sysdeps/unix/sysv/linux/writev.c

   1 /* writev supports all Linux kernels >= 2.0.
   2    Copyright (C) 1997 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Library General Public License as
   7    published by the Free Software Foundation; either version 2 of the
   8    License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Library General Public License for more details.
  14
  15    You should have received a copy of the GNU Library General Public
  16    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  17    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18    Boston, MA 02111-1307, USA.  */
  19
  20 #include <errno.h>
  21 #include <stddef.h>
  22 #include <sys/param.h>
  23 #include <sys/uio.h>
  24
  25 extern ssize_t __syscall_writev __P ((int, const struct iovec *, int));
  26 static ssize_t __atomic_writev_replacement __P ((int, const struct iovec *,
  27                                                  int)) internal_function;
  28
  29
  30 /* Not all versions of the kernel support the large number of records.  */
  31 #ifndef UIO_FASTIOV
  32 # define UIO_FASTIOV    8       /* 8 is a safe number.  */
  33 #endif
  34
  35
  36 /* We should deal with kernel which have a smaller UIO_FASTIOV as well
  37    as a very big count.  */
  38 ssize_t
  39 __writev (fd, vector, count)
  40      int fd;
  41      const struct iovec *vector;
  42      int count;
  43 {
  44   int errno_saved = errno;
  45   ssize_t bytes_written;
  46
  47   bytes_written = __syscall_writev (fd, vector, count);
  48
  49   if (bytes_written >= 0 || errno != EINVAL || count <= UIO_FASTIOV)
  50     return bytes_written;
  51
  52   /* Restore the old error value as if nothing happened.  */
  53   __set_errno (errno_saved);
  54
  55   return __atomic_writev_replacement (fd, vector, count);
  56 }
  57 weak_alias (__writev, writev)
  58
  59 #define __writev static internal_function __atomic_writev_replacement
  60 #include <sysdeps/posix/writev.c>