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/*
* 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 <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>
#ifdef AIX
#include <sys/select.h>
#endif
#include <sys/ipc.h>
#include <sys/shm.h>
extern int errno;
#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;
int devzero;
while(1){
switch(shmem_type){
case 0: // ========= MAP_ANON|MAP_SHARED ==========
p=mmap(0,size,PROT_READ|PROT_WRITE,MAP_ANON|MAP_SHARED,-1,0);
if(p==MAP_FAILED) break; // failed
printf("shmem: %d bytes allocated using mmap anon (%X)\n",size,p);
return p;
case 1: // ========= MAP_SHARED + /dev/zero ==========
if ((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
printf("shmem: %d bytes allocated using mmap /dev/zero (%X)\n",size,p);
return p;
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){
perror ("shmat()");
shmctl (shmemid, IPC_RMID, &shmemds);
break;
}
if (shmctl(shmemid, IPC_RMID, &shmemds) == -1) {
perror ("shmctl()");
if (shmdt(p) == -1) perror ("shmdt()");
break;
}
printf("shmem: %d bytes allocated using shmget() & shmat() (%X)\n",size,p);
return p;
}
default:
printf("FATAL: Cannot alloate %d bytes shared memory :(\n",size);
return NULL;
}
++shmem_type;
}
}
void shmem_free(void* p){
switch(shmem_type){
case 2:
if (shmdt(p) == -1) perror ("shmdt()");
break;
}
}
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