bits/select.h

   1 /* Copyright (C) 1997-2021 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #ifndef _SYS_SELECT_H
  19 # error "Never use <bits/select.h> directly; include <sys/select.h> instead."
  20 #endif
  21
  22
  23 /* We don't use `memset' because this would require a prototype and
  24    the array isn't too big.  */
  25 #define __FD_ZERO(s) \
  26   do {                                                                        \
  27     unsigned int __i;                                                         \
  28     fd_set *__arr = (s);                                                      \
  29     for (__i = 0; __i < sizeof (fd_set) / sizeof (__fd_mask); ++__i)          \
  30       __FDS_BITS (__arr)[__i] = 0;                                            \
  31   } while (0)
  32 #define __FD_SET(d, s) \
  33   ((void) (__FDS_BITS (s)[__FD_ELT(d)] |= __FD_MASK(d)))
  34 #define __FD_CLR(d, s) \
  35   ((void) (__FDS_BITS (s)[__FD_ELT(d)] &= ~__FD_MASK(d)))
  36 #define __FD_ISSET(d, s) \
  37   ((__FDS_BITS (s)[__FD_ELT (d)] & __FD_MASK (d)) != 0)