jack1/libjack/shm.c

/*
    Copyright (C) 2003 Paul Davis
    
    This program 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 2 of the License, or
    (at your option) any later version.

    This program 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 this program; if not, write to the Free Software
    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.

    $Id$
*/

#include <unistd.h>
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
#include <limits.h>
#include <errno.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>

#include <jack/shm.h>
#include <jack/internal.h>

typedef struct {
    shm_name_t name;
#ifdef USE_POSIX_SHM
    char *address;
#else
    int  shmid;
#endif
} jack_shm_registry_entry_t;

static jack_shm_registry_entry_t *jack_shm_registry;
static int                        jack_shm_id_cnt;

void
jack_register_shm (char *shm_name, char *addr, int id)
{
	if (jack_shm_id_cnt < MAX_SHM_ID) {
		snprintf (jack_shm_registry[jack_shm_id_cnt++].name, sizeof (shm_name_t), "%s", shm_name);
#ifdef USE_POSIX_SHM
		jack_shm_registry[jack_shm_id_cnt].address = addr;
#else
		jack_shm_registry[jack_shm_id_cnt].shmid = id;
#endif
	}
}

int
jack_initialize_shm ()
{
	void *addr;
	int id;

#ifdef USE_POSIX_SHM
	fprintf (stderr, "JACK compiled with POSIX SHM support\n");
#else
	fprintf (stderr, "JACK compiled with System V SHM support\n");
#endif

	if (jack_shm_registry != NULL) {
		return 0;
	}

	/* grab a chunk of memory to store shm ids in. this is 
	   to allow our parent to clean up all such ids when
	   if we exit. otherwise, they can get lost in crash
	   or debugger driven exits.
	*/
	
	if ((addr = jack_get_shm ("/jack-shm-registry", sizeof (jack_shm_registry_entry_t) * MAX_SHM_ID, 
				  O_RDWR|O_CREAT|O_TRUNC, 0600, PROT_READ|PROT_WRITE, &id)) == MAP_FAILED) {
		return -1;
	}

	jack_shm_registry = (jack_shm_registry_entry_t *) addr;
	jack_shm_id_cnt = 0;
	
	jack_register_shm ("/jack-shm-registry", addr, id);

	return 0;
}

void
jack_cleanup_shm ()
{
	int i;

	for (i = 0; i < jack_shm_id_cnt; i++) {
		jack_destroy_shm (jack_shm_registry[i].name);
	}
}

#if USE_POSIX_SHM

void
jack_destroy_shm (const char *shm_name)
{
	shm_unlink (shm_name);
}

void
jack_release_shm (char *addr, size_t size)
{
	munmap (addr, size);
}

char *
jack_get_shm (const char *shm_name, size_t size, int perm, int mode, int prot, int *not_really_used)
{
	int shm_fd;
	char *addr;

	if ((shm_fd = shm_open (shm_name, perm, mode)) < 0) {
		jack_error ("cannot create shm segment %s (%s)", shm_name, strerror (errno));
		return MAP_FAILED;
	}

	if (perm & O_CREAT) {
		if (ftruncate (shm_fd, size) < 0) {
			jack_error ("cannot set size of engine shm registry (%s)", strerror (errno));
			return MAP_FAILED;
		}
	}

	if ((addr = mmap (0, size, prot, MAP_SHARED, shm_fd, 0)) == MAP_FAILED) {
		jack_error ("cannot mmap shm segment %s (%s)", shm_name, strerror (errno));
		shm_unlink (shm_name);
		close (shm_fd);
		return MAP_FAILED;
	}

	close (shm_fd);
	*not_really_used = 0;
	return addr;
}

char *
jack_resize_shm (const char *shm_name, size_t size, int perm, int mode, int prot)
{
	int i;
	int shm_fd;
	char *addr;
	struct stat statbuf;

	for (i = 0; i < jack_shm_id_cnt; ++i) {
		if (strcmp (jack_shm_registry[i].name, shm_name) == 0) {
			break;
		}
	}

	if (i == jack_shm_id_cnt) {
		jack_error ("attempt to resize unknown shm segment \"%s\"", shm_name);
		return MAP_FAILED;
	}

	if ((shm_fd = shm_open (shm_name, perm, mode)) < 0) {
		jack_error ("cannot create shm segment %s (%s)", shm_name, strerror (errno));
		return MAP_FAILED;
	}

	fstat (shm_fd, &statbuf);
	
	munmap (jack_shm_registry[i].address, statbuf.st_size);

	if (perm & O_CREAT) {
		if (ftruncate (shm_fd, size) < 0) {
			jack_error ("cannot set size of engine shm registry (%s)", strerror (errno));
			return MAP_FAILED;
		}
	}
		
	if ((addr = mmap (0, size, prot, MAP_SHARED, shm_fd, 0)) == MAP_FAILED) {
		jack_error ("cannot mmap shm segment %s (%s)", shm_name, strerror (errno));
		shm_unlink (shm_name);
		close (shm_fd);
		return MAP_FAILED;
	}

	close (shm_fd);
	return addr;
}

#else /* USE_POSIX_SHM */

int
jack_get_shmid (const char *name)
{
	int i;

	/* **** NOT THREAD SAFE *****/

	for (i = 0; i < jack_shm_id_cnt; ++i) {
		if (strcmp (jack_shm_registry[i].name, name) == 0) {
			return jack_shm_registry[i].shmid;
		}
	}
	return -1;
}

void
jack_destroy_shm (const char *shm_name)
{
	int shmid = jack_get_shmid (shm_name);

	if (shmid >= 0) {
		shmctl (IPC_RMID, shmid, NULL);
	}
}

void
jack_release_shm (char *addr, size_t size)
{
	shmdt (addr);
}

char *
jack_get_shm (const char *shm_name, size_t size, int perm, int mode, int prot, int* shmid)
{
	char *addr;
	key_t key;
	int shmflags;
	char path[PATH_MAX+1];
	struct stat statbuf;
	int status;

	/* note: no trailing '/' on basic path because we expect shm_name to
	   begin with one (as per POSIX shm API).
	*/

	if (mkdir ("/tmp/jack", 0775)) {
		if (errno != EEXIST) {
			jack_error ("cannot create JACK directory (%s)", strerror (errno));
			return MAP_FAILED;
		}
	}

	if (mkdir ("/tmp/jack/shm", 0775)) {
		if (errno != EEXIST) {
			jack_error ("cannot create JACK shm directory (%s)", strerror (errno));
			return MAP_FAILED;
		}
	}

	snprintf (path, sizeof(path), "/tmp/jack/shm%s", shm_name);
	if ((status = stat (path, &statbuf)) < 0) {
		int fd;

		if ((fd = open (path, O_RDWR|O_CREAT, 0775)) < 0) {
			jack_error ("cannot create shm file node for %s (%s)", path, strerror (errno));
			return MAP_FAILED;
		}
		close (fd);
	}

	if ((key = ftok (path, 'j')) < 0) {
		jack_error ("cannot generate IPC key for shm segment %s (%s)", path, strerror (errno));
		unlink (path);
		return MAP_FAILED;
	}
	
	/* XXX need to figure out how to do this without causing the inode reallocation
	   the next time this function is called resulting in ftok() returning non-unique
	   keys.
	*/

	/* unlink (path); */

	shmflags = mode;

	if (perm & O_CREAT) {
		shmflags |= IPC_CREAT;
	}

	if (perm & O_TRUNC) {
		shmflags |= IPC_EXCL;
	}

	if ((*shmid = shmget (key, size, shmflags)) < 0) {

		if (errno == EEXIST && (shmflags & IPC_EXCL)) {

			shmflags &= ~IPC_EXCL;

			if ((*shmid = shmget (key, size, shmflags)) < 0) {
				jack_error ("cannot get existing shm segment for %s (%s)",
					    shm_name, strerror (errno));
				return MAP_FAILED;
			}

		} else {
			jack_error ("cannot create shm segment %s (%s)", shm_name, strerror (errno));
			return MAP_FAILED;
		}
	}

	if ((addr = shmat (*shmid, 0, 0)) < 0) {
		jack_error ("cannot attach shm segment %s (%s)", shm_name, strerror (errno));
		return MAP_FAILED;
	}

	return addr;
}

char *
jack_resize_shm (const char *shm_name, size_t size, int perm, int mode, int prot)
{
	jack_error ("jack_resize_shm() is not implemented for the System V shared memory API");
	return 0;
}

#endif /* USE_POSIX_SHM */