sysdeps/unix/sysv/linux/writev.c

   1 /* writev supports all Linux kernels >= 2.0.
   2    Copyright (C) 1997-2014 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, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <stddef.h>
  21 #include <sys/param.h>
  22 #include <sys/uio.h>
  23
  24 #include <sysdep-cancel.h>
  25 #include <sys/syscall.h>
  26 #include <kernel-features.h>
  27
  28 #ifndef __ASSUME_COMPLETE_READV_WRITEV
  29 static ssize_t __atomic_writev_replacement (int, const struct iovec *,
  30                                             int) internal_function;
  31 #endif
  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 ssize_t
  41 __libc_writev (fd, vector, count)
  42      int fd;
  43      const struct iovec *vector;
  44      int count;
  45 {
  46   ssize_t result;
  47
  48   if (SINGLE_THREAD_P)
  49     result = INLINE_SYSCALL (writev, 3, fd, vector, count);
  50   else
  51     {
  52       int oldtype = LIBC_CANCEL_ASYNC ();
  53
  54       result = INLINE_SYSCALL (writev, 3, fd, vector, count);
  55
  56       LIBC_CANCEL_RESET (oldtype);
  57     }
  58
  59 #ifdef __ASSUME_COMPLETE_READV_WRITEV
  60   return result;
  61 #else
  62   if (result >= 0 || errno != EINVAL || count <= UIO_FASTIOV)
  63     return result;
  64
  65   return __atomic_writev_replacement (fd, vector, count);
  66 #endif
  67 }
  68 strong_alias (__libc_writev, __writev)
  69 weak_alias (__libc_writev, writev)
  70
  71 #ifndef __ASSUME_COMPLETE_READV_WRITEV
  72 # define __libc_writev static internal_function __atomic_writev_replacement
  73 # include <sysdeps/posix/writev.c>
  74 #endif