| 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_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 | LTTNG_HIDDEN |
| 33 | void lttng_dynamic_buffer_init(struct lttng_dynamic_buffer *buffer); |
| 34 | |
| 35 | /* |
| 36 | * Append the content of a raw memory buffer to the end of a dynamic buffer |
| 37 | * (after its current "size"). The dynamic buffer's size is increased by |
| 38 | * "len", and its capacity is adjusted automatically. |
| 39 | */ |
| 40 | LTTNG_HIDDEN |
| 41 | int lttng_dynamic_buffer_append(struct lttng_dynamic_buffer *buffer, |
| 42 | const void *buf, size_t len); |
| 43 | |
| 44 | /* |
| 45 | * Performs the same action as lttng_dynamic_buffer_append(), but using another |
| 46 | * dynamic buffer as the source buffer. The source buffer's size is used in lieu |
| 47 | * of "len". |
| 48 | */ |
| 49 | LTTNG_HIDDEN |
| 50 | int lttng_dynamic_buffer_append_buffer(struct lttng_dynamic_buffer *dst_buffer, |
| 51 | const struct lttng_dynamic_buffer *src_buffer); |
| 52 | |
| 53 | /* |
| 54 | * Performs the same action as lttng_dynamic_buffer_append(), but using a |
| 55 | * buffer view as the source buffer. The source buffer's size is used in lieu |
| 56 | * of "len". |
| 57 | */ |
| 58 | LTTNG_HIDDEN |
| 59 | int lttng_dynamic_buffer_append_view(struct lttng_dynamic_buffer *buffer, |
| 60 | const struct lttng_buffer_view *view); |
| 61 | |
| 62 | /* |
| 63 | * Set the buffer's size to new_size. The capacity of the buffer will |
| 64 | * be expanded (if necessary) to accommodates new_size. Areas acquired by |
| 65 | * a size increase will be zeroed. |
| 66 | * |
| 67 | * Be careful to expand the buffer's size _before_ calling out external |
| 68 | * APIs (e.g. read(3)) which may populate the buffer as setting the size |
| 69 | * after will zero-out the result of the operation. |
| 70 | * |
| 71 | * Shrinking a buffer does not zero the old content. If the buffer may contain |
| 72 | * sensititve information, it must be cleared manually _before_ changing the |
| 73 | * size. |
| 74 | * |
| 75 | * NOTE: It is striclty _invalid_ to access memory after _size_, regardless |
| 76 | * of prior calls to set_capacity(). |
| 77 | */ |
| 78 | LTTNG_HIDDEN |
| 79 | int lttng_dynamic_buffer_set_size(struct lttng_dynamic_buffer *buffer, |
| 80 | size_t new_size); |
| 81 | |
| 82 | /* |
| 83 | * Set the buffer's capacity to accommodates the new_capacity, allocating memory |
| 84 | * as necessary. The buffer's content is preserved. Setting a buffer's capacity |
| 85 | * is meant as a _hint_ to the underlying buffer and is only optimization; no |
| 86 | * guarantee is offered that subsequent calls to append or set_size will succeed. |
| 87 | * |
| 88 | * If the current size > new_capacity, the operation will fail. |
| 89 | */ |
| 90 | LTTNG_HIDDEN |
| 91 | int lttng_dynamic_buffer_set_capacity(struct lttng_dynamic_buffer *buffer, |
| 92 | size_t new_capacity); |
| 93 | |
| 94 | /* Release any memory used by the dynamic buffer. */ |
| 95 | LTTNG_HIDDEN |
| 96 | void lttng_dynamic_buffer_reset(struct lttng_dynamic_buffer *buffer); |
| 97 | |
| 98 | /* Get the space left in the buffer before a new resize is needed. */ |
| 99 | LTTNG_HIDDEN |
| 100 | size_t lttng_dynamic_buffer_get_capacity_left( |
| 101 | struct lttng_dynamic_buffer *buffer); |
| 102 | |
| 103 | #endif /* LTTNG_DYNAMIC_BUFFER_H */ |