-#![allow(unused)]
-
//! Implements a map from integer indices to data.
//! Rather than storing data for every index, internally, this maps entire ranges to the data.
//! To this end, the APIs all work on ranges, not on individual integers. Ranges are split as
-//! necessary (e.g. when [0,5) is first associated with X, and then [1,2) is mutated).
+//! necessary (e.g., when [0,5) is first associated with X, and then [1,2) is mutated).
//! Users must not depend on whether a range is coalesced or not, even though this is observable
//! via the iteration APIs.
use std::ops;
-use std::num::NonZeroU64;
-use rustc::ty::layout::Size;
+use rustc_target::abi::Size;
#[derive(Clone, Debug)]
struct Elem<T> {
- range: ops::Range<u64>, // the range covered by this element, never empty
+ /// The range covered by this element; never empty.
+ range: ops::Range<u64>,
+ /// The data stored for this element.
data: T,
}
#[derive(Clone, Debug)]
}
impl<T> RangeMap<T> {
- /// Create a new RangeMap for the given size, and with the given initial value used for
+ /// Creates a new `RangeMap` for the given size, and with the given initial value used for
/// the entire range.
#[inline(always)]
pub fn new(size: Size, init: T) -> RangeMap<T> {
let size = size.bytes();
let mut map = RangeMap { v: Vec::new() };
if size > 0 {
- map.v.push(Elem {
- range: 0..size,
- data: init
- });
+ map.v.push(Elem { range: 0..size, data: init });
}
map
}
- /// Find the index containing the given offset.
+ /// Finds the index containing the given offset.
fn find_offset(&self, offset: u64) -> usize {
- // We do a binary search
+ // We do a binary search.
let mut left = 0usize; // inclusive
let mut right = self.v.len(); // exclusive
loop {
let candidate = left.checked_add(right).unwrap() / 2;
let elem = &self.v[candidate];
if offset < elem.range.start {
- // we are too far right (offset is further left)
+ // We are too far right (offset is further left).
debug_assert!(candidate < right); // we are making progress
right = candidate;
} else if offset >= elem.range.end {
- // we are too far left (offset is further right)
+ // We are too far left (offset is further right).
debug_assert!(candidate >= left); // we are making progress
- left = candidate+1;
+ left = candidate + 1;
} else {
// This is it!
return candidate;
}
}
- /// Provide read-only iteration over everything in the given range. This does
- /// *not* split items if they overlap with the edges. Do not use this to mutate
+ /// Provides read-only iteration over everything in the given range. This does
+ /// *not* split items if they overlap with the edges. Do not use this to mutate
/// through interior mutability.
- pub fn iter<'a>(&'a self, offset: Size, len: Size) -> impl Iterator<Item = &'a T> + 'a {
+ ///
+ /// The iterator also provides the offset of the given element.
+ pub fn iter<'a>(&'a self, offset: Size, len: Size) -> impl Iterator<Item = (Size, &'a T)> + 'a {
let offset = offset.bytes();
let len = len.bytes();
- // Compute a slice starting with the elements we care about
+ // Compute a slice starting with the elements we care about.
let slice: &[Elem<T>] = if len == 0 {
- // We just need any empty iterator. We don't even want to
- // yield the element that surrounds this position.
- &[]
- } else {
- let first_idx = self.find_offset(offset);
- &self.v[first_idx..]
- };
- let end = offset + len; // the first offset that is not included any more
- slice.iter()
- .take_while(move |elem| elem.range.start < end)
- .map(|elem| &elem.data)
+ // We just need any empty iterator. We don't even want to
+ // yield the element that surrounds this position.
+ &[]
+ } else {
+ let first_idx = self.find_offset(offset);
+ &self.v[first_idx..]
+ };
+ // The first offset that is not included any more.
+ let end = offset + len;
+ slice.iter().take_while(move |elem| elem.range.start < end).map(|elem| (Size::from_bytes(elem.range.start), &elem.data))
}
pub fn iter_mut_all<'a>(&'a mut self) -> impl Iterator<Item = &'a mut T> + 'a {
self.v.iter_mut().map(|elem| &mut elem.data)
}
- // Split the element situated at the given `index`, such that the 2nd one starts at offset `split_offset`.
- // Do nothing if the element already starts there.
- // Return whether a split was necessary.
+ // Splits the element situated at the given `index`, such that the 2nd one starts at offset
+ // `split_offset`. Do nothing if the element already starts there.
+ // Returns whether a split was necessary.
fn split_index(&mut self, index: usize, split_offset: u64) -> bool
where
T: Clone,
{
let elem = &mut self.v[index];
if split_offset == elem.range.start || split_offset == elem.range.end {
- // Nothing to do
+ // Nothing to do.
return false;
}
- debug_assert!(elem.range.contains(&split_offset),
- "The split_offset is not in the element to be split");
+ debug_assert!(
+ elem.range.contains(&split_offset),
+ "the `split_offset` is not in the element to be split"
+ );
- // Now we really have to split. Reduce length of first element.
+ // Now we really have to split. Reduce length of first element.
let second_range = split_offset..elem.range.end;
elem.range.end = split_offset;
- // Copy the data, and insert 2nd element
- let second = Elem {
- range: second_range,
- data: elem.data.clone(),
- };
- self.v.insert(index+1, second);
+ // Copy the data, and insert second element.
+ let second = Elem { range: second_range, data: elem.data.clone() };
+ self.v.insert(index + 1, second);
return true;
}
- /// Provide mutable iteration over everything in the given range. As a side-effect,
+ /// Provides mutable iteration over everything in the given range. As a side-effect,
/// this will split entries in the map that are only partially hit by the given range,
/// to make sure that when they are mutated, the effect is constrained to the given range.
+ /// Moreover, this will opportunistically merge neighbouring equal blocks.
+ ///
+ /// The iterator also provides the offset of the given element.
pub fn iter_mut<'a>(
&'a mut self,
offset: Size,
len: Size,
- ) -> impl Iterator<Item = &'a mut T> + 'a
+ ) -> impl Iterator<Item = (Size, &'a mut T)> + 'a
where
T: Clone + PartialEq,
{
let len = len.bytes();
// Compute a slice containing exactly the elements we care about
let slice: &mut [Elem<T>] = if len == 0 {
- // We just need any empty iterator. We don't even want to
- // yield the element that surrounds this position, nor do
- // any splitting.
- &mut []
- } else {
- // Make sure we got a clear beginning
- let mut first_idx = self.find_offset(offset);
- if self.split_index(first_idx, offset) {
- // The newly created 2nd element is ours
- first_idx += 1;
- }
- let first_idx = first_idx; // no more mutation
- // Find our end. Linear scan, but that's okay because the iteration
- // is doing the same linear scan anyway -- no increase in complexity.
- // We combine this scan with a scan for duplicates that we can merge, to reduce
- // the number of elements.
- let mut equal_since_idx = first_idx;
- let mut end_idx = first_idx; // when the loop is done, this is the first excluded element.
- loop {
- // Compute if `end` is the last element we need to look at.
- let done = (self.v[end_idx].range.end >= offset+len);
- // We definitely need to include `end`, so move the index.
- end_idx += 1;
- debug_assert!(done || end_idx < self.v.len(), "iter_mut: end-offset {} is out-of-bounds", offset+len);
- // see if we want to merge everything in `equal_since..end` (exclusive at the end!)
+ // We just need any empty iterator. We don't even want to
+ // yield the element that surrounds this position, nor do
+ // any splitting.
+ &mut []
+ } else {
+ // Make sure we got a clear beginning
+ let mut first_idx = self.find_offset(offset);
+ if self.split_index(first_idx, offset) {
+ // The newly created 2nd element is ours
+ first_idx += 1;
+ }
+ // No more mutation.
+ let first_idx = first_idx;
+ // Find our end. Linear scan, but that's ok because the iteration
+ // is doing the same linear scan anyway -- no increase in complexity.
+ // We combine this scan with a scan for duplicates that we can merge, to reduce
+ // the number of elements.
+ // We stop searching after the first "block" of size 1, to avoid spending excessive
+ // amounts of time on the merging.
+ let mut equal_since_idx = first_idx;
+ // Once we see too many non-mergeable blocks, we stop.
+ // The initial value is chosen via... magic. Benchmarking and magic.
+ let mut successful_merge_count = 3usize;
+ // When the loop is done, this is the first excluded element.
+ let mut end_idx = first_idx;
+ loop {
+ // Compute if `end` is the last element we need to look at.
+ let done = self.v[end_idx].range.end >= offset + len;
+ // We definitely need to include `end`, so move the index.
+ end_idx += 1;
+ debug_assert!(
+ done || end_idx < self.v.len(),
+ "iter_mut: end-offset {} is out-of-bounds",
+ offset + len
+ );
+ // see if we want to merge everything in `equal_since..end` (exclusive at the end!)
+ if successful_merge_count > 0 {
if done || self.v[end_idx].data != self.v[equal_since_idx].data {
- // Everything in `equal_since..end` was equal. Make them just one element covering
+ // Everything in `equal_since..end` was equal. Make them just one element covering
// the entire range.
- let equal_elems = end_idx - equal_since_idx; // number of equal elements
- if equal_elems > 1 {
+ let removed_elems = end_idx - equal_since_idx - 1; // number of elements that we would remove
+ if removed_elems > 0 {
// Adjust the range of the first element to cover all of them.
let equal_until = self.v[end_idx - 1].range.end; // end of range of last of the equal elements
self.v[equal_since_idx].range.end = equal_until;
// Delete the rest of them.
- self.v.splice(equal_since_idx+1..end_idx, std::iter::empty());
+ self.v.splice(equal_since_idx + 1..end_idx, std::iter::empty());
// Adjust `end_idx` because we made the list shorter.
- end_idx -= (equal_elems - 1);
+ end_idx -= removed_elems;
+ // Adjust the count for the cutoff.
+ successful_merge_count += removed_elems;
+ } else {
+ // Adjust the count for the cutoff.
+ successful_merge_count -= 1;
}
- // Go on scanning.
+ // Go on scanning for the next block starting here.
equal_since_idx = end_idx;
}
- // Leave loop if this is the last element.
- if done {
- break;
- }
}
- let end_idx = end_idx-1; // Move to last included instead of first excluded index.
- // We need to split the end as well. Even if this performs a
- // split, we don't have to adjust our index as we only care about
- // the first part of the split.
- self.split_index(end_idx, offset+len);
- // Now we yield the slice. `end` is inclusive.
- &mut self.v[first_idx..=end_idx]
- };
- slice.iter_mut().map(|elem| &mut elem.data)
+ // Leave loop if this is the last element.
+ if done {
+ break;
+ }
+ }
+ // Move to last included instead of first excluded index.
+ let end_idx = end_idx - 1;
+ // We need to split the end as well. Even if this performs a
+ // split, we don't have to adjust our index as we only care about
+ // the first part of the split.
+ self.split_index(end_idx, offset + len);
+ // Now we yield the slice. `end` is inclusive.
+ &mut self.v[first_idx..=end_idx]
+ };
+ slice.iter_mut().map(|elem| (Size::from_bytes(elem.range.start), &mut elem.data))
}
}
fn to_vec<T: Copy>(map: &RangeMap<T>, offset: u64, len: u64) -> Vec<T> {
(offset..offset + len)
.into_iter()
- .map(|i| map
- .iter(Size::from_bytes(i), Size::from_bytes(1))
- .next()
- .map(|&t| t)
- .unwrap()
- )
+ .map(|i| map.iter(Size::from_bytes(i), Size::from_bytes(1)).next().map(|(_, &t)| t).unwrap())
.collect()
}
#[test]
fn basic_insert() {
let mut map = RangeMap::<i32>::new(Size::from_bytes(20), -1);
- // Insert
- for x in map.iter_mut(Size::from_bytes(10), Size::from_bytes(1)) {
+ // Insert.
+ for (_, x) in map.iter_mut(Size::from_bytes(10), Size::from_bytes(1)) {
*x = 42;
}
- // Check
+ // Check.
assert_eq!(to_vec(&map, 10, 1), vec![42]);
assert_eq!(map.v.len(), 3);
- // Insert with size 0
- for x in map.iter_mut(Size::from_bytes(10), Size::from_bytes(0)) {
+ // Insert with size 0.
+ for (_, x) in map.iter_mut(Size::from_bytes(10), Size::from_bytes(0)) {
*x = 19;
}
- for x in map.iter_mut(Size::from_bytes(11), Size::from_bytes(0)) {
+ for (_, x) in map.iter_mut(Size::from_bytes(11), Size::from_bytes(0)) {
*x = 19;
}
assert_eq!(to_vec(&map, 10, 2), vec![42, -1]);
#[test]
fn gaps() {
let mut map = RangeMap::<i32>::new(Size::from_bytes(20), -1);
- for x in map.iter_mut(Size::from_bytes(11), Size::from_bytes(1)) {
+ for (_, x) in map.iter_mut(Size::from_bytes(11), Size::from_bytes(1)) {
*x = 42;
}
- for x in map.iter_mut(Size::from_bytes(15), Size::from_bytes(1)) {
+ for (_, x) in map.iter_mut(Size::from_bytes(15), Size::from_bytes(1)) {
*x = 43;
}
assert_eq!(map.v.len(), 5);
- assert_eq!(
- to_vec(&map, 10, 10),
- vec![-1, 42, -1, -1, -1, 43, -1, -1, -1, -1]
- );
+ assert_eq!(to_vec(&map, 10, 10), vec![-1, 42, -1, -1, -1, 43, -1, -1, -1, -1]);
- for x in map.iter_mut(Size::from_bytes(10), Size::from_bytes(10)) {
+ for (_, x) in map.iter_mut(Size::from_bytes(10), Size::from_bytes(10)) {
if *x < 42 {
*x = 23;
}
}
assert_eq!(map.v.len(), 6);
- assert_eq!(
- to_vec(&map, 10, 10),
- vec![23, 42, 23, 23, 23, 43, 23, 23, 23, 23]
- );
+ assert_eq!(to_vec(&map, 10, 10), vec![23, 42, 23, 23, 23, 43, 23, 23, 23, 23]);
assert_eq!(to_vec(&map, 13, 5), vec![23, 23, 43, 23, 23]);
-
- for x in map.iter_mut(Size::from_bytes(15), Size::from_bytes(5)) {
+ for (_, x) in map.iter_mut(Size::from_bytes(15), Size::from_bytes(5)) {
*x = 19;
}
assert_eq!(map.v.len(), 6);
+ assert_eq!(to_vec(&map, 10, 10), vec![23, 42, 23, 23, 23, 19, 19, 19, 19, 19]);
+ // Should be seeing two blocks with 19.
assert_eq!(
- to_vec(&map, 10, 10),
- vec![23, 42, 23, 23, 23, 19, 19, 19, 19, 19]
+ map.iter(Size::from_bytes(15), Size::from_bytes(2)).map(|(_, &t)| t).collect::<Vec<_>>(),
+ vec![19, 19]
);
- // Should be seeing two blocks with 19
- assert_eq!(map.iter(Size::from_bytes(15), Size::from_bytes(2))
- .map(|&t| t).collect::<Vec<_>>(), vec![19, 19]);
- // a NOP iter_mut should trigger merging
- for x in map.iter_mut(Size::from_bytes(15), Size::from_bytes(5)) { }
+ // A NOP `iter_mut` should trigger merging.
+ for _ in map.iter_mut(Size::from_bytes(15), Size::from_bytes(5)) {}
assert_eq!(map.v.len(), 5);
- assert_eq!(
- to_vec(&map, 10, 10),
- vec![23, 42, 23, 23, 23, 19, 19, 19, 19, 19]
- );
+ assert_eq!(to_vec(&map, 10, 10), vec![23, 42, 23, 23, 23, 19, 19, 19, 19, 19]);
}
}
projects / rust.git / blobdiff