Make lttng_dynamic_buffer_append_buffer const-correct
[lttng-tools.git] / src / common / dynamic-buffer.h
1 /*
2 * Copyright (C) 2017 Jérémie Galarneau <jeremie.galarneau@efficios.com>
3 *
4 * SPDX-License-Identifier: LGPL-2.1-only
5 *
6 */
7
8 #ifndef LTTNG_DYNAMIC_BUFFER_H
9 #define LTTNG_DYNAMIC_BUFFER_H
10
11 #include <stddef.h>
12 #include <stdint.h>
13 #include <common/macros.h>
14
15 struct lttng_dynamic_buffer {
16 char *data;
17 /* size is the buffer's currently used capacity. */
18 size_t size;
19 /*
20 * capacity shall not be accessed by users directly, it is meant for
21 * internal use only.
22 */
23 size_t _capacity;
24 };
25
26 /*
27 * Initialize a dynamic buffer. This performs no allocation and is meant
28 * to be used instead of memset or explicit initialization of the buffer.
29 */
30 LTTNG_HIDDEN
31 void lttng_dynamic_buffer_init(struct lttng_dynamic_buffer *buffer);
32
33 /*
34 * Append the content of a raw memory buffer to the end of a dynamic buffer
35 * (after its current "size"). The dynamic buffer's size is increased by
36 * "len", and its capacity is adjusted automatically.
37 */
38 LTTNG_HIDDEN
39 int lttng_dynamic_buffer_append(struct lttng_dynamic_buffer *buffer,
40 const void *buf, size_t len);
41
42 /*
43 * Performs the same action as lttng_dynamic_buffer_append(), but using another
44 * dynamic buffer as the source buffer. The source buffer's size is used in lieu
45 * of "len".
46 */
47 LTTNG_HIDDEN
48 int lttng_dynamic_buffer_append_buffer(struct lttng_dynamic_buffer *dst_buffer,
49 const struct lttng_dynamic_buffer *src_buffer);
50
51 /*
52 * Set the buffer's size to new_size. The capacity of the buffer will
53 * be expanded (if necessary) to accommodates new_size. Areas acquired by
54 * a size increase will be zeroed.
55 *
56 * Be careful to expand the buffer's size _before_ calling out external
57 * APIs (e.g. read(3)) which may populate the buffer as setting the size
58 * after will zero-out the result of the operation.
59 *
60 * Shrinking a buffer does not zero the old content. If the buffer may contain
61 * sensititve information, it must be cleared manually _before_ changing the
62 * size.
63 *
64 * NOTE: It is striclty _invalid_ to access memory after _size_, regardless
65 * of prior calls to set_capacity().
66 */
67 LTTNG_HIDDEN
68 int lttng_dynamic_buffer_set_size(struct lttng_dynamic_buffer *buffer,
69 size_t new_size);
70
71 /*
72 * Set the buffer's capacity to accommodates the new_capacity, allocating memory
73 * as necessary. The buffer's content is preserved. Setting a buffer's capacity
74 * is meant as a _hint_ to the underlying buffer and is only optimization; no
75 * guarantee is offered that subsequent calls to append or set_size will succeed.
76 *
77 * If the current size > new_capacity, the operation will fail.
78 */
79 LTTNG_HIDDEN
80 int lttng_dynamic_buffer_set_capacity(struct lttng_dynamic_buffer *buffer,
81 size_t new_capacity);
82
83 /* Release any memory used by the dynamic buffer. */
84 LTTNG_HIDDEN
85 void lttng_dynamic_buffer_reset(struct lttng_dynamic_buffer *buffer);
86
87 /* Get the space left in the buffer before a new resize is needed. */
88 LTTNG_HIDDEN
89 size_t lttng_dynamic_buffer_get_capacity_left(
90 struct lttng_dynamic_buffer *buffer);
91
92 #endif /* LTTNG_DYNAMIC_BUFFER_H */
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