shm.c

它通过提供glibc兼容使得应用程序移植到较小的c 库时相当得容易. 它能够应用到带虚拟存储的Linux和uClinux上.在大多数带MMU部件的平台上为使它更加紧凑,它也能够编译成共享库.uClib

/* Copyright (C) 1995, 1997, 1998 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <[e-mail]>, August 1995.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Library General Public License as
   published by the Free Software Foundation; either version 2 of the
   License, or (at your option) any later version.

   The GNU C Library 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
   Library General Public License for more details.

   You should have received a copy of the GNU Library General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If not,
   write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
   Boston, MA 02111-1307, USA.  */

#include <stdlib.h>
#include <errno.h>
#include <sys/shm.h>
#include <syscall.h>
#include "ipc.h"

#ifdef L_shmat
/* Attach the shared memory segment associated with SHMID to the data
   segment of the calling process.  SHMADDR and SHMFLG determine how
   and where the segment is attached.  */
#if defined (__alpha__)
#define __NR_shmat  __NR_osf_shmat
#endif
#ifdef __NR_shmat
_syscall3(void *, shmat, int, shmid, const void *,shmaddr, int, shmflg);
#else
void * shmat (int shmid, const void *shmaddr, int shmflg)
{
    int retval;
    unsigned long raddr;

    retval = __ipc(IPCOP_shmat, shmid, shmflg, (int) &raddr, (void *) shmaddr);
    return ((unsigned long int) retval > -(unsigned long int) SHMLBA
	    ? (void *) retval : (void *) raddr);
}
#endif
#endif

#ifdef L_shmctl
/* Provide operations to control over shared memory segments.  */
#ifdef __NR_shmctl
_syscall3(int, shmctl, int, shmid, int, cmd, struct shmid_ds *, buf);
#else
int shmctl (int shmid, int cmd, struct shmid_ds *buf)
{
    return __ipc(IPCOP_shmctl, shmid, cmd, 0, buf);
}
#endif
#endif


#ifdef L_shmdt
/* Detach shared memory segment starting at address specified by SHMADDR
   from the caller's data segment.  */
#ifdef __NR_shmdt
_syscall1(int, shmdt, const void *, shmaddr);
#else
int shmdt (const void *shmaddr)
{
    return __ipc(IPCOP_shmdt, 0, 0, 0, (void *) shmaddr);
}
#endif
#endif

#ifdef L_shmget
/* Return an identifier for an shared memory segment of at least size SIZE
   which is associated with KEY.  */
#ifdef __NR_shmget
_syscall3(int, shmget, key_t, key, size_t, size, int, shmflg);
#else
int shmget (key_t key, size_t size, int shmflg)
{
    return __ipc(IPCOP_shmget, key, size, shmflg, NULL);
}
#endif
#endif