From 9c29c8ddfcfb8b413c004240fda95bb56c7d106c Mon Sep 17 00:00:00 2001
From: Tim Wojtulewicz <tim@corelight.com>
Date: Wed, 11 Aug 2021 15:40:09 -0700
Subject: [PATCH] GH-1713: Avoid unneeded reallocs in
 SerializationFormat::WriteData

---
 src/SerializationFormat.cc | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/SerializationFormat.cc b/src/SerializationFormat.cc
index ad9e2b26d9..fe5d34bbe2 100644
--- a/src/SerializationFormat.cc
+++ b/src/SerializationFormat.cc
@@ -82,10 +82,18 @@ bool SerializationFormat::ReadData(void* b, size_t count)
 bool SerializationFormat::WriteData(const void* b, size_t count)
 	{
 	// Increase buffer if necessary.
+	bool size_changed = false;
 	while ( output_pos + count > output_size )
+		{
 		output_size *= GROWTH_FACTOR;
+		size_changed = true;
+		}
 
-	output = (char*)util::safe_realloc(output, output_size);
+	// The glibc standard states explicitly that calling realloc with the same
+	// size is a no-op, but the same claim can't be made on other platforms.
+	// There's really no reason to do that though.
+	if ( size_changed )
+		output = (char*)util::safe_realloc(output, output_size);
 
 	memcpy(output + output_pos, b, count);
 	output_pos += count;