Move entity into a separate crate (#297)

lib/entity/src/primary.rs

@@ -0,0 +1,233 @@
+//! Densely numbered entity references as mapping keys.
+use {EntityRef, Iter, IterMut, Keys};
+use std::marker::PhantomData;
+use std::ops::{Index, IndexMut};
+use std::slice;
+use std::vec::Vec;
+
+/// A primary mapping `K -> V` allocating dense entity references.
+///
+/// The `PrimaryMap` data structure uses the dense index space to implement a map with a vector.
+///
+/// A primary map contains the main definition of an entity, and it can be used to allocate new
+/// entity references with the `push` method.
+///
+/// There should only be a single `PrimaryMap` instance for a given `EntityRef` type, otherwise
+/// conflicting references will be created. Using unknown keys for indexing will cause a panic.
+#[derive(Debug, Clone)]
+pub struct PrimaryMap<K, V>
+where
+    K: EntityRef,
+{
+    elems: Vec<V>,
+    unused: PhantomData<K>,
+}
+
+impl<K, V> PrimaryMap<K, V>
+where
+    K: EntityRef,
+{
+    /// Create a new empty map.
+    pub fn new() -> Self {
+        Self {
+            elems: Vec::new(),
+            unused: PhantomData,
+        }
+    }
+
+    /// Check if `k` is a valid key in the map.
+    pub fn is_valid(&self, k: K) -> bool {
+        k.index() < self.elems.len()
+    }
+
+    /// Get the element at `k` if it exists.
+    pub fn get(&self, k: K) -> Option<&V> {
+        self.elems.get(k.index())
+    }
+
+    /// Is this map completely empty?
+    pub fn is_empty(&self) -> bool {
+        self.elems.is_empty()
+    }
+
+    /// Get the total number of entity references created.
+    pub fn len(&self) -> usize {
+        self.elems.len()
+    }
+
+    /// Iterate over all the keys in this map.
+    pub fn keys(&self) -> Keys<K> {
+        Keys::new(self.elems.len())
+    }
+
+    /// Iterate over all the values in this map.
+    pub fn values(&self) -> slice::Iter<V> {
+        self.elems.iter()
+    }
+
+    /// Iterate over all the values in this map, mutable edition.
+    pub fn values_mut(&mut self) -> slice::IterMut<V> {
+        self.elems.iter_mut()
+    }
+
+    /// Iterate over all the keys and values in this map.
+    pub fn iter(&self) -> Iter<K, V> {
+        Iter::new(K::new(0), self.elems.iter())
+    }
+
+    /// Iterate over all the keys and values in this map, mutable edition.
+    pub fn iter_mut(&mut self) -> IterMut<K, V> {
+        IterMut::new(K::new(0), self.elems.iter_mut())
+    }
+
+    /// Remove all entries from this map.
+    pub fn clear(&mut self) {
+        self.elems.clear()
+    }
+
+    /// Get the key that will be assigned to the next pushed value.
+    pub fn next_key(&self) -> K {
+        K::new(self.elems.len())
+    }
+
+    /// Append `v` to the mapping, assigning a new key which is returned.
+    pub fn push(&mut self, v: V) -> K {
+        let k = self.next_key();
+        self.elems.push(v);
+        k
+    }
+}
+
+/// Immutable indexing into an `PrimaryMap`.
+/// The indexed value must be in the map.
+impl<K, V> Index<K> for PrimaryMap<K, V>
+where
+    K: EntityRef,
+{
+    type Output = V;
+
+    fn index(&self, k: K) -> &V {
+        &self.elems[k.index()]
+    }
+}
+
+/// Mutable indexing into an `PrimaryMap`.
+impl<K, V> IndexMut<K> for PrimaryMap<K, V>
+where
+    K: EntityRef,
+{
+    fn index_mut(&mut self, k: K) -> &mut V {
+        &mut self.elems[k.index()]
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    // `EntityRef` impl for testing.
+    #[derive(Clone, Copy, Debug, PartialEq, Eq)]
+    struct E(u32);
+
+    impl EntityRef for E {
+        fn new(i: usize) -> Self {
+            E(i as u32)
+        }
+        fn index(self) -> usize {
+            self.0 as usize
+        }
+    }
+
+    #[test]
+    fn basic() {
+        let r0 = E(0);
+        let r1 = E(1);
+        let m = PrimaryMap::<E, isize>::new();
+
+        let v: Vec<E> = m.keys().collect();
+        assert_eq!(v, []);
+
+        assert!(!m.is_valid(r0));
+        assert!(!m.is_valid(r1));
+    }
+
+    #[test]
+    fn push() {
+        let mut m = PrimaryMap::new();
+        let k0: E = m.push(12);
+        let k1 = m.push(33);
+
+        assert_eq!(m[k0], 12);
+        assert_eq!(m[k1], 33);
+
+        let v: Vec<E> = m.keys().collect();
+        assert_eq!(v, [k0, k1]);
+    }
+
+    #[test]
+    fn iter() {
+        let mut m: PrimaryMap<E, usize> = PrimaryMap::new();
+        m.push(12);
+        m.push(33);
+
+        let mut i = 0;
+        for (key, value) in m.iter() {
+            assert_eq!(key.index(), i);
+            match i {
+                0 => assert_eq!(*value, 12),
+                1 => assert_eq!(*value, 33),
+                _ => panic!(),
+            }
+            i += 1;
+        }
+        i = 0;
+        for (key_mut, value_mut) in m.iter_mut() {
+            assert_eq!(key_mut.index(), i);
+            match i {
+                0 => assert_eq!(*value_mut, 12),
+                1 => assert_eq!(*value_mut, 33),
+                _ => panic!(),
+            }
+            i += 1;
+        }
+    }
+
+    #[test]
+    fn keys() {
+        let mut m: PrimaryMap<E, usize> = PrimaryMap::new();
+        m.push(12);
+        m.push(33);
+
+        let mut i = 0;
+        for key in m.keys() {
+            assert_eq!(key.index(), i);
+            i += 1;
+        }
+    }
+
+    #[test]
+    fn values() {
+        let mut m: PrimaryMap<E, usize> = PrimaryMap::new();
+        m.push(12);
+        m.push(33);
+
+        let mut i = 0;
+        for value in m.values() {
+            match i {
+                0 => assert_eq!(*value, 12),
+                1 => assert_eq!(*value, 33),
+                _ => panic!(),
+            }
+            i += 1;
+        }
+        i = 0;
+        for value_mut in m.values_mut() {
+            match i {
+                0 => assert_eq!(*value_mut, 12),
+                1 => assert_eq!(*value_mut, 33),
+                _ => panic!(),
+            }
+            i += 1;
+        }
+    }
+}