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+/*
+    Copyright (c) 2007-2013 Contributors as noted in the AUTHORS file
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the GNU Lesser General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZMQ_MSG_HPP_INCLUDE__
+#define __ZMQ_MSG_HPP_INCLUDE__
+
+#include <stddef.h>
+#include <stdio.h>
+
+#include "config.hpp"
+#include "atomic_counter.hpp"
+
+//  Signature for free function to deallocate the message content.
+//  Note that it has to be declared as "C" so that it is the same as
+//  zmq_free_fn defined in zmq.h.
+extern "C"
+{
+    typedef void (msg_free_fn) (void *data, void *hint);
+}
+
+namespace zmq
+{
+
+    //  Note that this structure needs to be explicitly constructed
+    //  (init functions) and destructed (close function).
+
+    class msg_t
+    {
+    public:
+
+        //  Message flags.
+        enum
+        {
+            more = 1,           //  Followed by more parts
+            command = 2,        //  Command frame (see ZMTP spec)
+            identity = 64,
+            shared = 128
+        };
+
+        bool check ();
+        int init ();
+        int init_size (size_t size_);
+        int init_data (void *data_, size_t size_, msg_free_fn *ffn_,
+            void *hint_);
+        int init_delimiter ();
+        int close ();
+        int move (msg_t &src_);
+        int copy (msg_t &src_);
+        void *data ();
+        size_t size ();
+        unsigned char flags ();
+        void set_flags (unsigned char flags_);
+        void reset_flags (unsigned char flags_);
+        bool is_identity () const;
+        bool is_delimiter ();
+        bool is_vsm ();
+        bool is_cmsg ();
+
+        //  After calling this function you can copy the message in POD-style
+        //  refs_ times. No need to call copy.
+        void add_refs (int refs_);
+
+        //  Removes references previously added by add_refs. If the number of
+        //  references drops to 0, the message is closed and false is returned.
+        bool rm_refs (int refs_);
+
+    private:
+
+        //  Size in bytes of the largest message that is still copied around
+        //  rather than being reference-counted.
+        enum {max_vsm_size = 29};
+
+        //  Shared message buffer. Message data are either allocated in one
+        //  continuous block along with this structure - thus avoiding one
+        //  malloc/free pair or they are stored in used-supplied memory.
+        //  In the latter case, ffn member stores pointer to the function to be
+        //  used to deallocate the data. If the buffer is actually shared (there
+        //  are at least 2 references to it) refcount member contains number of
+        //  references.
+        struct content_t
+        {
+            void *data;
+            size_t size;
+            msg_free_fn *ffn;
+            void *hint;
+            zmq::atomic_counter_t refcnt;
+        };
+
+        //  Different message types.
+        enum type_t
+        {
+            type_min = 101,
+            //  VSM messages store the content in the message itself
+            type_vsm = 101,
+            //  LMSG messages store the content in malloc-ed memory
+            type_lmsg = 102,
+            //  Delimiter messages are used in envelopes
+            type_delimiter = 103,
+            //  CMSG messages point to constant data
+            type_cmsg = 104,
+            type_max = 104
+        };
+
+        //  Note that fields shared between different message types are not
+        //  moved to tha parent class (msg_t). This way we ger tighter packing
+        //  of the data. Shared fields can be accessed via 'base' member of
+        //  the union.
+        union {
+            struct {
+                unsigned char unused [max_vsm_size + 1];
+                unsigned char type;
+                unsigned char flags;
+            } base;
+            struct {
+                unsigned char data [max_vsm_size];
+                unsigned char size;
+                unsigned char type;
+                unsigned char flags;
+            } vsm;
+            struct {
+                content_t *content;
+                unsigned char unused [max_vsm_size + 1 - sizeof (content_t*)];
+                unsigned char type;
+                unsigned char flags;
+            } lmsg;
+            struct {
+                void* data;
+                size_t size;
+                unsigned char unused
+                    [max_vsm_size + 1 - sizeof (void*) - sizeof (size_t)];
+                unsigned char type;
+                unsigned char flags;
+            } cmsg;
+            struct {
+                unsigned char unused [max_vsm_size + 1];
+                unsigned char type;
+                unsigned char flags;
+            } delimiter;
+        } u;
+    };
+
+}
+
+#endif