Adding upstream version 86.0.1.upstream/86.0.1upstream

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

1 files changed, 259 insertions, 0 deletions

diff --git a/third_party/rust/uluru/lib.rs b/third_party/rust/uluru/lib.rs
new file mode 100644
index 0000000000..12eff24120
--- /dev/null
+++ b/third_party/rust/uluru/lib.rs
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+/* 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]
+
+//! 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.
+
+extern crate arrayvec;
+
+use arrayvec::{Array, ArrayVec};
+
+#[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, Entry};
+///
+/// struct MyValue {
+///     id: u32,
+///     name: &'static str,
+/// }
+///
+/// // A cache with a capacity of three.
+/// type MyCache = LRUCache<[Entry<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<A: Array> {
+    /// 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<A>,
+    /// 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.
+pub 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<A: Array> Default for LRUCache<A> {
+    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, A: Array<Item=Entry<T>>> LRUCache<A> {
+    /// Returns the number of elements in the cache.
+    pub fn num_entries(&self) -> usize {
+        self.entries.len()
+    }
+
+    #[inline]
+    /// Touch a given entry, putting it first in the list.
+    fn touch(&mut self, idx: u16) {
+        if idx != self.head {
+            self.remove(idx);
+            self.push_front(idx);
+        }
+    }
+
+    /// 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)
+    }
+
+    /// Iterate mutably over the contents of this cache.
+    fn iter_mut(&mut self) -> LRUCacheMutIterator<A> {
+        LRUCacheMutIterator {
+            pos: self.head,
+            done: self.entries.len() == 0,
+            cache: self,
+        }
+    }
+
+    /// 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;
+        for (i, candidate) in self.iter_mut() {
+            if let Some(r) = test_one(candidate) {
+                result = Some((i, r));
+                break;
+            }
+        };
+
+        match result {
+            None => None,
+            Some((i, r)) => {
+                self.touch(i);
+                Some(r)
+            }
+        }
+    }
+
+    /// Returns the first item in the cache that matches the given predicate.
+    /// Touches the result on a hit.
+    pub fn find<F>(&mut self, mut pred: F) -> Option<&mut T>
+    where
+        F: FnMut(&T) -> bool
+    {
+        match self.iter_mut().find(|&(_, ref x)| pred(x)) {
+            Some((i, _)) => {
+                self.touch(i);
+                self.front_mut()
+            }
+            None => None
+        }
+    }
+
+    /// 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.
+    pub fn insert(&mut self, val: 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 = if self.entries.len() == self.entries.capacity() {
+            let i = self.pop_back();
+            self.entries[i as usize] = entry;
+            i
+        } else {
+            self.entries.push(entry);
+            self.entries.len() as u16 - 1
+        };
+
+        self.push_front(new_head);
+    }
+
+    /// 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
+    }
+
+    /// Evict all elements from the cache.
+    pub fn evict_all(&mut self) {
+        self.entries.clear();
+    }
+}
+
+/// Mutable iterator over values in an LRUCache, from most-recently-used to least-recently-used.
+struct LRUCacheMutIterator<'a, A: 'a + Array> {
+    cache: &'a mut LRUCache<A>,
+    pos: u16,
+    done: bool,
+}
+
+impl<'a, T, A> Iterator for LRUCacheMutIterator<'a, A>
+where T: 'a,
+      A: 'a + Array<Item=Entry<T>>
+{
+    type Item = (u16, &'a mut T);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        if self.done { return None }
+
+        // Use a raw pointer because the compiler doesn't know that subsequent calls can't alias.
+        let entry = unsafe {
+            &mut *(&mut self.cache.entries[self.pos as usize] as *mut Entry<T>)
+        };
+
+        let index = self.pos;
+        if self.pos == self.cache.tail {
+            self.done = true;
+        }
+        self.pos = entry.next;
+
+        Some((index, &mut entry.val))
+    }
+}