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Auto merge of #109787 - scottmcm:index-slice, r=cjgillot
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Add `IndexSlice` to go with `IndexVec`

Moves the methods that don't need full `IndexVec`-ness over to `IndexSlice`, and have `IndexVec` deref to `IndexSlice` so everything keeps working.

Doing this for later use in rust-lang/compiler-team#606, where I'm hitting a bunch of things that are just slices and thus there's no way to index with the `FieldIdx`.
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@bors
bors committed Mar 31, 2023
2 parents 22a7a19 + 408e2ac commit 480068c
Showing 1 changed file with 160 additions and 70 deletions.
230 changes: 160 additions & 70 deletions compiler/rustc_index/src/vec.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,7 +5,7 @@ use std::fmt;
use std::fmt::Debug;
use std::hash::Hash;
use std::marker::PhantomData;
use std::ops::{Index, IndexMut, RangeBounds};
use std::ops::{Deref, DerefMut, Index, IndexMut, RangeBounds};
use std::slice;
use std::vec;

Expand Down Expand Up @@ -52,15 +52,27 @@ impl Idx for u32 {
}

#[derive(Clone, PartialEq, Eq, Hash)]
#[repr(transparent)]
pub struct IndexVec<I: Idx, T> {
pub raw: Vec<T>,
_marker: PhantomData<fn(&I)>,
}

#[derive(PartialEq, Eq, Hash)]
#[repr(transparent)]
pub struct IndexSlice<I: Idx, T> {
_marker: PhantomData<fn(&I)>,
pub raw: [T],
}

// Whether `IndexVec` is `Send` depends only on the data,
// not the phantom data.
unsafe impl<I: Idx, T> Send for IndexVec<I, T> where T: Send {}

// Whether `IndexSlice` is `Send` depends only on the data,
// not the phantom data.
unsafe impl<I: Idx, T> Send for IndexSlice<I, T> where T: Send {}

#[cfg(feature = "rustc_serialize")]
impl<S: Encoder, I: Idx, T: Encodable<S>> Encodable<S> for IndexVec<I, T> {
fn encode(&self, s: &mut S) {
Expand Down Expand Up @@ -122,6 +134,16 @@ impl<I: Idx, T> IndexVec<I, T> {
Self::from_raw(indices.map(func).collect())
}

#[inline]
pub fn as_slice(&self) -> &IndexSlice<I, T> {
IndexSlice::from_raw(&self.raw)
}

#[inline]
pub fn as_mut_slice(&mut self) -> &mut IndexSlice<I, T> {
IndexSlice::from_raw_mut(&mut self.raw)
}

#[inline]
pub fn push(&mut self, d: T) -> I {
let idx = I::new(self.len());
Expand All @@ -135,32 +157,119 @@ impl<I: Idx, T> IndexVec<I, T> {
}

#[inline]
pub fn len(&self) -> usize {
self.raw.len()
pub fn into_iter(self) -> vec::IntoIter<T> {
self.raw.into_iter()
}

/// Gives the next index that will be assigned when `push` is
/// called.
#[inline]
pub fn next_index(&self) -> I {
I::new(self.len())
pub fn into_iter_enumerated(
self,
) -> impl DoubleEndedIterator<Item = (I, T)> + ExactSizeIterator {
self.raw.into_iter().enumerate().map(|(n, t)| (I::new(n), t))
}

#[inline]
pub fn is_empty(&self) -> bool {
self.raw.is_empty()
pub fn drain<'a, R: RangeBounds<usize>>(
&'a mut self,
range: R,
) -> impl Iterator<Item = T> + 'a {
self.raw.drain(range)
}

#[inline]
pub fn into_iter(self) -> vec::IntoIter<T> {
self.raw.into_iter()
pub fn drain_enumerated<'a, R: RangeBounds<usize>>(
&'a mut self,
range: R,
) -> impl Iterator<Item = (I, T)> + 'a {
let begin = match range.start_bound() {
std::ops::Bound::Included(i) => *i,
std::ops::Bound::Excluded(i) => i.checked_add(1).unwrap(),
std::ops::Bound::Unbounded => 0,
};
self.raw.drain(range).enumerate().map(move |(n, t)| (I::new(begin + n), t))
}

#[inline]
pub fn into_iter_enumerated(
self,
) -> impl DoubleEndedIterator<Item = (I, T)> + ExactSizeIterator {
self.raw.into_iter().enumerate().map(|(n, t)| (I::new(n), t))
pub fn shrink_to_fit(&mut self) {
self.raw.shrink_to_fit()
}

#[inline]
pub fn truncate(&mut self, a: usize) {
self.raw.truncate(a)
}

pub fn convert_index_type<Ix: Idx>(self) -> IndexVec<Ix, T> {
IndexVec { raw: self.raw, _marker: PhantomData }
}

/// Grows the index vector so that it contains an entry for
/// `elem`; if that is already true, then has no
/// effect. Otherwise, inserts new values as needed by invoking
/// `fill_value`.
#[inline]
pub fn ensure_contains_elem(&mut self, elem: I, fill_value: impl FnMut() -> T) {
let min_new_len = elem.index() + 1;
if self.len() < min_new_len {
self.raw.resize_with(min_new_len, fill_value);
}
}

#[inline]
pub fn resize_to_elem(&mut self, elem: I, fill_value: impl FnMut() -> T) {
let min_new_len = elem.index() + 1;
self.raw.resize_with(min_new_len, fill_value);
}
}

impl<I: Idx, T> Deref for IndexVec<I, T> {
type Target = IndexSlice<I, T>;

#[inline]
fn deref(&self) -> &Self::Target {
self.as_slice()
}
}

impl<I: Idx, T> DerefMut for IndexVec<I, T> {
#[inline]
fn deref_mut(&mut self) -> &mut Self::Target {
self.as_mut_slice()
}
}

impl<I: Idx, T> IndexSlice<I, T> {
#[inline]
pub fn from_raw(raw: &[T]) -> &Self {
let ptr: *const [T] = raw;
// SAFETY: `IndexSlice` is `repr(transparent)` over a normal slice
unsafe { &*(ptr as *const Self) }
}

#[inline]
pub fn from_raw_mut(raw: &mut [T]) -> &mut Self {
let ptr: *mut [T] = raw;
// SAFETY: `IndexSlice` is `repr(transparent)` over a normal slice
unsafe { &mut *(ptr as *mut Self) }
}

#[inline]
pub fn len(&self) -> usize {
self.raw.len()
}

/// Gives the next index that will be assigned when `push` is called.
///
/// Manual bounds checks can be done using `idx < slice.next_index()`
/// (as opposed to `idx.index() < slice.len()`).
#[inline]
pub fn next_index(&self) -> I {
I::new(self.len())
}

#[inline]
pub fn is_empty(&self) -> bool {
self.raw.is_empty()
}

#[inline]
Expand Down Expand Up @@ -194,47 +303,16 @@ impl<I: Idx, T> IndexVec<I, T> {
self.raw.iter_mut().enumerate().map(|(n, t)| (I::new(n), t))
}

#[inline]
pub fn drain<'a, R: RangeBounds<usize>>(
&'a mut self,
range: R,
) -> impl Iterator<Item = T> + 'a {
self.raw.drain(range)
}

#[inline]
pub fn drain_enumerated<'a, R: RangeBounds<usize>>(
&'a mut self,
range: R,
) -> impl Iterator<Item = (I, T)> + 'a {
let begin = match range.start_bound() {
std::ops::Bound::Included(i) => *i,
std::ops::Bound::Excluded(i) => i.checked_add(1).unwrap(),
std::ops::Bound::Unbounded => 0,
};
self.raw.drain(range).enumerate().map(move |(n, t)| (I::new(begin + n), t))
}

#[inline]
pub fn last_index(&self) -> Option<I> {
self.len().checked_sub(1).map(I::new)
}

#[inline]
pub fn shrink_to_fit(&mut self) {
self.raw.shrink_to_fit()
}

#[inline]
pub fn swap(&mut self, a: I, b: I) {
self.raw.swap(a.index(), b.index())
}

#[inline]
pub fn truncate(&mut self, a: usize) {
self.raw.truncate(a)
}

#[inline]
pub fn get(&self, index: I) -> Option<&T> {
self.raw.get(index.index())
Expand Down Expand Up @@ -274,28 +352,6 @@ impl<I: Idx, T> IndexVec<I, T> {
let ptr = self.raw.as_mut_ptr();
unsafe { (&mut *ptr.add(ai), &mut *ptr.add(bi), &mut *ptr.add(ci)) }
}

pub fn convert_index_type<Ix: Idx>(self) -> IndexVec<Ix, T> {
IndexVec { raw: self.raw, _marker: PhantomData }
}

/// Grows the index vector so that it contains an entry for
/// `elem`; if that is already true, then has no
/// effect. Otherwise, inserts new values as needed by invoking
/// `fill_value`.
#[inline]
pub fn ensure_contains_elem(&mut self, elem: I, fill_value: impl FnMut() -> T) {
let min_new_len = elem.index() + 1;
if self.len() < min_new_len {
self.raw.resize_with(min_new_len, fill_value);
}
}

#[inline]
pub fn resize_to_elem(&mut self, elem: I, fill_value: impl FnMut() -> T) {
let min_new_len = elem.index() + 1;
self.raw.resize_with(min_new_len, fill_value);
}
}

/// `IndexVec` is often used as a map, so it provides some map-like APIs.
Expand Down Expand Up @@ -336,7 +392,7 @@ impl<I: Idx, T: Ord> IndexVec<I, T> {
}
}

impl<I: Idx, T> Index<I> for IndexVec<I, T> {
impl<I: Idx, T> Index<I> for IndexSlice<I, T> {
type Output = T;

#[inline]
Expand All @@ -345,7 +401,7 @@ impl<I: Idx, T> Index<I> for IndexVec<I, T> {
}
}

impl<I: Idx, T> IndexMut<I> for IndexVec<I, T> {
impl<I: Idx, T> IndexMut<I> for IndexSlice<I, T> {
#[inline]
fn index_mut(&mut self, index: I) -> &mut T {
&mut self.raw[index.index()]
Expand All @@ -359,6 +415,20 @@ impl<I: Idx, T> Default for IndexVec<I, T> {
}
}

impl<I: Idx, T> Default for &IndexSlice<I, T> {
#[inline]
fn default() -> Self {
IndexSlice::from_raw(Default::default())
}
}

impl<I: Idx, T> Default for &mut IndexSlice<I, T> {
#[inline]
fn default() -> Self {
IndexSlice::from_raw_mut(Default::default())
}
}

impl<I: Idx, T> Extend<T> for IndexVec<I, T> {
#[inline]
fn extend<J: IntoIterator<Item = T>>(&mut self, iter: J) {
Expand Down Expand Up @@ -418,5 +488,25 @@ impl<'a, I: Idx, T> IntoIterator for &'a mut IndexVec<I, T> {
}
}

impl<'a, I: Idx, T> IntoIterator for &'a IndexSlice<I, T> {
type Item = &'a T;
type IntoIter = slice::Iter<'a, T>;

#[inline]
fn into_iter(self) -> slice::Iter<'a, T> {
self.raw.iter()
}
}

impl<'a, I: Idx, T> IntoIterator for &'a mut IndexSlice<I, T> {
type Item = &'a mut T;
type IntoIter = slice::IterMut<'a, T>;

#[inline]
fn into_iter(self) -> slice::IterMut<'a, T> {
self.raw.iter_mut()
}
}

#[cfg(test)]
mod tests;

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