Back to index

glibc  2.9
shm_open.c
Go to the documentation of this file.
00001 /* shm_open -- open a POSIX shared memory object.  Generic POSIX file version.
00002    Copyright (C) 2001,2002,2005 Free Software Foundation, Inc.
00003    This file is part of the GNU C Library.
00004 
00005    The GNU C Library is free software; you can redistribute it and/or
00006    modify it under the terms of the GNU Lesser General Public
00007    License as published by the Free Software Foundation; either
00008    version 2.1 of the License, or (at your option) any later version.
00009 
00010    The GNU C Library is distributed in the hope that it will be useful,
00011    but WITHOUT ANY WARRANTY; without even the implied warranty of
00012    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00013    Lesser General Public License for more details.
00014 
00015    You should have received a copy of the GNU Lesser General Public
00016    License along with the GNU C Library; if not, write to the Free
00017    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
00018    02111-1307 USA.  */
00019 
00020 #include <unistd.h>
00021 
00022 #if ! _POSIX_MAPPED_FILES
00023 #include <rt/shm_open.c>
00024 
00025 #else
00026 
00027 #include <errno.h>
00028 #include <sys/mman.h>
00029 #include <fcntl.h>
00030 #include <string.h>
00031 #include <stdlib.h>
00032 #include <paths.h>
00033 
00034 #define SHMDIR       (_PATH_DEV "shm/")
00035 
00036 /* Open shared memory object.  */
00037 int
00038 shm_open (const char *name, int oflag, mode_t mode)
00039 {
00040   size_t namelen;
00041   char *fname;
00042   int fd;
00043 
00044   /* Construct the filename.  */
00045   while (name[0] == '/')
00046     ++name;
00047 
00048   if (name[0] == '\0')
00049     {
00050       /* The name "/" is not supported.  */
00051       __set_errno (EINVAL);
00052       return -1;
00053     }
00054 
00055   namelen = strlen (name);
00056   fname = (char *) __alloca (sizeof SHMDIR - 1 + namelen + 1);
00057   __mempcpy (__mempcpy (fname, SHMDIR, sizeof SHMDIR - 1),
00058             name, namelen + 1);
00059 
00060   fd = open (name, oflag, mode);
00061   if (fd != -1)
00062     {
00063       /* We got a descriptor.  Now set the FD_CLOEXEC bit.  */
00064       int flags = fcntl (fd, F_GETFD, 0);
00065 
00066       if (__builtin_expect (flags, 0) != -1)
00067        {
00068          flags |= FD_CLOEXEC;
00069          flags = fcntl (fd, F_SETFD, flags);
00070        }
00071 
00072       if (flags == -1)
00073        {
00074          /* Something went wrong.  We cannot return the descriptor.  */
00075          int save_errno = errno;
00076          close (fd);
00077          fd = -1;
00078          __set_errno (save_errno);
00079        }
00080     }
00081 
00082   return fd;
00083 }
00084 
00085 #endif