From 35d6ad1f3367e25f6b69fa24d878cfbc80898c63 Mon Sep 17 00:00:00 2001
From: Tomek Czajka <tczajka@gmail.com>
Date: Fri, 23 Oct 2020 20:36:52 -0700
Subject: [PATCH] Shrink overallocated capacity if a number gets a lot smaller.

If a number gets below 1/4 of capacity, shrink_to_fit. Since Vec grows by 2, this amortizes well
for any sequence of sizes.
---
 src/biguint.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/biguint.rs b/src/biguint.rs
index 0a582e02..7d8ab710 100644
--- a/src/biguint.rs
+++ b/src/biguint.rs
@@ -2617,6 +2617,9 @@ impl BigUint {
         while let Some(&0) = self.data.last() {
             self.data.pop();
         }
+        if self.data.len() < self.data.capacity() / 4 {
+            self.data.shrink_to_fit();
+        }
     }
 
     /// Returns a normalized `BigUint`.