miri/concurrency/range_object_map.rs
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 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270
//! Implements a map from allocation ranges to data. This is somewhat similar to RangeMap, but the
//! ranges and data are discrete and non-splittable -- they represent distinct "objects". An
//! allocation in the map will always have the same range until explicitly removed
use std::ops::{Index, IndexMut, Range};
use rustc_abi::Size;
use rustc_const_eval::interpret::AllocRange;
#[derive(Clone, Debug)]
struct Elem<T> {
/// The range covered by this element; never empty.
range: AllocRange,
/// The data stored for this element.
data: T,
}
/// Index of an allocation within the map
type Position = usize;
#[derive(Clone, Debug)]
pub struct RangeObjectMap<T> {
v: Vec<Elem<T>>,
}
#[derive(Clone, Debug, PartialEq)]
pub enum AccessType {
/// The access perfectly overlaps (same offset and range) with the existing allocation
PerfectlyOverlapping(Position),
/// The access does not touch any existing allocation
Empty(Position),
/// The access overlaps with one or more existing allocations
ImperfectlyOverlapping(Range<Position>),
}
impl<T> RangeObjectMap<T> {
pub fn new() -> Self {
Self { v: Vec::new() }
}
/// Finds the position of the allocation containing the given offset. If the offset is not
/// in an existing allocation, then returns Err containing the position
/// where such allocation should be inserted
fn find_offset(&self, offset: Size) -> Result<Position, Position> {
self.v.binary_search_by(|elem| -> std::cmp::Ordering {
if offset < elem.range.start {
// We are too far right (offset is further left).
// (`Greater` means that `elem` is greater than the desired target.)
std::cmp::Ordering::Greater
} else if offset >= elem.range.end() {
// We are too far left (offset is further right).
std::cmp::Ordering::Less
} else {
// This is it!
std::cmp::Ordering::Equal
}
})
}
/// Determines whether a given access on `range` overlaps with
/// an existing allocation
pub fn access_type(&self, range: AllocRange) -> AccessType {
match self.find_offset(range.start) {
Ok(pos) => {
// Start of the range belongs to an existing object, now let's check the overlapping situation
let elem = &self.v[pos];
// FIXME: derive Eq for AllocRange in rustc
if elem.range.start == range.start && elem.range.size == range.size {
// Happy case: perfectly overlapping access
AccessType::PerfectlyOverlapping(pos)
} else {
// FIXME: add a last() method to AllocRange that returns the last inclusive offset (end() is exclusive)
let end_pos = match self.find_offset(range.end() - Size::from_bytes(1)) {
// If the end lands in an existing object, add one to get the exclusive position
Ok(inclusive_pos) => inclusive_pos + 1,
Err(exclusive_pos) => exclusive_pos,
};
AccessType::ImperfectlyOverlapping(pos..end_pos)
}
}
Err(pos) => {
// Start of the range doesn't belong to an existing object
match self.find_offset(range.end() - Size::from_bytes(1)) {
// Neither does the end
Err(end_pos) =>
if pos == end_pos {
// There's nothing between the start and the end, so the range thing is empty
AccessType::Empty(pos)
} else {
// Otherwise we have entirely covered an existing object
AccessType::ImperfectlyOverlapping(pos..end_pos)
},
// Otherwise at least part of it overlaps with something else
Ok(end_pos) => AccessType::ImperfectlyOverlapping(pos..end_pos + 1),
}
}
}
}
/// Inserts an object and its occupied range at given position
// The Position can be calculated from AllocRange, but the only user of AllocationMap
// always calls access_type before calling insert/index/index_mut, and we don't
// want to repeat the binary search on each time, so we ask the caller to supply Position
pub fn insert_at_pos(&mut self, pos: Position, range: AllocRange, data: T) {
self.v.insert(pos, Elem { range, data });
// If we aren't the first element, then our start must be greater than the previous element's end
if pos > 0 {
assert!(self.v[pos - 1].range.end() <= range.start);
}
// If we aren't the last element, then our end must be smaller than next element's start
if pos < self.v.len() - 1 {
assert!(range.end() <= self.v[pos + 1].range.start);
}
}
pub fn remove_pos_range(&mut self, pos_range: Range<Position>) {
self.v.drain(pos_range);
}
pub fn remove_from_pos(&mut self, pos: Position) {
self.v.remove(pos);
}
pub fn iter(&self) -> impl Iterator<Item = &T> {
self.v.iter().map(|e| &e.data)
}
}
impl<T> Index<Position> for RangeObjectMap<T> {
type Output = T;
fn index(&self, pos: Position) -> &Self::Output {
&self.v[pos].data
}
}
impl<T> IndexMut<Position> for RangeObjectMap<T> {
fn index_mut(&mut self, pos: Position) -> &mut Self::Output {
&mut self.v[pos].data
}
}
#[cfg(test)]
mod tests {
use rustc_const_eval::interpret::alloc_range;
use super::*;
#[test]
fn empty_map() {
// FIXME: make Size::from_bytes const
let four = Size::from_bytes(4);
let map = RangeObjectMap::<()>::new();
// Correctly tells where we should insert the first element (at position 0)
assert_eq!(map.find_offset(Size::from_bytes(3)), Err(0));
// Correctly tells the access type along with the supposed position
assert_eq!(map.access_type(alloc_range(Size::ZERO, four)), AccessType::Empty(0));
}
#[test]
#[should_panic]
fn no_overlapping_inserts() {
let four = Size::from_bytes(4);
let mut map = RangeObjectMap::<&str>::new();
// |_|_|_|_|#|#|#|#|_|_|_|_|...
// 0 1 2 3 4 5 6 7 8 9 a b c d
map.insert_at_pos(0, alloc_range(four, four), "#");
// |_|_|_|_|#|#|#|#|_|_|_|_|...
// 0 ^ ^ ^ ^ 5 6 7 8 9 a b c d
map.insert_at_pos(0, alloc_range(Size::from_bytes(1), four), "@");
}
#[test]
fn boundaries() {
let four = Size::from_bytes(4);
let mut map = RangeObjectMap::<&str>::new();
// |#|#|#|#|_|_|...
// 0 1 2 3 4 5
map.insert_at_pos(0, alloc_range(Size::ZERO, four), "#");
// |#|#|#|#|_|_|...
// 0 1 2 3 ^ 5
assert_eq!(map.find_offset(four), Err(1));
// |#|#|#|#|_|_|_|_|_|...
// 0 1 2 3 ^ ^ ^ ^ 8
assert_eq!(map.access_type(alloc_range(four, four)), AccessType::Empty(1));
let eight = Size::from_bytes(8);
// |#|#|#|#|_|_|_|_|@|@|@|@|_|_|...
// 0 1 2 3 4 5 6 7 8 9 a b c d
map.insert_at_pos(1, alloc_range(eight, four), "@");
// |#|#|#|#|_|_|_|_|@|@|@|@|_|_|...
// 0 1 2 3 4 5 6 ^ 8 9 a b c d
assert_eq!(map.find_offset(Size::from_bytes(7)), Err(1));
// |#|#|#|#|_|_|_|_|@|@|@|@|_|_|...
// 0 1 2 3 ^ ^ ^ ^ 8 9 a b c d
assert_eq!(map.access_type(alloc_range(four, four)), AccessType::Empty(1));
}
#[test]
fn perfectly_overlapping() {
let four = Size::from_bytes(4);
let mut map = RangeObjectMap::<&str>::new();
// |#|#|#|#|_|_|...
// 0 1 2 3 4 5
map.insert_at_pos(0, alloc_range(Size::ZERO, four), "#");
// |#|#|#|#|_|_|...
// ^ ^ ^ ^ 4 5
assert_eq!(map.find_offset(Size::ZERO), Ok(0));
assert_eq!(
map.access_type(alloc_range(Size::ZERO, four)),
AccessType::PerfectlyOverlapping(0)
);
// |#|#|#|#|@|@|@|@|_|...
// 0 1 2 3 4 5 6 7 8
map.insert_at_pos(1, alloc_range(four, four), "@");
// |#|#|#|#|@|@|@|@|_|...
// 0 1 2 3 ^ ^ ^ ^ 8
assert_eq!(map.find_offset(four), Ok(1));
assert_eq!(map.access_type(alloc_range(four, four)), AccessType::PerfectlyOverlapping(1));
}
#[test]
fn straddling() {
let four = Size::from_bytes(4);
let mut map = RangeObjectMap::<&str>::new();
// |_|_|_|_|#|#|#|#|_|_|_|_|...
// 0 1 2 3 4 5 6 7 8 9 a b c d
map.insert_at_pos(0, alloc_range(four, four), "#");
// |_|_|_|_|#|#|#|#|_|_|_|_|...
// 0 1 ^ ^ ^ ^ 6 7 8 9 a b c d
assert_eq!(
map.access_type(alloc_range(Size::from_bytes(2), four)),
AccessType::ImperfectlyOverlapping(0..1)
);
// |_|_|_|_|#|#|#|#|_|_|_|_|...
// 0 1 2 3 4 5 ^ ^ ^ ^ a b c d
assert_eq!(
map.access_type(alloc_range(Size::from_bytes(6), four)),
AccessType::ImperfectlyOverlapping(0..1)
);
// |_|_|_|_|#|#|#|#|_|_|_|_|...
// 0 1 ^ ^ ^ ^ ^ ^ ^ ^ a b c d
assert_eq!(
map.access_type(alloc_range(Size::from_bytes(2), Size::from_bytes(8))),
AccessType::ImperfectlyOverlapping(0..1)
);
// |_|_|_|_|#|#|#|#|_|_|@|@|_|_|...
// 0 1 2 3 4 5 6 7 8 9 a b c d
map.insert_at_pos(1, alloc_range(Size::from_bytes(10), Size::from_bytes(2)), "@");
// |_|_|_|_|#|#|#|#|_|_|@|@|_|_|...
// 0 1 2 3 4 5 ^ ^ ^ ^ ^ ^ ^ ^
assert_eq!(
map.access_type(alloc_range(Size::from_bytes(6), Size::from_bytes(8))),
AccessType::ImperfectlyOverlapping(0..2)
);
}
}