Consistently indented some preprocessor directives.

Added a str() method and companion operator<<(std::ostream) similar to multipart_t.
Added some comments to mark the end of preprocessor instructions / class def / namespace def.

zmq.hpp

@@ -42,13 +42,17 @@
 
 #include <zmq.h>
 
-#include <algorithm>
 #include <cassert>
 #include <cstring>
-#include <string>
+
+#include <algorithm>
 #include <exception>
-#include <vector>
+#include <iomanip>
 #include <iterator>
+#include <sstream>
+#include <string>
+#include <vector>
+
 
 #ifdef ZMQ_CPP11
     #include <chrono>
@@ -378,6 +382,42 @@ namespace zmq
             return value;
         }
 #endif
+        /** Dump content to string. Ascii chars are readable, the rest is printed as hex.
+         *  Probably ridiculously slow.
+         */
+        inline std::string str() const
+        {
+            // Partly mutuated from the same method in zmq::multipart_t
+            std::stringstream os;
+
+            const unsigned char* msg_data = this->data<unsigned char>();
+            unsigned char byte;
+            size_t size = this->size();
+            int is_ascii[2] = {0, 0};
+
+            os << "zmq::message_t [size " << std::dec << std::setw(3) << std::setfill('0') << size << "] (";
+            // Totally arbitrary
+            if (size >= 1000) {
+                os << "... too big to print)";
+            } else {
+                while (size--) {
+                    byte = *msg_data++;
+
+                    is_ascii[1] = (byte >= 33 && byte  < 127);
+                    if (is_ascii[1] != is_ascii[0])
+                        os << " ";  // Separate text/non text
+
+                    if (is_ascii[1]) {
+                        os << byte;
+                    } else {
+                        os << std::hex << std::uppercase << std::setw(2) << std::setfill('0') << static_cast<short>(byte);
+                    }
+                    is_ascii[0] = is_ascii[1];
+                }
+                os << ")";
+            }
+            return os.str();
+        }
 
     private:
         //  The underlying message
@@ -995,9 +1035,15 @@ namespace zmq
     private:
         void *poller_ptr;
         std::vector<zmq_poller_event_t> poller_events;
-    };
+    };  // class poller_t
 #endif //  defined(ZMQ_BUILD_DRAFT_API) && defined(ZMQ_CPP11) && defined(ZMQ_HAVE_POLLER)
 
+
+inline std::ostream& operator<<(std::ostream& os, const message_t& msg)
+{
+    return os << msg.str();
 }
 
-#endif
+}  // namespace zmq
+
+#endif  // __ZMQ_HPP_INCLUDED__