git add missing file

libs/neon-shmem/src/hash/entry.rs

@@ -0,0 +1,91 @@
+//! Like std::collections::hash_map::Entry;
+
+use crate::hash::core::{CoreHashMap, FullError, INVALID_POS};
+
+use std::hash::Hash;
+use std::mem;
+
+pub enum Entry<'a, 'b, K, V> {
+    Occupied(OccupiedEntry<'a, 'b, K, V>),
+    Vacant(VacantEntry<'a, 'b, K, V>),
+}
+
+pub(crate) enum PrevPos {
+    First(u32),
+    Chained(u32),
+}
+
+pub struct OccupiedEntry<'a, 'b, K, V> {
+    pub(crate) map: &'b mut CoreHashMap<'a, K, V>,
+    pub(crate) _key: K, // The key of the occupied entry
+    pub(crate) prev_pos: PrevPos,
+    pub(crate) bucket_pos: u32, // The position of the bucket in the CoreHashMap's buckets array
+}
+
+impl<'a, 'b, K, V> OccupiedEntry<'a, 'b, K, V> {
+    pub fn get(&self) -> &V {
+        &self.map.buckets[self.bucket_pos as usize]
+            .inner
+            .as_ref()
+            .unwrap()
+            .1
+    }
+
+    pub fn get_mut(&mut self) -> &mut V {
+        &mut self.map.buckets[self.bucket_pos as usize]
+            .inner
+            .as_mut()
+            .unwrap()
+            .1
+    }
+
+    pub fn insert(&mut self, value: V) -> V {
+        let bucket = &mut self.map.buckets[self.bucket_pos as usize];
+        // This assumes inner is Some, which it must be for an OccupiedEntry
+        let old_value = mem::replace(&mut bucket.inner.as_mut().unwrap().1, value);
+        old_value
+    }
+
+    pub fn remove(self) -> V {
+        // CoreHashMap::remove returns Option<(K, V)>. We know it's Some for an OccupiedEntry.
+        let bucket = &mut self.map.buckets[self.bucket_pos as usize];
+
+        // unlink it from the chain
+        match self.prev_pos {
+            PrevPos::First(dict_pos) => self.map.dictionary[dict_pos as usize] = bucket.next,
+            PrevPos::Chained(bucket_pos) => {
+                self.map.buckets[bucket_pos as usize].next = bucket.next
+            }
+        }
+
+        // and add it to the freelist
+        let bucket = &mut self.map.buckets[self.bucket_pos as usize];
+        let old_value = bucket.inner.take();
+        bucket.next = self.map.free_head;
+        self.map.free_head = self.bucket_pos;
+        self.map.buckets_in_use -= 1;
+
+        return old_value.unwrap().1;
+    }
+}
+
+pub struct VacantEntry<'a, 'b, K, V> {
+    pub(crate) map: &'b mut CoreHashMap<'a, K, V>,
+    pub(crate) key: K, // The key to insert
+    pub(crate) dict_pos: u32,
+}
+
+impl<'a, 'b, K: Clone + Hash + Eq, V> VacantEntry<'a, 'b, K, V> {
+    pub fn insert(self, value: V) -> Result<&'b mut V, FullError> {
+        let pos = self.map.alloc_bucket(self.key, value)?;
+        if pos == INVALID_POS {
+            return Err(FullError());
+        }
+        let bucket = &mut self.map.buckets[pos as usize];
+        bucket.next = self.map.dictionary[self.dict_pos as usize];
+        self.map.dictionary[self.dict_pos as usize] = pos;
+
+        let result = &mut self.map.buckets[pos as usize].inner.as_mut().unwrap().1;
+        return Ok(result);
+    }
+}