/* Variable-sized buffer with on-stack default allocation.

   Copyright (C) 2015-2018 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/>.  */

#ifndef _LIBC

# include <libc-config.h>

#endif

#include <scratch_buffer.h>

#include <errno.h>

#include <limits.h>

bool

__libc_scratch_buffer_set_array_size (struct scratch_buffer *buffer,

				      size_t nelem, size_t size)

{

  size_t new_length = nelem * size;

  /* Avoid overflow check if both values are small. */

  if ((nelem | size) >> (sizeof (size_t) * CHAR_BIT / 2) != 0

      && nelem != 0 && size != new_length / nelem)

    {

      /* Overflow.  Discard the old buffer, but it must remain valid

	 to free.  */

      scratch_buffer_free (buffer);

      scratch_buffer_init (buffer);

      __set_errno (ENOMEM);

      return false;

    }

  if (new_length <= buffer->length)

    return true;

  /* Discard old buffer.  */

  scratch_buffer_free (buffer);

  char *new_ptr = malloc (new_length);

  if (new_ptr == NULL)

    {

      /* Buffer must remain valid to free.  */

      scratch_buffer_init (buffer);

      return false;

    }

  /* Install new heap-based buffer.  */

  buffer->data = new_ptr;

  buffer->length = new_length;

  return true;

}

libc_hidden_def (__libc_scratch_buffer_set_array_size)