sysdeps/unix/sysv/linux/readv.c

   1 /* readv supports all Linux kernels >= 2.0.
   2    Copyright (C) 1997, 1998, 2000 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    read 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 #include <sysdep.h>
  26 #include <sys/syscall.h>
  27
  28 extern ssize_t __syscall_readv (int, __const struct iovec *, int);
  29 static ssize_t __atomic_readv_replacement (int, __const struct iovec *,
  30                                            int) internal_function;
  31
  32
  33 /* Not all versions of the kernel support the large number of records.  */
  34 #ifndef UIO_FASTIOV
  35 # define UIO_FASTIOV    8       /* 8 is a safe number.  */
  36 #endif
  37
  38
  39 /* We should deal with kernel which have a smaller UIO_FASTIOV as well
  40    as a very big count.  */
  41 ssize_t
  42 __readv (fd, vector, count)
  43      int fd;
  44      const struct iovec *vector;
  45      int count;
  46 {
  47   int errno_saved = errno;
  48   ssize_t bytes_read;
  49
  50   bytes_read = INLINE_SYSCALL (readv, 3, fd, vector, count);
  51
  52   if (bytes_read >= 0 || errno != EINVAL || count <= UIO_FASTIOV)
  53     return bytes_read;
  54
  55   /* Restore the old error value as if nothing happened.  */
  56   __set_errno (errno_saved);
  57
  58   return __atomic_readv_replacement (fd, vector, count);
  59 }
  60 weak_alias (__readv, readv)
  61
  62 #define __readv static internal_function __atomic_readv_replacement
  63 #include <sysdeps/posix/readv.c>