From 6cb6d1b59dfd96fe2cf10c2acb18e791c1b077e4 Mon Sep 17 00:00:00 2001
From: bluurryy <164359728+bluurryy@users.noreply.github.com>
Date: Tue, 29 Oct 2024 23:48:00 +0100
Subject: [PATCH] perf: use regular `mul` instead of `checked_mul` when
 doubling capacity

---
 src/bump_vec.rs         | 5 +++--
 src/mut_bump_vec.rs     | 5 +++--
 src/mut_bump_vec_rev.rs | 5 +++--
 3 files changed, 9 insertions(+), 6 deletions(-)

diff --git a/src/bump_vec.rs b/src/bump_vec.rs
index a40d878..801e132 100644
--- a/src/bump_vec.rs
+++ b/src/bump_vec.rs
@@ -1616,8 +1616,9 @@ where
             return Ok(());
         }
 
-        let new_cap = self.capacity().checked_mul(2).unwrap_or(required_cap).max(required_cap);
-        let new_cap = new_cap.max(min_non_zero_cap(T::SIZE));
+        // This guarantees exponential growth. The doubling cannot overflow
+        // because `capacity <= isize::MAX` and the type of `capacity` is usize;
+        let new_cap = (self.capacity() * 2).max(required_cap).max(min_non_zero_cap(T::SIZE));
 
         self.generic_grow_to(new_cap)
     }
diff --git a/src/mut_bump_vec.rs b/src/mut_bump_vec.rs
index f5bd03c..05a256c 100644
--- a/src/mut_bump_vec.rs
+++ b/src/mut_bump_vec.rs
@@ -1309,8 +1309,9 @@ where
             return Ok(());
         }
 
-        let new_cap = self.capacity().checked_mul(2).unwrap_or(required_cap).max(required_cap);
-        let new_cap = new_cap.max(min_non_zero_cap(T::SIZE));
+        // This guarantees exponential growth. The doubling cannot overflow
+        // because `capacity <= isize::MAX` and the type of `capacity` is usize;
+        let new_cap = (self.capacity() * 2).max(required_cap).max(min_non_zero_cap(T::SIZE));
 
         unsafe { self.generic_grow_to(new_cap) }
     }
diff --git a/src/mut_bump_vec_rev.rs b/src/mut_bump_vec_rev.rs
index 327b2f6..3bdec7d 100644
--- a/src/mut_bump_vec_rev.rs
+++ b/src/mut_bump_vec_rev.rs
@@ -1334,8 +1334,9 @@ where
             return Ok(());
         }
 
-        let new_cap = self.capacity().checked_mul(2).unwrap_or(required_cap).max(required_cap);
-        let new_cap = new_cap.max(min_non_zero_cap(T::SIZE));
+        // This guarantees exponential growth. The doubling cannot overflow
+        // because `capacity <= isize::MAX` and the type of `capacity` is usize;
+        let new_cap = (self.capacity() * 2).max(required_cap).max(min_non_zero_cap(T::SIZE));
 
         unsafe { self.generic_grow_to(new_cap) }
     }