Added constructor from another HeaderList type

include/cppkafka/buffer.h

@@ -89,7 +89,7 @@ public:
      * \param last An iterator to the end of data (not included)
      */
     template <typename Iter>
-    Buffer(const Iter first, Iter last)
+    Buffer(const Iter first, const Iter last)
     : Buffer(&*first, std::distance(first, last)) {
     }
 

include/cppkafka/header_list.h

@@ -51,6 +51,9 @@ namespace cppkafka {
 template <typename HeaderType>
 class HeaderList {
 public:
+    template <typename OtherHeaderType>
+    friend class HeaderList;
+    
     using BufferType = typename HeaderType::ValueType;
     using Iterator = HeaderIterator<HeaderType>;
     /**
@@ -75,6 +78,16 @@ public:
      */
     explicit HeaderList(rd_kafka_headers_t* handle);
     
+    /**
+     * \brief Create a header list from another header list type
+     * \param other The other list
+     */
+    template <typename OtherHeaderType>
+    HeaderList(const HeaderList<OtherHeaderType>& other);
+
+    template <typename OtherHeaderType>
+    HeaderList(HeaderList<OtherHeaderType>&& other);
+    
     /**
      * \brief Add a header to the list. This translates to rd_kafka_header_add().
      * \param header The header.
@@ -219,6 +232,20 @@ HeaderList<HeaderType>::HeaderList(rd_kafka_headers_t* handle, NonOwningTag)
     assert(handle);
 }
 
+template <typename HeaderType>
+template <typename OtherHeaderType>
+HeaderList<HeaderType>::HeaderList(const HeaderList<OtherHeaderType>& other)
+: handle_(other.handle_) {
+
+}
+
+template <typename HeaderType>
+template <typename OtherHeaderType>
+HeaderList<HeaderType>::HeaderList(HeaderList<OtherHeaderType>&& other)
+: handle_(std::move(other.handle_)) {
+
+}
+
 // Methods
 template <typename HeaderType>
 Error HeaderList<HeaderType>::add(const HeaderType& header) {
@@ -279,13 +306,15 @@ bool HeaderList<HeaderType>::empty() const {
 template <typename HeaderType>
 typename HeaderList<HeaderType>::Iterator
 HeaderList<HeaderType>::begin() const {
-    return empty() ? end() : Iterator(make_non_owning(handle_.get()), 0);
+    return empty() ? Iterator(HeaderList<HeaderType>(), 0) :
+                     Iterator(make_non_owning(handle_.get()), 0);
 }
 
 template <typename HeaderType>
 typename HeaderList<HeaderType>::Iterator
 HeaderList<HeaderType>::end() const {
-    return Iterator(empty() ? HeaderList<HeaderType>() : make_non_owning(handle_.get()), size());
+    return empty() ? Iterator(HeaderList<HeaderType>(), size()) :
+                     Iterator(make_non_owning(handle_.get()), size());
 }
 
 template <typename HeaderType>

include/cppkafka/message_builder.h

@@ -244,6 +244,9 @@ BasicMessageBuilder<T, C>::BasicMessageBuilder(const Message& message)
 : topic_(message.get_topic()),
   key_(Buffer(message.get_key().get_data(), message.get_key().get_size())),
 #if (RD_KAFKA_VERSION >= RD_KAFKA_HEADERS_SUPPORT_VERSION)
+  //Here we must copy explicitly the Message headers since they are non-owning and this class
+  //assumes full ownership. Otherwise we will be holding an invalid handle when Message goes
+  //out of scope and rdkafka frees its resource.
   header_list_(message.get_header_list() ?
                HeaderListType(rd_kafka_headers_copy(message.get_header_list().get_handle())) : HeaderListType()), //copy headers
 #endif
@@ -261,8 +264,7 @@ BasicMessageBuilder<T, C>::BasicMessageBuilder(const BasicMessageBuilder<U, V>&
 : topic_(rhs.topic()),
   partition_(rhs.partition()),
 #if (RD_KAFKA_VERSION >= RD_KAFKA_HEADERS_SUPPORT_VERSION)
-  header_list_(rhs.header_list() ?
+  header_list_(rhs.header_list()), //copy headers
-               HeaderListType(rd_kafka_headers_copy(rhs.header_list().get_handle())) : HeaderListType()), //copy headers
 #endif
   timestamp_(rhs.timestamp()),
   user_data_(rhs.user_data()),
@@ -277,8 +279,7 @@ BasicMessageBuilder<T, C>::BasicMessageBuilder(BasicMessageBuilder<U, V>&& rhs)
 : topic_(rhs.topic()),
   partition_(rhs.partition()),
 #if (RD_KAFKA_VERSION >= RD_KAFKA_HEADERS_SUPPORT_VERSION)
-  header_list_(rhs.header_list() ?
+  header_list_(std::move(header_list())), //assume header ownership
-               HeaderListType(rhs.header_list().release_handle()) : HeaderListType()), //assume header ownership
 #endif
   timestamp_(rhs.timestamp()),
   user_data_(rhs.user_data()),