/* 23 Mar 1991 by Eric Grosse.  Copyright (c) 1991 by AT&T.
 * Permission to use, copy, modify, and distribute this software for any
 * purpose without fee is hereby granted, provided that this entire notice
 * is included in all copies of any software which is or includes a copy
 * or modification of this software and in all copies of the supporting
 * documentation for such software.
 * THIS SOFTWARE IS BEING PROVIDED "AS IS", WITHOUT ANY EXPRESS OR IMPLIED
 * WARRANTY.  IN PARTICULAR, NEITHER THE AUTHORS NOR AT&T MAKE ANY
 * REPRESENTATION OR WARRANTY OF ANY KIND CONCERNING THE MERCHANTABILITY
 * OF THIS SOFTWARE OR ITS FITNESS FOR ANY PARTICULAR PURPOSE.
 */

/* function protypes, for snarfing...
char* shm_create(char*, mode_t, int);
char* shm_open(char*);
int shm_close(char*);
*/

#include <stdio.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>

#define BAD (char *)(-1)

/* returns 0 on failure */
char*
shm_create(char* name, mode_t mode, int nbytes)
{
	int	shmid;
	char* 	shm = 0;
	shmid = shmget(IPC_PRIVATE, 128+nbytes, mode|IPC_CREAT);
	if (shmid >= 0) {
		shm = (char *)shmat(shmid, 0, 0);
		if (shm == BAD) {
			fprintf(stderr,"couldn't attach %d\n",shmid);
			shm = 0;
		} else {
			sprintf(shm, "%d %.100s%c\n", shmid, name, 0);
		}
	}
	return(shm);
}


/* returns 0 on failure */
char*
shm_open(char* id)
{
	int	shmid, n;
	char* 	shm = 0;
	n = sscanf(id, "%d", &shmid);
	if (n == 1) {
		shm = (char*)shmat(shmid, 0, SHM_RDONLY);
		if (shm == BAD || shm == 0) {
			shm = 0;
		} else {
			/* finally, check that shm matches id */
			n = strlen(id);
			if (id[n-1] == '\n')
				n--;
			if (strncmp(shm, id, n) != 0)
				shm = 0;
		}
	}
	return(shm);
}


/* returns non-0 on failure */
int
shm_close(char* shm)
{
	return( shmdt(shm) );
}