sysdeps/unix/sysv/linux/writev.c

   1 /* writev supports all Linux kernels >= 2.0.
   2    Copyright (C) 1997,1998,2000,2002,2003,2009 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 Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the 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    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    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-cancel.h>
  26 #include <sys/syscall.h>
  27 #include <bp-checks.h>
  28 #include <kernel-features.h>
  29
  30 static ssize_t __atomic_writev_replacement (int, const struct iovec *,
  31                                             int) internal_function;
  32
  33
  34 /* Not all versions of the kernel support the large number of records.  */
  35 #ifndef UIO_FASTIOV
  36 # define UIO_FASTIOV    8       /* 8 is a safe number.  */
  37 #endif
  38
  39
  40 /* We should deal with kernel which have a smaller UIO_FASTIOV as well
  41    as a very big count.  */
  42 static ssize_t
  43 do_writev (int fd, const struct iovec *vector, int count)
  44 {
  45   ssize_t bytes_written;
  46
  47   bytes_written = INLINE_SYSCALL (writev, 3, fd, CHECK_N (vector, count),
  48                                   count);
  49
  50 #ifdef __ASSUME_COMPLETE_READV_WRITEV
  51   return bytes_written;
  52 #else
  53   if (bytes_written >= 0 || errno != EINVAL || count <= UIO_FASTIOV)
  54     return bytes_written;
  55
  56   return __atomic_writev_replacement (fd, vector, count);
  57 #endif
  58 }
  59
  60 ssize_t
  61 __libc_writev (fd, vector, count)
  62      int fd;
  63      const struct iovec *vector;
  64      int count;
  65 {
  66   if (SINGLE_THREAD_P)
  67     return do_writev (fd, vector, count);
  68
  69   int oldtype = LIBC_CANCEL_ASYNC ();
  70
  71   ssize_t result = do_writev (fd, vector, count);
  72
  73   LIBC_CANCEL_RESET (oldtype);
  74
  75   return result;
  76 }
  77 strong_alias (__libc_writev, __writev)
  78 weak_alias (__libc_writev, writev)
  79
  80 #ifndef __ASSUME_COMPLETE_READV_WRITEV
  81 # define __libc_writev static internal_function __atomic_writev_replacement
  82 # include <sysdeps/posix/writev.c>
  83 #endif