/* Copyright (C) 1991-2018 Free Software Foundation, Inc.

   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or

   modify it under the terms of the GNU Lesser General Public

   License as published by the Free Software Foundation; either

   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public

   License along with the GNU C Library; if not, see

   <http://www.gnu.org/licenses/>.  */

#include <stdlib.h>

#include <unistd.h>

#include <string.h>

#include <limits.h>

#include <stdbool.h>

#include <sys/param.h>

#include <sys/uio.h>

#include <errno.h>

static void

ifree (char **ptrp)

{

  free (*ptrp);

}

/* Write data pointed by the buffers described by VECTOR, which

   is a vector of COUNT 'struct iovec's, to file descriptor FD.

   The data is written in the order specified.

   Operates just like 'write' (see <unistd.h>) except that the data

   are taken from VECTOR instead of a contiguous buffer.  */

ssize_t

__writev (int fd, const struct iovec *vector, int count)

{

  /* Find the total number of bytes to be written.  */

  size_t bytes = 0;

  for (int i = 0; i < count; ++i)

    {

      /* Check for ssize_t overflow.  */

      if (SSIZE_MAX - bytes < vector[i].iov_len)

	{

	  __set_errno (EINVAL);

	  return -1;

	}

      bytes += vector[i].iov_len;

    }

  /* Allocate a temporary buffer to hold the data.  We should normally

     use alloca since it's faster and does not require synchronization

     with other threads.  But we cannot if the amount of memory

     required is too large.  */

  char *buffer;

  char *malloced_buffer __attribute__ ((__cleanup__ (ifree))) = NULL;

  if (__libc_use_alloca (bytes))

    buffer = (char *) __alloca (bytes);

  else

    {

      malloced_buffer = buffer = (char *) malloc (bytes);

      if (buffer == NULL)

	/* XXX I don't know whether it is acceptable to try writing

	   the data in chunks.  Probably not so we just fail here.  */

	return -1;

    }

  /* Copy the data into BUFFER.  */

  size_t to_copy = bytes;

  char *bp = buffer;

  for (int i = 0; i < count; ++i)

    {

      size_t copy = MIN (vector[i].iov_len, to_copy);

      bp = __mempcpy ((void *) bp, (void *) vector[i].iov_base, copy);

      to_copy -= copy;

      if (to_copy == 0)

	break;

    }

  ssize_t bytes_written = __write (fd, buffer, bytes);

  return bytes_written;

}

libc_hidden_def (__writev)

weak_alias (__writev, writev)