From 4ad74c5736b3b97bcb0d420a4dc1230cbd602eaa Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=87a=C4=9Ftay=20Fabry?= <cagtay.fabry@bam.de>
Date: Tue, 2 Sep 2025 10:28:08 +0200
Subject: [PATCH] allow AdsWrite for zero length buffer

backport of https://github.com/Beckhoff/ADS/commit/8bee2f64b62724aa5313997d8e60d0c68c789da6

see https://github.com/Beckhoff/ADS/issues/264
---
 AdsLib/AdsLib.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/AdsLib/AdsLib.cpp b/AdsLib/AdsLib.cpp
index c60c7f97..aeee6ecc 100644
--- a/AdsLib/AdsLib.cpp
+++ b/AdsLib/AdsLib.cpp
@@ -217,7 +217,7 @@ long AdsSyncWriteReqEx(long           port,
                        const void*    buffer)
 {
     ASSERT_PORT_AND_AMSADDR(port, pAddr);
-    if (!buffer) {
+    if (!buffer && bufferLength) {
         return ADSERR_CLIENT_INVALIDPARM;
     }
 
@@ -332,3 +332,4 @@ long AdsSyncSetTimeoutEx(long port, uint32_t timeout)
     ASSERT_PORT(port);
     return GetRouter().SetTimeout((uint16_t)port, timeout);
 }
+