#21 Optimize loops by exploiting invariant self.next <= N

yegor256 · Apr 18, 2023 · 23d81bb · 23d81bb
1 parent 2c3864f
commit 23d81bb
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Showing 3 changed files with 9 additions and 36 deletions.
diff --git a/src/debug.rs b/src/debug.rs
@@ -35,10 +35,7 @@ impl<K: Copy + PartialEq + Display, V: Clone + Copy + Display, const N: usize> D
 {
     fn fmt(&self, f: &mut Formatter) -> fmt::Result {
         let mut parts = vec![];
-        for i in 0..N {
-            if self.next <= i {
-                break;
-            }
+        for i in 0..self.next {
             if let Present((k, v)) = &self.pairs[i] {
                 parts.push(format!("{k}: {v}"));
             }

diff --git a/src/iterators.rs b/src/iterators.rs
@@ -26,10 +26,7 @@ impl<'a, K: Clone, V: Clone, const N: usize> Iterator for Iter<'a, K, V, N> {
     #[inline]
     #[must_use]
     fn next(&mut self) -> Option<Self::Item> {
-        while self.pos < N {
-            if self.next <= self.pos {
-                break;
-            }
+        while self.pos < self.next {
             if let Present(p) = &self.pairs[self.pos] {
                 self.pos += 1;
                 return Some((&p.0, &p.1));
@@ -46,10 +43,7 @@ impl<'a, K: Clone, V: Clone, const N: usize> Iterator for IntoIter<'a, K, V, N>
     #[inline]
     #[must_use]
     fn next(&mut self) -> Option<Self::Item> {
-        while self.pos < N {
-            if self.next <= self.pos {
-                break;
-            }
+        while self.pos < self.next {
             if self.pairs[self.pos].is_some() {
                 let pair = self.pairs[self.pos].clone().unwrap();
                 self.pos += 1;

diff --git a/src/map.rs b/src/map.rs
@@ -65,10 +65,7 @@ impl<K: Copy + PartialEq, V: Clone + Copy, const N: usize> Map<K, V, N> {
             return 0;
         }
         let mut busy = 0;
-        for i in 0..N {
-            if self.next <= i {
-                break;
-            }
+        for i in 0..self.next {
             if self.pairs[i].is_some() {
                 busy += 1;
             }
@@ -79,10 +76,7 @@ impl<K: Copy + PartialEq, V: Clone + Copy, const N: usize> Map<K, V, N> {
     /// Does the map contain this key?
     #[inline]
     pub fn contains_key(&self, k: &K) -> bool {
-        for i in 0..N {
-            if self.next <= i {
-                break;
-            }
+        for i in 0..self.next {
             if let Present((bk, _bv)) = &self.pairs[i] {
                 if bk == k {
                     return true;
@@ -95,10 +89,7 @@ impl<K: Copy + PartialEq, V: Clone + Copy, const N: usize> Map<K, V, N> {
     /// Remove by key.
     #[inline]
     pub fn remove(&mut self, k: &K) {
-        for i in 0..N {
-            if self.next <= i {
-                break;
-            }
+        for i in 0..self.next {
             if let Present((bk, _bv)) = &self.pairs[i] {
                 if bk == k {
                     self.pairs[i] = Absent;
@@ -116,10 +107,7 @@ impl<K: Copy + PartialEq, V: Clone + Copy, const N: usize> Map<K, V, N> {
     #[inline]
     pub fn insert(&mut self, k: K, v: V) {
         self.remove(&k);
-        for i in 0..N {
-            if self.next <= i {
-                break;
-            }
+        for i in 0..self.next {
             if !self.pairs[i].is_some() {
                 self.pairs[i] = Present((k, v));
                 return;
@@ -137,10 +125,7 @@ impl<K: Copy + PartialEq, V: Clone + Copy, const N: usize> Map<K, V, N> {
     #[inline]
     #[must_use]
     pub fn get(&self, k: &K) -> Option<&V> {
-        for i in 0..N {
-            if self.next <= i {
-                break;
-            }
+        for i in 0..self.next {
             if let Present(p) = &self.pairs[i] {
                 if p.0 == *k {
                     return Some(&p.1);
@@ -158,10 +143,7 @@ impl<K: Copy + PartialEq, V: Clone + Copy, const N: usize> Map<K, V, N> {
     #[inline]
     #[must_use]
     pub fn get_mut(&mut self, k: &K) -> Option<&mut V> {
-        for i in 0..N {
-            if self.next <= i {
-                break;
-            }
+        for i in 0..self.next {
             if let Present(p) = &mut self.pairs[i] {
                 if p.0 == *k {
                     return Some(&mut self.pairs[i].as_mut().unwrap().1);