Add dynamically-sized slices of maps and sets

Author: cuviper

src/map.rs

@@ -2,7 +2,9 @@
 //! pairs is independent of the hash values of the keys.
 
 mod core;
+mod slice;
 
+pub use self::slice::Slice;
 pub use crate::mutable_keys::MutableKeys;
 
 #[cfg(feature = "rayon")]

src/map/slice.rs

@@ -0,0 +1,320 @@
+use super::{Bucket, Entries, IndexMap, Iter, IterMut, Keys, Values, ValuesMut};
+
+use core::cmp::Ordering;
+use core::fmt;
+use core::hash::{Hash, Hasher};
+use core::ops::{Index, IndexMut};
+use core::ops::{Range, RangeFrom, RangeFull, RangeInclusive, RangeTo, RangeToInclusive};
+
+/// A dynamically-sized slice of key-value pairs in an `IndexMap`.
+///
+/// This supports indexed operations much like a `[(K, V)]` slice,
+/// but not any hashed operations on the map keys.
+///
+/// Unlike `IndexMap`, `Slice` does consider the order for `PartialEq`
+/// and `Eq`, and it also implements `PartialOrd`, `Ord`, and `Hash`.
+#[repr(transparent)]
+pub struct Slice<K, V> {
+    entries: [Bucket<K, V>],
+}
+
+#[allow(unsafe_code)]
+impl<K, V> Slice<K, V> {
+    fn from_slice(entries: &[Bucket<K, V>]) -> &Self {
+        // SAFETY: `Slice<K, V>` is a transparent wrapper around `[Bucket<K, V>]`,
+        // and the lifetimes are bound together by this function's signature.
+        unsafe { &*(entries as *const [Bucket<K, V>] as *const Self) }
+    }
+
+    fn from_mut_slice(entries: &mut [Bucket<K, V>]) -> &mut Self {
+        // SAFETY: `Slice<K, V>` is a transparent wrapper around `[Bucket<K, V>]`,
+        // and the lifetimes are bound together by this function's signature.
+        unsafe { &mut *(entries as *mut [Bucket<K, V>] as *mut Self) }
+    }
+}
+
+impl<K, V, S> IndexMap<K, V, S> {
+    /// Returns a slice of all the entries in the map.
+    pub fn as_slice(&self) -> &Slice<K, V> {
+        Slice::from_slice(self.as_entries())
+    }
+
+    /// Returns a mutable slice of all the entries in the map.
+    pub fn as_mut_slice(&mut self) -> &mut Slice<K, V> {
+        Slice::from_mut_slice(self.as_entries_mut())
+    }
+}
+
+impl<K, V> Iter<'_, K, V> {
+    /// Returns a slice of the remaining entries in the iterator.
+    pub fn as_slice(&self) -> &Slice<K, V> {
+        Slice::from_slice(self.iter.as_slice())
+    }
+}
+
+impl<'a, K, V> IterMut<'a, K, V> {
+    /// Returns a slice of the remaining entries in the iterator.
+    ///
+    /// To avoid creating `&mut` references that alias, this is forced to consume the iterator.
+    pub fn into_slice(self) -> &'a mut Slice<K, V> {
+        Slice::from_mut_slice(self.iter.into_slice())
+    }
+}
+
+impl<K, V> Slice<K, V> {
+    /// Return the number of key-value pairs in the map slice.
+    #[inline]
+    pub fn len(&self) -> usize {
+        self.entries.len()
+    }
+
+    /// Returns true if the map slice contains no elements.
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        self.entries.is_empty()
+    }
+
+    /// Get a key-value pair by index.
+    ///
+    /// Valid indices are *0 <= index < self.len()*
+    pub fn get_index(&self, index: usize) -> Option<(&K, &V)> {
+        self.entries.get(index).map(Bucket::refs)
+    }
+
+    /// Get a key-value pair by index, with mutable access to the value.
+    ///
+    /// Valid indices are *0 <= index < self.len()*
+    pub fn get_index_mut(&mut self, index: usize) -> Option<(&K, &mut V)> {
+        // NB: we're not returning `&mut K` like `IndexMap::get_index_mut`,
+        // because that was a mistake that should have required `MutableKeys`.
+        self.entries.get_mut(index).map(Bucket::ref_mut)
+    }
+
+    /// Get the first key-value pair.
+    pub fn first(&self) -> Option<(&K, &V)> {
+        self.entries.first().map(Bucket::refs)
+    }
+
+    /// Get the first key-value pair, with mutable access to the value.
+    pub fn first_mut(&mut self) -> Option<(&K, &mut V)> {
+        self.entries.first_mut().map(Bucket::ref_mut)
+    }
+
+    /// Get the last key-value pair.
+    pub fn last(&self) -> Option<(&K, &V)> {
+        self.entries.last().map(Bucket::refs)
+    }
+
+    /// Get the last key-value pair, with mutable access to the value.
+    pub fn last_mut(&mut self) -> Option<(&K, &mut V)> {
+        self.entries.last_mut().map(Bucket::ref_mut)
+    }
+
+    /// Divides one slice into two at an index.
+    ///
+    /// ***Panics*** if `index > len`.
+    pub fn split_at(&self, index: usize) -> (&Self, &Self) {
+        let (first, second) = self.entries.split_at(index);
+        (Self::from_slice(first), Self::from_slice(second))
+    }
+
+    /// Divides one mutable slice into two at an index.
+    ///
+    /// ***Panics*** if `index > len`.
+    pub fn split_at_mut(&mut self, index: usize) -> (&mut Self, &mut Self) {
+        let (first, second) = self.entries.split_at_mut(index);
+        (Self::from_mut_slice(first), Self::from_mut_slice(second))
+    }
+
+    /// Returns the first key-value pair and the rest of the slice,
+    /// or `None` if it is empty.
+    pub fn split_first(&self) -> Option<((&K, &V), &Self)> {
+        if let Some((first, rest)) = self.entries.split_first() {
+            Some((first.refs(), Self::from_slice(rest)))
+        } else {
+            None
+        }
+    }
+
+    /// Returns the first key-value pair and the rest of the slice,
+    /// with mutable access to the value, or `None` if it is empty.
+    pub fn split_first_mut(&mut self) -> Option<((&K, &mut V), &mut Self)> {
+        if let Some((first, rest)) = self.entries.split_first_mut() {
+            Some((first.ref_mut(), Self::from_mut_slice(rest)))
+        } else {
+            None
+        }
+    }
+
+    /// Returns the last key-value pair and the rest of the slice,
+    /// or `None` if it is empty.
+    pub fn split_last(&self) -> Option<((&K, &V), &Self)> {
+        if let Some((last, rest)) = self.entries.split_last() {
+            Some((last.refs(), Self::from_slice(rest)))
+        } else {
+            None
+        }
+    }
+
+    /// Returns the last key-value pair and the rest of the slice,
+    /// with mutable access to the value, or `None` if it is empty.
+    pub fn split_last_mut(&mut self) -> Option<((&K, &mut V), &mut Self)> {
+        if let Some((last, rest)) = self.entries.split_last_mut() {
+            Some((last.ref_mut(), Self::from_mut_slice(rest)))
+        } else {
+            None
+        }
+    }
+
+    /// Return an iterator over the key-value pairs of the map slice.
+    pub fn iter(&self) -> Iter<'_, K, V> {
+        Iter {
+            iter: self.entries.iter(),
+        }
+    }
+
+    /// Return an iterator over the key-value pairs of the map slice.
+    pub fn iter_mut(&mut self) -> IterMut<'_, K, V> {
+        IterMut {
+            iter: self.entries.iter_mut(),
+        }
+    }
+
+    /// Return an iterator over the keys of the map slice.
+    pub fn keys(&self) -> Keys<'_, K, V> {
+        Keys {
+            iter: self.entries.iter(),
+        }
+    }
+
+    /// Return an iterator over the values of the map slice.
+    pub fn values(&self) -> Values<'_, K, V> {
+        Values {
+            iter: self.entries.iter(),
+        }
+    }
+
+    /// Return an iterator over mutable references to the the values of the map slice.
+    pub fn values_mut(&mut self) -> ValuesMut<'_, K, V> {
+        ValuesMut {
+            iter: self.entries.iter_mut(),
+        }
+    }
+}
+
+impl<'a, K, V> IntoIterator for &'a Slice<K, V> {
+    type IntoIter = Iter<'a, K, V>;
+    type Item = (&'a K, &'a V);
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.iter()
+    }
+}
+
+impl<'a, K, V> IntoIterator for &'a mut Slice<K, V> {
+    type IntoIter = IterMut<'a, K, V>;
+    type Item = (&'a K, &'a mut V);
+
+    fn into_iter(self) -> Self::IntoIter {
+        self.iter_mut()
+    }
+}
+
+impl<K, V> Default for &'_ Slice<K, V> {
+    fn default() -> Self {
+        Slice::from_slice(&[])
+    }
+}
+
+impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for Slice<K, V> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.debug_list().entries(self).finish()
+    }
+}
+
+impl<K: PartialEq, V: PartialEq> PartialEq for Slice<K, V> {
+    fn eq(&self, other: &Self) -> bool {
+        self.len() == other.len() && self.iter().eq(other)
+    }
+}
+
+impl<K: Eq, V: Eq> Eq for Slice<K, V> {}
+
+impl<K: PartialOrd, V: PartialOrd> PartialOrd for Slice<K, V> {
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        self.iter().partial_cmp(other)
+    }
+}
+
+impl<K: Ord, V: Ord> Ord for Slice<K, V> {
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.iter().cmp(other)
+    }
+}
+
+impl<K: Hash, V: Hash> Hash for Slice<K, V> {
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.len().hash(state);
+        for (key, value) in self {
+            key.hash(state);
+            value.hash(state);
+        }
+    }
+}
+
+impl<K, V> Index<usize> for Slice<K, V> {
+    type Output = V;
+
+    fn index(&self, index: usize) -> &V {
+        &self.entries[index].value
+    }
+}
+
+impl<K, V> IndexMut<usize> for Slice<K, V> {
+    fn index_mut(&mut self, index: usize) -> &mut V {
+        &mut self.entries[index].value
+    }
+}
+
+// We can't have `impl<I: RangeBounds<usize>> Index<I>` because that conflicts
+// both upstream with `Index<usize>` and downstream with `Index<&Q>`.
+// Instead, we repeat the implementations for all the core range types.
+macro_rules! impl_index {
+    ($($range:ty),*) => {$(
+        impl<K, V, S> Index<$range> for IndexMap<K, V, S> {
+            type Output = Slice<K, V>;
+
+            fn index(&self, range: $range) -> &Self::Output {
+                Slice::from_slice(&self.as_entries()[range])
+            }
+        }
+
+        impl<K, V, S> IndexMut<$range> for IndexMap<K, V, S> {
+            fn index_mut(&mut self, range: $range) -> &mut Self::Output {
+                Slice::from_mut_slice(&mut self.as_entries_mut()[range])
+            }
+        }
+
+        impl<K, V> Index<$range> for Slice<K, V> {
+            type Output = Slice<K, V>;
+
+            fn index(&self, range: $range) -> &Self {
+                Self::from_slice(&self.entries[range])
+            }
+        }
+
+        impl<K, V> IndexMut<$range> for Slice<K, V> {
+            fn index_mut(&mut self, range: $range) -> &mut Self {
+                Self::from_mut_slice(&mut self.entries[range])
+            }
+        }
+    )*}
+}
+impl_index!(
+    Range<usize>,
+    RangeFrom<usize>,
+    RangeFull,
+    RangeInclusive<usize>,
+    RangeTo<usize>,
+    RangeToInclusive<usize>
+);

src/set.rs

@@ -1,5 +1,9 @@
 //! A hash set implemented using `IndexMap`
 
+mod slice;
+
+pub use self::slice::Slice;
+
 #[cfg(feature = "rayon")]
 pub use crate::rayon::set as rayon;
 
@@ -12,7 +16,7 @@ use core::fmt;
 use core::hash::{BuildHasher, Hash};
 use core::iter::{Chain, FromIterator};
 use core::ops::{BitAnd, BitOr, BitXor, Index, RangeBounds, Sub};
-use core::slice;
+use core::slice::Iter as SliceIter;
 
 use super::{Entries, Equivalent, IndexMap};
 
@@ -189,7 +193,7 @@ impl<T, S> IndexSet<T, S> {
     /// Return an iterator over the values of the set, in their order
     pub fn iter(&self) -> Iter<'_, T> {
         Iter {
-            iter: self.map.keys().iter,
+            iter: self.map.as_entries().iter(),
         }
     }
 
@@ -734,7 +738,7 @@ impl<T: fmt::Debug> fmt::Debug for IntoIter<T> {
 /// [`IndexSet`]: struct.IndexSet.html
 /// [`iter`]: struct.IndexSet.html#method.iter
 pub struct Iter<'a, T> {
-    iter: slice::Iter<'a, Bucket<T>>,
+    iter: SliceIter<'a, Bucket<T>>,
 }
 
 impl<'a, T> Iterator for Iter<'a, T> {