/* 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);

}

/* Read data from file descriptor FD, and put the result in the

   buffers described by VECTOR, which is a vector of COUNT 'struct iovec's.

   The buffers are filled in the order specified.

   Operates just like 'read' (see <unistd.h>) except that data are

   put in VECTOR instead of a contiguous buffer.  */

ssize_t

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

{

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

  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)

	return -1;

    }

  /* Read the data.  */

  ssize_t bytes_read = __read (fd, buffer, bytes);

  if (bytes_read < 0)

    return -1;

  /* Copy the data from BUFFER into the memory specified by VECTOR.  */

  bytes = bytes_read;

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

    {

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

      (void) memcpy ((void *) vector[i].iov_base, (void *) buffer, copy);

      buffer += copy;

      bytes -= copy;

      if (bytes == 0)

	break;

    }

  return bytes_read;

}

libc_hidden_def (__readv)

weak_alias (__readv, readv)