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 #ifndef __ASSUME_COMPLETE_READV_WRITEV
  31 static ssize_t __atomic_writev_replacement (int, const struct iovec *,
  32                                             int) internal_function;
  33 #endif
  34
  35
  36 /* Not all versions of the kernel support the large number of records.  */
  37 #ifndef UIO_FASTIOV
  38 # define UIO_FASTIOV    8       /* 8 is a safe number.  */
  39 #endif
  40
  41
  42 ssize_t
  43 __libc_writev (fd, vector, count)
  44      int fd;
  45      const struct iovec *vector;
  46      int count;
  47 {
  48   ssize_t result;
  49
  50   if (SINGLE_THREAD_P)
  51     result = INLINE_SYSCALL (writev, 3, fd, CHECK_N (vector, count), count);
  52   else
  53     {
  54       int oldtype = LIBC_CANCEL_ASYNC ();
  55
  56       result = INLINE_SYSCALL (writev, 3, fd, CHECK_N (vector, count), count);
  57
  58       LIBC_CANCEL_RESET (oldtype);
  59     }
  60
  61 #ifdef __ASSUME_COMPLETE_READV_WRITEV
  62   return result;
  63 #else
  64   if (result >= 0 || errno != EINVAL || count <= UIO_FASTIOV)
  65     return result;
  66
  67   return __atomic_writev_replacement (fd, vector, count);
  68 #endif
  69 }
  70 strong_alias (__libc_writev, __writev)
  71 weak_alias (__libc_writev, writev)
  72
  73 #ifndef __ASSUME_COMPLETE_READV_WRITEV
  74 # define __libc_writev static internal_function __atomic_writev_replacement
  75 # include <sysdeps/posix/writev.c>
  76 #endif