1 /* Variable-sized buffer with on-stack default allocation.
2    Copyright (C) 2015-2022 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    <https://www.gnu.org/licenses/>.  */
18 
19 #ifndef _LIBC
20 # include <libc-config.h>
21 #endif
22 
23 #include <scratch_buffer.h>
24 #include <errno.h>
25 #include <string.h>
26 
27 bool
__libc_scratch_buffer_grow_preserve(struct scratch_buffer * buffer)28 __libc_scratch_buffer_grow_preserve (struct scratch_buffer *buffer)
29 {
30   size_t new_length = 2 * buffer->length;
31   void *new_ptr;
32 
33   if (buffer->data == buffer->__space.__c)
34     {
35       /* Move buffer to the heap.  No overflow is possible because
36 	 buffer->length describes a small buffer on the stack.  */
37       new_ptr = malloc (new_length);
38       if (new_ptr == NULL)
39 	return false;
40       memcpy (new_ptr, buffer->__space.__c, buffer->length);
41     }
42   else
43     {
44       /* Buffer was already on the heap.  Check for overflow.  */
45       if (__glibc_likely (new_length >= buffer->length))
46 	new_ptr = realloc (buffer->data, new_length);
47       else
48 	{
49 	  __set_errno (ENOMEM);
50 	  new_ptr = NULL;
51 	}
52 
53       if (__glibc_unlikely (new_ptr == NULL))
54 	{
55 	  /* Deallocate, but buffer must remain valid to free.  */
56 	  free (buffer->data);
57 	  scratch_buffer_init (buffer);
58 	  return false;
59 	}
60     }
61 
62   /* Install new heap-based buffer.  */
63   buffer->data = new_ptr;
64   buffer->length = new_length;
65   return true;
66 }
67 libc_hidden_def (__libc_scratch_buffer_grow_preserve)
68