Clean-up: coverity warns of uncaught exception during logging
[lttng-tools.git] / src / common / dynamic-buffer.hpp
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.hpp>
14
15 struct lttng_buffer_view;
16
17 struct lttng_dynamic_buffer {
18 char *data;
19 /* size is the buffer's currently used capacity. */
20 size_t size;
21 /*
22 * capacity shall not be accessed by users directly, it is meant for
23 * internal use only.
24 */
25 size_t _capacity;
26 };
27
28 /*
29 * Initialize a dynamic buffer. This performs no allocation and is meant
30 * to be used instead of memset or explicit initialization of the buffer.
31 */
32 void lttng_dynamic_buffer_init(struct lttng_dynamic_buffer *buffer);
33
34 /*
35 * Append the content of a raw memory buffer to the end of a dynamic buffer
36 * (after its current "size"). The dynamic buffer's size is increased by
37 * "len", and its capacity is adjusted automatically.
38 */
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 int lttng_dynamic_buffer_append_buffer(struct lttng_dynamic_buffer *dst_buffer,
48 const struct lttng_dynamic_buffer *src_buffer);
49
50 /*
51 * Performs the same action as lttng_dynamic_buffer_append(), but using a
52 * buffer view as the source buffer. The source buffer's size is used in lieu
53 * of "len".
54 */
55 int lttng_dynamic_buffer_append_view(struct lttng_dynamic_buffer *buffer,
56 const struct lttng_buffer_view *view);
57
58 /*
59 * Set the buffer's size to new_size. The capacity of the buffer will
60 * be expanded (if necessary) to accommodates new_size. Areas acquired by
61 * a size increase will be zeroed.
62 *
63 * Be careful to expand the buffer's size _before_ calling out external
64 * APIs (e.g. read(3)) which may populate the buffer as setting the size
65 * after will zero-out the result of the operation.
66 *
67 * Shrinking a buffer does not zero the old content. If the buffer may contain
68 * sensititve information, it must be cleared manually _before_ changing the
69 * size.
70 *
71 * NOTE: It is striclty _invalid_ to access memory after _size_, regardless
72 * of prior calls to set_capacity().
73 */
74 int lttng_dynamic_buffer_set_size(struct lttng_dynamic_buffer *buffer,
75 size_t new_size);
76
77 /*
78 * Set the buffer's capacity to accommodates the new_capacity, allocating memory
79 * as necessary. The buffer's content is preserved. Setting a buffer's capacity
80 * is meant as a _hint_ to the underlying buffer and is only optimization; no
81 * guarantee is offered that subsequent calls to append or set_size will succeed.
82 *
83 * If the current size > new_capacity, the operation will fail.
84 */
85 int lttng_dynamic_buffer_set_capacity(struct lttng_dynamic_buffer *buffer,
86 size_t new_capacity);
87
88 /* Release any memory used by the dynamic buffer. */
89 void lttng_dynamic_buffer_reset(struct lttng_dynamic_buffer *buffer);
90
91 /* Get the space left in the buffer before a new resize is needed. */
92 size_t lttng_dynamic_buffer_get_capacity_left(
93 struct lttng_dynamic_buffer *buffer);
94
95 #endif /* LTTNG_DYNAMIC_BUFFER_H */
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