Add dynamically-sized slices of maps and sets

.github/workflows/ci.yml

@@ -16,7 +16,7 @@ jobs:
     strategy:
       matrix:
         include:
-          - rust: 1.56.0 # MSRV
+          - rust: 1.56.1 # MSRV
             features:
           - rust: stable
             features: serde
@@ -57,7 +57,7 @@ jobs:
     strategy:
       matrix:
         include:
-          - rust: 1.56.0
+          - rust: 1.56.1
             target: thumbv6m-none-eabi
           - rust: stable
             target: thumbv6m-none-eabi

Cargo.toml

@@ -9,7 +9,7 @@ license = "Apache-2.0 OR MIT"
 description = "A hash table with consistent order and fast iteration."
 keywords = ["hashmap", "no_std"]
 categories = ["data-structures", "no-std"]
-rust-version = "1.56"
+rust-version = "1.56.1"
 
 [lib]
 bench = false

README.md

@@ -3,7 +3,7 @@
 [![build status](https://github.com/bluss/indexmap/workflows/Continuous%20integration/badge.svg?branch=master)](https://github.com/bluss/indexmap/actions)
 [![crates.io](https://img.shields.io/crates/v/indexmap.svg)](https://crates.io/crates/indexmap)
 [![docs](https://docs.rs/indexmap/badge.svg)](https://docs.rs/indexmap)
-[![rustc](https://img.shields.io/badge/rust-1.56%2B-orange.svg)](https://img.shields.io/badge/rust-1.56%2B-orange.svg)
+[![rustc](https://img.shields.io/badge/rust-1.56.1%2B-orange.svg)](https://img.shields.io/badge/rust-1.56.1%2B-orange.svg)
 
 A pure-Rust hash table which preserves (in a limited sense) insertion order.
 

RELEASES.md

@@ -1,6 +1,6 @@
 - 2.0.0 (pending)
 
-  - **MSRV**: Rust 1.56 or later is now required.
+  - **MSRV**: Rust 1.56.1 or later is now required.
 
   - The `hashbrown` dependency has been updated to version 0.12.
 
@@ -19,6 +19,11 @@
   - The new `IndexMap::shrink_to` and `IndexSet::shrink_to` methods shrink
     the capacity with a lower bound.
 
+  - The new `map::Slice<K, V>` and `set::Slice<T>` offer a linear view of maps
+    and sets, behaving a lot like normal `[(K, V)]` and `[T]` slices. Notably,
+    comparison traits like `Eq` only consider items in order, rather than hash
+    lookups, and slices even implement `Hash`.
+
 - 1.8.1
 
   - The new `IndexSet::replace_full` will return the index of the item along

src/lib.rs

@@ -53,7 +53,7 @@
 //!
 //! ### Rust Version
 //!
-//! This version of indexmap requires Rust 1.56 or later.
+//! This version of indexmap requires Rust 1.56.1 or later.
 //!
 //! The indexmap 2.x release series will use a carefully considered version
 //! upgrade policy, where in a later 2.x version, we will raise the minimum

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")]
@@ -15,13 +17,14 @@ use ::core::hash::{BuildHasher, Hash, Hasher};
 use ::core::iter::FusedIterator;
 use ::core::ops::{Index, IndexMut, RangeBounds};
 use ::core::slice::{Iter as SliceIter, IterMut as SliceIterMut};
+use alloc::boxed::Box;
 
 #[cfg(feature = "std")]
 use std::collections::hash_map::RandomState;
 
 use self::core::IndexMapCore;
 use crate::equivalent::Equivalent;
-use crate::util::third;
+use crate::util::{third, try_simplify_range};
 use crate::{Bucket, Entries, HashValue};
 
 pub use self::core::{Entry, OccupiedEntry, VacantEntry};
@@ -758,6 +761,27 @@ where
 }
 
 impl<K, V, S> IndexMap<K, V, S> {
+    /// Returns a slice of all the key-value pairs in the map.
+    ///
+    /// Computes in **O(1)** time.
+    pub fn as_slice(&self) -> &Slice<K, V> {
+        Slice::from_slice(self.as_entries())
+    }
+
+    /// Returns a mutable slice of all the key-value pairs in the map.
+    ///
+    /// Computes in **O(1)** time.
+    pub fn as_mut_slice(&mut self) -> &mut Slice<K, V> {
+        Slice::from_mut_slice(self.as_entries_mut())
+    }
+
+    /// Converts into a boxed slice of all the key-value pairs in the map.
+    ///
+    /// Note that this will drop the inner hash table and any excess capacity.
+    pub fn into_boxed_slice(self) -> Box<Slice<K, V>> {
+        Slice::from_boxed(self.into_entries().into_boxed_slice())
+    }
+
     /// Get a key-value pair by index
     ///
     /// Valid indices are *0 <= index < self.len()*
@@ -776,6 +800,28 @@ impl<K, V, S> IndexMap<K, V, S> {
         self.as_entries_mut().get_mut(index).map(Bucket::ref_mut)
     }
 
+    /// Returns a slice of key-value pairs in the given range of indices.
+    ///
+    /// Valid indices are *0 <= index < self.len()*
+    ///
+    /// Computes in **O(1)** time.
+    pub fn get_range<R: RangeBounds<usize>>(&self, range: R) -> Option<&Slice<K, V>> {
+        let entries = self.as_entries();
+        let range = try_simplify_range(range, entries.len())?;
+        entries.get(range).map(Slice::from_slice)
+    }
+
+    /// Returns a mutable slice of key-value pairs in the given range of indices.
+    ///
+    /// Valid indices are *0 <= index < self.len()*
+    ///
+    /// Computes in **O(1)** time.
+    pub fn get_range_mut<R: RangeBounds<usize>>(&mut self, range: R) -> Option<&mut Slice<K, V>> {
+        let entries = self.as_entries_mut();
+        let range = try_simplify_range(range, entries.len())?;
+        entries.get_mut(range).map(Slice::from_mut_slice)
+    }
+
     /// Get the first key-value pair
     ///
     /// Computes in **O(1)** time.
@@ -846,7 +892,7 @@ impl<K, V, S> IndexMap<K, V, S> {
 /// [`keys`]: struct.IndexMap.html#method.keys
 /// [`IndexMap`]: struct.IndexMap.html
 pub struct Keys<'a, K, V> {
-    pub(crate) iter: SliceIter<'a, Bucket<K, V>>,
+    iter: SliceIter<'a, Bucket<K, V>>,
 }
 
 impl<'a, K, V> Iterator for Keys<'a, K, V> {
@@ -1045,6 +1091,13 @@ pub struct Iter<'a, K, V> {
     iter: SliceIter<'a, Bucket<K, V>>,
 }
 
+impl<'a, K, V> Iter<'a, K, V> {
+    /// Returns a slice of the remaining entries in the iterator.
+    pub fn as_slice(&self) -> &'a Slice<K, V> {
+        Slice::from_slice(self.iter.as_slice())
+    }
+}
+
 impl<'a, K, V> Iterator for Iter<'a, K, V> {
     type Item = (&'a K, &'a V);
 
@@ -1089,6 +1142,15 @@ pub struct IterMut<'a, K, V> {
     iter: SliceIterMut<'a, Bucket<K, V>>,
 }
 
+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<'a, K, V> Iterator for IterMut<'a, K, V> {
     type Item = (&'a K, &'a mut V);
 
@@ -1122,7 +1184,7 @@ impl<K: fmt::Debug, V: fmt::Debug> fmt::Debug for IterMut<'_, K, V> {
 /// [`into_iter`]: struct.IndexMap.html#method.into_iter
 /// [`IndexMap`]: struct.IndexMap.html
 pub struct IntoIter<K, V> {
-    pub(crate) iter: vec::IntoIter<Bucket<K, V>>,
+    iter: vec::IntoIter<Bucket<K, V>>,
 }
 
 impl<K, V> Iterator for IntoIter<K, V> {