fcntl.c

glibc 库, 不仅可以学习使用库函数,还可以学习函数的具体实现,是提高功力的好资料

/* Copyright (C) 2000, 2002, 2003, 2004 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 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
   Lesser General Public License for more details.

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

#include <assert.h>
#include <errno.h>
#include <sysdep-cancel.h>	/* Must come before <fcntl.h>.  */
#include <fcntl.h>
#include <stdarg.h>

#include <sys/syscall.h>


#ifndef NO_CANCELLATION
int
__fcntl_nocancel (int fd, int cmd, ...)
{
  va_list ap;
  void *arg;

  va_start (ap, cmd);
  arg = va_arg (ap, void *);
  va_end (ap);

  return INLINE_SYSCALL (fcntl, 3, fd, cmd, arg);
}
#endif


int
__libc_fcntl (int fd, int cmd, ...)
{
  va_list ap;
  void *arg;

  va_start (ap, cmd);
  arg = va_arg (ap, void *);
  va_end (ap);

  if (cmd >= F_GETLK64 && cmd <= F_SETLKW64)
    cmd -= F_GETLK64 - F_GETLK;

  if (SINGLE_THREAD_P || cmd != F_SETLKW)
    return INLINE_SYSCALL (fcntl, 3, fd, cmd, arg);

  int oldtype = LIBC_CANCEL_ASYNC ();

  int result = INLINE_SYSCALL (fcntl, 3, fd, cmd, arg);

  LIBC_CANCEL_RESET (oldtype);

  return result;
}
libc_hidden_def (__libc_fcntl)

weak_alias (__libc_fcntl, __fcntl)
libc_hidden_weak (__fcntl)
weak_alias (__libc_fcntl, fcntl)