Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 341 insertions, 0 deletions

diff --git a/third_party/rust/uluru/src/lib.rs b/third_party/rust/uluru/src/lib.rs
new file mode 100644
index 0000000000..0c410509c1
--- /dev/null
+++ b/third_party/rust/uluru/src/lib.rs
@@ -0,0 +1,341 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#![no_std]
+#![deny(unsafe_code)]
+
+//! A simple, fast, least-recently-used (LRU) cache.
+//!
+//! [`LRUCache`] uses a fixed-capacity array for storage. It provides `O(1)` insertion, and `O(n)`
+//! lookup.  It does not require an allocator and can be used in `no_std` crates.
+//!
+//! See the [`LRUCache`](LRUCache) docs for details.
+
+use arrayvec::ArrayVec;
+use core::{fmt, mem::replace};
+
+#[cfg(test)]
+mod tests;
+
+/// A LRU cache using a statically-sized array for storage.
+///
+/// `LRUCache` uses a fixed-capacity array for storage. It provides `O(1)` insertion, and `O(n)`
+/// lookup.
+///
+/// All items are stored inline within the `LRUCache`, so it does not impose any heap allocation or
+/// indirection.  A linked list is used to record the cache order, so the items themselves do not
+/// need to be moved when the order changes.  (This is important for speed if the items are large.)
+///
+/// # Example
+///
+/// ```
+/// use uluru::LRUCache;
+///
+/// struct MyValue {
+///     id: u32,
+///     name: &'static str,
+/// }
+///
+/// // A cache with a capacity of three.
+/// type MyCache = LRUCache<MyValue, 3>;
+///
+/// // Create an empty cache, then insert some items.
+/// let mut cache = MyCache::default();
+/// cache.insert(MyValue { id: 1, name: "Mercury" });
+/// cache.insert(MyValue { id: 2, name: "Venus" });
+/// cache.insert(MyValue { id: 3, name: "Earth" });
+///
+/// // Use the `find` method to retrieve an item from the cache.
+/// // This also "touches" the item, marking it most-recently-used.
+/// let item = cache.find(|x| x.id == 1);
+/// assert_eq!(item.unwrap().name, "Mercury");
+///
+/// // If the cache is full, inserting a new item evicts the least-recently-used item:
+/// cache.insert(MyValue { id: 4, name: "Mars" });
+/// assert!(cache.find(|x| x.id == 2).is_none());
+/// ```
+pub struct LRUCache<T, const N: usize> {
+    /// The most-recently-used entry is at index `head`. The entries form a linked list, linked to
+    /// each other by indices within the `entries` array.  After an entry is added to the array,
+    /// its index never changes, so these links are never invalidated.
+    entries: ArrayVec<Entry<T>, N>,
+    /// Index of the first entry. If the cache is empty, ignore this field.
+    head: u16,
+    /// Index of the last entry. If the cache is empty, ignore this field.
+    tail: u16,
+}
+
+/// An entry in an `LRUCache`.
+#[derive(Debug, Clone)]
+struct Entry<T> {
+    val: T,
+    /// Index of the previous entry. If this entry is the head, ignore this field.
+    prev: u16,
+    /// Index of the next entry. If this entry is the tail, ignore this field.
+    next: u16,
+}
+
+impl<T, const N: usize> Default for LRUCache<T, N> {
+    fn default() -> Self {
+        let cache = LRUCache {
+            entries: ArrayVec::new(),
+            head: 0,
+            tail: 0,
+        };
+        assert!(
+            cache.entries.capacity() < u16::max_value() as usize,
+            "Capacity overflow"
+        );
+        cache
+    }
+}
+
+impl<T, const N: usize> LRUCache<T, N> {
+    /// Insert a given key in the cache.
+    ///
+    /// This item becomes the front (most-recently-used) item in the cache.  If the cache is full,
+    /// the back (least-recently-used) item will be removed and returned.
+    pub fn insert(&mut self, val: T) -> Option<T> {
+        let entry = Entry {
+            val,
+            prev: 0,
+            next: 0,
+        };
+
+        // If the cache is full, replace the oldest entry. Otherwise, add an entry.
+        let (new_head, previous_entry) = if self.entries.len() == self.entries.capacity() {
+            let i = self.pop_back();
+            let previous_entry = replace(&mut self.entries[i as usize], entry);
+            (i, Some(previous_entry.val))
+        } else {
+            self.entries.push(entry);
+            (self.entries.len() as u16 - 1, None)
+        };
+
+        self.push_front(new_head);
+        previous_entry
+    }
+
+    /// Returns the first item in the cache that matches the given predicate.
+    /// Touches the result (makes it most-recently-used) on a hit.
+    pub fn find<F>(&mut self, pred: F) -> Option<&mut T>
+    where
+        F: FnMut(&T) -> bool,
+    {
+        if self.touch(pred) {
+            self.front_mut()
+        } else {
+            None
+        }
+    }
+
+    /// Performs a lookup on the cache with the given test routine. Touches
+    /// the result on a hit.
+    pub fn lookup<F, R>(&mut self, mut test_one: F) -> Option<R>
+    where
+        F: FnMut(&mut T) -> Option<R>,
+    {
+        let mut result = None;
+        let mut iter = self.iter_mut();
+        while let Some((i, val)) = iter.next() {
+            if let Some(r) = test_one(val) {
+                result = Some((i, r));
+                break;
+            }
+        }
+
+        match result {
+            None => None,
+            Some((i, r)) => {
+                self.touch_index(i);
+                Some(r)
+            }
+        }
+    }
+
+    /// Returns the number of elements in the cache.
+    #[inline]
+    pub fn len(&self) -> usize {
+        self.entries.len()
+    }
+
+    /// Returns true if the cache is empty.
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        self.entries.is_empty()
+    }
+
+    /// Evict all elements from the cache.
+    #[inline]
+    pub fn clear(&mut self) {
+        self.entries.clear();
+    }
+
+    /// Returns the front entry in the list (most recently used).
+    pub fn front(&self) -> Option<&T> {
+        self.entries.get(self.head as usize).map(|e| &e.val)
+    }
+
+    /// Returns a mutable reference to the front entry in the list (most recently used).
+    pub fn front_mut(&mut self) -> Option<&mut T> {
+        self.entries.get_mut(self.head as usize).map(|e| &mut e.val)
+    }
+
+    /// Returns the n-th entry in the list (most recently used).
+    pub fn get(&self, index: usize) -> Option<&T> {
+        self.iter().nth(index)
+    }
+
+    /// Touches the first item in the cache that matches the given predicate (marks it as
+    /// most-recently-used).
+    /// Returns `true` on a hit, `false` if no matches.
+    pub fn touch<F>(&mut self, mut pred: F) -> bool
+    where
+        F: FnMut(&T) -> bool,
+    {
+        let mut iter = self.iter_mut();
+        while let Some((i, val)) = iter.next() {
+            if pred(val) {
+                self.touch_index(i);
+                return true;
+            }
+        }
+        false
+    }
+
+    /// Iterate over the contents of this cache in order from most-recently-used to
+    /// least-recently-used.
+    pub fn iter(&self) -> Iter<'_, T, N> {
+        Iter {
+            pos: self.head,
+            cache: self,
+        }
+    }
+
+    /// Iterate mutably over the contents of this cache in order from most-recently-used to
+    /// least-recently-used.
+    fn iter_mut(&mut self) -> IterMut<'_, T, N> {
+        IterMut {
+            pos: self.head,
+            cache: self,
+        }
+    }
+
+    /// Touch a given entry, putting it first in the list.
+    #[inline]
+    fn touch_index(&mut self, idx: u16) {
+        if idx != self.head {
+            self.remove(idx);
+            self.push_front(idx);
+        }
+    }
+
+    /// Remove an entry from the linked list.
+    ///
+    /// Note: This only unlinks the entry from the list; it does not remove it from the array.
+    fn remove(&mut self, i: u16) {
+        let prev = self.entries[i as usize].prev;
+        let next = self.entries[i as usize].next;
+
+        if i == self.head {
+            self.head = next;
+        } else {
+            self.entries[prev as usize].next = next;
+        }
+
+        if i == self.tail {
+            self.tail = prev;
+        } else {
+            self.entries[next as usize].prev = prev;
+        }
+    }
+
+    /// Insert a new entry at the head of the list.
+    fn push_front(&mut self, i: u16) {
+        if self.entries.len() == 1 {
+            self.tail = i;
+        } else {
+            self.entries[i as usize].next = self.head;
+            self.entries[self.head as usize].prev = i;
+        }
+        self.head = i;
+    }
+
+    /// Remove the last entry from the linked list. Returns the index of the removed entry.
+    ///
+    /// Note: This only unlinks the entry from the list; it does not remove it from the array.
+    fn pop_back(&mut self) -> u16 {
+        let old_tail = self.tail;
+        let new_tail = self.entries[old_tail as usize].prev;
+        self.tail = new_tail;
+        old_tail
+    }
+}
+
+impl<T, const N: usize> Clone for LRUCache<T, N>
+where
+    T: Clone,
+{
+    fn clone(&self) -> Self {
+        Self {
+            entries: self.entries.clone(),
+            head: self.head,
+            tail: self.tail,
+        }
+    }
+}
+
+impl<T, const N: usize> fmt::Debug for LRUCache<T, N>
+where
+    T: fmt::Debug,
+{
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_struct("LRUCache")
+            .field("head", &self.head)
+            .field("tail", &self.tail)
+            .field("entries", &self.entries)
+            .finish()
+    }
+}
+
+/// Mutable iterator over values in an `LRUCache`, from most-recently-used to least-recently-used.
+struct IterMut<'a, T, const N: usize> {
+    cache: &'a mut LRUCache<T, N>,
+    pos: u16,
+}
+
+impl<'a, T, const N: usize> IterMut<'a, T, N> {
+    fn next(&mut self) -> Option<(u16, &mut T)> {
+        let index = self.pos;
+        let entry = self.cache.entries.get_mut(index as usize)?;
+
+        self.pos = if index == self.cache.tail {
+            N as u16 // Point past the end of the array to signal we are done.
+        } else {
+            entry.next
+        };
+        Some((index, &mut entry.val))
+    }
+}
+
+/// Iterator over values in an [`LRUCache`], from most-recently-used to least-recently-used.
+pub struct Iter<'a, T, const N: usize> {
+    cache: &'a LRUCache<T, N>,
+    pos: u16,
+}
+
+impl<'a, T, const N: usize> Iterator for Iter<'a, T, N> {
+    type Item = &'a T;
+
+    fn next(&mut self) -> Option<&'a T> {
+        let entry = self.cache.entries.get(self.pos as usize)?;
+
+        self.pos = if self.pos == self.cache.tail {
+            N as u16 // Point past the end of the array to signal we are done.
+        } else {
+            entry.next
+        };
+        Some(&entry.val)
+    }
+}