sharedMemSegment.hpp

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/** \file sharedMemSegment.hpp
 * \author Jared R. Males (jaredmales@gmail.com)
 * \brief Declarations for the mxlib shared memory facility
 * \ingroup IPC_sharedmem
 * \ingroup IPC
 *
 */
 
//***********************************************************************//
// Copyright 2015, 2016, 2017, 2018, 2021 Jared R. Males (jaredmales@gmail.com)
//
// This file is part of mxlib.
//
// mxlib is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// mxlib 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 General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with mxlib.  If not, see <http://www.gnu.org/licenses/>.
//***********************************************************************//
 
#ifndef ipc_sharedMemSegment_hpp
#define ipc_sharedMemSegment_hpp
 
#include <sys/shm.h>
#include <stdint.h>
#include <stdio.h>
 
#include "ipc.hpp"
 
namespace mx
{
namespace ipc
{
 
/** \addtogroup IPC_sharedmem
 * @{
 */
 
/// A c++ class to manage a System V shared memory segment with memory mapping
/** The associated functions create and/or attach to a shared memory segment.  If a segment is created, a block of
 * size sizeof(uintptr_t) is reserved where the address is stored.  This address is used when subsequently
 * attaching to the segment so that pointers stored in the block are valid, etc.
 *
 */
class sharedMemSegment
{
  public:
    /// The path to use for key creation
    char key_path[MX_IPC_KEYLEN];
 
    /// The id to use for key creation
    int key_id;
 
    /// The shared memory key
    key_t key;
 
    /// The shared memory id associated with the key
    int shmemid;
 
    /// The base address of the segment
    void *addr;
 
    /// The size of the segment
    size_t size;
 
    /// Flag indicating whether or not the segment is attached
    int attached;
 
  public:
    /// Initialize the class
    void initialize();
 
    /// Set the key
    /** If path == 0, then the key is set directly to id, without using ftok.
     *
     * \param path is the full path to use in a call to ftok
     * \param id is the id number to use in a call to ftok
     *
     * \returns the key value, which is also set in the msgq
     */
    key_t setKey( const char *path, const int id );
 
    /// Create and attach to the segment
    /** A segment of size = sz + sizeof(uintptr_t) is actually created.
     *
     * \note key must be set before calling this function.
     *
     * \param sz the size of the segment to create
     *
     */
    int create( size_t sz );
 
    /// Attach to a segment without creating it.
    /** If donot_set_addr == false, then the address is mapped to match that stored in the first uintptr_t of the
     * segment.
     *
     * \param donot_set_addr if > 0 (true) then the address is not mapped to match that stored in the segment
     */
    int attach( bool donot_set_addr = false );
 
    /// Detach from the segment
    /**
     *
     */
    int detach();
};
class sharedMemSegment {…};
 
/// @}
 
} // namespace ipc
} // namespace mx
 
#endif // ipc_sharedMemSegment_hpp