From 1fa03934791189f02208e1807d822128b216f087 Mon Sep 17 00:00:00 2001
From: Daniel Pauls <daniel1708.de+git@gmail.com>
Date: Tue, 5 Apr 2022 21:16:11 +0200
Subject: [PATCH] libutil: Reserve memory when en/decoding base64

The size of the output when encoding to and decoding from base64 is
(roughly) known so we can allocate it in advance to prevent
reallocation.
---
 src/libutil/util.cc | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/libutil/util.cc b/src/libutil/util.cc
index 59e3aad6d..cca66d5bf 100644
--- a/src/libutil/util.cc
+++ b/src/libutil/util.cc
@@ -1471,6 +1471,7 @@ constexpr char base64Chars[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuv
 std::string base64Encode(std::string_view s)
 {
     std::string res;
+    res.reserve((s.size() + 2) / 3 * 4);
     int data = 0, nbits = 0;
 
     for (char c : s) {
@@ -1502,6 +1503,9 @@ std::string base64Decode(std::string_view s)
     }();
 
     std::string res;
+    // Some sequences are missing the padding consisting of up to two '='.
+    //                    vvv
+    res.reserve((s.size() + 2) / 4 * 3);
     unsigned int d = 0, bits = 0;
 
     for (char c : s) {