malloc/scratch_buffer_grow.c

   1 /* Variable-sized buffer with on-stack default allocation.
   2    Copyright (C) 2015-2017 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 <scratch_buffer.h>
  20 #include <errno.h>
  21
  22 bool
  23 __libc_scratch_buffer_grow (struct scratch_buffer *buffer)
  24 {
  25   void *new_ptr;
  26   size_t new_length = buffer->length * 2;
  27
  28   /* Discard old buffer.  */
  29   scratch_buffer_free (buffer);
  30
  31   /* Check for overflow.  */
  32   if (__glibc_likely (new_length >= buffer->length))
  33     new_ptr = malloc (new_length);
  34   else
  35     {
  36       __set_errno (ENOMEM);
  37       new_ptr = NULL;
  38     }
  39
  40   if (__glibc_unlikely (new_ptr == NULL))
  41     {
  42       /* Buffer must remain valid to free.  */
  43       scratch_buffer_init (buffer);
  44       return false;
  45     }
  46
  47   /* Install new heap-based buffer.  */
  48   buffer->data = new_ptr;
  49   buffer->length = new_length;
  50   return true;
  51 }
  52 libc_hidden_def (__libc_scratch_buffer_grow);