shm_segment.h

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#ifndef SHM_SEGMENT_H
#define SHM_SEGMENT_H 1

#include <sys/types.h> 
#include <sys/ipc.h>
#include <sys/shm.h>
#include <exception>
#include <cstdlib>

namespace std { using ::malloc; using ::free; }

class shm_segment
{
 public:
  shm_segment( int i, int flg ) ;
  shm_segment( int key, int size, int perm );
  ~shm_segment();
  void* get_base() const { return attach ; } ;
  int get_flag() const { return shmflg ; } ;
  int get_key() const { return key ; } ;
  int get_id() const { return shmid ; } ;
  int get_size() const { return size ; } ;
  bool persist( bool p ) { return persistant = p ; } ;
 
  void destroy();
 private:
  key_t  key;  
  int  shmflg;  
  int  shmid;  
  int  size;    
  void* attach;  
  bool persistant;
  struct shmid_ds * shmctlds;
};
 
shm_segment::shm_segment( int i, int flg ) :
  shmid( i ), shmflg( flg ), persistant( 0 )
{
  int j = 1;
  struct shmid_ds * shmidds;
  shmidds = (shmid_ds *)malloc( sizeof( struct shmid_ds ) );
  if ( 0 < shmid ) {
    attach = shmat( shmid, 0,0 );
    shmctl( shmid, IPC_STAT, shmidds );
//    size = shmidds->shm_segsz;
//    key = shmidds->shm_perm.__key;
    shmctlds = shmidds;
  } else {
    shmctlds = 0x0;
  }
}

shm_segment::shm_segment( int k, int sz, int flg ) :
  key( k ), size( sz ), shmflg( flg ), persistant( 0 )
{
  shmid = shmget( key, size, flg ); 
  if ( 0 < shmid ) {
    attach = shmat( shmid, 0,0 );
  }
}

shm_segment::~shm_segment() {
  int result;
  if ( ! persistant ) {
    shmctl( shmid, IPC_RMID, NULL);
  }
  result = shmdt( attach );
}

class shm_create_exception : public std::exception
{
 public:
  const char* what() const throw()
  { return "error creating shared memory segment"; }
};

#endif

/*
 * $Log: shm_segment.h,v $
 * Revision 1.3  2008/05/25 15:32:02  oommoo
 * modifications to make shared object and install headers (may require additional adds to get ltmain.sh for example
 *
 * Revision 1.2  2006/09/02 18:47:28  oommoo
 * documentation enhancement
 *
 * Revision 1.1.1.1  2006/08/30 12:14:59  oommoo
 * Initial checkin of project library
 *
 *
 * SharedMemory notes from :
 *
 * http://home.earthlink.net/~joshwalker1/writing/SharedMemory.html
 *
 */

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