Merge pull request #20 from LukasKalbertodt/iter-opt

Implement `size_hint` and `ExactSizeIterator` for all three iterators

Author: LukasKalbertodt

CHANGELOG.md

@@ -6,6 +6,11 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ## [Unreleased]
 
+## [0.2.2] - 2019-01-07
+### Added
+- All three iterators implement `Iterator::size_hint` and `ExactSizeIterator`
+  now and report the correct length.
+
 ## [0.2.1] - 2018-09-26
 ### Added
 - `StableVec::insert_into_hole()`
@@ -65,7 +70,8 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Everything.
 
 
-[Unreleased]: https://github.com/LukasKalbertodt/stable-vec/compare/v0.2.1...HEAD
+[Unreleased]: https://github.com/LukasKalbertodt/stable-vec/compare/v0.2.2...HEAD
+[0.2.2]: https://github.com/LukasKalbertodt/stable-vec/compare/v0.2.1...v0.2.2
 [0.2.1]: https://github.com/LukasKalbertodt/stable-vec/compare/v0.2.0...v0.2.1
 [0.2.0]: https://github.com/LukasKalbertodt/stable-vec/compare/v0.1.2...v0.2.0
 [0.1.2]: https://github.com/LukasKalbertodt/stable-vec/compare/v0.1.1...v0.1.2

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "stable-vec"
-version = "0.2.1"
+version = "0.2.2"
 authors = ["Lukas Kalbertodt <lukas.kalbertodt@gmail.com>"]
 
 description = """

src/lib.rs

@@ -731,7 +731,7 @@ impl<T> StableVec<T> {
     /// }
     /// ```
     pub fn iter(&self) -> Iter<T> {
-        Iter { sv: self, pos: 0 }
+        Iter { sv: self, pos: 0, count: self.used_count }
     }
 
     /// Returns an iterator over mutable references to the existing elements
@@ -781,6 +781,7 @@ impl<T> StableVec<T> {
     pub fn iter_mut(&mut self) -> IterMut<T> {
         IterMut {
             deleted: &mut self.deleted,
+            count: self.used_count,
             used_count: &mut self.used_count,
             vec_iter: self.data.iter_mut(),
             pos: 0,
@@ -817,6 +818,7 @@ impl<T> StableVec<T> {
         Keys {
             deleted: &self.deleted,
             pos: 0,
+            count: self.used_count,
         }
     }
 
@@ -884,8 +886,8 @@ impl<T> StableVec<T> {
 
     /// Retains only the elements specified by the given predicate.
     ///
-    /// Each element `e` for which `predicate(&e)` returns `false` is removed
-    /// from the stable vector.
+    /// Each element `e` for which `should_be_kept(&e)` returns `false` is
+    /// removed from the stable vector.
     ///
     /// # Example
     ///
@@ -896,14 +898,15 @@ impl<T> StableVec<T> {
     ///
     /// assert_eq!(sv, &[2, 4] as &[_]);
     /// ```
-    pub fn retain<P>(&mut self, mut predicate: P)
+    pub fn retain<P>(&mut self, mut should_be_kept: P)
     where
         P: FnMut(&T) -> bool,
     {
-        let mut it = self.iter_mut();
-        while let Some(e) = it.next() {
-            if !predicate(e) {
-                it.remove_current();
+        let mut pos = 0;
+
+        while let Some(idx) = next_valid_index(&mut pos, &self.deleted) {
+            if !should_be_kept(&self[idx]) {
+                self.remove(idx);
             }
         }
     }
@@ -1068,16 +1071,28 @@ impl<'a, T> IntoIterator for &'a mut StableVec<T> {
 pub struct Iter<'a, T: 'a> {
     sv: &'a StableVec<T>,
     pos: usize,
+    count: usize,
 }
 
 impl<'a, T: 'a> Iterator for Iter<'a, T> {
     type Item = &'a T;
     fn next(&mut self) -> Option<Self::Item> {
-        next_valid_index(&mut self.pos, &self.sv.deleted)
-            .map(|i| &self.sv.data[i])
+        let out = next_valid_index(&mut self.pos, &self.sv.deleted)
+            .map(|i| &self.sv.data[i]);
+        if out.is_some() {
+            self.count -= 1;
+        }
+
+        out
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (self.count, Some(self.count))
     }
 }
 
+impl<T> ExactSizeIterator for Iter<'_, T> {}
+
 /// Iterator over mutable references to the elements of a `StableVec`.
 ///
 /// Use the method [`StableVec::iter_mut()`](struct.StableVec.html#method.iter_mut)
@@ -1089,6 +1104,7 @@ pub struct IterMut<'a, T: 'a> {
     used_count: &'a mut usize,
     vec_iter: ::std::slice::IterMut<'a, T>,
     pos: usize,
+    count: usize,
 }
 
 impl<'a, T: 'a> IterMut<'a, T> {
@@ -1124,11 +1140,19 @@ impl<'a, T> Iterator for IterMut<'a, T> {
         } else {
             // Advance the iterator by one and return current element.
             self.pos += 1;
+            self.count -= 1;
             self.vec_iter.next()
         }
     }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (self.count, Some(self.count))
+    }
 }
 
+impl<T> ExactSizeIterator for IterMut<'_, T> {}
+
+
 /// Iterator over all valid indices of a `StableVec`.
 ///
 /// Use the method [`StableVec::keys()`](struct.StableVec.html#method.keys) to
@@ -1137,15 +1161,27 @@ impl<'a, T> Iterator for IterMut<'a, T> {
 pub struct Keys<'a> {
     deleted: &'a BitVec,
     pos: usize,
+    count: usize,
 }
 
 impl<'a> Iterator for Keys<'a> {
     type Item = usize;
     fn next(&mut self) -> Option<Self::Item> {
-        next_valid_index(&mut self.pos, self.deleted)
+        let out = next_valid_index(&mut self.pos, self.deleted);
+        if out.is_some() {
+            self.count -= 1;
+        }
+
+        out
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        (self.count, Some(self.count))
     }
 }
 
+impl ExactSizeIterator for Keys<'_> {}
+
 /// Advances the index `pos` while it points to a deleted element. Stops
 /// advancing once an existing element is found or the end is reached. In the
 /// former case, this element's index is returned; in the latter case, `None`

src/tests.rs

@@ -112,3 +112,35 @@ fn insert_into_hole_and_grow() {
     assert_eq!(sv.num_elements(), 3);
     assert_eq!(sv.clone().into_vec(), &['a', 'c', 'd']);
 }
+
+#[test]
+fn size_hints() {
+    let mut sv = StableVec::<()>::new();
+
+    assert_eq!(sv.iter().size_hint(), (0, Some(0)));
+    assert_eq!(sv.iter_mut().size_hint(), (0, Some(0)));
+    assert_eq!(sv.keys().size_hint(), (0, Some(0)));
+
+
+    let mut sv = StableVec::from(&[0, 1, 2, 3, 4]);
+    sv.remove(1);
+
+    macro_rules! check_iter {
+        ($it:expr) => {{
+            let mut it = $it;
+            assert_eq!(it.size_hint(), (4, Some(4)));
+            assert!(it.next().is_some());
+            assert_eq!(it.size_hint(), (3, Some(3)));
+            assert!(it.next().is_some());
+            assert_eq!(it.size_hint(), (2, Some(2)));
+            assert!(it.next().is_some());
+            assert_eq!(it.size_hint(), (1, Some(1)));
+            assert!(it.next().is_some());
+            assert_eq!(it.size_hint(), (0, Some(0)));
+        }}
+    }
+
+    check_iter!(sv.iter());
+    check_iter!(sv.iter_mut());
+    check_iter!(sv.keys());
+}