From 02c5d60f825cb36b4154baa7ee4f854e8016dbc1 Mon Sep 17 00:00:00 2001
From: Zixuan Chen <remch183@outlook.com>
Date: Sun, 22 Oct 2023 00:20:48 +0800
Subject: [PATCH] fix: take currently free slots into account

---
 src/arena.rs | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/arena.rs b/src/arena.rs
index 92e7fea..24991c1 100644
--- a/src/arena.rs
+++ b/src/arena.rs
@@ -167,9 +167,10 @@ impl<T> Arena<T> {
     }
 
     /// Reserve capacity for at least `additional` more elements to be inserted
-    #[inline(always)]
     pub fn reserve(&mut self, additional: usize) {
-        self.storage.reserve(additional)
+        let currently_free = self.storage.len().saturating_sub(self.len as usize);
+        let to_reserve = additional.saturating_sub(currently_free);
+        self.storage.reserve(to_reserve);
     }
 
     /// Returns whether the arena is empty.