1 /* Variable-sized buffer with on-stack default allocation.
2 Copyright (C) 2015-2023 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
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)