add API to set msg counter

CHANGELOG.md

@@ -10,7 +10,6 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## Fixes
 
-
 - Important bugfix in CFDP PDU header format: The entity length field and the transaction sequence
   number fields stored the actual length of the field instead of the length minus 1 like specified
   in the CFDP standard.
@@ -26,6 +25,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 - add CFDP subsystem ID
   https://egit.irs.uni-stuttgart.de/fsfw/fsfw/pulls/742
+- `PusTmZcWriter` now exposes API to set message counter field.
 
 ## Changed
 - Bump ETL version to 20.35.14

src/fsfw/tmtcpacket/pus/tm/PusTmZcWriter.cpp

@@ -24,3 +24,9 @@ void PusTmZeroCopyWriter::updateErrorControl() {
   crcStart[0] = (crc16 >> 8) & 0xff;
   crcStart[1] = crc16 & 0xff;
 }
+
+void PusTmZeroCopyWriter::setMessageCount(uint16_t msgCount) {
+  size_t serSize = 0;
+  SerializeAdapter::serialize(&msgCount, const_cast<uint8_t*>(pointers.secHeaderStart + 3),
+                              &serSize, 2, SerializeIF::Endianness::NETWORK);
+}

src/fsfw/tmtcpacket/pus/tm/PusTmZcWriter.h

@@ -14,6 +14,7 @@ class PusTmZeroCopyWriter : public PusTmReader {
   PusTmZeroCopyWriter(TimeReaderIF& timeReader, uint8_t* data, size_t size);
 
   void setSequenceCount(uint16_t seqCount);
+  void setMessageCount(uint16_t msgCount);
   void updateErrorControl();
 
  private: