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+//////////////////////////////////////////////////////////////////////////////
+//
+// (C) Copyright Ion Gaztanaga 2005-2011. Distributed under the Boost
+// Software License, Version 1.0. (See accompanying file
+// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
+//
+// See http://www.boost.org/libs/interprocess for documentation.
+//
+//////////////////////////////////////////////////////////////////////////////
+
+#ifndef BOOST_INTERPROCESS_MESSAGE_QUEUE_HPP
+#define BOOST_INTERPROCESS_MESSAGE_QUEUE_HPP
+
+#include <boost/interprocess/detail/config_begin.hpp>
+#include <boost/interprocess/detail/workaround.hpp>
+
+#include <boost/interprocess/shared_memory_object.hpp>
+#include <boost/interprocess/detail/managed_open_or_create_impl.hpp>
+#include <boost/interprocess/sync/interprocess_condition.hpp>
+#include <boost/interprocess/sync/interprocess_mutex.hpp>
+#include <boost/interprocess/sync/scoped_lock.hpp>
+#include <boost/interprocess/detail/utilities.hpp>
+#include <boost/interprocess/offset_ptr.hpp>
+#include <boost/interprocess/creation_tags.hpp>
+#include <boost/interprocess/exceptions.hpp>
+#include <boost/interprocess/permissions.hpp>
+#include <boost/detail/no_exceptions_support.hpp>
+#include <boost/interprocess/detail/type_traits.hpp>
+#include <boost/intrusive/pointer_traits.hpp>
+#include <boost/type_traits/make_unsigned.hpp>
+#include <boost/type_traits/alignment_of.hpp>
+#include <boost/intrusive/pointer_traits.hpp>
+#include <algorithm> //std::lower_bound
+#include <cstddef> //std::size_t
+#include <cstring> //memcpy
+
+
+//!\file
+//!Describes an inter-process message queue. This class allows sending
+//!messages between processes and allows blocking, non-blocking and timed
+//!sending and receiving.
+
+namespace boost{ namespace interprocess{
+
+//!A class that allows sending messages
+//!between processes.
+template<class VoidPointer>
+class message_queue_t
+{
+ /// @cond
+ //Blocking modes
+ enum block_t { blocking, timed, non_blocking };
+
+ message_queue_t();
+ /// @endcond
+
+ public:
+ typedef VoidPointer void_pointer;
+ typedef typename boost::intrusive::
+ pointer_traits<void_pointer>::template
+ rebind_pointer<char>::type char_ptr;
+ typedef typename boost::intrusive::pointer_traits<char_ptr>::difference_type difference_type;
+ typedef typename boost::make_unsigned<difference_type>::type size_type;
+
+ //!Creates a process shared message queue with name "name". For this message queue,
+ //!the maximum number of messages will be "max_num_msg" and the maximum message size
+ //!will be "max_msg_size". Throws on error and if the queue was previously created.
+ message_queue_t(create_only_t create_only,
+ const char *name,
+ size_type max_num_msg,
+ size_type max_msg_size,
+ const permissions &perm = permissions());
+
+ //!Opens or creates a process shared message queue with name "name".
+ //!If the queue is created, the maximum number of messages will be "max_num_msg"
+ //!and the maximum message size will be "max_msg_size". If queue was previously
+ //!created the queue will be opened and "max_num_msg" and "max_msg_size" parameters
+ //!are ignored. Throws on error.
+ message_queue_t(open_or_create_t open_or_create,
+ const char *name,
+ size_type max_num_msg,
+ size_type max_msg_size,
+ const permissions &perm = permissions());
+
+ //!Opens a previously created process shared message queue with name "name".
+ //!If the queue was not previously created or there are no free resources,
+ //!throws an error.
+ message_queue_t(open_only_t open_only,
+ const char *name);
+
+ //!Destroys *this and indicates that the calling process is finished using
+ //!the resource. All opened message queues are still
+ //!valid after destruction. The destructor function will deallocate
+ //!any system resources allocated by the system for use by this process for
+ //!this resource. The resource can still be opened again calling
+ //!the open constructor overload. To erase the message queue from the system
+ //!use remove().
+ ~message_queue_t();
+
+ //!Sends a message stored in buffer "buffer" with size "buffer_size" in the
+ //!message queue with priority "priority". If the message queue is full
+ //!the sender is blocked. Throws interprocess_error on error.*/
+ void send (const void *buffer, size_type buffer_size,
+ unsigned int priority);
+
+ //!Sends a message stored in buffer "buffer" with size "buffer_size" through the
+ //!message queue with priority "priority". If the message queue is full
+ //!the sender is not blocked and returns false, otherwise returns true.
+ //!Throws interprocess_error on error.
+ bool try_send (const void *buffer, size_type buffer_size,
+ unsigned int priority);
+
+ //!Sends a message stored in buffer "buffer" with size "buffer_size" in the
+ //!message queue with priority "priority". If the message queue is full
+ //!the sender retries until time "abs_time" is reached. Returns true if
+ //!the message has been successfully sent. Returns false if timeout is reached.
+ //!Throws interprocess_error on error.
+ bool timed_send (const void *buffer, size_type buffer_size,
+ unsigned int priority, const boost::posix_time::ptime& abs_time);
+
+ //!Receives a message from the message queue. The message is stored in buffer
+ //!"buffer", which has size "buffer_size". The received message has size
+ //!"recvd_size" and priority "priority". If the message queue is empty
+ //!the receiver is blocked. Throws interprocess_error on error.
+ void receive (void *buffer, size_type buffer_size,
+ size_type &recvd_size,unsigned int &priority);
+
+ //!Receives a message from the message queue. The message is stored in buffer
+ //!"buffer", which has size "buffer_size". The received message has size
+ //!"recvd_size" and priority "priority". If the message queue is empty
+ //!the receiver is not blocked and returns false, otherwise returns true.
+ //!Throws interprocess_error on error.
+ bool try_receive (void *buffer, size_type buffer_size,
+ size_type &recvd_size,unsigned int &priority);
+
+ //!Receives a message from the message queue. The message is stored in buffer
+ //!"buffer", which has size "buffer_size". The received message has size
+ //!"recvd_size" and priority "priority". If the message queue is empty
+ //!the receiver retries until time "abs_time" is reached. Returns true if
+ //!the message has been successfully sent. Returns false if timeout is reached.
+ //!Throws interprocess_error on error.
+ bool timed_receive (void *buffer, size_type buffer_size,
+ size_type &recvd_size,unsigned int &priority,
+ const boost::posix_time::ptime &abs_time);
+
+ //!Returns the maximum number of messages allowed by the queue. The message
+ //!queue must be opened or created previously. Otherwise, returns 0.
+ //!Never throws
+ size_type get_max_msg() const;
+
+ //!Returns the maximum size of message allowed by the queue. The message
+ //!queue must be opened or created previously. Otherwise, returns 0.
+ //!Never throws
+ size_type get_max_msg_size() const;
+
+ //!Returns the number of messages currently stored.
+ //!Never throws
+ size_type get_num_msg();
+
+ //!Removes the message queue from the system.
+ //!Returns false on error. Never throws
+ static bool remove(const char *name);
+
+ /// @cond
+ private:
+ typedef boost::posix_time::ptime ptime;
+ bool do_receive(block_t block,
+ void *buffer, size_type buffer_size,
+ size_type &recvd_size, unsigned int &priority,
+ const ptime &abs_time);
+
+ bool do_send(block_t block,
+ const void *buffer, size_type buffer_size,
+ unsigned int priority, const ptime &abs_time);
+
+ //!Returns the needed memory size for the shared message queue.
+ //!Never throws
+ static size_type get_mem_size(size_type max_msg_size, size_type max_num_msg);
+
+ ipcdetail::managed_open_or_create_impl<shared_memory_object> m_shmem;
+ /// @endcond
+};
+
+/// @cond
+
+namespace ipcdetail {
+
+//!This header is the prefix of each message in the queue
+template<class VoidPointer>
+class msg_hdr_t
+{
+ typedef VoidPointer void_pointer;
+ typedef typename boost::intrusive::
+ pointer_traits<void_pointer>::template
+ rebind_pointer<char>::type char_ptr;
+ typedef typename boost::intrusive::pointer_traits<char_ptr>::difference_type difference_type;
+ typedef typename boost::make_unsigned<difference_type>::type size_type;
+
+ public:
+ size_type len; // Message length
+ unsigned int priority;// Message priority
+ //!Returns the data buffer associated with this this message
+ void * data(){ return this+1; } //
+};
+
+//!This functor is the predicate to order stored messages by priority
+template<class VoidPointer>
+class priority_functor
+{
+ typedef typename boost::intrusive::
+ pointer_traits<VoidPointer>::template
+ rebind_pointer<msg_hdr_t<VoidPointer> >::type msg_hdr_ptr_t;
+
+ public:
+ bool operator()(const msg_hdr_ptr_t &msg1,
+ const msg_hdr_ptr_t &msg2) const
+ { return msg1->priority < msg2->priority; }
+};
+
+//!This header is placed in the beginning of the shared memory and contains
+//!the data to control the queue. This class initializes the shared memory
+//!in the following way: in ascending memory address with proper alignment
+//!fillings:
+//!
+//!-> mq_hdr_t:
+//! Main control block that controls the rest of the elements
+//!
+//!-> offset_ptr<msg_hdr_t> index [max_num_msg]
+//! An array of pointers with size "max_num_msg" called index. Each pointer
+//! points to a preallocated message. The elements of this array are
+//! reordered in runtime in the following way:
+//!
+//! When the current number of messages is "cur_num_msg", the first
+//! "cur_num_msg" pointers point to inserted messages and the rest
+//! point to free messages. The first "cur_num_msg" pointers are
+//! ordered by the priority of the pointed message and by insertion order
+//! if two messages have the same priority. So the next message to be
+//! used in a "receive" is pointed by index [cur_num_msg-1] and the first free
+//! message ready to be used in a "send" operation is index [cur_num_msg].
+//! This transforms index in a fixed size priority queue with an embedded free
+//! message queue.
+//!
+//!-> struct message_t
+//! {
+//! msg_hdr_t header;
+//! char[max_msg_size] data;
+//! } messages [max_num_msg];
+//!
+//! An array of buffers of preallocated messages, each one prefixed with the
+//! msg_hdr_t structure. Each of this message is pointed by one pointer of
+//! the index structure.
+template<class VoidPointer>
+class mq_hdr_t
+ : public ipcdetail::priority_functor<VoidPointer>
+{
+ typedef VoidPointer void_pointer;
+ typedef msg_hdr_t<void_pointer> msg_header;
+ typedef typename boost::intrusive::
+ pointer_traits<void_pointer>::template
+ rebind_pointer<msg_header>::type msg_hdr_ptr_t;
+ typedef typename boost::intrusive::pointer_traits
+ <msg_hdr_ptr_t>::difference_type difference_type;
+ typedef typename boost::make_unsigned<difference_type>::type size_type;
+ typedef typename boost::intrusive::
+ pointer_traits<void_pointer>::template
+ rebind_pointer<msg_hdr_ptr_t>::type msg_hdr_ptr_ptr_t;
+
+ public:
+ //!Constructor. This object must be constructed in the beginning of the
+ //!shared memory of the size returned by the function "get_mem_size".
+ //!This constructor initializes the needed resources and creates
+ //!the internal structures like the priority index. This can throw.*/
+ mq_hdr_t(size_type max_num_msg, size_type max_msg_size)
+ : m_max_num_msg(max_num_msg),
+ m_max_msg_size(max_msg_size),
+ m_cur_num_msg(0)
+ { this->initialize_memory(); }
+
+ //!Returns the inserted message with top priority
+ msg_header * top_msg()
+ { return mp_index[m_cur_num_msg-1].get(); }
+
+ //!Returns true if the message queue is full
+ bool is_full() const
+ { return m_cur_num_msg == m_max_num_msg; }
+
+ //!Returns true if the message queue is empty
+ bool is_empty() const
+ { return !m_cur_num_msg; }
+
+ //!Frees the top priority message and saves it in the free message list
+ void free_top_msg()
+ { --m_cur_num_msg; }
+
+ //!Returns the first free msg of the free message queue
+ msg_header * free_msg()
+ { return mp_index[m_cur_num_msg].get(); }
+
+ //!Inserts the first free message in the priority queue
+ void queue_free_msg()
+ {
+ //Get free msg
+ msg_hdr_ptr_t free = mp_index[m_cur_num_msg];
+ //Get priority queue's range
+ msg_hdr_ptr_t *it = &mp_index[0], *it_end = &mp_index[m_cur_num_msg];
+ //Check where the free message should be placed
+ it = std::lower_bound(it, it_end, free, static_cast<priority_functor<VoidPointer>&>(*this));
+ //Make room in that position
+ std::copy_backward(it, it_end, it_end+1);
+ //Insert the free message in the correct position
+ *it = free;
+ ++m_cur_num_msg;
+ }
+
+ //!Returns the number of bytes needed to construct a message queue with
+ //!"max_num_size" maximum number of messages and "max_msg_size" maximum
+ //!message size. Never throws.
+ static size_type get_mem_size
+ (size_type max_msg_size, size_type max_num_msg)
+ {
+ const size_type
+ msg_hdr_align = ::boost::alignment_of<msg_header>::value,
+ index_align = ::boost::alignment_of<msg_hdr_ptr_t>::value,
+ r_hdr_size = ipcdetail::ct_rounded_size<sizeof(mq_hdr_t), index_align>::value,
+ r_index_size = ipcdetail::get_rounded_size(sizeof(msg_hdr_ptr_t)*max_num_msg, msg_hdr_align),
+ r_max_msg_size = ipcdetail::get_rounded_size(max_msg_size, msg_hdr_align) + sizeof(msg_header);
+ return r_hdr_size + r_index_size + (max_num_msg*r_max_msg_size) +
+ ipcdetail::managed_open_or_create_impl<shared_memory_object>::ManagedOpenOrCreateUserOffset;
+ }
+
+ //!Initializes the memory structures to preallocate messages and constructs the
+ //!message index. Never throws.
+ void initialize_memory()
+ {
+ const size_type
+ msg_hdr_align = ::boost::alignment_of<msg_header>::value,
+ index_align = ::boost::alignment_of<msg_hdr_ptr_t>::value,
+ r_hdr_size = ipcdetail::ct_rounded_size<sizeof(mq_hdr_t), index_align>::value,
+ r_index_size = ipcdetail::get_rounded_size(sizeof(msg_hdr_ptr_t)*m_max_num_msg, msg_hdr_align),
+ r_max_msg_size = ipcdetail::get_rounded_size(m_max_msg_size, msg_hdr_align) + sizeof(msg_header);
+
+ //Pointer to the index
+ msg_hdr_ptr_t *index = reinterpret_cast<msg_hdr_ptr_t*>
+ (reinterpret_cast<char*>(this)+r_hdr_size);
+
+ //Pointer to the first message header
+ msg_header *msg_hdr = reinterpret_cast<msg_header*>
+ (reinterpret_cast<char*>(this)+r_hdr_size+r_index_size);
+
+ //Initialize the pointer to the index
+ mp_index = index;
+
+ //Initialize the index so each slot points to a preallocated message
+ for(size_type i = 0; i < m_max_num_msg; ++i){
+ index[i] = msg_hdr;
+ msg_hdr = reinterpret_cast<msg_header*>
+ (reinterpret_cast<char*>(msg_hdr)+r_max_msg_size);
+ }
+ }
+
+ public:
+ //Pointer to the index
+ msg_hdr_ptr_ptr_t mp_index;
+ //Maximum number of messages of the queue
+ const size_type m_max_num_msg;
+ //Maximum size of messages of the queue
+ const size_type m_max_msg_size;
+ //Current number of messages
+ size_type m_cur_num_msg;
+ //Mutex to protect data structures
+ interprocess_mutex m_mutex;
+ //Condition block receivers when there are no messages
+ interprocess_condition m_cond_recv;
+ //Condition block senders when the queue is full
+ interprocess_condition m_cond_send;
+};
+
+
+//!This is the atomic functor to be executed when creating or opening
+//!shared memory. Never throws
+template<class VoidPointer>
+class initialization_func_t
+{
+ public:
+ typedef typename boost::intrusive::
+ pointer_traits<VoidPointer>::template
+ rebind_pointer<char>::type char_ptr;
+ typedef typename boost::intrusive::pointer_traits<char_ptr>::difference_type difference_type;
+ typedef typename boost::make_unsigned<difference_type>::type size_type;
+
+ initialization_func_t(size_type maxmsg = 0,
+ size_type maxmsgsize = 0)
+ : m_maxmsg (maxmsg), m_maxmsgsize(maxmsgsize) {}
+
+ bool operator()(void *address, size_type, bool created)
+ {
+ char *mptr;
+
+ if(created){
+ mptr = reinterpret_cast<char*>(address);
+ //Construct the message queue header at the beginning
+ BOOST_TRY{
+ new (mptr) mq_hdr_t<VoidPointer>(m_maxmsg, m_maxmsgsize);
+ }
+ BOOST_CATCH(...){
+ return false;
+ }
+ BOOST_CATCH_END
+ }
+ return true;
+ }
+ const size_type m_maxmsg;
+ const size_type m_maxmsgsize;
+};
+
+} //namespace ipcdetail {
+
+template<class VoidPointer>
+inline message_queue_t<VoidPointer>::~message_queue_t()
+{}
+
+template<class VoidPointer>
+inline typename message_queue_t<VoidPointer>::size_type message_queue_t<VoidPointer>::get_mem_size
+ (size_type max_msg_size, size_type max_num_msg)
+{ return ipcdetail::mq_hdr_t<VoidPointer>::get_mem_size(max_msg_size, max_num_msg); }
+
+template<class VoidPointer>
+inline message_queue_t<VoidPointer>::message_queue_t(create_only_t create_only,
+ const char *name,
+ size_type max_num_msg,
+ size_type max_msg_size,
+ const permissions &perm)
+ //Create shared memory and execute functor atomically
+ : m_shmem(create_only,
+ name,
+ get_mem_size(max_msg_size, max_num_msg),
+ read_write,
+ static_cast<void*>(0),
+ //Prepare initialization functor
+ ipcdetail::initialization_func_t<VoidPointer> (max_num_msg, max_msg_size),
+ perm)
+{}
+
+template<class VoidPointer>
+inline message_queue_t<VoidPointer>::message_queue_t(open_or_create_t open_or_create,
+ const char *name,
+ size_type max_num_msg,
+ size_type max_msg_size,
+ const permissions &perm)
+ //Create shared memory and execute functor atomically
+ : m_shmem(open_or_create,
+ name,
+ get_mem_size(max_msg_size, max_num_msg),
+ read_write,
+ static_cast<void*>(0),
+ //Prepare initialization functor
+ ipcdetail::initialization_func_t<VoidPointer> (max_num_msg, max_msg_size),
+ perm)
+{}
+
+template<class VoidPointer>
+inline message_queue_t<VoidPointer>::message_queue_t(open_only_t open_only,
+ const char *name)
+ //Create shared memory and execute functor atomically
+ : m_shmem(open_only,
+ name,
+ read_write,
+ static_cast<void*>(0),
+ //Prepare initialization functor
+ ipcdetail::initialization_func_t<VoidPointer> ())
+{}
+
+template<class VoidPointer>
+inline void message_queue_t<VoidPointer>::send
+ (const void *buffer, size_type buffer_size, unsigned int priority)
+{ this->do_send(blocking, buffer, buffer_size, priority, ptime()); }
+
+template<class VoidPointer>
+inline bool message_queue_t<VoidPointer>::try_send
+ (const void *buffer, size_type buffer_size, unsigned int priority)
+{ return this->do_send(non_blocking, buffer, buffer_size, priority, ptime()); }
+
+template<class VoidPointer>
+inline bool message_queue_t<VoidPointer>::timed_send
+ (const void *buffer, size_type buffer_size
+ ,unsigned int priority, const boost::posix_time::ptime &abs_time)
+{
+ if(abs_time == boost::posix_time::pos_infin){
+ this->send(buffer, buffer_size, priority);
+ return true;
+ }
+ return this->do_send(timed, buffer, buffer_size, priority, abs_time);
+}
+
+template<class VoidPointer>
+inline bool message_queue_t<VoidPointer>::do_send(block_t block,
+ const void *buffer, size_type buffer_size,
+ unsigned int priority, const boost::posix_time::ptime &abs_time)
+{
+ ipcdetail::mq_hdr_t<VoidPointer> *p_hdr = static_cast<ipcdetail::mq_hdr_t<VoidPointer>*>(m_shmem.get_user_address());
+ //Check if buffer is smaller than maximum allowed
+ if (buffer_size > p_hdr->m_max_msg_size) {
+ throw interprocess_exception(size_error);
+ }
+
+ //---------------------------------------------
+ scoped_lock<interprocess_mutex> lock(p_hdr->m_mutex);
+ //---------------------------------------------
+ {
+ //If the queue is full execute blocking logic
+ if (p_hdr->is_full()) {
+
+ switch(block){
+ case non_blocking :
+ return false;
+ break;
+
+ case blocking :
+ do{
+ p_hdr->m_cond_send.wait(lock);
+ }
+ while (p_hdr->is_full());
+ break;
+
+ case timed :
+ do{
+ if(!p_hdr->m_cond_send.timed_wait(lock, abs_time)){
+ if(p_hdr->is_full())
+ return false;
+ break;
+ }
+ }
+ while (p_hdr->is_full());
+ break;
+ default:
+ break;
+ }
+ }
+
+ //Get the first free message from free message queue
+ ipcdetail::msg_hdr_t<VoidPointer> *free_msg = p_hdr->free_msg();
+ if (free_msg == 0) {
+ throw interprocess_exception("boost::interprocess::message_queue corrupted");
+ }
+
+ //Copy control data to the free message
+ free_msg->priority = priority;
+ free_msg->len = buffer_size;
+
+ //Copy user buffer to the message
+ std::memcpy(free_msg->data(), buffer, buffer_size);
+
+// bool was_empty = p_hdr->is_empty();
+ //Insert the first free message in the priority queue
+ p_hdr->queue_free_msg();
+
+ //If this message changes the queue empty state, notify it to receivers
+// if (was_empty){
+ p_hdr->m_cond_recv.notify_one();
+// }
+ } // Lock end
+
+ return true;
+}
+
+template<class VoidPointer>
+inline void message_queue_t<VoidPointer>::receive(void *buffer, size_type buffer_size,
+ size_type &recvd_size, unsigned int &priority)
+{ this->do_receive(blocking, buffer, buffer_size, recvd_size, priority, ptime()); }
+
+template<class VoidPointer>
+inline bool
+ message_queue_t<VoidPointer>::try_receive(void *buffer, size_type buffer_size,
+ size_type &recvd_size, unsigned int &priority)
+{ return this->do_receive(non_blocking, buffer, buffer_size, recvd_size, priority, ptime()); }
+
+template<class VoidPointer>
+inline bool
+ message_queue_t<VoidPointer>::timed_receive(void *buffer, size_type buffer_size,
+ size_type &recvd_size, unsigned int &priority,
+ const boost::posix_time::ptime &abs_time)
+{
+ if(abs_time == boost::posix_time::pos_infin){
+ this->receive(buffer, buffer_size, recvd_size, priority);
+ return true;
+ }
+ return this->do_receive(timed, buffer, buffer_size, recvd_size, priority, abs_time);
+}
+
+template<class VoidPointer>
+inline bool
+ message_queue_t<VoidPointer>::do_receive(block_t block,
+ void *buffer, size_type buffer_size,
+ size_type &recvd_size, unsigned int &priority,
+ const boost::posix_time::ptime &abs_time)
+{
+ ipcdetail::mq_hdr_t<VoidPointer> *p_hdr = static_cast<ipcdetail::mq_hdr_t<VoidPointer>*>(m_shmem.get_user_address());
+ //Check if buffer is big enough for any message
+ if (buffer_size < p_hdr->m_max_msg_size) {
+ throw interprocess_exception(size_error);
+ }
+
+ //---------------------------------------------
+ scoped_lock<interprocess_mutex> lock(p_hdr->m_mutex);
+ //---------------------------------------------
+ {
+ //If there are no messages execute blocking logic
+ if (p_hdr->is_empty()) {
+ switch(block){
+ case non_blocking :
+ return false;
+ break;
+
+ case blocking :
+ do{
+ p_hdr->m_cond_recv.wait(lock);
+ }
+ while (p_hdr->is_empty());
+ break;
+
+ case timed :
+ do{
+ if(!p_hdr->m_cond_recv.timed_wait(lock, abs_time)){
+ if(p_hdr->is_empty())
+ return false;
+ break;
+ }
+ }
+ while (p_hdr->is_empty());
+ break;
+
+ //Paranoia check
+ default:
+ break;
+ }
+ }
+
+ //Thre is at least message ready to pick, get the top one
+ ipcdetail::msg_hdr_t<VoidPointer> *top_msg = p_hdr->top_msg();
+
+ //Paranoia check
+ if (top_msg == 0) {
+ throw interprocess_exception("boost::interprocess::message_queue corrupted");
+ }
+
+ //Get data from the message
+ recvd_size = top_msg->len;
+ priority = top_msg->priority;
+
+ //Copy data to receiver's bufers
+ std::memcpy(buffer, top_msg->data(), recvd_size);
+
+// bool was_full = p_hdr->is_full();
+
+ //Free top message and put it in the free message list
+ p_hdr->free_top_msg();
+
+ //If this reception changes the queue full state, notify senders
+// if (was_full){
+ p_hdr->m_cond_send.notify_one();
+// }
+ } //Lock end
+
+ return true;
+}
+
+template<class VoidPointer>
+inline typename message_queue_t<VoidPointer>::size_type message_queue_t<VoidPointer>::get_max_msg() const
+{
+ ipcdetail::mq_hdr_t<VoidPointer> *p_hdr = static_cast<ipcdetail::mq_hdr_t<VoidPointer>*>(m_shmem.get_user_address());
+ return p_hdr ? p_hdr->m_max_num_msg : 0; }
+
+template<class VoidPointer>
+inline typename message_queue_t<VoidPointer>::size_type message_queue_t<VoidPointer>::get_max_msg_size() const
+{
+ ipcdetail::mq_hdr_t<VoidPointer> *p_hdr = static_cast<ipcdetail::mq_hdr_t<VoidPointer>*>(m_shmem.get_user_address());
+ return p_hdr ? p_hdr->m_max_msg_size : 0;
+}
+
+template<class VoidPointer>
+inline typename message_queue_t<VoidPointer>::size_type message_queue_t<VoidPointer>::get_num_msg()
+{
+ ipcdetail::mq_hdr_t<VoidPointer> *p_hdr = static_cast<ipcdetail::mq_hdr_t<VoidPointer>*>(m_shmem.get_user_address());
+ if(p_hdr){
+ //---------------------------------------------
+ scoped_lock<interprocess_mutex> lock(p_hdr->m_mutex);
+ //---------------------------------------------
+ return p_hdr->m_cur_num_msg;
+ }
+
+ return 0;
+}
+
+template<class VoidPointer>
+inline bool message_queue_t<VoidPointer>::remove(const char *name)
+{ return shared_memory_object::remove(name); }
+
+/// @endcond
+
+}} //namespace boost{ namespace interprocess{
+
+#include <boost/interprocess/detail/config_end.hpp>
+
+#endif //#ifndef BOOST_INTERPROCESS_MESSAGE_QUEUE_HPP
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