fixed length strings get written null-terminated by default

protocols/acn/pdu-stream.cpp

@@ -87,10 +87,14 @@ uint8_t * pdu_stream::base()
  */
 void pdu_stream::readString(std::string &str, const int fixed_length)
 {
-  if (!fixed_length) {
+  // if fixed_length == 0, use all available data on the stream
+  if (!fixed_length)
+    {
       str += std::string(reinterpret_cast<char*>(data()), available());
       return setstate(std::ios_base::eofbit);
     }
+
+  // otherwise, construct a buffer and read into that.
   uint8_t buffer[fixed_length];
   read(buffer, fixed_length);
   if (gcount() != fixed_length)
@@ -102,16 +106,34 @@ void pdu_stream::readString(std::string &str, const int fixed_length)
 /**
  * @brief pdu_stream::writeString
  * @param str
- * @param fixed_length write this length to the stream, padding with null if
- * str is shorter than fixed_length.  If 0 will write only the contents of str.
+ * @param fixed_length write this length to the stream, padding with null
+ * if str is shorter than fixed_length.  If 0, will write the unrestricted
+ * contents of str.
+ * @param terminated If true, the last byte of fixed_length is guaranteed to
+ * be a 0 (null) byte.
  */
-void pdu_stream::writeString(const std::string &str, const int fixed_length)
+void pdu_stream::writeString(const std::string &str, const size_t fixed_length,
+                             const bool terminated)
 {
-  for (size_t i = 0; i < (fixed_length > 0 ? fixed_length : str.size()); i++)
-    if (i < str.size())
-      writeType<char>(str.at(i));
-    else
-      writeType<uint8_t>(0);
+  // fixed_length == 0 means dynamic length.
+  bool fixed = fixed_length > 0 ? true : false;
+
+  // fixed length strings restricted to fixed_lengh characters
+  size_t maxlen = fixed ? fixed_length : str.size();
+
+  // write no more of the string than is available
+  size_t wrtlen = str.size() < maxlen ? str.size() : maxlen;
+
+  // terminated fixed-length strings get a guaranteed padding byte
+  if (fixed && terminated && wrtlen == maxlen)
+    --wrtlen;
+
+  // output the correct ammount of data from the string
+  write(reinterpret_cast<const uint8_t*>(str.data()), wrtlen);
+
+  // output any required padding bytes
+  for (size_t i = wrtlen; i < maxlen; i++)
+    put(0);
 }
 
 

protocols/acn/pdu-stream.h

@@ -81,7 +81,8 @@ public:
 
   // strings
   void readString(std::string& str, const int fixed_length = 0);
-  void writeString(const std::string& str, const int fixed_length = 0);
+  void writeString(const std::string& str, const size_t fixed_length = 0,
+                   const bool terminated = true);
 
   // reinterpreted i/o
   /**