mpv/linux/shmem.c

/*
 *   shmem.c - Shared memory allocation
 *   
 *   based on mpg123's xfermem.c by
 *   Oliver Fromme  <oliver.fromme@heim3.tu-clausthal.de>
 *   Sun Apr  6 02:26:26 MET DST 1997
 */

#include "../config.h"

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/uio.h>
#include <sys/mman.h>
#include <sys/socket.h>
#include <fcntl.h>

#include "../mp_msg.h"

#ifdef AIX
#include <sys/select.h>
#endif

#ifdef HAVE_SHM
#include <sys/ipc.h>
#include <sys/shm.h>
#endif

#if defined(MAP_ANONYMOUS) && !defined(MAP_ANON)
#define MAP_ANON MAP_ANONYMOUS
#endif

static int shmem_type=0;

void* shmem_alloc(int size){
void* p;
static int devzero = -1;
while(1){
  switch(shmem_type){
  case 0:  // ========= MAP_ANON|MAP_SHARED ==========
#ifdef MAP_ANON
    p=mmap(0,size,PROT_READ|PROT_WRITE,MAP_ANON|MAP_SHARED,-1,0);
    if(p==MAP_FAILED) break; // failed
    mp_dbg(MSGT_OSDEP, MSGL_DBG2, "shmem: %d bytes allocated using mmap anon (%p)\n",size,p);
    return p;
#else
// system does not support MAP_ANON at all (e.g. solaris 2.5.1/2.6), just fail
    mp_dbg(MSGT_OSDEP, MSGL_DBG3, "shmem: using mmap anon failed\n");
#endif
    break;
  case 1:  // ========= MAP_SHARED + /dev/zero ==========
    if (devzero == -1 && (devzero = open("/dev/zero", O_RDWR, 0)) == -1) break;
    p=mmap(0,size,PROT_READ|PROT_WRITE,MAP_SHARED,devzero,0);
    if(p==MAP_FAILED) break; // failed
    mp_dbg(MSGT_OSDEP, MSGL_DBG2, "shmem: %d bytes allocated using mmap /dev/zero (%p)\n",size,p);
    return p;
#ifdef HAVE_SHM
  case 2: { // ========= shmget() ==========
    struct shmid_ds shmemds;
    int shmemid;
    if ((shmemid = shmget(IPC_PRIVATE, size, IPC_CREAT | 0600)) == -1) break;
    if ((int)(p = shmat(shmemid, 0, 0)) == -1){
      mp_msg(MSGT_OSDEP, MSGL_ERR, "shmem: shmat() failed: %s\n", strerror(errno));
      shmctl (shmemid, IPC_RMID, &shmemds);
      break;
    }
    if (shmctl(shmemid, IPC_RMID, &shmemds) == -1) {
      mp_msg(MSGT_OSDEP, MSGL_ERR, "shmem: shmctl() failed: %s\n", strerror(errno));
      if (shmdt(p) == -1) perror ("shmdt()");
      break;
    }
    mp_dbg(MSGT_OSDEP, MSGL_DBG2, "shmem: %d bytes allocated using SHM (%p)\n",size,p);
    return p;
#else
    mp_msg(MSGT_OSDEP, MSGL_FATAL, "shmem: no SHM support was compiled in!\n");
    return(NULL);
#endif
	}
  default:
    mp_msg(MSGT_OSDEP, MSGL_FATAL,
	"FATAL: Cannot allocate %d bytes of shared memory :(\n",size);
    return NULL;
  }
  ++shmem_type;
}
}

void shmem_free(void* p){
  switch(shmem_type){
    case 2:
#ifdef HAVE_SHM
	    if (shmdt(p) == -1)
		mp_msg(MSGT_OSDEP, MSGL_ERR, "shmfree: shmdt() failed: %s\n",
		    strerror(errno));
#else
	    mp_msg(MSGT_OSDEP, MSGL_ERR, "shmfree: no SHM support was compiled in!\n");
#endif
      break;
  }
}