>) { + (0, Some(self.old_len - self.idx)) + } +} + +#[cfg(feature = "drain_filter")] +impl <T, F> Drop for DrainFilter<'_, T, F> +where + F: FnMut(&mut T::Item) -> bool, + T: Array, +{ + fn drop(&mut self) { + struct BackshiftOnDrop<'a, 'b, T, F> + where + F: FnMut(&mut T::Item) -> bool, + T: Array + { + drain: &'b mut DrainFilter<'a, T, F>, + } + + impl<'a, 'b, T, F> Drop for BackshiftOnDrop<'a, 'b, T, F> + where + F: FnMut(&mut T::Item) -> bool, + T: Array + { + fn drop(&mut self) { + unsafe { + if self.drain.idx < self.drain.old_len && self.drain.del > 0 { + // This is a pretty messed up state, and there isn't really an + // obviously right thing to do. We don't want to keep trying + // to execute `pred`, so we just backshift all the unprocessed + // elements and tell the vec that they still exist. The backshift + // is required to prevent a double-drop of the last successfully + // drained item prior to a panic in the predicate. + let ptr = self.drain.vec.as_mut_ptr(); + let src = ptr.add(self.drain.idx); + let dst = src.sub(self.drain.del); + let tail_len = self.drain.old_len - self.drain.idx; + src.copy_to(dst, tail_len); + } + self.drain.vec.set_len(self.drain.old_len - self.drain.del); + } + } + } + + let backshift = BackshiftOnDrop { drain: self }; + + // Attempt to consume any remaining elements if the filter predicate + // has not yet panicked. We'll backshift any remaining elements + // whether we've already panicked or if the consumption here panics. + if !backshift.drain.panic_flag { + backshift.drain.for_each(drop); + } + } +} + +#[cfg(feature = "drain_keep_rest")] +impl <T, F> DrainFilter<'_, T, F> +where + F: FnMut(&mut T::Item) -> bool, + T: Array +{ + /// Keep unyielded elements in the source `Vec`. + /// + /// # Examples + /// + /// ``` + /// # use smallvec::{smallvec, SmallVec}; + /// + /// let mut vec: SmallVec<[char; 2]> = smallvec!['a', 'b', 'c']; + /// let mut drain = vec.drain_filter(|_| true); + /// + /// assert_eq!(drain.next().unwrap(), 'a'); + /// + /// // This call keeps 'b' and 'c' in the vec. + /// drain.keep_rest(); + /// + /// // If we wouldn't call `keep_rest()`, + /// // `vec` would be empty. + /// assert_eq!(vec, SmallVec::<[char; 2]>::from_slice(&['b', 'c'])); + /// ``` + pub fn keep_rest(self) + { + // At this moment layout looks like this: + // + // _____________________/-- old_len + // / \ + // [kept] [yielded] [tail] + // \_______/ ^-- idx + // \-- del + // + // Normally `Drop` impl would drop [tail] (via .for_each(drop), ie still calling `pred`) + // + // 1. Move [tail] after [kept] + // 2. Update length of the original vec to `old_len - del` + // a. In case of ZST, this is the only thing we want to do + // 3. Do *not* drop self, as everything is put in a consistent state already, there is nothing to do + let mut this = ManuallyDrop::new(self); + + unsafe { + // ZSTs have no identity, so we don't need to move them around. + let needs_move = mem::size_of::<T>() != 0; + + if needs_move && this.idx < this.old_len && this.del > 0 { + let ptr = this.vec.as_mut_ptr(); + let src = ptr.add(this.idx); + let dst = src.sub(this.del); + let tail_len = this.old_len - this.idx; + src.copy_to(dst, tail_len); + } + + let new_len = this.old_len - this.del; + this.vec.set_len(new_len); + } + } +} + +#[cfg(feature = "union")] +union SmallVecData<A: Array> { + inline: core::mem::ManuallyDrop<MaybeUninit<A>>, + heap: (NonNull<A::Item>, usize), +} + +#[cfg(all(feature = "union", feature = "const_new"))] +impl<T, const N: usize> SmallVecData<[T; N]> { + #[cfg_attr(docsrs, doc(cfg(feature = "const_new")))] + #[inline] + const fn from_const(inline: MaybeUninit<[T; N]>) -> Self { + SmallVecData { + inline: core::mem::ManuallyDrop::new(inline), + } + } +} + +#[cfg(feature = "union")] +impl<A: Array> SmallVecData<A> { + #[inline] + unsafe fn inline(&self) -> ConstNonNull<A::Item> { + ConstNonNull::new(self.inline.as_ptr() as *const A::Item).unwrap() + } + #[inline] + unsafe fn inline_mut(&mut self) -> NonNull<A::Item> { + NonNull::new(self.inline.as_mut_ptr() as *mut A::Item).unwrap() + } + #[inline] + fn from_inline(inline: MaybeUninit<A>) -> SmallVecData<A> { + SmallVecData { + inline: core::mem::ManuallyDrop::new(inline), + } + } + #[inline] + unsafe fn into_inline(self) -> MaybeUninit<A> { + core::mem::ManuallyDrop::into_inner(self.inline) + } + #[inline] + unsafe fn heap(&self) -> (ConstNonNull<A::Item>, usize) { + (ConstNonNull(self.heap.0), self.heap.1) + } + #[inline] + unsafe fn heap_mut(&mut self) -> (NonNull<A::Item>, &mut usize) { + let h = &mut self.heap; + (h.0, &mut h.1) + } + #[inline] + fn from_heap(ptr: NonNull<A::Item>, len: usize) -> SmallVecData<A> { + SmallVecData { heap: (ptr, len) } + } +} + +#[cfg(not(feature = "union"))] +enum SmallVecData<A: Array> { + Inline(MaybeUninit<A>), + // Using NonNull and NonZero here allows to reduce size of `SmallVec`. + Heap { + // Since we never allocate on heap + // unless our capacity is bigger than inline capacity + // heap capacity cannot be less than 1. + // Therefore, pointer cannot be null too. + ptr: NonNull<A::Item>, + len: usize, + }, +} + +#[cfg(all(not(feature = "union"), feature = "const_new"))] +impl<T, const N: usize> SmallVecData<[T; N]> { + #[cfg_attr(docsrs, doc(cfg(feature = "const_new")))] + #[inline] + const fn from_const(inline: MaybeUninit<[T; N]>) -> Self { + SmallVecData::Inline(inline) + } +} + +#[cfg(not(feature = "union"))] +impl<A: Array> SmallVecData<A> { + #[inline] + unsafe fn inline(&self) -> ConstNonNull<A::Item> { + match self { + SmallVecData::Inline(a) => ConstNonNull::new(a.as_ptr() as *const A::Item).unwrap(), + _ => debug_unreachable!(), + } + } + #[inline] + unsafe fn inline_mut(&mut self) -> NonNull<A::Item> { + match self { + SmallVecData::Inline(a) => NonNull::new(a.as_mut_ptr() as *mut A::Item).unwrap(), + _ => debug_unreachable!(), + } + } + #[inline] + fn from_inline(inline: MaybeUninit<A>) -> SmallVecData<A> { + SmallVecData::Inline(inline) + } + #[inline] + unsafe fn into_inline(self) -> MaybeUninit<A> { + match self { + SmallVecData::Inline(a) => a, + _ => debug_unreachable!(), + } + } + #[inline] + unsafe fn heap(&self) -> (ConstNonNull<A::Item>, usize) { + match self { + SmallVecData::Heap { ptr, len } => (ConstNonNull(*ptr), *len), + _ => debug_unreachable!(), + } + } + #[inline] + unsafe fn heap_mut(&mut self) -> (NonNull<A::Item>, &mut usize) { + match self { + SmallVecData::Heap { ptr, len } => (*ptr, len), + _ => debug_unreachable!(), + } + } + #[inline] + fn from_heap(ptr: NonNull<A::Item>, len: usize) -> SmallVecData<A> { + SmallVecData::Heap { ptr, len } + } +} + +unsafe impl<A: Array + Send> Send for SmallVecData<A> {} +unsafe impl<A: Array + Sync> Sync for SmallVecData<A> {} + +/// A `Vec`-like container that can store a small number of elements inline. +/// +/// `SmallVec` acts like a vector, but can store a limited amount of data inline within the +/// `SmallVec` struct rather than in a separate allocation. If the data exceeds this limit, the +/// `SmallVec` will "spill" its data onto the heap, allocating a new buffer to hold it. +/// +/// The amount of data that a `SmallVec` can store inline depends on its backing store. The backing +/// store can be any type that implements the `Array` trait; usually it is a small fixed-sized +/// array. For example a `SmallVec<[u64; 8]>` can hold up to eight 64-bit integers inline. +/// +/// ## Example +/// +/// ```rust +/// use smallvec::SmallVec; +/// let mut v = SmallVec::<[u8; 4]>::new(); // initialize an empty vector +/// +/// // The vector can hold up to 4 items without spilling onto the heap. +/// v.extend(0..4); +/// assert_eq!(v.len(), 4); +/// assert!(!v.spilled()); +/// +/// // Pushing another element will force the buffer to spill: +/// v.push(4); +/// assert_eq!(v.len(), 5); +/// assert!(v.spilled()); +/// ``` +pub struct SmallVec<A: Array> { + // The capacity field is used to determine which of the storage variants is active: + // If capacity <= Self::inline_capacity() then the inline variant is used and capacity holds the current length of the vector (number of elements actually in use). + // If capacity > Self::inline_capacity() then the heap variant is used and capacity holds the size of the memory allocation. + capacity: usize, + data: SmallVecData<A>, +} + +impl<A: Array> SmallVec<A> { + /// Construct an empty vector + #[inline] + pub fn new() -> SmallVec<A> { + // Try to detect invalid custom implementations of `Array`. Hopefully, + // this check should be optimized away entirely for valid ones. + assert!( + mem::size_of::<A>() == A::size() * mem::size_of::<A::Item>() + && mem::align_of::<A>() >= mem::align_of::<A::Item>() + ); + SmallVec { + capacity: 0, + data: SmallVecData::from_inline(MaybeUninit::uninit()), + } + } + + /// Construct an empty vector with enough capacity pre-allocated to store at least `n` + /// elements. + /// + /// Will create a heap allocation only if `n` is larger than the inline capacity. + /// + /// ``` + /// # use smallvec::SmallVec; + /// + /// let v: SmallVec<[u8; 3]> = SmallVec::with_capacity(100); + /// + /// assert!(v.is_empty()); + /// assert!(v.capacity() >= 100); + /// ``` + #[inline] + pub fn with_capacity(n: usize) -> Self { + let mut v = SmallVec::new(); + v.reserve_exact(n); + v + } + + /// Construct a new `SmallVec` from a `Vec<A::Item>`. + /// + /// Elements will be copied to the inline buffer if `vec.capacity() <= Self::inline_capacity()`. + /// + /// ```rust + /// use smallvec::SmallVec; + /// + /// let vec = vec![1, 2, 3, 4, 5]; + /// let small_vec: SmallVec<[_; 3]> = SmallVec::from_vec(vec); + /// + /// assert_eq!(&*small_vec, &[1, 2, 3, 4, 5]); + /// ``` + #[inline] + pub fn from_vec(mut vec: Vec<A::Item>) -> SmallVec<A> { + if vec.capacity() <= Self::inline_capacity() { + // Cannot use Vec with smaller capacity + // because we use value of `Self::capacity` field as indicator. + unsafe { + let mut data = SmallVecData::<A>::from_inline(MaybeUninit::uninit()); + let len = vec.len(); + vec.set_len(0); + ptr::copy_nonoverlapping(vec.as_ptr(), data.inline_mut().as_ptr(), len); + + SmallVec { + capacity: len, + data, + } + } + } else { + let (ptr, cap, len) = (vec.as_mut_ptr(), vec.capacity(), vec.len()); + mem::forget(vec); + let ptr = NonNull::new(ptr) + // See docs: https://doc.rust-lang.org/std/vec/struct.Vec.html#method.as_mut_ptr + .expect("Cannot be null by `Vec` invariant"); + + SmallVec { + capacity: cap, + data: SmallVecData::from_heap(ptr, len), + } + } + } + + /// Constructs a new `SmallVec` on the stack from an `A` without + /// copying elements. + /// + /// ```rust + /// use smallvec::SmallVec; + /// + /// let buf = [1, 2, 3, 4, 5]; + /// let small_vec: SmallVec<_> = SmallVec::from_buf(buf); + /// + /// assert_eq!(&*small_vec, &[1, 2, 3, 4, 5]); + /// ``` + #[inline] + pub fn from_buf(buf: A) -> SmallVec<A> { + SmallVec { + capacity: A::size(), + data: SmallVecData::from_inline(MaybeUninit::new(buf)), + } + } + + /// Constructs a new `SmallVec` on the stack from an `A` without + /// copying elements. Also sets the length, which must be less or + /// equal to the size of `buf`. + /// + /// ```rust + /// use smallvec::SmallVec; + /// + /// let buf = [1, 2, 3, 4, 5, 0, 0, 0]; + /// let small_vec: SmallVec<_> = SmallVec::from_buf_and_len(buf, 5); + /// + /// assert_eq!(&*small_vec, &[1, 2, 3, 4, 5]); + /// ``` + #[inline] + pub fn from_buf_and_len(buf: A, len: usize) -> SmallVec<A> { + assert!(len <= A::size()); + unsafe { SmallVec::from_buf_and_len_unchecked(MaybeUninit::new(buf), len) } + } + + /// Constructs a new `SmallVec` on the stack from an `A` without + /// copying elements. Also sets the length. The user is responsible + /// for ensuring that `len <= A::size()`. + /// + /// ```rust + /// use smallvec::SmallVec; + /// use std::mem::MaybeUninit; + /// + /// let buf = [1, 2, 3, 4, 5, 0, 0, 0]; + /// let small_vec: SmallVec<_> = unsafe { + /// SmallVec::from_buf_and_len_unchecked(MaybeUninit::new(buf), 5) + /// }; + /// + /// assert_eq!(&*small_vec, &[1, 2, 3, 4, 5]); + /// ``` + #[inline] + pub unsafe fn from_buf_and_len_unchecked(buf: MaybeUninit<A>, len: usize) -> SmallVec<A> { + SmallVec { + capacity: len, + data: SmallVecData::from_inline(buf), + } + } + + /// Sets the length of a vector. + /// + /// This will explicitly set the size of the vector, without actually + /// modifying its buffers, so it is up to the caller to ensure that the + /// vector is actually the specified size. + pub unsafe fn set_len(&mut self, new_len: usize) { + let (_, len_ptr, _) = self.triple_mut(); + *len_ptr = new_len; + } + + /// The maximum number of elements this vector can hold inline + #[inline] + fn inline_capacity() -> usize { + if mem::size_of::<A::Item>() > 0 { + A::size() + } else { + // For zero-size items code like `ptr.add(offset)` always returns the same pointer. + // Therefore all items are at the same address, + // and any array size has capacity for infinitely many items. + // The capacity is limited by the bit width of the length field. + // + // `Vec` also does this: + // https://github.com/rust-lang/rust/blob/1.44.0/src/liballoc/raw_vec.rs#L186 + // + // In our case, this also ensures that a smallvec of zero-size items never spills, + // and we never try to allocate zero bytes which `std::alloc::alloc` disallows. + core::usize::MAX + } + } + + /// The maximum number of elements this vector can hold inline + #[inline] + pub fn inline_size(&self) -> usize { + Self::inline_capacity() + } + + /// The number of elements stored in the vector + #[inline] + pub fn len(&self) -> usize { + self.triple().1 + } + + /// Returns `true` if the vector is empty + #[inline] + pub fn is_empty(&self) -> bool { + self.len() == 0 + } + + /// The number of items the vector can hold without reallocating + #[inline] + pub fn capacity(&self) -> usize { + self.triple().2 + } + + /// Returns a tuple with (data ptr, len, capacity) + /// Useful to get all `SmallVec` properties with a single check of the current storage variant. + #[inline] + fn triple(&self) -> (ConstNonNull<A::Item>, usize, usize) { + unsafe { + if self.spilled() { + let (ptr, len) = self.data.heap(); + (ptr, len, self.capacity) + } else { + (self.data.inline(), self.capacity, Self::inline_capacity()) + } + } + } + + /// Returns a tuple with (data ptr, len ptr, capacity) + #[inline] + fn triple_mut(&mut self) -> (NonNull<A::Item>, &mut usize, usize) { + unsafe { + if self.spilled() { + let (ptr, len_ptr) = self.data.heap_mut(); + (ptr, len_ptr, self.capacity) + } else { + ( + self.data.inline_mut(), + &mut self.capacity, + Self::inline_capacity(), + ) + } + } + } + + /// Returns `true` if the data has spilled into a separate heap-allocated buffer. + #[inline] + pub fn spilled(&self) -> bool { + self.capacity > Self::inline_capacity() + } + + /// Creates a draining iterator that removes the specified range in the vector + /// and yields the removed items. + /// + /// Note 1: The element range is removed even if the iterator is only + /// partially consumed or not consumed at all. + /// + /// Note 2: It is unspecified how many elements are removed from the vector + /// if the `Drain` value is leaked. + /// + /// # Panics + /// + /// Panics if the starting point is greater than the end point or if + /// the end point is greater than the length of the vector. + pub fn drain<R>(&mut self, range: R) -> Drain<'_, A> + where + R: RangeBounds<usize>, + { + use core::ops::Bound::*; + + let len = self.len(); + let start = match range.start_bound() { + Included(&n) => n, + Excluded(&n) => n.checked_add(1).expect("Range start out of bounds"), + Unbounded => 0, + }; + let end = match range.end_bound() { + Included(&n) => n.checked_add(1).expect("Range end out of bounds"), + Excluded(&n) => n, + Unbounded => len, + }; + + assert!(start <= end); + assert!(end <= len); + + unsafe { + self.set_len(start); + + let range_slice = slice::from_raw_parts(self.as_ptr().add(start), end - start); + + Drain { + tail_start: end, + tail_len: len - end, + iter: range_slice.iter(), + // Since self is a &mut, passing it to a function would invalidate the slice iterator. + vec: NonNull::new_unchecked(self as *mut _), + } + } + } + + #[cfg(feature = "drain_filter")] + /// Creates an iterator which uses a closure to determine if an element should be removed. + /// + /// If the closure returns true, the element is removed and yielded. If the closure returns + /// false, the element will remain in the vector and will not be yielded by the iterator. + /// + /// Using this method is equivalent to the following code: + /// ``` + /// # use smallvec::SmallVec; + /// # let some_predicate = |x: &mut i32| { *x == 2 || *x == 3 || *x == 6 }; + /// # let mut vec: SmallVec<[i32; 8]> = SmallVec::from_slice(&[1i32, 2, 3, 4, 5, 6]); + /// let mut i = 0; + /// while i < vec.len() { + /// if some_predicate(&mut vec[i]) { + /// let val = vec.remove(i); + /// // your code here + /// } else { + /// i += 1; + /// } + /// } + /// + /// # assert_eq!(vec, SmallVec::<[i32; 8]>::from_slice(&[1i32, 4, 5])); + /// ``` + /// /// + /// But `drain_filter` is easier to use. `drain_filter` is also more efficient, + /// because it can backshift the elements of the array in bulk. + /// + /// Note that `drain_filter` also lets you mutate every element in the filter closure, + /// regardless of whether you choose to keep or remove it. + /// + /// # Examples + /// + /// Splitting an array into evens and odds, reusing the original allocation: + /// + /// ``` + /// # use smallvec::SmallVec; + /// let mut numbers: SmallVec<[i32; 16]> = SmallVec::from_slice(&[1i32, 2, 3, 4, 5, 6, 8, 9, 11, 13, 14, 15]); + /// + /// let evens = numbers.drain_filter(|x| *x % 2 == 0).collect::<SmallVec<[i32; 16]>>(); + /// let odds = numbers; + /// + /// assert_eq!(evens, SmallVec::<[i32; 16]>::from_slice(&[2i32, 4, 6, 8, 14])); + /// assert_eq!(odds, SmallVec::<[i32; 16]>::from_slice(&[1i32, 3, 5, 9, 11, 13, 15])); + /// ``` + pub fn drain_filter<F>(&mut self, filter: F) -> DrainFilter<'_, A, F,> + where + F: FnMut(&mut A::Item) -> bool, + { + let old_len = self.len(); + + // Guard against us getting leaked (leak amplification) + unsafe { + self.set_len(0); + } + + DrainFilter { vec: self, idx: 0, del: 0, old_len, pred: filter, panic_flag: false } + } + + /// Append an item to the vector. + #[inline] + pub fn push(&mut self, value: A::Item) { + unsafe { + let (mut ptr, mut len, cap) = self.triple_mut(); + if *len == cap { + self.reserve_one_unchecked(); + let (heap_ptr, heap_len) = self.data.heap_mut(); + ptr = heap_ptr; + len = heap_len; + } + ptr::write(ptr.as_ptr().add(*len), value); + *len += 1; + } + } + + /// Remove an item from the end of the vector and return it, or None if empty. + #[inline] + pub fn pop(&mut self) -> Option<A::Item> { + unsafe { + let (ptr, len_ptr, _) = self.triple_mut(); + let ptr: *const _ = ptr.as_ptr(); + if *len_ptr == 0 { + return None; + } + let last_index = *len_ptr - 1; + *len_ptr = last_index; + Some(ptr::read(ptr.add(last_index))) + } + } + + /// Moves all the elements of `other` into `self`, leaving `other` empty. + /// + /// # Example + /// + /// ``` + /// # use smallvec::{SmallVec, smallvec}; + /// let mut v0: SmallVec<[u8; 16]> = smallvec![1, 2, 3]; + /// let mut v1: SmallVec<[u8; 32]> = smallvec![4, 5, 6]; + /// v0.append(&mut v1); + /// assert_eq!(*v0, [1, 2, 3, 4, 5, 6]); + /// assert_eq!(*v1, []); + /// ``` + pub fn append<B>(&mut self, other: &mut SmallVec<B>) + where + B: Array<Item = A::Item>, + { + self.extend(other.drain(..)) + } + + /// Re-allocate to set the capacity to `max(new_cap, inline_size())`. + /// + /// Panics if `new_cap` is less than the vector's length + /// or if the capacity computation overflows `usize`. + pub fn grow(&mut self, new_cap: usize) { + infallible(self.try_grow(new_cap)) + } + + /// Re-allocate to set the capacity to `max(new_cap, inline_size())`. + /// + /// Panics if `new_cap` is less than the vector's length + pub fn try_grow(&mut self, new_cap: usize) -> Result<(), CollectionAllocErr> { + unsafe { + let unspilled = !self.spilled(); + let (ptr, &mut len, cap) = self.triple_mut(); + assert!(new_cap >= len); + if new_cap <= Self::inline_capacity() { + if unspilled { + return Ok(()); + } + self.data = SmallVecData::from_inline(MaybeUninit::uninit()); + ptr::copy_nonoverlapping(ptr.as_ptr(), self.data.inline_mut().as_ptr(), len); + self.capacity = len; + deallocate(ptr, cap); + } else if new_cap != cap { + let layout = layout_array::<A::Item>(new_cap)?; + debug_assert!(layout.size() > 0); + let new_alloc; + if unspilled { + new_alloc = NonNull::new(alloc::alloc::alloc(layout)) + .ok_or(CollectionAllocErr::AllocErr { layout })? + .cast(); + ptr::copy_nonoverlapping(ptr.as_ptr(), new_alloc.as_ptr(), len); + } else { + // This should never fail since the same succeeded + // when previously allocating `ptr`. + let old_layout = layout_array::<A::Item>(cap)?; + + let new_ptr = + alloc::alloc::realloc(ptr.as_ptr() as *mut u8, old_layout, layout.size()); + new_alloc = NonNull::new(new_ptr) + .ok_or(CollectionAllocErr::AllocErr { layout })? + .cast(); + } + self.data = SmallVecData::from_heap(new_alloc, len); + self.capacity = new_cap; + } + Ok(()) + } + } + + /// Reserve capacity for `additional` more elements to be inserted. + /// + /// May reserve more space to avoid frequent reallocations. + /// + /// Panics if the capacity computation overflows `usize`. + #[inline] + pub fn reserve(&mut self, additional: usize) { + infallible(self.try_reserve(additional)) + } + + /// Internal method used to grow in push() and insert(), where we know already we have to grow. + #[cold] + fn reserve_one_unchecked(&mut self) { + debug_assert_eq!(self.len(), self.capacity()); + let new_cap = self.len() + .checked_add(1) + .and_then(usize::checked_next_power_of_two) + .expect("capacity overflow"); + infallible(self.try_grow(new_cap)) + } + + /// Reserve capacity for `additional` more elements to be inserted. + /// + /// May reserve more space to avoid frequent reallocations. + pub fn try_reserve(&mut self, additional: usize) -> Result<(), CollectionAllocErr> { + // prefer triple_mut() even if triple() would work so that the optimizer removes duplicated + // calls to it from callers. + let (_, &mut len, cap) = self.triple_mut(); + if cap - len >= additional { + return Ok(()); + } + let new_cap = len + .checked_add(additional) + .and_then(usize::checked_next_power_of_two) + .ok_or(CollectionAllocErr::CapacityOverflow)?; + self.try_grow(new_cap) + } + + /// Reserve the minimum capacity for `additional` more elements to be inserted. + /// + /// Panics if the new capacity overflows `usize`. + pub fn reserve_exact(&mut self, additional: usize) { + infallible(self.try_reserve_exact(additional)) + } + + /// Reserve the minimum capacity for `additional` more elements to be inserted. + pub fn try_reserve_exact(&mut self, additional: usize) -> Result<(), CollectionAllocErr> { + let (_, &mut len, cap) = self.triple_mut(); + if cap - len >= additional { + return Ok(()); + } + let new_cap = len + .checked_add(additional) + .ok_or(CollectionAllocErr::CapacityOverflow)?; + self.try_grow(new_cap) + } + + /// Shrink the capacity of the vector as much as possible. + /// + /// When possible, this will move data from an external heap buffer to the vector's inline + /// storage. + pub fn shrink_to_fit(&mut self) { + if !self.spilled() { + return; + } + let len = self.len(); + if self.inline_size() >= len { + unsafe { + let (ptr, len) = self.data.heap(); + self.data = SmallVecData::from_inline(MaybeUninit::uninit()); + ptr::copy_nonoverlapping(ptr.as_ptr(), self.data.inline_mut().as_ptr(), len); + deallocate(ptr.0, self.capacity); + self.capacity = len; + } + } else if self.capacity() > len { + self.grow(len); + } + } + + /// Shorten the vector, keeping the first `len` elements and dropping the rest. + /// + /// If `len` is greater than or equal to the vector's current length, this has no + /// effect. + /// + /// This does not re-allocate. If you want the vector's capacity to shrink, call + /// `shrink_to_fit` after truncating. + pub fn truncate(&mut self, len: usize) { + unsafe { + let (ptr, len_ptr, _) = self.triple_mut(); + let ptr = ptr.as_ptr(); + while len < *len_ptr { + let last_index = *len_ptr - 1; + *len_ptr = last_index; + ptr::drop_in_place(ptr.add(last_index)); + } + } + } + + /// Extracts a slice containing the entire vector. + /// + /// Equivalent to `&s[..]`. + pub fn as_slice(&self) -> &[A::Item] { + self + } + + /// Extracts a mutable slice of the entire vector. + /// + /// Equivalent to `&mut s[..]`. + pub fn as_mut_slice(&mut self) -> &mut [A::Item] { + self + } + + /// Remove the element at position `index`, replacing it with the last element. + /// + /// This does not preserve ordering, but is O(1). + /// + /// Panics if `index` is out of bounds. + #[inline] + pub fn swap_remove(&mut self, index: usize) -> A::Item { + let len = self.len(); + self.swap(len - 1, index); + self.pop() + .unwrap_or_else(|| unsafe { unreachable_unchecked() }) + } + + /// Remove all elements from the vector. + #[inline] + pub fn clear(&mut self) { + self.truncate(0); + } + + /// Remove and return the element at position `index`, shifting all elements after it to the + /// left. + /// + /// Panics if `index` is out of bounds. + pub fn remove(&mut self, index: usize) -> A::Item { + unsafe { + let (ptr, len_ptr, _) = self.triple_mut(); + let len = *len_ptr; + assert!(index < len); + *len_ptr = len - 1; + let ptr = ptr.as_ptr().add(index); + let item = ptr::read(ptr); + ptr::copy(ptr.add(1), ptr, len - index - 1); + item + } + } + + /// Insert an element at position `index`, shifting all elements after it to the right. + /// + /// Panics if `index > len`. + pub fn insert(&mut self, index: usize, element: A::Item) { + unsafe { + let (mut ptr, mut len_ptr, cap) = self.triple_mut(); + if *len_ptr == cap { + self.reserve_one_unchecked(); + let (heap_ptr, heap_len_ptr) = self.data.heap_mut(); + ptr = heap_ptr; + len_ptr = heap_len_ptr; + } + let mut ptr = ptr.as_ptr(); + let len = *len_ptr; + ptr = ptr.add(index); + if index < len { + ptr::copy(ptr, ptr.add(1), len - index); + } else if index == len { + // No elements need shifting. + } else { + panic!("index exceeds length"); + } + *len_ptr = len + 1; + ptr::write(ptr, element); + } + } + + /// Insert multiple elements at position `index`, shifting all following elements toward the + /// back. + pub fn insert_many<I: IntoIterator<Item = A::Item>>(&mut self, index: usize, iterable: I) { + let mut iter = iterable.into_iter(); + if index == self.len() { + return self.extend(iter); + } + + let (lower_size_bound, _) = iter.size_hint(); + assert!(lower_size_bound <= core::isize::MAX as usize); // Ensure offset is indexable + assert!(index + lower_size_bound >= index); // Protect against overflow + + let mut num_added = 0; + let old_len = self.len(); + assert!(index <= old_len); + + unsafe { + // Reserve space for `lower_size_bound` elements. + self.reserve(lower_size_bound); + let start = self.as_mut_ptr(); + let ptr = start.add(index); + + // Move the trailing elements. + ptr::copy(ptr, ptr.add(lower_size_bound), old_len - index); + + // In case the iterator panics, don't double-drop the items we just copied above. + self.set_len(0); + let mut guard = DropOnPanic { + start, + skip: index..(index + lower_size_bound), + len: old_len + lower_size_bound, + }; + + // The set_len above invalidates the previous pointers, so we must re-create them. + let start = self.as_mut_ptr(); + let ptr = start.add(index); + + while num_added < lower_size_bound { + let element = match iter.next() { + Some(x) => x, + None => break, + }; + let cur = ptr.add(num_added); + ptr::write(cur, element); + guard.skip.start += 1; + num_added += 1; + } + + if num_added < lower_size_bound { + // Iterator provided fewer elements than the hint. Move the tail backward. + ptr::copy( + ptr.add(lower_size_bound), + ptr.add(num_added), + old_len - index, + ); + } + // There are no more duplicate or uninitialized slots, so the guard is not needed. + self.set_len(old_len + num_added); + mem::forget(guard); + } + + // Insert any remaining elements one-by-one. + for element in iter { + self.insert(index + num_added, element); + num_added += 1; + } + + struct DropOnPanic<T> { + start: *mut T, + skip: Range<usize>, // Space we copied-out-of, but haven't written-to yet. + len: usize, + } + + impl<T> Drop for DropOnPanic<T> { + fn drop(&mut self) { + for i in 0..self.len { + if !self.skip.contains(&i) { + unsafe { + ptr::drop_in_place(self.start.add(i)); + } + } + } + } + } + } + + /// Convert a `SmallVec` to a `Vec`, without reallocating if the `SmallVec` has already spilled onto + /// the heap. + pub fn into_vec(mut self) -> Vec<A::Item> { + if self.spilled() { + unsafe { + let (ptr, &mut len) = self.data.heap_mut(); + let v = Vec::from_raw_parts(ptr.as_ptr(), len, self.capacity); + mem::forget(self); + v + } + } else { + self.into_iter().collect() + } + } + + /// Converts a `SmallVec` into a `Box<[T]>` without reallocating if the `SmallVec` has already spilled + /// onto the heap. + /// + /// Note that this will drop any excess capacity. + pub fn into_boxed_slice(self) -> Box<[A::Item]> { + self.into_vec().into_boxed_slice() + } + + /// Convert the `SmallVec` into an `A` if possible. Otherwise return `Err(Self)`. + /// + /// This method returns `Err(Self)` if the `SmallVec` is too short (and the `A` contains uninitialized elements), + /// or if the `SmallVec` is too long (and all the elements were spilled to the heap). + pub fn into_inner(self) -> Result<A, Self> { + if self.spilled() || self.len() != A::size() { + // Note: A::size, not Self::inline_capacity + Err(self) + } else { + unsafe { + let data = ptr::read(&self.data); + mem::forget(self); + Ok(data.into_inline().assume_init()) + } + } + } + + /// Retains only the elements specified by the predicate. + /// + /// In other words, remove all elements `e` such that `f(&e)` returns `false`. + /// This method operates in place and preserves the order of the retained + /// elements. + pub fn retain<F: FnMut(&mut A::Item) -> bool>(&mut self, mut f: F) { + let mut del = 0; + let len = self.len(); + for i in 0..len { + if !f(&mut self[i]) { + del += 1; + } else if del > 0 { + self.swap(i - del, i); + } + } + self.truncate(len - del); + } + + /// Retains only the elements specified by the predicate. + /// + /// This method is identical in behaviour to [`retain`]; it is included only + /// to maintain api-compatability with `std::Vec`, where the methods are + /// separate for historical reasons. + pub fn retain_mut<F: FnMut(&mut A::Item) -> bool>(&mut self, f: F) { + self.retain(f) + } + + /// Removes consecutive duplicate elements. + pub fn dedup(&mut self) + where + A::Item: PartialEq<A::Item>, + { + self.dedup_by(|a, b| a == b); + } + + /// Removes consecutive duplicate elements using the given equality relation. + pub fn dedup_by<F>(&mut self, mut same_bucket: F) + where + F: FnMut(&mut A::Item, &mut A::Item) -> bool, + { + // See the implementation of Vec::dedup_by in the + // standard library for an explanation of this algorithm. + let len = self.len(); + if len <= 1 { + return; + } + + let ptr = self.as_mut_ptr(); + let mut w: usize = 1; + + unsafe { + for r in 1..len { + let p_r = ptr.add(r); + let p_wm1 = ptr.add(w - 1); + if !same_bucket(&mut *p_r, &mut *p_wm1) { + if r != w { + let p_w = p_wm1.add(1); + mem::swap(&mut *p_r, &mut *p_w); + } + w += 1; + } + } + } + + self.truncate(w); + } + + /// Removes consecutive elements that map to the same key. + pub fn dedup_by_key<F, K>(&mut self, mut key: F) + where + F: FnMut(&mut A::Item) -> K, + K: PartialEq<K>, + { + self.dedup_by(|a, b| key(a) == key(b)); + } + + /// Resizes the `SmallVec` in-place so that `len` is equal to `new_len`. + /// + /// If `new_len` is greater than `len`, the `SmallVec` is extended by the difference, with each + /// additional slot filled with the result of calling the closure `f`. The return values from `f` + /// will end up in the `SmallVec` in the order they have been generated. + /// + /// If `new_len` is less than `len`, the `SmallVec` is simply truncated. + /// + /// This method uses a closure to create new values on every push. If you'd rather `Clone` a given + /// value, use `resize`. If you want to use the `Default` trait to generate values, you can pass + /// `Default::default()` as the second argument. + /// + /// Added for `std::vec::Vec` compatibility (added in Rust 1.33.0) + /// + /// ``` + /// # use smallvec::{smallvec, SmallVec}; + /// let mut vec : SmallVec<[_; 4]> = smallvec![1, 2, 3]; + /// vec.resize_with(5, Default::default); + /// assert_eq!(&*vec, &[1, 2, 3, 0, 0]); + /// + /// let mut vec : SmallVec<[_; 4]> = smallvec![]; + /// let mut p = 1; + /// vec.resize_with(4, || { p *= 2; p }); + /// assert_eq!(&*vec, &[2, 4, 8, 16]); + /// ``` + pub fn resize_with<F>(&mut self, new_len: usize, f: F) + where + F: FnMut() -> A::Item, + { + let old_len = self.len(); + if old_len < new_len { + let mut f = f; + let additional = new_len - old_len; + self.reserve(additional); + for _ in 0..additional { + self.push(f()); + } + } else if old_len > new_len { + self.truncate(new_len); + } + } + + /// Creates a `SmallVec` directly from the raw components of another + /// `SmallVec`. + /// + /// # Safety + /// + /// This is highly unsafe, due to the number of invariants that aren't + /// checked: + /// + /// * `ptr` needs to have been previously allocated via `SmallVec` for its + /// spilled storage (at least, it's highly likely to be incorrect if it + /// wasn't). + /// * `ptr`'s `A::Item` type needs to be the same size and alignment that + /// it was allocated with + /// * `length` needs to be less than or equal to `capacity`. + /// * `capacity` needs to be the capacity that the pointer was allocated + /// with. + /// + /// Violating these may cause problems like corrupting the allocator's + /// internal data structures. + /// + /// Additionally, `capacity` must be greater than the amount of inline + /// storage `A` has; that is, the new `SmallVec` must need to spill over + /// into heap allocated storage. This condition is asserted against. + /// + /// The ownership of `ptr` is effectively transferred to the + /// `SmallVec` which may then deallocate, reallocate or change the + /// contents of memory pointed to by the pointer at will. Ensure + /// that nothing else uses the pointer after calling this + /// function. + /// + /// # Examples + /// + /// ``` + /// # use smallvec::{smallvec, SmallVec}; + /// use std::mem; + /// use std::ptr; + /// + /// fn main() { + /// let mut v: SmallVec<[_; 1]> = smallvec![1, 2, 3]; + /// + /// // Pull out the important parts of `v`. + /// let p = v.as_mut_ptr(); + /// let len = v.len(); + /// let cap = v.capacity(); + /// let spilled = v.spilled(); + /// + /// unsafe { + /// // Forget all about `v`. The heap allocation that stored the + /// // three values won't be deallocated. + /// mem::forget(v); + /// + /// // Overwrite memory with [4, 5, 6]. + /// // + /// // This is only safe if `spilled` is true! Otherwise, we are + /// // writing into the old `SmallVec`'s inline storage on the + /// // stack. + /// assert!(spilled); + /// for i in 0..len { + /// ptr::write(p.add(i), 4 + i); + /// } + /// + /// // Put everything back together into a SmallVec with a different + /// // amount of inline storage, but which is still less than `cap`. + /// let rebuilt = SmallVec::<[_; 2]>::from_raw_parts(p, len, cap); + /// assert_eq!(&*rebuilt, &[4, 5, 6]); + /// } + /// } + #[inline] + pub unsafe fn from_raw_parts(ptr: *mut A::Item, length: usize, capacity: usize) -> SmallVec<A> { + // SAFETY: We require caller to provide same ptr as we alloc + // and we never alloc null pointer. + let ptr = unsafe { + debug_assert!(!ptr.is_null(), "Called `from_raw_parts` with null pointer."); + NonNull::new_unchecked(ptr) + }; + assert!(capacity > Self::inline_capacity()); + SmallVec { + capacity, + data: SmallVecData::from_heap(ptr, length), + } + } + + /// Returns a raw pointer to the vector's buffer. + pub fn as_ptr(&self) -> *const A::Item { + // We shadow the slice method of the same name to avoid going through + // `deref`, which creates an intermediate reference that may place + // additional safety constraints on the contents of the slice. + self.triple().0.as_ptr() + } + + /// Returns a raw mutable pointer to the vector's buffer. + pub fn as_mut_ptr(&mut self) -> *mut A::Item { + // We shadow the slice method of the same name to avoid going through + // `deref_mut`, which creates an intermediate reference that may place + // additional safety constraints on the contents of the slice. + self.triple_mut().0.as_ptr() + } +} + +impl<A: Array> SmallVec<A> +where + A::Item: Copy, +{ + /// Copy the elements from a slice into a new `SmallVec`. + /// + /// For slices of `Copy` types, this is more efficient than `SmallVec::from(slice)`. + pub fn from_slice(slice: &[A::Item]) -> Self { + let len = slice.len(); + if len <= Self::inline_capacity() { + SmallVec { + capacity: len, + data: SmallVecData::from_inline(unsafe { + let mut data: MaybeUninit<A> = MaybeUninit::uninit(); + ptr::copy_nonoverlapping( + slice.as_ptr(), + data.as_mut_ptr() as *mut A::Item, + len, + ); + data + }), + } + } else { + let mut b = slice.to_vec(); + let cap = b.capacity(); + let ptr = NonNull::new(b.as_mut_ptr()).expect("Vec always contain non null pointers."); + mem::forget(b); + SmallVec { + capacity: cap, + data: SmallVecData::from_heap(ptr, len), + } + } + } + + /// Copy elements from a slice into the vector at position `index`, shifting any following + /// elements toward the back. + /// + /// For slices of `Copy` types, this is more efficient than `insert`. + #[inline] + pub fn insert_from_slice(&mut self, index: usize, slice: &[A::Item]) { + self.reserve(slice.len()); + + let len = self.len(); + assert!(index <= len); + + unsafe { + let slice_ptr = slice.as_ptr(); + let ptr = self.as_mut_ptr().add(index); + ptr::copy(ptr, ptr.add(slice.len()), len - index); + ptr::copy_nonoverlapping(slice_ptr, ptr, slice.len()); + self.set_len(len + slice.len()); + } + } + + /// Copy elements from a slice and append them to the vector. + /// + /// For slices of `Copy` types, this is more efficient than `extend`. + #[inline] + pub fn extend_from_slice(&mut self, slice: &[A::Item]) { + let len = self.len(); + self.insert_from_slice(len, slice); + } +} + +impl<A: Array> SmallVec<A> +where + A::Item: Clone, +{ + /// Resizes the vector so that its length is equal to `len`. + /// + /// If `len` is less than the current length, the vector simply truncated. + /// + /// If `len` is greater than the current length, `value` is appended to the + /// vector until its length equals `len`. + pub fn resize(&mut self, len: usize, value: A::Item) { + let old_len = self.len(); + + if len > old_len { + self.extend(repeat(value).take(len - old_len)); + } else { + self.truncate(len); + } + } + + /// Creates a `SmallVec` with `n` copies of `elem`. + /// ``` + /// use smallvec::SmallVec; + /// + /// let v = SmallVec::<[char; 128]>::from_elem('d', 2); + /// assert_eq!(v, SmallVec::from_buf(['d', 'd'])); + /// ``` + pub fn from_elem(elem: A::Item, n: usize) -> Self { + if n > Self::inline_capacity() { + vec![elem; n].into() + } else { + let mut v = SmallVec::<A>::new(); + unsafe { + let (ptr, len_ptr, _) = v.triple_mut(); + let ptr = ptr.as_ptr(); + let mut local_len = SetLenOnDrop::new(len_ptr); + + for i in 0..n { + ::core::ptr::write(ptr.add(i), elem.clone()); + local_len.increment_len(1); + } + } + v + } + } +} + +impl<A: Array> ops::Deref for SmallVec<A> { + type Target = [A::Item]; + #[inline] + fn deref(&self) -> &[A::Item] { + unsafe { + let (ptr, len, _) = self.triple(); + slice::from_raw_parts(ptr.as_ptr(), len) + } + } +} + +impl<A: Array> ops::DerefMut for SmallVec<A> { + #[inline] + fn deref_mut(&mut self) -> &mut [A::Item] { + unsafe { + let (ptr, &mut len, _) = self.triple_mut(); + slice::from_raw_parts_mut(ptr.as_ptr(), len) + } + } +} + +impl<A: Array> AsRef<[A::Item]> for SmallVec<A> { + #[inline] + fn as_ref(&self) -> &[A::Item] { + self + } +} + +impl<A: Array> AsMut<[A::Item]> for SmallVec<A> { + #[inline] + fn as_mut(&mut self) -> &mut [A::Item] { + self + } +} + +impl<A: Array> Borrow<[A::Item]> for SmallVec<A> { + #[inline] + fn borrow(&self) -> &[A::Item] { + self + } +} + +impl<A: Array> BorrowMut<[A::Item]> for SmallVec<A> { + #[inline] + fn borrow_mut(&mut self) -> &mut [A::Item] { + self + } +} + +#[cfg(feature = "write")] +#[cfg_attr(docsrs, doc(cfg(feature = "write")))] +impl<A: Array<Item = u8>> io::Write for SmallVec<A> { + #[inline] + fn write(&mut self, buf: &[u8]) -> io::Result<usize> { + self.extend_from_slice(buf); + Ok(buf.len()) + } + + #[inline] + fn write_all(&mut self, buf: &[u8]) -> io::Result<()> { + self.extend_from_slice(buf); + Ok(()) + } + + #[inline] + fn flush(&mut self) -> io::Result<()> { + Ok(()) + } +} + +#[cfg(feature = "serde")] +#[cfg_attr(docsrs, doc(cfg(feature = "serde")))] +impl<A: Array> Serialize for SmallVec<A> +where + A::Item: Serialize, +{ + fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> { + let mut state = serializer.serialize_seq(Some(self.len()))?; + for item in self { + state.serialize_element(&item)?; + } + state.end() + } +} + +#[cfg(feature = "serde")] +#[cfg_attr(docsrs, doc(cfg(feature = "serde")))] +impl<'de, A: Array> Deserialize<'de> for SmallVec<A> +where + A::Item: Deserialize<'de>, +{ + fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> { + deserializer.deserialize_seq(SmallVecVisitor { + phantom: PhantomData, + }) + } +} + +#[cfg(feature = "serde")] +struct SmallVecVisitor<A> { + phantom: PhantomData<A>, +} + +#[cfg(feature = "serde")] +impl<'de, A: Array> Visitor<'de> for SmallVecVisitor<A> +where + A::Item: Deserialize<'de>, +{ + type Value = SmallVec<A>; + + fn expecting(&self, formatter: &mut fmt::Formatter<'_>) -> fmt::Result { + formatter.write_str("a sequence") + } + + fn visit_seq<B>(self, mut seq: B) -> Result<Self::Value, B::Error> + where + B: SeqAccess<'de>, + { + use serde::de::Error; + let len = seq.size_hint().unwrap_or(0); + let mut values = SmallVec::new(); + values.try_reserve(len).map_err(B::Error::custom)?; + + while let Some(value) = seq.next_element()? { + values.push(value); + } + + Ok(values) + } +} + +#[cfg(feature = "specialization")] +trait SpecFrom<A: Array, S> { + fn spec_from(slice: S) -> SmallVec<A>; +} + +#[cfg(feature = "specialization")] +mod specialization; + +#[cfg(feature = "arbitrary")] +mod arbitrary; + +#[cfg(feature = "specialization")] +impl<'a, A: Array> SpecFrom<A, &'a [A::Item]> for SmallVec<A> +where + A::Item: Copy, +{ + #[inline] + fn spec_from(slice: &'a [A::Item]) -> SmallVec<A> { + SmallVec::from_slice(slice) + } +} + +impl<'a, A: Array> From<&'a [A::Item]> for SmallVec<A> +where + A::Item: Clone, +{ + #[cfg(not(feature = "specialization"))] + #[inline] + fn from(slice: &'a [A::Item]) -> SmallVec<A> { + slice.iter().cloned().collect() + } + + #[cfg(feature = "specialization")] + #[inline] + fn from(slice: &'a [A::Item]) -> SmallVec<A> { + SmallVec::spec_from(slice) + } +} + +impl<A: Array> From<Vec<A::Item>> for SmallVec<A> { + #[inline] + fn from(vec: Vec<A::Item>) -> SmallVec<A> { + SmallVec::from_vec(vec) + } +} + +impl<A: Array> From<A> for SmallVec<A> { + #[inline] + fn from(array: A) -> SmallVec<A> { + SmallVec::from_buf(array) + } +} + +impl<A: Array, I: SliceIndex<[A::Item]>> ops::Index<I> for SmallVec<A> { + type Output = I::Output; + + fn index(&self, index: I) -> &I::Output { + &(**self)[index] + } +} + +impl<A: Array, I: SliceIndex<[A::Item]>> ops::IndexMut<I> for SmallVec<A> { + fn index_mut(&mut self, index: I) -> &mut I::Output { + &mut (&mut **self)[index] + } +} + +#[allow(deprecated)] +impl<A: Array> ExtendFromSlice<A::Item> for SmallVec<A> +where + A::Item: Copy, +{ + fn extend_from_slice(&mut self, other: &[A::Item]) { + SmallVec::extend_from_slice(self, other) + } +} + +impl<A: Array> FromIterator<A::Item> for SmallVec<A> { + #[inline] + fn from_iter<I: IntoIterator<Item = A::Item>>(iterable: I) -> SmallVec<A> { + let mut v = SmallVec::new(); + v.extend(iterable); + v + } +} + +impl<A: Array> Extend<A::Item> for SmallVec<A> { + fn extend<I: IntoIterator<Item = A::Item>>(&mut self, iterable: I) { + let mut iter = iterable.into_iter(); + let (lower_size_bound, _) = iter.size_hint(); + self.reserve(lower_size_bound); + + unsafe { + let (ptr, len_ptr, cap) = self.triple_mut(); + let ptr = ptr.as_ptr(); + let mut len = SetLenOnDrop::new(len_ptr); + while len.get() < cap { + if let Some(out) = iter.next() { + ptr::write(ptr.add(len.get()), out); + len.increment_len(1); + } else { + return; + } + } + } + + for elem in iter { + self.push(elem); + } + } +} + +impl<A: Array> fmt::Debug for SmallVec<A> +where + A::Item: fmt::Debug, +{ + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_list().entries(self.iter()).finish() + } +} + +impl<A: Array> Default for SmallVec<A> { + #[inline] + fn default() -> SmallVec<A> { + SmallVec::new() + } +} + +#[cfg(feature = "may_dangle")] +unsafe impl<#[may_dangle] A: Array> Drop for SmallVec<A> { + fn drop(&mut self) { + unsafe { + if self.spilled() { + let (ptr, &mut len) = self.data.heap_mut(); + Vec::from_raw_parts(ptr.as_ptr(), len, self.capacity); + } else { + ptr::drop_in_place(&mut self[..]); + } + } + } +} + +#[cfg(not(feature = "may_dangle"))] +impl<A: Array> Drop for SmallVec<A> { + fn drop(&mut self) { + unsafe { + if self.spilled() { + let (ptr, &mut len) = self.data.heap_mut(); + drop(Vec::from_raw_parts(ptr.as_ptr(), len, self.capacity)); + } else { + ptr::drop_in_place(&mut self[..]); + } + } + } +} + +impl<A: Array> Clone for SmallVec<A> +where + A::Item: Clone, +{ + #[inline] + fn clone(&self) -> SmallVec<A> { + SmallVec::from(self.as_slice()) + } + + fn clone_from(&mut self, source: &Self) { + // Inspired from `impl Clone for Vec`. + + // drop anything that will not be overwritten + self.truncate(source.len()); + + // self.len <= other.len due to the truncate above, so the + // slices here are always in-bounds. + let (init, tail) = source.split_at(self.len()); + + // reuse the contained values' allocations/resources. + self.clone_from_slice(init); + self.extend(tail.iter().cloned()); + } +} + +impl<A: Array, B: Array> PartialEq<SmallVec<B>> for SmallVec<A> +where + A::Item: PartialEq<B::Item>, +{ + #[inline] + fn eq(&self, other: &SmallVec<B>) -> bool { + self[..] == other[..] + } +} + +impl<A: Array> Eq for SmallVec<A> where A::Item: Eq {} + +impl<A: Array> PartialOrd for SmallVec<A> +where + A::Item: PartialOrd, +{ + #[inline] + fn partial_cmp(&self, other: &SmallVec<A>) -> Option<cmp::Ordering> { + PartialOrd::partial_cmp(&**self, &**other) + } +} + +impl<A: Array> Ord for SmallVec<A> +where + A::Item: Ord, +{ + #[inline] + fn cmp(&self, other: &SmallVec<A>) -> cmp::Ordering { + Ord::cmp(&**self, &**other) + } +} + +impl<A: Array> Hash for SmallVec<A> +where + A::Item: Hash, +{ + fn hash<H: Hasher>(&self, state: &mut H) { + (**self).hash(state) + } +} + +unsafe impl<A: Array> Send for SmallVec<A> where A::Item: Send {} + +/// An iterator that consumes a `SmallVec` and yields its items by value. +/// +/// Returned from [`SmallVec::into_iter`][1]. +/// +/// [1]: struct.SmallVec.html#method.into_iter +pub struct IntoIter<A: Array> { + data: SmallVec<A>, + current: usize, + end: usize, +} + +impl<A: Array> fmt::Debug for IntoIter<A> +where + A::Item: fmt::Debug, +{ + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_tuple("IntoIter").field(&self.as_slice()).finish() + } +} + +impl<A: Array + Clone> Clone for IntoIter<A> +where + A::Item: Clone, +{ + fn clone(&self) -> IntoIter<A> { + SmallVec::from(self.as_slice()).into_iter() + } +} + +impl<A: Array> Drop for IntoIter<A> { + fn drop(&mut self) { + for _ in self {} + } +} + +impl<A: Array> Iterator for IntoIter<A> { + type Item = A::Item; + + #[inline] + fn next(&mut self) -> Option<A::Item> { + if self.current == self.end { + None + } else { + unsafe { + let current = self.current; + self.current += 1; + Some(ptr::read(self.data.as_ptr().add(current))) + } + } + } + + #[inline] + fn size_hint(&self) -> (usize, Option<usize>) { + let size = self.end - self.current; + (size, Some(size)) + } +} + +impl<A: Array> DoubleEndedIterator for IntoIter<A> { + #[inline] + fn next_back(&mut self) -> Option<A::Item> { + if self.current == self.end { + None + } else { + unsafe { + self.end -= 1; + Some(ptr::read(self.data.as_ptr().add(self.end))) + } + } + } +} + +impl<A: Array> ExactSizeIterator for IntoIter<A> {} +impl<A: Array> FusedIterator for IntoIter<A> {} + +impl<A: Array> IntoIter<A> { + /// Returns the remaining items of this iterator as a slice. + pub fn as_slice(&self) -> &[A::Item] { + let len = self.end - self.current; + unsafe { core::slice::from_raw_parts(self.data.as_ptr().add(self.current), len) } + } + + /// Returns the remaining items of this iterator as a mutable slice. + pub fn as_mut_slice(&mut self) -> &mut [A::Item] { + let len = self.end - self.current; + unsafe { core::slice::from_raw_parts_mut(self.data.as_mut_ptr().add(self.current), len) } + } +} + +impl<A: Array> IntoIterator for SmallVec<A> { + type IntoIter = IntoIter<A>; + type Item = A::Item; + fn into_iter(mut self) -> Self::IntoIter { + unsafe { + // Set SmallVec len to zero as `IntoIter` drop handles dropping of the elements + let len = self.len(); + self.set_len(0); + IntoIter { + data: self, + current: 0, + end: len, + } + } + } +} + +impl<'a, A: Array> IntoIterator for &'a SmallVec<A> { + type IntoIter = slice::Iter<'a, A::Item>; + type Item = &'a A::Item; + fn into_iter(self) -> Self::IntoIter { + self.iter() + } +} + +impl<'a, A: Array> IntoIterator for &'a mut SmallVec<A> { + type IntoIter = slice::IterMut<'a, A::Item>; + type Item = &'a mut A::Item; + fn into_iter(self) -> Self::IntoIter { + self.iter_mut() + } +} + +/// Types that can be used as the backing store for a [`SmallVec`]. +pub unsafe trait Array { + /// The type of the array's elements. + type Item; + /// Returns the number of items the array can hold. + fn size() -> usize; +} + +/// Set the length of the vec when the `SetLenOnDrop` value goes out of scope. +/// +/// Copied from <https://github.com/rust-lang/rust/pull/36355> +struct SetLenOnDrop<'a> { + len: &'a mut usize, + local_len: usize, +} + +impl<'a> SetLenOnDrop<'a> { + #[inline] + fn new(len: &'a mut usize) -> Self { + SetLenOnDrop { + local_len: *len, + len, + } + } + + #[inline] + fn get(&self) -> usize { + self.local_len + } + + #[inline] + fn increment_len(&mut self, increment: usize) { + self.local_len += increment; + } +} + +impl<'a> Drop for SetLenOnDrop<'a> { + #[inline] + fn drop(&mut self) { + *self.len = self.local_len; + } +} + +#[cfg(feature = "const_new")] +impl<T, const N: usize> SmallVec<[T; N]> { + /// Construct an empty vector. + /// + /// This is a `const` version of [`SmallVec::new`] that is enabled by the feature `const_new`, with the limitation that it only works for arrays. + #[cfg_attr(docsrs, doc(cfg(feature = "const_new")))] + #[inline] + pub const fn new_const() -> Self { + SmallVec { + capacity: 0, + data: SmallVecData::from_const(MaybeUninit::uninit()), + } + } + + /// The array passed as an argument is moved to be an inline version of `SmallVec`. + /// + /// This is a `const` version of [`SmallVec::from_buf`] that is enabled by the feature `const_new`, with the limitation that it only works for arrays. + #[cfg_attr(docsrs, doc(cfg(feature = "const_new")))] + #[inline] + pub const fn from_const(items: [T; N]) -> Self { + SmallVec { + capacity: N, + data: SmallVecData::from_const(MaybeUninit::new(items)), + } + } +} + +#[cfg(feature = "const_generics")] +#[cfg_attr(docsrs, doc(cfg(feature = "const_generics")))] +unsafe impl<T, const N: usize> Array for [T; N] { + type Item = T; + #[inline] + fn size() -> usize { + N + } +} + +#[cfg(not(feature = "const_generics"))] +macro_rules! impl_array( + ($($size:expr),+) => { + $( + unsafe impl<T> Array for [T; $size] { + type Item = T; + #[inline] + fn size() -> usize { $size } + } + )+ + } +); + +#[cfg(not(feature = "const_generics"))] +impl_array!( + 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, + 26, 27, 28, 29, 30, 31, 32, 36, 0x40, 0x60, 0x80, 0x100, 0x200, 0x400, 0x600, 0x800, 0x1000, + 0x2000, 0x4000, 0x6000, 0x8000, 0x10000, 0x20000, 0x40000, 0x60000, 0x80000, 0x10_0000 +); + +/// Convenience trait for constructing a `SmallVec` +pub trait ToSmallVec<A: Array> { + /// Construct a new `SmallVec` from a slice. + fn to_smallvec(&self) -> SmallVec<A>; +} + +impl<A: Array> ToSmallVec<A> for [A::Item] +where + A::Item: Copy, +{ + #[inline] + fn to_smallvec(&self) -> SmallVec<A> { + SmallVec::from_slice(self) + } +} + +// Immutable counterpart for `NonNull<T>`. +#[repr(transparent)] +struct ConstNonNull<T>(NonNull<T>); + +impl<T> ConstNonNull<T> { + #[inline] + fn new(ptr: *const T) -> Option<Self> { + NonNull::new(ptr as *mut T).map(Self) + } + #[inline] + fn as_ptr(self) -> *const T { + self.0.as_ptr() + } +} + +impl<T> Clone for ConstNonNull<T> { + #[inline] + fn clone(&self) -> Self { + *self + } +} + +impl<T> Copy for ConstNonNull<T> {} |