Get AIX 6.1 compiling again by making msg_t class explicit

Older versions of gcc have problems with in-line forward declarations
when there's a naming conflict with a global symbol.

Signed-off-by: AJ Lewis <aj.lewis@quantum.com>

Expand the original patch to all such forward declarations.
Signed-off-by: Martin Sustrik <sustrik@250bpm.com>

40 files changed, 361 insertions, 221 deletions

diff --git a/src/command.hpp b/src/command.hpp
index ecf2d93..8378369 100644
--- a/src/command.hpp
+++ b/src/command.hpp
@@ -27,12 +27,18 @@
 namespace zmq
 {
 
+    class object_t;
+    class own_t;
+    struct i_engine;
+    class pipe_t;
+    class socket_base_t;
+
     //  This structure defines the commands that can be sent between threads.
 
     struct command_t
     {
         //  Object to process the command.
-        class object_t *destination;
+        zmq::object_t *destination;
 
         enum type_t
         {
@@ -67,7 +73,7 @@ namespace zmq
 
             //  Sent to socket to let it know about the newly created object.
             struct {
-                class own_t *object;
+                zmq::own_t *object;
             } own;
 
             //  Attach the engine to the session. If engine is NULL, it informs
@@ -79,7 +85,7 @@ namespace zmq
             //  Sent from session to socket to establish pipe(s) between them.
             //  Caller have used inc_seqnum beforehand sending the command.
             struct {
-                class pipe_t *pipe;
+                zmq::pipe_t *pipe;
             } bind;
 
             //  Sent by pipe writer to inform dormant pipe reader that there
@@ -112,7 +118,7 @@ namespace zmq
             //  Sent by I/O object ot the socket to request the shutdown of
             //  the I/O object.
             struct {
-                class own_t *object;
+                zmq::own_t *object;
             } term_req;
 
             //  Sent by socket to I/O object to start its shutdown.
@@ -128,7 +134,7 @@ namespace zmq
             //  Transfers the ownership of the closed socket
             //  to the reaper thread.
             struct {
-                class socket_base_t *socket;
+                zmq::socket_base_t *socket;
             } reap;
 
             //  Closed socket notifies the reaper that it's already deallocated.
diff --git a/src/ctx.hpp b/src/ctx.hpp
index 619d57e..e09149d 100644
--- a/src/ctx.hpp
+++ b/src/ctx.hpp
@@ -36,6 +36,12 @@
 
 namespace zmq
 {
+
+    class object_t;
+    class io_thread_t;
+    class socket_base_t;
+    class reaper_t;
+
     //  Information associated with inproc endpoint. Note that endpoint options
     //  are registered as well so that the peer can access them without a need
     //  for synchronisation, handshaking or similar.
@@ -66,8 +72,8 @@ namespace zmq
         int terminate ();
 
         //  Create and destroy a socket.
-        class socket_base_t *create_socket (int type_);
-        void destroy_socket (class socket_base_t *socket_);
+        zmq::socket_base_t *create_socket (int type_);
+        void destroy_socket (zmq::socket_base_t *socket_);
 
         //  Send command to the destination thread.
         void send_command (uint32_t tid_, const command_t &command_);
@@ -75,14 +81,14 @@ namespace zmq
         //  Returns the I/O thread that is the least busy at the moment.
         //  Affinity specifies which I/O threads are eligible (0 = all).
         //  Returns NULL is no I/O thread is available.
-        class io_thread_t *choose_io_thread (uint64_t affinity_);
+        zmq::io_thread_t *choose_io_thread (uint64_t affinity_);
 
         //  Returns reaper thread object.
-        class object_t *get_reaper ();
+        zmq::object_t *get_reaper ();
 
         //  Management of inproc endpoints.
         int register_endpoint (const char *addr_, endpoint_t &endpoint_);
-        void unregister_endpoints (class socket_base_t *socket_);
+        void unregister_endpoints (zmq::socket_base_t *socket_);
         endpoint_t find_endpoint (const char *addr_);
 
         //  Logging.
@@ -120,10 +126,10 @@ namespace zmq
         mutex_t slot_sync;
 
         //  The reaper thread.
-        class reaper_t *reaper;
+        zmq::reaper_t *reaper;
 
         //  I/O threads.
-        typedef std::vector <class io_thread_t*> io_threads_t;
+        typedef std::vector <zmq::io_thread_t*> io_threads_t;
         io_threads_t io_threads;
 
         //  Array of pointers to mailboxes for both application and I/O threads.
@@ -142,7 +148,7 @@ namespace zmq
 
         //  PUB socket for logging. The socket is shared among all the threads,
         //  thus it is synchronised by a mutex.
-        class socket_base_t *log_socket;
+        zmq::socket_base_t *log_socket;
         mutex_t log_sync;
 
         ctx_t (const ctx_t&);
diff --git a/src/decoder.hpp b/src/decoder.hpp
index c6f9100..4afd018 100644
--- a/src/decoder.hpp
+++ b/src/decoder.hpp
@@ -34,6 +34,8 @@
 namespace zmq
 {
 
+    class session_base_t;
+
     //  Helper base class for decoders that know the amount of data to read
     //  in advance at any moment. Knowing the amount in advance is a property
     //  of the protocol used. 0MQ framing protocol is based size-prefixed
@@ -193,7 +195,7 @@ namespace zmq
         decoder_t (size_t bufsize_, int64_t maxmsgsize_);
         ~decoder_t ();
 
-        void set_session (class session_base_t *session_);
+        void set_session (zmq::session_base_t *session_);
 
     private:
 
@@ -202,7 +204,7 @@ namespace zmq
         bool flags_ready ();
         bool message_ready ();
 
-        class session_base_t *session;
+        zmq::session_base_t *session;
         unsigned char tmpbuf [8];
         msg_t in_progress;
 
diff --git a/src/devpoll.hpp b/src/devpoll.hpp
index 1de1af0..382be0f 100644
--- a/src/devpoll.hpp
+++ b/src/devpoll.hpp
@@ -35,6 +35,8 @@
 namespace zmq
 {
 
+    struct i_poll_events;
+
     //  Implements socket polling mechanism using the "/dev/poll" interface.
 
     class devpoll_t : public poller_base_t
@@ -47,7 +49,7 @@ namespace zmq
         ~devpoll_t ();
 
         //  "poller" concept.
-        handle_t add_fd (fd_t fd_, struct i_poll_events *events_);
+        handle_t add_fd (fd_t fd_, zmq::i_poll_events *events_);
         void rm_fd (handle_t handle_);
         void set_pollin (handle_t handle_);
         void reset_pollin (handle_t handle_);
@@ -70,7 +72,7 @@ namespace zmq
         struct fd_entry_t
         {
             short events;
-            struct i_poll_events *reactor;
+            zmq::i_poll_events *reactor;
             bool valid;
             bool accepted;
         };
diff --git a/src/dist.hpp b/src/dist.hpp
index a72de6e..be86ab2 100644
--- a/src/dist.hpp
+++ b/src/dist.hpp
@@ -29,6 +29,9 @@
 namespace zmq
 {
 
+    class pipe_t;
+    class msg_t;
+
     //  Class manages a set of outbound pipes. It sends each messages to
     //  each of them.
     class dist_t
@@ -39,26 +42,26 @@ namespace zmq
         ~dist_t ();
 
         //  Adds the pipe to the distributor object.
-        void attach (class pipe_t *pipe_);
+        void attach (zmq::pipe_t *pipe_);
 
         //  Activates pipe that have previously reached high watermark.
-        void activated (class pipe_t *pipe_);
+        void activated (zmq::pipe_t *pipe_);
 
         //  Mark the pipe as matching. Subsequent call to send_to_matching
         //  will send message also to this pipe.
-        void match (class pipe_t *pipe_);
+        void match (zmq::pipe_t *pipe_);
 
         //  Mark all pipes as non-matching.
         void unmatch ();
 
         //  Removes the pipe from the distributor object.
-        void terminated (class pipe_t *pipe_);
+        void terminated (zmq::pipe_t *pipe_);
 
         //  Send the message to the matching outbound pipes.
-        int send_to_matching (class msg_t *msg_, int flags_);
+        int send_to_matching (zmq::msg_t *msg_, int flags_);
 
         //  Send the message to all the outbound pipes.
-        int send_to_all (class msg_t *msg_, int flags_);
+        int send_to_all (zmq::msg_t *msg_, int flags_);
 
         bool has_out ();
 
@@ -66,13 +69,13 @@ namespace zmq
 
         //  Write the message to the pipe. Make the pipe inactive if writing
         //  fails. In such a case false is returned.
-        bool write (class pipe_t *pipe_, class msg_t *msg_);
+        bool write (zmq::pipe_t *pipe_, zmq::msg_t *msg_);
 
         //  Put the message to all active pipes.
-        void distribute (class msg_t *msg_, int flags_);
+        void distribute (zmq::msg_t *msg_, int flags_);
 
         //  List of outbound pipes.
-        typedef array_t <class pipe_t, 2> pipes_t;
+        typedef array_t <zmq::pipe_t, 2> pipes_t;
         pipes_t pipes;
 
         //  Number of all the pipes to send the next message to.
diff --git a/src/encoder.hpp b/src/encoder.hpp
index 8001c4e..f521b6b 100644
--- a/src/encoder.hpp
+++ b/src/encoder.hpp
@@ -33,6 +33,8 @@
 namespace zmq
 {
 
+    class session_base_t;
+
     //  Helper base class for encoders. It implements the state machine that
     //  fills the outgoing buffer. Derived classes should implement individual
     //  state machine actions.
@@ -173,14 +175,14 @@ namespace zmq
         encoder_t (size_t bufsize_);
         ~encoder_t ();
 
-        void set_session (class session_base_t *session_);
+        void set_session (zmq::session_base_t *session_);
 
     private:
 
         bool size_ready ();
         bool message_ready ();
 
-        class session_base_t *session;
+        zmq::session_base_t *session;
         msg_t in_progress;
         unsigned char tmpbuf [10];
 
diff --git a/src/epoll.hpp b/src/epoll.hpp
index 9bc31a5..3fd4262 100644
--- a/src/epoll.hpp
+++ b/src/epoll.hpp
@@ -36,6 +36,8 @@
 namespace zmq
 {
 
+    struct i_poll_events;
+
     //  This class implements socket polling mechanism using the Linux-specific
     //  epoll mechanism.
 
@@ -49,7 +51,7 @@ namespace zmq
         ~epoll_t ();
 
         //  "poller" concept.
-        handle_t add_fd (fd_t fd_, struct i_poll_events *events_);
+        handle_t add_fd (fd_t fd_, zmq::i_poll_events *events_);
         void rm_fd (handle_t handle_);
         void set_pollin (handle_t handle_);
         void reset_pollin (handle_t handle_);
@@ -73,7 +75,7 @@ namespace zmq
         {
             fd_t fd;
             epoll_event ev;
-            struct i_poll_events *events;
+            zmq::i_poll_events *events;
         };
 
         //  List of retired event sources.
diff --git a/src/i_engine.hpp b/src/i_engine.hpp
index 19359b7..93cd8b1 100644
--- a/src/i_engine.hpp
+++ b/src/i_engine.hpp
@@ -25,6 +25,8 @@
 namespace zmq
 {
 
+    class io_thread_t;
+
     //  Abstract interface to be implemented by various engines.
 
     struct i_engine
@@ -32,7 +34,7 @@ namespace zmq
         virtual ~i_engine () {}
 
         //  Plug the engine to the session.
-        virtual void plug (class io_thread_t *io_thread_,
+        virtual void plug (zmq::io_thread_t *io_thread_,
             class session_base_t *session_) = 0;
 
         //  Unplug the engine from the session.
diff --git a/src/io_object.hpp b/src/io_object.hpp
index bf7a625..689b221 100644
--- a/src/io_object.hpp
+++ b/src/io_object.hpp
@@ -31,6 +31,8 @@
 namespace zmq
 {
 
+    class io_thread_t;
+
     //  Simple base class for objects that live in I/O threads.
     //  It makes communication with the poller object easier and
     //  makes defining unneeded event handlers unnecessary.
@@ -39,12 +41,12 @@ namespace zmq
     {
     public:
 
-        io_object_t (class io_thread_t *io_thread_ = NULL);
+        io_object_t (zmq::io_thread_t *io_thread_ = NULL);
         ~io_object_t ();
 
         //  When migrating an object from one I/O thread to another, first
         //  unplug it, then migrate it, then plug it to the new thread.
-        void plug (class io_thread_t *io_thread_);
+        void plug (zmq::io_thread_t *io_thread_);
         void unplug ();
 
     protected:
diff --git a/src/io_thread.hpp b/src/io_thread.hpp
index 986c88d..00bd9a6 100644
--- a/src/io_thread.hpp
+++ b/src/io_thread.hpp
@@ -33,6 +33,8 @@
 namespace zmq
 {
 
+    class ctx_t;
+
     //  Generic part of the I/O thread. Polling-mechanism-specific features
     //  are implemented in separate "polling objects".
 
@@ -40,7 +42,7 @@ namespace zmq
     {
     public:
 
-        io_thread_t (class ctx_t *ctx_, uint32_t tid_);
+        io_thread_t (zmq::ctx_t *ctx_, uint32_t tid_);
 
         //  Clean-up. If the thread was started, it's neccessary to call 'stop'
         //  before invoking destructor. Otherwise the destructor would hang up.
diff --git a/src/ipc_connecter.hpp b/src/ipc_connecter.hpp
index c02245a..d2d1752 100644
--- a/src/ipc_connecter.hpp
+++ b/src/ipc_connecter.hpp
@@ -34,14 +34,17 @@
 namespace zmq
 {
 
+    class io_thread_t;
+    class session_base_t;
+
     class ipc_connecter_t : public own_t, public io_object_t
     {
     public:
 
         //  If 'delay' is true connecter first waits for a while, then starts
         //  connection process.
-        ipc_connecter_t (class io_thread_t *io_thread_,
-            class session_base_t *session_, const options_t &options_,
+        ipc_connecter_t (zmq::io_thread_t *io_thread_,
+            zmq::session_base_t *session_, const options_t &options_,
             const char *address_, bool delay_);
         ~ipc_connecter_t ();
 
@@ -101,7 +104,7 @@ namespace zmq
         bool wait;
 
         //  Reference to the session we belong to.
-        class session_base_t *session;
+        zmq::session_base_t *session;
 
         //  Current reconnect ivl, updated for backoff strategy
         int current_reconnect_ivl;
diff --git a/src/ipc_listener.hpp b/src/ipc_listener.hpp
index 0f06d23..e1f4817 100644
--- a/src/ipc_listener.hpp
+++ b/src/ipc_listener.hpp
@@ -35,12 +35,15 @@
 namespace zmq
 {
 
+    class io_thread_t;
+    class socket_base_t;
+
     class ipc_listener_t : public own_t, public io_object_t
     {
     public:
 
-        ipc_listener_t (class io_thread_t *io_thread_,
-            class socket_base_t *socket_, const options_t &options_);
+        ipc_listener_t (zmq::io_thread_t *io_thread_,
+            zmq::socket_base_t *socket_, const options_t &options_);
         ~ipc_listener_t ();
 
         //  Set address to listen on.
@@ -76,7 +79,7 @@ namespace zmq
         handle_t handle;
 
         //  Socket the listerner belongs to.
-        class socket_base_t *socket;
+        zmq::socket_base_t *socket;
 
         ipc_listener_t (const ipc_listener_t&);
         const ipc_listener_t &operator = (const ipc_listener_t&);
diff --git a/src/kqueue.hpp b/src/kqueue.hpp
index 14f4e49..b1352df 100644
--- a/src/kqueue.hpp
+++ b/src/kqueue.hpp
@@ -35,6 +35,8 @@
 namespace zmq
 {
 
+    struct i_poll_events;
+
     //  Implements socket polling mechanism using the BSD-specific
     //  kqueue interface.
 
@@ -48,7 +50,7 @@ namespace zmq
         ~kqueue_t ();
 
         //  "poller" concept.
-        handle_t add_fd (fd_t fd_, struct i_poll_events *events_);
+        handle_t add_fd (fd_t fd_, zmq::i_poll_events *events_);
         void rm_fd (handle_t handle_);
         void set_pollin (handle_t handle_);
         void reset_pollin (handle_t handle_);
@@ -79,7 +81,7 @@ namespace zmq
             fd_t fd;
             bool flag_pollin;
             bool flag_pollout;
-            i_poll_events *reactor;
+            zmq::i_poll_events *reactor;
         };
 
         //  List of retired event sources.
diff --git a/src/lb.hpp b/src/lb.hpp
index 1de8549..91189f5 100644
--- a/src/lb.hpp
+++ b/src/lb.hpp
@@ -48,7 +48,7 @@ namespace zmq
     private:
 
         //  List of outbound pipes.
-        typedef array_t <class pipe_t, 2> pipes_t;
+        typedef array_t <pipe_t, 2> pipes_t;
         pipes_t pipes;
 
         //  Number of active pipes. All the active pipes are located at the
diff --git a/src/mtrie.hpp b/src/mtrie.hpp
index 8bbc22d..11ef940 100644
--- a/src/mtrie.hpp
+++ b/src/mtrie.hpp
@@ -29,6 +29,8 @@
 namespace zmq
 {
 
+    class pipe_t;
+
     //  Multi-trie. Each node in the trie is a set of pointers to pipes.
 
     class mtrie_t
@@ -40,35 +42,35 @@ namespace zmq
 
         //  Add key to the trie. Returns true if it's a new subscription
         //  rather than a duplicate.
-        bool add (unsigned char *prefix_, size_t size_, class pipe_t *pipe_);
+        bool add (unsigned char *prefix_, size_t size_, zmq::pipe_t *pipe_);
 
         //  Remove all subscriptions for a specific peer from the trie.
         //  If there are no subscriptions left on some topics, invoke the
         //  supplied callback function.
-        void rm (class pipe_t *pipe_,
+        void rm (zmq::pipe_t *pipe_,
             void (*func_) (unsigned char *data_, size_t size_, void *arg_),
             void *arg_);
 
         //  Remove specific subscription from the trie. Return true is it was
         //  actually removed rather than de-duplicated.
-        bool rm (unsigned char *prefix_, size_t size_, class pipe_t *pipe_);
+        bool rm (unsigned char *prefix_, size_t size_, zmq::pipe_t *pipe_);
 
         //  Signal all the matching pipes.
         void match (unsigned char *data_, size_t size_,
-            void (*func_) (class pipe_t *pipe_, void *arg_), void *arg_);
+            void (*func_) (zmq::pipe_t *pipe_, void *arg_), void *arg_);
 
     private:
 
         bool add_helper (unsigned char *prefix_, size_t size_,
-            class pipe_t *pipe_);
-        void rm_helper (class pipe_t *pipe_, unsigned char **buff_,
+            zmq::pipe_t *pipe_);
+        void rm_helper (zmq::pipe_t *pipe_, unsigned char **buff_,
             size_t buffsize_, size_t maxbuffsize_,
             void (*func_) (unsigned char *data_, size_t size_, void *arg_),
             void *arg_);
         bool rm_helper (unsigned char *prefix_, size_t size_,
-            class pipe_t *pipe_);
+            zmq::pipe_t *pipe_);
 
-        typedef std::set <class pipe_t*> pipes_t;
+        typedef std::set <zmq::pipe_t*> pipes_t;
         pipes_t pipes;
 
         unsigned char min;
diff --git a/src/object.hpp b/src/object.hpp
index f832596..932cea7 100644
--- a/src/object.hpp
+++ b/src/object.hpp
@@ -26,6 +26,17 @@
 
 namespace zmq
 {
+
+    struct i_engine;
+    struct endpoint_t;
+    struct command_t;
+    class ctx_t;
+    class pipe_t;
+    class socket_base_t;
+    class session_base_t;
+    class io_thread_t;
+    class own_t;
+
     //  Base class for all objects that participate in inter-thread
     //  communication.
 
@@ -33,51 +44,51 @@ namespace zmq
     {
     public:
 
-        object_t (class ctx_t *ctx_, uint32_t tid_);
+        object_t (zmq::ctx_t *ctx_, uint32_t tid_);
         object_t (object_t *parent_);
         virtual ~object_t ();
 
         uint32_t get_tid ();
         ctx_t *get_ctx ();
-        void process_command (struct command_t &cmd_);
+        void process_command (zmq::command_t &cmd_);
 
     protected:
 
         //  Using following function, socket is able to access global
         //  repository of inproc endpoints.
-        int register_endpoint (const char *addr_, struct endpoint_t &endpoint_);
-        void unregister_endpoints (class socket_base_t *socket_);
-        struct endpoint_t find_endpoint (const char *addr_);
-        void destroy_socket (class socket_base_t *socket_);
+        int register_endpoint (const char *addr_, zmq::endpoint_t &endpoint_);
+        void unregister_endpoints (zmq::socket_base_t *socket_);
+        zmq::endpoint_t find_endpoint (const char *addr_);
+        void destroy_socket (zmq::socket_base_t *socket_);
 
         //  Logs an message.
         void log (const char *format_, ...);
 
         //  Chooses least loaded I/O thread.
-        class io_thread_t *choose_io_thread (uint64_t affinity_);
+        zmq::io_thread_t *choose_io_thread (uint64_t affinity_);
 
         //  Derived object can use these functions to send commands
         //  to other objects.
         void send_stop ();
-        void send_plug (class own_t *destination_,
+        void send_plug (zmq::own_t *destination_,
             bool inc_seqnum_ = true);
-        void send_own (class own_t *destination_,
-            class own_t *object_);
-        void send_attach (class session_base_t *destination_,
-             struct i_engine *engine_, bool inc_seqnum_ = true);
-        void send_bind (class own_t *destination_, class pipe_t *pipe_,
+        void send_own (zmq::own_t *destination_,
+            zmq::own_t *object_);
+        void send_attach (zmq::session_base_t *destination_,
+             zmq::i_engine *engine_, bool inc_seqnum_ = true);
+        void send_bind (zmq::own_t *destination_, zmq::pipe_t *pipe_,
              bool inc_seqnum_ = true);
-        void send_activate_read (class pipe_t *destination_);
-        void send_activate_write (class pipe_t *destination_,
+        void send_activate_read (zmq::pipe_t *destination_);
+        void send_activate_write (zmq::pipe_t *destination_,
              uint64_t msgs_read_);
-        void send_hiccup (class pipe_t *destination_, void *pipe_);
-        void send_pipe_term (class pipe_t *destination_);
-        void send_pipe_term_ack (class pipe_t *destination_);
-        void send_term_req (class own_t *destination_,
-            class own_t *object_);
-        void send_term (class own_t *destination_, int linger_);
-        void send_term_ack (class own_t *destination_);
-        void send_reap (class socket_base_t *socket_);
+        void send_hiccup (zmq::pipe_t *destination_, void *pipe_);
+        void send_pipe_term (zmq::pipe_t *destination_);
+        void send_pipe_term_ack (zmq::pipe_t *destination_);
+        void send_term_req (zmq::own_t *destination_,
+            zmq::own_t *object_);
+        void send_term (zmq::own_t *destination_, int linger_);
+        void send_term_ack (zmq::own_t *destination_);
+        void send_reap (zmq::socket_base_t *socket_);
         void send_reaped ();
         void send_done ();
 
@@ -85,18 +96,18 @@ namespace zmq
         //  called when command arrives from another thread.
         virtual void process_stop ();
         virtual void process_plug ();
-        virtual void process_own (class own_t *object_);
-        virtual void process_attach (struct i_engine *engine_);
-        virtual void process_bind (class pipe_t *pipe_);
+        virtual void process_own (zmq::own_t *object_);
+        virtual void process_attach (zmq::i_engine *engine_);
+        virtual void process_bind (zmq::pipe_t *pipe_);
         virtual void process_activate_read ();
         virtual void process_activate_write (uint64_t msgs_read_);
         virtual void process_hiccup (void *pipe_);
         virtual void process_pipe_term ();
         virtual void process_pipe_term_ack ();
-        virtual void process_term_req (class own_t *object_);
+        virtual void process_term_req (zmq::own_t *object_);
         virtual void process_term (int linger_);
         virtual void process_term_ack ();
-        virtual void process_reap (class socket_base_t *socket_);
+        virtual void process_reap (zmq::socket_base_t *socket_);
         virtual void process_reaped ();
 
         //  Special handler called after a command that requires a seqnum
@@ -107,7 +118,7 @@ namespace zmq
     private:
 
         //  Context provides access to the global state.
-        class ctx_t *ctx;
+        zmq::ctx_t *ctx;
 
         //  Thread ID of the thread the object belongs to.
         uint32_t tid;
diff --git a/src/own.hpp b/src/own.hpp
index ad5c452..2969ffd 100644
--- a/src/own.hpp
+++ b/src/own.hpp
@@ -32,6 +32,9 @@
 namespace zmq
 {
 
+    class ctx_t;
+    class io_thread_t;
+
     //  Base class for objects forming a part of ownership hierarchy.
     //  It handles initialisation and destruction of such objects.
 
@@ -44,10 +47,10 @@ namespace zmq
 
         //  The object is not living within an I/O thread. It has it's own
         //  thread outside of 0MQ infrastructure.
-        own_t (class ctx_t *parent_, uint32_t tid_);
+        own_t (zmq::ctx_t *parent_, uint32_t tid_);
 
         //  The object is living within I/O thread.
-        own_t (class io_thread_t *io_thread_, const options_t &options_);
+        own_t (zmq::io_thread_t *io_thread_, const options_t &options_);
 
         //  When another owned object wants to send command to this object
         //  it calls this function to let it know it should not shut down
diff --git a/src/pair.hpp b/src/pair.hpp
index 67de2fd..fb447f1 100644
--- a/src/pair.hpp
+++ b/src/pair.hpp
@@ -28,27 +28,32 @@
 namespace zmq
 {
 
+    class ctx_t;
+    class msg_t;
+    class pipe_t;
+    class io_thread_t;
+
     class pair_t :
         public socket_base_t
     {
     public:
 
-        pair_t (class ctx_t *parent_, uint32_t tid_);
+        pair_t (zmq::ctx_t *parent_, uint32_t tid_);
         ~pair_t ();
 
         //  Overloads of functions from socket_base_t.
-        void xattach_pipe (class pipe_t *pipe_);
-        int xsend (class msg_t *msg_, int flags_);
-        int xrecv (class msg_t *msg_, int flags_);
+        void xattach_pipe (zmq::pipe_t *pipe_);
+        int xsend (zmq::msg_t *msg_, int flags_);
+        int xrecv (zmq::msg_t *msg_, int flags_);
         bool xhas_in ();
         bool xhas_out ();
-        void xread_activated (class pipe_t *pipe_);
-        void xwrite_activated (class pipe_t *pipe_);
-        void xterminated (class pipe_t *pipe_);
+        void xread_activated (zmq::pipe_t *pipe_);
+        void xwrite_activated (zmq::pipe_t *pipe_);
+        void xterminated (zmq::pipe_t *pipe_);
 
     private:
 
-        class pipe_t *pipe;
+        zmq::pipe_t *pipe;
 
         pair_t (const pair_t&);
         const pair_t &operator = (const pair_t&);
@@ -58,8 +63,8 @@ namespace zmq
     {
     public:
 
-        pair_session_t (class io_thread_t *io_thread_, bool connect_,
-            class socket_base_t *socket_, const options_t &options_,
+        pair_session_t (zmq::io_thread_t *io_thread_, bool connect_,
+            socket_base_t *socket_, const options_t &options_,
             const char *protocol_, const char *address_);
         ~pair_session_t ();
 
diff --git a/src/pgm_receiver.hpp b/src/pgm_receiver.hpp
index 3c1d394..7c97d5a 100644
--- a/src/pgm_receiver.hpp
+++ b/src/pgm_receiver.hpp
@@ -43,19 +43,22 @@
 namespace zmq
 {
 
+    class io_thread_t;
+    class session_base_t;
+
     class pgm_receiver_t : public io_object_t, public i_engine
     {
     
     public:
 
-        pgm_receiver_t (class io_thread_t *parent_, const options_t &options_);
+        pgm_receiver_t (zmq::io_thread_t *parent_, const options_t &options_);
         ~pgm_receiver_t ();
 
         int init (bool udp_encapsulation_, const char *network_);
 
         //  i_engine interface implementation.
-        void plug (class io_thread_t *io_thread_,
-            class session_base_t *session_);
+        void plug (zmq::io_thread_t *io_thread_,
+            zmq::session_base_t *session_);
         void unplug ();
         void terminate ();
         void activate_in ();
@@ -108,7 +111,7 @@ namespace zmq
         options_t options;
 
         //  Associated session.
-        class session_base_t *session;
+        zmq::session_base_t *session;
 
         //  Most recently used decoder.
         decoder_t *mru_decoder;
diff --git a/src/pgm_sender.hpp b/src/pgm_sender.hpp
index d8f046d..99405f0 100644
--- a/src/pgm_sender.hpp
+++ b/src/pgm_sender.hpp
@@ -41,19 +41,22 @@
 namespace zmq
 {
 
+    class io_thread_t;
+    class session_base_t;
+
     class pgm_sender_t : public io_object_t, public i_engine
     {
 
     public:
 
-        pgm_sender_t (class io_thread_t *parent_, const options_t &options_);
+        pgm_sender_t (zmq::io_thread_t *parent_, const options_t &options_);
         ~pgm_sender_t ();
 
         int init (bool udp_encapsulation_, const char *network_);
 
         //  i_engine interface implementation.
-        void plug (class io_thread_t *io_thread_,
-            class session_base_t *session_);
+        void plug (zmq::io_thread_t *io_thread_,
+            zmq::session_base_t *session_);
         void unplug ();
         void terminate ();
         void activate_in ();
diff --git a/src/pipe.hpp b/src/pipe.hpp
index 75a2021..f438257 100644
--- a/src/pipe.hpp
+++ b/src/pipe.hpp
@@ -34,23 +34,26 @@
 namespace zmq
 {
 
+    class object_t;
+    class pipe_t;
+
     //  Create a pipepair for bi-directional transfer of messages.
     //  First HWM is for messages passed from first pipe to the second pipe.
     //  Second HWM is for messages passed from second pipe to the first pipe.
     //  Delay specifies how the pipe behaves when the peer terminates. If true
     //  pipe receives all the pending messages before terminating, otherwise it
     //  terminates straight away.
-    int pipepair (class object_t *parents_ [2], class pipe_t* pipes_ [2],
+    int pipepair (zmq::object_t *parents_ [2], zmq::pipe_t* pipes_ [2],
         int hwms_ [2], bool delays_ [2]);
 
     struct i_pipe_events
     {
         virtual ~i_pipe_events () {}
 
-        virtual void read_activated (class pipe_t *pipe_) = 0;
-        virtual void write_activated (class pipe_t *pipe_) = 0;
-        virtual void hiccuped (class pipe_t *pipe_) = 0;
-        virtual void terminated (class pipe_t *pipe_) = 0;
+        virtual void read_activated (zmq::pipe_t *pipe_) = 0;
+        virtual void write_activated (zmq::pipe_t *pipe_) = 0;
+        virtual void hiccuped (zmq::pipe_t *pipe_) = 0;
+        virtual void terminated (zmq::pipe_t *pipe_) = 0;
     };
 
     //  Note that pipe can be stored in three different arrays.
@@ -64,8 +67,8 @@ namespace zmq
         public array_item_t <3>
     {
         //  This allows pipepair to create pipe objects.
-        friend int pipepair (class object_t *parents_ [2],
-            class pipe_t* pipes_ [2], int hwms_ [2], bool delays_ [2]);
+        friend int pipepair (zmq::object_t *parents_ [2],
+            zmq::pipe_t* pipes_ [2], int hwms_ [2], bool delays_ [2]);
 
     public:
 
diff --git a/src/poll.hpp b/src/poll.hpp
index 700256d..9a7fbc3 100644
--- a/src/poll.hpp
+++ b/src/poll.hpp
@@ -37,6 +37,8 @@
 namespace zmq
 {
 
+    struct i_poll_events;
+
     //  Implements socket polling mechanism using the POSIX.1-2001
     //  poll() system call.
 
@@ -50,7 +52,7 @@ namespace zmq
         ~poll_t ();
 
         //  "poller" concept.
-        handle_t add_fd (fd_t fd_, struct i_poll_events *events_);
+        handle_t add_fd (fd_t fd_, zmq::i_poll_events *events_);
         void rm_fd (handle_t handle_);
         void set_pollin (handle_t handle_);
         void reset_pollin (handle_t handle_);
@@ -70,7 +72,7 @@ namespace zmq
         struct fd_entry_t
         {
             fd_t index;
-            struct i_poll_events *events;
+            zmq::i_poll_events *events;
         };
 
         //  This table stores data for registered descriptors.
diff --git a/src/poller_base.hpp b/src/poller_base.hpp
index 808ed38..c184358 100644
--- a/src/poller_base.hpp
+++ b/src/poller_base.hpp
@@ -29,6 +29,8 @@
 namespace zmq
 {
 
+    struct i_poll_events;
+
     class poller_base_t
     {
     public:
@@ -43,10 +45,10 @@ namespace zmq
         //  Add a timeout to expire in timeout_ milliseconds. After the
         //  expiration timer_event on sink_ object will be called with
         //  argument set to id_.
-        void add_timer (int timeout_, struct i_poll_events *sink_, int id_);
+        void add_timer (int timeout_, zmq::i_poll_events *sink_, int id_);
 
         //  Cancel the timer created by sink_ object with ID equal to id_.
-        void cancel_timer (struct i_poll_events *sink_, int id_);
+        void cancel_timer (zmq::i_poll_events *sink_, int id_);
 
     protected:
 
@@ -65,7 +67,7 @@ namespace zmq
         //  List of active timers.
         struct timer_info_t
         {
-            struct i_poll_events *sink;
+            zmq::i_poll_events *sink;
             int id;
         };
         typedef std::multimap <uint64_t, timer_info_t> timers_t;
diff --git a/src/pub.hpp b/src/pub.hpp
index d418fd4..4672600 100644
--- a/src/pub.hpp
+++ b/src/pub.hpp
@@ -27,15 +27,20 @@
 namespace zmq
 {
 
+    class ctx_t;
+    class io_thread_t;
+    class socket_base_t;
+    class msg_t;
+
     class pub_t : public xpub_t
     {
     public:
 
-        pub_t (class ctx_t *parent_, uint32_t tid_);
+        pub_t (zmq::ctx_t *parent_, uint32_t tid_);
         ~pub_t ();
 
         //  Implementations of virtual functions from socket_base_t.
-        int xrecv (class msg_t *msg_, int flags_);
+        int xrecv (zmq::msg_t *msg_, int flags_);
         bool xhas_in ();
 
     private:
@@ -48,8 +53,8 @@ namespace zmq
     {
     public:
 
-        pub_session_t (class io_thread_t *io_thread_, bool connect_,
-            class socket_base_t *socket_, const options_t &options_,
+        pub_session_t (zmq::io_thread_t *io_thread_, bool connect_,
+            zmq::socket_base_t *socket_, const options_t &options_,
             const char *protocol_, const char *address_);
         ~pub_session_t ();
 
diff --git a/src/pull.hpp b/src/pull.hpp
index fa36d49..da3bee1 100644
--- a/src/pull.hpp
+++ b/src/pull.hpp
@@ -29,22 +29,27 @@
 namespace zmq
 {
 
+    class ctx_t;
+    class pipe_t;
+    class msg_t;
+    class io_thread_t;
+
     class pull_t :
         public socket_base_t
     {
     public:
 
-        pull_t (class ctx_t *parent_, uint32_t tid_);
+        pull_t (zmq::ctx_t *parent_, uint32_t tid_);
         ~pull_t ();
 
     protected:
 
         //  Overloads of functions from socket_base_t.
-        void xattach_pipe (class pipe_t *pipe_);
-        int xrecv (class msg_t *msg_, int flags_);
+        void xattach_pipe (zmq::pipe_t *pipe_);
+        int xrecv (zmq::msg_t *msg_, int flags_);
         bool xhas_in ();
-        void xread_activated (class pipe_t *pipe_);
-        void xterminated (class pipe_t *pipe_);
+        void xread_activated (zmq::pipe_t *pipe_);
+        void xterminated (zmq::pipe_t *pipe_);
 
     private:
 
@@ -60,8 +65,8 @@ namespace zmq
     {
     public:
 
-        pull_session_t (class io_thread_t *io_thread_, bool connect_,
-            class socket_base_t *socket_, const options_t &options_,
+        pull_session_t (zmq::io_thread_t *io_thread_, bool connect_,
+            socket_base_t *socket_, const options_t &options_,
             const char *protocol_, const char *address_);
         ~pull_session_t ();
 
diff --git a/src/push.hpp b/src/push.hpp
index ea93693..edee19d 100644
--- a/src/push.hpp
+++ b/src/push.hpp
@@ -29,22 +29,27 @@
 namespace zmq
 {
 
+    class ctx_t;
+    class pipe_t;
+    class msg_t;
+    class io_thread_t;
+
     class push_t :
         public socket_base_t
     {
     public:
 
-        push_t (class ctx_t *parent_, uint32_t tid_);
+        push_t (zmq::ctx_t *parent_, uint32_t tid_);
         ~push_t ();
 
     protected:
 
         //  Overloads of functions from socket_base_t.
-        void xattach_pipe (class pipe_t *pipe_);
-        int xsend (class msg_t *msg_, int flags_);
+        void xattach_pipe (zmq::pipe_t *pipe_);
+        int xsend (zmq::msg_t *msg_, int flags_);
         bool xhas_out ();
-        void xwrite_activated (class pipe_t *pipe_);
-        void xterminated (class pipe_t *pipe_);
+        void xwrite_activated (zmq::pipe_t *pipe_);
+        void xterminated (zmq::pipe_t *pipe_);
 
     private:
 
@@ -59,8 +64,8 @@ namespace zmq
     {
     public:
 
-        push_session_t (class io_thread_t *io_thread_, bool connect_,
-            class socket_base_t *socket_, const options_t &options_,
+        push_session_t (zmq::io_thread_t *io_thread_, bool connect_,
+            socket_base_t *socket_, const options_t &options_,
             const char *protocol_, const char *address_);
         ~push_session_t ();
 
diff --git a/src/reaper.hpp b/src/reaper.hpp
index 1c1533f..66a3db9 100644
--- a/src/reaper.hpp
+++ b/src/reaper.hpp
@@ -29,11 +29,14 @@
 namespace zmq
 {
 
+    class ctx_t;
+    class socket_base_t;
+
     class reaper_t : public object_t, public i_poll_events
     {
     public:
 
-        reaper_t (class ctx_t *ctx_, uint32_t tid_);
+        reaper_t (zmq::ctx_t *ctx_, uint32_t tid_);
         ~reaper_t ();
 
         mailbox_t *get_mailbox ();
@@ -50,7 +53,7 @@ namespace zmq
 
         //  Command handlers.
         void process_stop ();
-        void process_reap (class socket_base_t *socket_);
+        void process_reap (zmq::socket_base_t *socket_);
         void process_reaped ();
 
         //  Reaper thread accesses incoming commands via this mailbox.
diff --git a/src/rep.hpp b/src/rep.hpp
index de9c2b8..04b3d86 100644
--- a/src/rep.hpp
+++ b/src/rep.hpp
@@ -27,16 +27,21 @@
 namespace zmq
 {
 
+    class ctx_t;
+    class msg_t;
+    class io_thread_t;
+    class socket_base_t;
+
     class rep_t : public xrep_t
     {
     public:
 
-        rep_t (class ctx_t *parent_, uint32_t tid_);
+        rep_t (zmq::ctx_t *parent_, uint32_t tid_);
         ~rep_t ();
 
         //  Overloads of functions from socket_base_t.
-        int xsend (class msg_t *msg_, int flags_);
-        int xrecv (class msg_t *msg_, int flags_);
+        int xsend (zmq::msg_t *msg_, int flags_);
+        int xrecv (zmq::msg_t *msg_, int flags_);
         bool xhas_in ();
         bool xhas_out ();
 
@@ -59,8 +64,8 @@ namespace zmq
     {
     public:
 
-        rep_session_t (class io_thread_t *io_thread_, bool connect_,
-            class socket_base_t *socket_, const options_t &options_,
+        rep_session_t (zmq::io_thread_t *io_thread_, bool connect_,
+            zmq::socket_base_t *socket_, const options_t &options_,
             const char *protocol_, const char *address_);
         ~rep_session_t ();
 
diff --git a/src/req.hpp b/src/req.hpp
index 8fae9d4..e743cb8 100644
--- a/src/req.hpp
+++ b/src/req.hpp
@@ -29,16 +29,21 @@
 namespace zmq
 {
 
+    class ctx_t;
+    class msg_t;
+    class io_thread_t;
+    class socket_base_t;
+
     class req_t : public xreq_t
     {
     public:
 
-        req_t (class ctx_t *parent_, uint32_t tid_);
+        req_t (zmq::ctx_t *parent_, uint32_t tid_);
         ~req_t ();
 
         //  Overloads of functions from socket_base_t.
-        int xsend (class msg_t *msg_, int flags_);
-        int xrecv (class msg_t *msg_, int flags_);
+        int xsend (zmq::msg_t *msg_, int flags_);
+        int xrecv (zmq::msg_t *msg_, int flags_);
         bool xhas_in ();
         bool xhas_out ();
 
@@ -60,8 +65,8 @@ namespace zmq
     {
     public:
 
-        req_session_t (class io_thread_t *io_thread_, bool connect_,
-            class socket_base_t *socket_, const options_t &options_,
+        req_session_t (zmq::io_thread_t *io_thread_, bool connect_,
+            zmq::socket_base_t *socket_, const options_t &options_,
             const char *protocol_, const char *address_);
         ~req_session_t ();
 
diff --git a/src/select.hpp b/src/select.hpp
index 9231b6c..9f19a0f 100644
--- a/src/select.hpp
+++ b/src/select.hpp
@@ -47,6 +47,8 @@
 namespace zmq
 {
 
+    struct i_poll_events;
+
     //  Implements socket polling mechanism using POSIX.1-2001 select()
     //  function.
 
@@ -60,7 +62,7 @@ namespace zmq
         ~select_t ();
 
         //  "poller" concept.
-        handle_t add_fd (fd_t fd_, struct i_poll_events *events_);
+        handle_t add_fd (fd_t fd_, zmq::i_poll_events *events_);
         void rm_fd (handle_t handle_);
         void set_pollin (handle_t handle_);
         void reset_pollin (handle_t handle_);
@@ -80,7 +82,7 @@ namespace zmq
         struct fd_entry_t
         {
             fd_t fd;
-            struct i_poll_events *events;
+            zmq::i_poll_events *events;
         };
 
         //  Checks if an fd_entry_t is retired.
diff --git a/src/session_base.hpp b/src/session_base.hpp
index c89628f..6be110b 100644
--- a/src/session_base.hpp
+++ b/src/session_base.hpp
@@ -26,13 +26,17 @@
 #include <string>
 
 #include "own.hpp"
-#include "i_engine.hpp"
 #include "io_object.hpp"
 #include "pipe.hpp"
 
 namespace zmq
 {
 
+    class pipe_t;
+    class io_thread_t;
+    class socket_base_t;
+    struct i_engine;
+
     class session_base_t :
         public own_t,
         public io_object_t,
@@ -41,13 +45,13 @@ namespace zmq
     public:
 
         //  Create a session of the particular type.
-        static session_base_t *create (class io_thread_t *io_thread_,
-            bool connect_, class socket_base_t *socket_,
+        static session_base_t *create (zmq::io_thread_t *io_thread_,
+            bool connect_, zmq::socket_base_t *socket_,
             const options_t &options_, const char *protocol_,
             const char *address_);
 
         //  To be used once only, when creating the session.
-        void attach_pipe (class pipe_t *pipe_);
+        void attach_pipe (zmq::pipe_t *pipe_);
 
         //  Following functions are the interface exposed towards the engine.
         virtual int read (msg_t *msg_);
@@ -56,15 +60,15 @@ namespace zmq
         void detach ();
 
         //  i_pipe_events interface implementation.
-        void read_activated (class pipe_t *pipe_);
-        void write_activated (class pipe_t *pipe_);
-        void hiccuped (class pipe_t *pipe_);
-        void terminated (class pipe_t *pipe_);
+        void read_activated (zmq::pipe_t *pipe_);
+        void write_activated (zmq::pipe_t *pipe_);
+        void hiccuped (zmq::pipe_t *pipe_);
+        void terminated (zmq::pipe_t *pipe_);
 
     protected:
 
-        session_base_t (class io_thread_t *io_thread_, bool connect_,
-            class socket_base_t *socket_, const options_t &options_,
+        session_base_t (zmq::io_thread_t *io_thread_, bool connect_,
+            zmq::socket_base_t *socket_, const options_t &options_,
             const char *protocol_, const char *address_);
         ~session_base_t ();
 
@@ -76,7 +80,7 @@ namespace zmq
 
         //  Handlers for incoming commands.
         void process_plug ();
-        void process_attach (struct i_engine *engine_);
+        void process_attach (zmq::i_engine *engine_);
         void process_term (int linger_);
 
         //  i_poll_events handlers.
@@ -94,7 +98,7 @@ namespace zmq
         bool connect;
 
         //  Pipe connecting the session to its socket.
-        class pipe_t *pipe;
+        zmq::pipe_t *pipe;
 
         //  This flag is true if the remainder of the message being processed
         //  is still in the in pipe.
@@ -105,14 +109,14 @@ namespace zmq
         bool pending;
 
         //  The protocol I/O engine connected to the session.
-        struct i_engine *engine;
+        zmq::i_engine *engine;
 
         //  The socket the session belongs to.
-        class socket_base_t *socket;
+        zmq::socket_base_t *socket;
 
         //  I/O thread the session is living in. It will be used to plug in
         //  the engines into the same thread.
-        class io_thread_t *io_thread;
+        zmq::io_thread_t *io_thread;
 
         //  ID of the linger timer
         enum {linger_timer_id = 0x20};
diff --git a/src/socket_base.hpp b/src/socket_base.hpp
index bc978ba..dda87f4 100644
--- a/src/socket_base.hpp
+++ b/src/socket_base.hpp
@@ -38,6 +38,10 @@
 namespace zmq
 {
 
+    class ctx_t;
+    class msg_t;
+    class pipe_t;
+
     class socket_base_t :
         public own_t,
         public array_item_t <>,
@@ -52,7 +56,7 @@ namespace zmq
         bool check_tag ();
 
         //  Create a socket of a specified type.
-        static socket_base_t *create (int type_, class ctx_t *parent_,
+        static socket_base_t *create (int type_, zmq::ctx_t *parent_,
             uint32_t tid_);
 
         //  Returns the mailbox associated with this socket.
@@ -67,8 +71,8 @@ namespace zmq
         int getsockopt (int option_, void *optval_, size_t *optvallen_);
         int bind (const char *addr_);
         int connect (const char *addr_);
-        int send (class msg_t *msg_, int flags_);
-        int recv (class msg_t *msg_, int flags_);
+        int send (zmq::msg_t *msg_, int flags_);
+        int recv (zmq::msg_t *msg_, int flags_);
         int close ();
 
         //  These functions are used by the polling mechanism to determine
@@ -94,12 +98,12 @@ namespace zmq
 
     protected:
 
-        socket_base_t (class ctx_t *parent_, uint32_t tid_);
+        socket_base_t (zmq::ctx_t *parent_, uint32_t tid_);
         virtual ~socket_base_t ();
 
         //  Concrete algorithms for the x- methods are to be defined by
         //  individual socket types.
-        virtual void xattach_pipe (class pipe_t *pipe_) = 0;
+        virtual void xattach_pipe (zmq::pipe_t *pipe_) = 0;
 
         //  The default implementation assumes there are no specific socket
         //  options for the particular socket type. If not so, overload this
@@ -109,11 +113,11 @@ namespace zmq
 
         //  The default implementation assumes that send is not supported.
         virtual bool xhas_out ();
-        virtual int xsend (class msg_t *msg_, int flags_);
+        virtual int xsend (zmq::msg_t *msg_, int flags_);
 
         //  The default implementation assumes that recv in not supported.
         virtual bool xhas_in ();
-        virtual int xrecv (class msg_t *msg_, int flags_);
+        virtual int xrecv (zmq::msg_t *msg_, int flags_);
 
         //  i_pipe_events will be forwarded to these functions.
         virtual void xread_activated (pipe_t *pipe_);
@@ -154,7 +158,7 @@ namespace zmq
         int check_protocol (const std::string &protocol_);
 
         //  Register the pipe with this socket.
-        void attach_pipe (class pipe_t *pipe_);
+        void attach_pipe (zmq::pipe_t *pipe_);
 
         //  Processes commands sent to this socket (if any). If timeout is -1,
         //  returns only after at least one command was processed.
@@ -164,7 +168,7 @@ namespace zmq
 
         //  Handlers for incoming commands.
         void process_stop ();
-        void process_bind (class pipe_t *pipe_);
+        void process_bind (zmq::pipe_t *pipe_);
         void process_unplug ();
         void process_term (int linger_);
 
diff --git a/src/stream_engine.hpp b/src/stream_engine.hpp
index 6d122ed..30b190b 100644
--- a/src/stream_engine.hpp
+++ b/src/stream_engine.hpp
@@ -34,6 +34,9 @@
 namespace zmq
 {
 
+    class io_thread_t;
+    class session_base_t;
+
     //  This engine handles any socket with SOCK_STREAM semantics,
     //  e.g. TCP socket or an UNIX domain socket.
 
@@ -45,8 +48,8 @@ namespace zmq
         ~stream_engine_t ();
 
         //  i_engine interface implementation.
-        void plug (class io_thread_t *io_thread_,
-           class session_base_t *session_);
+        void plug (zmq::io_thread_t *io_thread_,
+           zmq::session_base_t *session_);
         void unplug ();
         void terminate ();
         void activate_in ();
@@ -86,10 +89,10 @@ namespace zmq
         encoder_t encoder;
 
         //  The session this engine is attached to.
-        class session_base_t *session;
+        zmq::session_base_t *session;
 
         //  Detached transient session.
-        class session_base_t *leftover_session;
+        zmq::session_base_t *leftover_session;
 
         options_t options;
 
diff --git a/src/sub.hpp b/src/sub.hpp
index bb46641..1c69b06 100644
--- a/src/sub.hpp
+++ b/src/sub.hpp
@@ -27,17 +27,22 @@
 namespace zmq
 {
 
+    class ctx_t;
+    class msg_t;
+    class io_thread_t;
+    class socket_base_t;
+
     class sub_t : public xsub_t
     {
     public:
 
-        sub_t (class ctx_t *parent_, uint32_t tid_);
+        sub_t (zmq::ctx_t *parent_, uint32_t tid_);
         ~sub_t ();
 
     protected:
 
         int xsetsockopt (int option_, const void *optval_, size_t optvallen_);
-        int xsend (class msg_t *msg_, int flags_);
+        int xsend (zmq::msg_t *msg_, int flags_);
         bool xhas_out ();
 
     private:
@@ -50,8 +55,8 @@ namespace zmq
     {
     public:
 
-        sub_session_t (class io_thread_t *io_thread_, bool connect_,
-            class socket_base_t *socket_, const options_t &options_,
+        sub_session_t (zmq::io_thread_t *io_thread_, bool connect_,
+            zmq::socket_base_t *socket_, const options_t &options_,
             const char *protocol_, const char *address_);
         ~sub_session_t ();
 
diff --git a/src/tcp_connecter.hpp b/src/tcp_connecter.hpp
index e420c82..fc3b9f2 100644
--- a/src/tcp_connecter.hpp
+++ b/src/tcp_connecter.hpp
@@ -31,14 +31,17 @@
 namespace zmq
 {
 
+    class io_thread_t;
+    class session_base_t;
+
     class tcp_connecter_t : public own_t, public io_object_t
     {
     public:
 
         //  If 'delay' is true connecter first waits for a while, then starts
         //  connection process.
-        tcp_connecter_t (class io_thread_t *io_thread_,
-            class session_base_t *session_, const options_t &options_,
+        tcp_connecter_t (zmq::io_thread_t *io_thread_,
+            zmq::session_base_t *session_, const options_t &options_,
             const char *address_, bool delay_);
         ~tcp_connecter_t ();
 
@@ -98,7 +101,7 @@ namespace zmq
         bool wait;
 
         //  Reference to the session we belong to.
-        class session_base_t *session;
+        zmq::session_base_t *session;
 
         //  Current reconnect ivl, updated for backoff strategy
         int current_reconnect_ivl;
diff --git a/src/tcp_listener.hpp b/src/tcp_listener.hpp
index e712998..c2116b3 100644
--- a/src/tcp_listener.hpp
+++ b/src/tcp_listener.hpp
@@ -31,12 +31,15 @@
 namespace zmq
 {
 
+    class io_thread_t;
+    class socket_base_t;
+
     class tcp_listener_t : public own_t, public io_object_t
     {
     public:
 
-        tcp_listener_t (class io_thread_t *io_thread_,
-            class socket_base_t *socket_, const options_t &options_);
+        tcp_listener_t (zmq::io_thread_t *io_thread_,
+            zmq::socket_base_t *socket_, const options_t &options_);
         ~tcp_listener_t ();
 
         //  Set address to listen on.
@@ -72,7 +75,7 @@ namespace zmq
         handle_t handle;
 
         //  Socket the listerner belongs to.
-        class socket_base_t *socket;
+        zmq::socket_base_t *socket;
 
         tcp_listener_t (const tcp_listener_t&);
         const tcp_listener_t &operator = (const tcp_listener_t&);
diff --git a/src/xpub.hpp b/src/xpub.hpp
index 14ffc58..3f80d4a 100644
--- a/src/xpub.hpp
+++ b/src/xpub.hpp
@@ -33,23 +33,28 @@
 namespace zmq
 {
 
+    class ctx_t;
+    class msg_t;
+    class pipe_t;
+    class io_thread_t;
+
     class xpub_t :
         public socket_base_t
     {
     public:
 
-        xpub_t (class ctx_t *parent_, uint32_t tid_);
+        xpub_t (zmq::ctx_t *parent_, uint32_t tid_);
         ~xpub_t ();
 
         //  Implementations of virtual functions from socket_base_t.
-        void xattach_pipe (class pipe_t *pipe_);
-        int xsend (class msg_t *msg_, int flags_);
+        void xattach_pipe (zmq::pipe_t *pipe_);
+        int xsend (zmq::msg_t *msg_, int flags_);
         bool xhas_out ();
-        int xrecv (class msg_t *msg_, int flags_);
+        int xrecv (zmq::msg_t *msg_, int flags_);
         bool xhas_in ();
-        void xread_activated (class pipe_t *pipe_);
-        void xwrite_activated (class pipe_t *pipe_);
-        void xterminated (class pipe_t *pipe_);
+        void xread_activated (zmq::pipe_t *pipe_);
+        void xwrite_activated (zmq::pipe_t *pipe_);
+        void xterminated (zmq::pipe_t *pipe_);
 
     private:
 
@@ -59,7 +64,7 @@ namespace zmq
             void *arg_);
 
         //  Function to be applied to each matching pipes.
-        static void mark_as_matching (class pipe_t *pipe_, void *arg_);
+        static void mark_as_matching (zmq::pipe_t *pipe_, void *arg_);
 
         //  List of all subscriptions mapped to corresponding pipes.
         mtrie_t subscriptions;
@@ -84,8 +89,8 @@ namespace zmq
     {
     public:
 
-        xpub_session_t (class io_thread_t *io_thread_, bool connect_,
-            class socket_base_t *socket_, const options_t &options_,
+        xpub_session_t (zmq::io_thread_t *io_thread_, bool connect_,
+            socket_base_t *socket_, const options_t &options_,
             const char *protocol_, const char *address_);
         ~xpub_session_t ();
 
diff --git a/src/xrep.hpp b/src/xrep.hpp
index fc02b11..df82d00 100644
--- a/src/xrep.hpp
+++ b/src/xrep.hpp
@@ -35,24 +35,27 @@
 namespace zmq
 {
 
+    class ctx_t;
+    class pipe_t;
+
     //  TODO: This class uses O(n) scheduling. Rewrite it to use O(1) algorithm.
     class xrep_t :
         public socket_base_t
     {
     public:
 
-        xrep_t (class ctx_t *parent_, uint32_t tid_);
+        xrep_t (zmq::ctx_t *parent_, uint32_t tid_);
         ~xrep_t ();
 
         //  Overloads of functions from socket_base_t.
-        void xattach_pipe (class pipe_t *pipe_);
-        int xsend (class msg_t *msg_, int flags_);
-        int xrecv (class msg_t *msg_, int flags_);
+        void xattach_pipe (zmq::pipe_t *pipe_);
+        int xsend (msg_t *msg_, int flags_);
+        int xrecv (msg_t *msg_, int flags_);
         bool xhas_in ();
         bool xhas_out ();
-        void xread_activated (class pipe_t *pipe_);
-        void xwrite_activated (class pipe_t *pipe_);
-        void xterminated (class pipe_t *pipe_);
+        void xread_activated (zmq::pipe_t *pipe_);
+        void xwrite_activated (zmq::pipe_t *pipe_);
+        void xterminated (zmq::pipe_t *pipe_);
 
     protected:
 
@@ -75,7 +78,7 @@ namespace zmq
 
         struct outpipe_t
         {
-            class pipe_t *pipe;
+            zmq::pipe_t *pipe;
             bool active;
         };
 
@@ -84,7 +87,7 @@ namespace zmq
         outpipes_t outpipes;
 
         //  The pipe we are currently writing to.
-        class pipe_t *current_out;
+        zmq::pipe_t *current_out;
 
         //  If true, more outgoing message parts are expected.
         bool more_out;
@@ -101,8 +104,8 @@ namespace zmq
     {
     public:
 
-        xrep_session_t (class io_thread_t *io_thread_, bool connect_,
-            class socket_base_t *socket_, const options_t &options_,
+        xrep_session_t (zmq::io_thread_t *io_thread_, bool connect_,
+            socket_base_t *socket_, const options_t &options_,
             const char *protocol_, const char *address_);
         ~xrep_session_t ();
 
diff --git a/src/xreq.hpp b/src/xreq.hpp
index 1d979c5..4c94cad 100644
--- a/src/xreq.hpp
+++ b/src/xreq.hpp
@@ -29,25 +29,31 @@
 namespace zmq
 {
 
+    class ctx_t;
+    class msg_t;
+    class pipe_t;
+    class io_thread_t;
+    class socket_base_t;
+
     class xreq_t :
         public socket_base_t
     {
     public:
 
-        xreq_t (class ctx_t *parent_, uint32_t tid_);
+        xreq_t (zmq::ctx_t *parent_, uint32_t tid_);
         ~xreq_t ();
 
     protected:
 
         //  Overloads of functions from socket_base_t.
-        void xattach_pipe (class pipe_t *pipe_);
-        int xsend (class msg_t *msg_, int flags_);
-        int xrecv (class msg_t *msg_, int flags_);
+        void xattach_pipe (zmq::pipe_t *pipe_);
+        int xsend (zmq::msg_t *msg_, int flags_);
+        int xrecv (zmq::msg_t *msg_, int flags_);
         bool xhas_in ();
         bool xhas_out ();
-        void xread_activated (class pipe_t *pipe_);
-        void xwrite_activated (class pipe_t *pipe_);
-        void xterminated (class pipe_t *pipe_);
+        void xread_activated (zmq::pipe_t *pipe_);
+        void xwrite_activated (zmq::pipe_t *pipe_);
+        void xterminated (zmq::pipe_t *pipe_);
 
     private:
 
@@ -64,8 +70,8 @@ namespace zmq
     {
     public:
 
-        xreq_session_t (class io_thread_t *io_thread_, bool connect_,
-            class socket_base_t *socket_, const options_t &options_,
+        xreq_session_t (zmq::io_thread_t *io_thread_, bool connect_,
+            zmq::socket_base_t *socket_, const options_t &options_,
             const char *protocol_, const char *address_);
         ~xreq_session_t ();
 
diff --git a/src/xsub.hpp b/src/xsub.hpp
index 1eac390..24f8157 100644
--- a/src/xsub.hpp
+++ b/src/xsub.hpp
@@ -26,36 +26,39 @@
 #include "dist.hpp"
 #include "fq.hpp"
 #include "trie.hpp"
-#include "msg.hpp"
 
 namespace zmq
 {
 
+    class ctx_t;
+    class pipe_t;
+    class io_thread_t;
+
     class xsub_t :
         public socket_base_t
     {
     public:
 
-        xsub_t (class ctx_t *parent_, uint32_t tid_);
+        xsub_t (zmq::ctx_t *parent_, uint32_t tid_);
         ~xsub_t ();
 
     protected:
 
         //  Overloads of functions from socket_base_t.
-        void xattach_pipe (class pipe_t *pipe_);
-        int xsend (class msg_t *msg_, int flags_);
+        void xattach_pipe (zmq::pipe_t *pipe_);
+        int xsend (zmq::msg_t *msg_, int flags_);
         bool xhas_out ();
-        int xrecv (class msg_t *msg_, int flags_);
+        int xrecv (zmq::msg_t *msg_, int flags_);
         bool xhas_in ();
-        void xread_activated (class pipe_t *pipe_);
-        void xwrite_activated (class pipe_t *pipe_);
+        void xread_activated (zmq::pipe_t *pipe_);
+        void xwrite_activated (zmq::pipe_t *pipe_);
         void xhiccuped (pipe_t *pipe_);
-        void xterminated (class pipe_t *pipe_);
+        void xterminated (zmq::pipe_t *pipe_);
 
     private:
 
         //  Check whether the message matches at least one subscription.
-        bool match (class msg_t *msg_);
+        bool match (zmq::msg_t *msg_);
 
         //  Function to be applied to the trie to send all the subsciptions
         //  upstream.
@@ -89,7 +92,7 @@ namespace zmq
     public:
 
         xsub_session_t (class io_thread_t *io_thread_, bool connect_,
-            class socket_base_t *socket_, const options_t &options_,
+            socket_base_t *socket_, const options_t &options_,
             const char *protocol_, const char *address_);
         ~xsub_session_t ();