malloc/dynarray_emplace_enlarge.c

   1 /* Increase the size of a dynamic array in preparation of an emplace operation.
   2    Copyright (C) 2017 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 <dynarray.h>
  20 #include <malloc-internal.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23
  24 bool
  25 __libc_dynarray_emplace_enlarge (struct dynarray_header *list,
  26                                  void *scratch, size_t element_size)
  27 {
  28   size_t new_allocated;
  29   if (list->allocated == 0)
  30     {
  31       /* No scratch buffer provided.  Choose a reasonable default
  32          size.  */
  33       if (element_size < 4)
  34         new_allocated = 16;
  35       if (element_size < 8)
  36         new_allocated = 8;
  37       else
  38         new_allocated = 4;
  39     }
  40   else
  41     /* Increase the allocated size, using an exponential growth
  42        policy.  */
  43     {
  44       new_allocated = list->allocated + list->allocated / 2 + 1;
  45       if (new_allocated <= list->allocated)
  46         /* Overflow.  */
  47         return false;
  48     }
  49
  50   size_t new_size;
  51   if (check_mul_overflow_size_t (new_allocated, element_size, &new_size))
  52     return false;
  53   void *new_array;
  54   if (list->array == scratch)
  55     {
  56       /* The previous array was not heap-allocated.  */
  57       new_array = malloc (new_size);
  58       if (new_array != NULL && list->array != NULL)
  59         memcpy (new_array, list->array, list->used * element_size);
  60     }
  61   else
  62     new_array = realloc (list->array, new_size);
  63   if (new_array == NULL)
  64     return false;
  65   list->array = new_array;
  66   list->allocated = new_allocated;
  67   return true;
  68 }
  69 libc_hidden_def (__libc_dynarray_emplace_enlarge)