select.h

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) 1997, 1998, 2001 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.  */

#ifndef _SYS_SELECT_H
# error "Never use <bits/select.h> directly; include <sys/select.h> instead."
#endif


/* We don't use `memset' because this would require a prototype and
   the array isn't too big.  */
#define __FD_ZERO(s) \
  do {									      \
    unsigned int __i;							      \
    fd_set *__arr = (s);						      \
    for (__i = 0; __i < sizeof (fd_set) / sizeof (__fd_mask); ++__i)	      \
      __FDS_BITS (__arr)[__i] = 0;					      \
  } while (0)
#define __FD_SET(d, s)     (__FDS_BITS (s)[__FDELT(d)] |= __FDMASK(d))
#define __FD_CLR(d, s)     (__FDS_BITS (s)[__FDELT(d)] &= ~__FDMASK(d))
#define __FD_ISSET(d, s)   ((__FDS_BITS (s)[__FDELT(d)] & __FDMASK(d)) != 0)