src/common/dynamic-buffer.c

   1 /*
   2  * Copyright (C) 2017 - Jérémie Galarneau <jeremie.galarneau@efficios.com>
   3  *
   4  * This program is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU Lesser General Public License, version 2.1 only,
   6  * as published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
  11  * for more details.
  12  *
  13  * You should have received a copy of the GNU Lesser General Public License
  14  * along with this program; if not, write to the Free Software Foundation,
  15  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  16  */
  17
  18 #include <common/dynamic-buffer.h>
  19 #include <common/macros.h>
  20 #include <common/utils.h>
  21 #include <assert.h>
  22
  23 static
  24 size_t round_to_power_of_2(size_t val)
  25 {
  26         int order;
  27         size_t rounded;
  28
  29         order = utils_get_count_order_u64(val);
  30         assert(order >= 0);
  31         rounded = (1ULL << order);
  32         assert(rounded >= val);
  33
  34         return rounded;
  35 }
  36
  37 void lttng_dynamic_buffer_init(struct lttng_dynamic_buffer *buffer)
  38 {
  39         assert(buffer);
  40         memset(buffer, 0, sizeof(*buffer));
  41 }
  42
  43 int lttng_dynamic_buffer_append(struct lttng_dynamic_buffer *buffer,
  44                 const void *buf, size_t len)
  45 {
  46         int ret = 0;
  47
  48         if (!buffer || (!buf && len)) {
  49                 ret = -1;
  50                 goto end;
  51         }
  52
  53         if (len == 0) {
  54                 /* Not an error, no-op. */
  55                 goto end;
  56         }
  57
  58         assert(buffer->capacity >= buffer->size);
  59         if (buffer->capacity < (len + buffer->size)) {
  60                 ret = lttng_dynamic_buffer_set_capacity(buffer,
  61                                 buffer->capacity +
  62                                 (len - (buffer->capacity - buffer->size)));
  63                 if (ret) {
  64                         goto end;
  65                 }
  66         }
  67
  68         memcpy(buffer->data + buffer->size, buf, len);
  69         buffer->size += len;
  70 end:
  71         return ret;
  72 }
  73
  74 int lttng_dynamic_buffer_append_buffer(struct lttng_dynamic_buffer *dst_buffer,
  75                 struct lttng_dynamic_buffer *src_buffer)
  76 {
  77         int ret;
  78
  79         if (!dst_buffer || !src_buffer) {
  80                 ret = -1;
  81                 goto end;
  82         }
  83
  84         ret = lttng_dynamic_buffer_append(dst_buffer, src_buffer->data,
  85                         src_buffer->size);
  86 end:
  87         return ret;
  88 }
  89
  90 int lttng_dynamic_buffer_set_size(struct lttng_dynamic_buffer *buffer,
  91                 size_t new_size)
  92 {
  93         int ret = 0;
  94
  95         if (!buffer) {
  96                 goto end;
  97         }
  98
  99         if (new_size == buffer->size) {
 100                 goto end;
 101         }
 102
 103         if (new_size > buffer->capacity) {
 104                 size_t original_size = buffer->size;
 105                 size_t original_capacity = buffer->capacity;
 106
 107                 ret = lttng_dynamic_buffer_set_capacity(buffer, new_size);
 108                 if (ret) {
 109                         goto end;
 110                 }
 111
 112                 /*
 113                  * Zero-initialize the space that was left in the buffer at the
 114                  * before we increased its capacity (original capacity - original size).
 115                  * The newly acquired capacity (new capacity - original capacity)
 116                  * is zeroed by lttng_dynamic_buffer_set_capacity().
 117                  */
 118                 memset(buffer->data + original_size, 0,
 119                                 original_capacity - original_size);
 120         } else if (new_size > buffer->size) {
 121                 memset(buffer->data + buffer->size, 0, new_size - buffer->size);
 122         } else {
 123                 /*
 124                  * Shrinking size. There is no need to zero-out the newly
 125                  * released memory as it will either be:
 126                  *   - overwritten by lttng_dynamic_buffer_append,
 127                  *   - expanded later, which will zero-out the memory
 128                  *
 129                  * Users of external APIs are encouraged to set the buffer's
 130                  * size _before_ making such calls.
 131                  */
 132         }
 133         buffer->size = new_size;
 134 end:
 135         return ret;
 136 }
 137
 138 int lttng_dynamic_buffer_set_capacity(struct lttng_dynamic_buffer *buffer,
 139                 size_t demanded_capacity)
 140 {
 141         int ret = 0;
 142         void *new_buf;
 143         size_t new_capacity = round_to_power_of_2(demanded_capacity);
 144
 145         if (!buffer || demanded_capacity < buffer->size) {
 146                 /*
 147                  * Shrinking a buffer's size by changing its capacity is
 148                  * unsupported.
 149                  */
 150                 ret = -1;
 151                 goto end;
 152         }
 153
 154         if (new_capacity == buffer->capacity) {
 155                 goto end;
 156         }
 157
 158         /* Memory is initialized by the size increases. */
 159         new_buf = realloc(buffer->data, new_capacity);
 160         if (!new_buf) {
 161                 ret = -1;
 162                 goto end;
 163         }
 164         buffer->data = new_buf;
 165         buffer->capacity = new_capacity;
 166 end:
 167         return ret;
 168 }
 169
 170 /* Release any memory used by the dynamic buffer. */
 171 void lttng_dynamic_buffer_reset(struct lttng_dynamic_buffer *buffer)
 172 {
 173         if (!buffer) {
 174                 return;
 175         }
 176         buffer->size = 0;
 177         buffer->capacity = 0;
 178         free(buffer->data);
 179 }