1 files changed, 83 insertions, 0 deletions
diff --git a/linux/shmem.c b/linux/shmem.c
new file mode 100644
index 0000000000..7563175fb0
--- /dev/null
+++ b/linux/shmem.c
@@ -0,0 +1,83 @@
+/*
+ *   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;
+  }
+}