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/utils.h>
  20 #include <assert.h>
  21
  22 /*
  23  * Round to (upper) power of two, val is returned if it already is a power of
  24  * two.
  25  */
  26 static
  27 size_t round_to_power_of_2(size_t val)
  28 {
  29         int order;
  30         size_t rounded;
  31
  32         order = utils_get_count_order_u64(val);
  33         assert(order >= 0);
  34         rounded = (1ULL << order);
  35         assert(rounded >= val);
  36
  37         return rounded;
  38 }
  39
  40 LTTNG_HIDDEN
  41 void lttng_dynamic_buffer_init(struct lttng_dynamic_buffer *buffer)
  42 {
  43         assert(buffer);
  44         memset(buffer, 0, sizeof(*buffer));
  45 }
  46
  47 LTTNG_HIDDEN
  48 int lttng_dynamic_buffer_append(struct lttng_dynamic_buffer *buffer,
  49                 const void *buf, size_t len)
  50 {
  51         int ret = 0;
  52
  53         if (!buffer || (!buf && len)) {
  54                 ret = -1;
  55                 goto end;
  56         }
  57
  58         if (len == 0) {
  59                 /* Not an error, no-op. */
  60                 goto end;
  61         }
  62
  63         assert(buffer->_capacity >= buffer->size);
  64         if (buffer->_capacity < (len + buffer->size)) {
  65                 ret = lttng_dynamic_buffer_set_capacity(buffer,
  66                                 buffer->_capacity +
  67                                 (len - (buffer->_capacity - buffer->size)));
  68                 if (ret) {
  69                         goto end;
  70                 }
  71         }
  72
  73         memcpy(buffer->data + buffer->size, buf, len);
  74         buffer->size += len;
  75 end:
  76         return ret;
  77 }
  78
  79 LTTNG_HIDDEN
  80 int lttng_dynamic_buffer_append_buffer(struct lttng_dynamic_buffer *dst_buffer,
  81                 struct lttng_dynamic_buffer *src_buffer)
  82 {
  83         int ret;
  84
  85         if (!dst_buffer || !src_buffer) {
  86                 ret = -1;
  87                 goto end;
  88         }
  89
  90         ret = lttng_dynamic_buffer_append(dst_buffer, src_buffer->data,
  91                         src_buffer->size);
  92 end:
  93         return ret;
  94 }
  95
  96 LTTNG_HIDDEN
  97 int lttng_dynamic_buffer_set_size(struct lttng_dynamic_buffer *buffer,
  98                 size_t new_size)
  99 {
 100         int ret = 0;
 101
 102         if (!buffer) {
 103                 goto end;
 104         }
 105
 106         if (new_size == buffer->size) {
 107                 goto end;
 108         }
 109
 110         if (new_size > buffer->_capacity) {
 111                 size_t original_size = buffer->size;
 112                 size_t original_capacity = buffer->_capacity;
 113
 114                 ret = lttng_dynamic_buffer_set_capacity(buffer, new_size);
 115                 if (ret) {
 116                         goto end;
 117                 }
 118
 119                 /*
 120                  * Zero-initialize the space that was left in the buffer at the
 121                  * before we increased its capacity (original capacity - original size).
 122                  * The newly acquired capacity (new capacity - original capacity)
 123                  * is zeroed by lttng_dynamic_buffer_set_capacity().
 124                  */
 125                 memset(buffer->data + original_size, 0,
 126                                 original_capacity - original_size);
 127         } else if (new_size > buffer->size) {
 128                 memset(buffer->data + buffer->size, 0, new_size - buffer->size);
 129         } else {
 130                 /*
 131                  * Shrinking size. There is no need to zero-out the newly
 132                  * released memory as it will either be:
 133                  *   - overwritten by lttng_dynamic_buffer_append,
 134                  *   - expanded later, which will zero-out the memory
 135                  *
 136                  * Users of external APIs are encouraged to set the buffer's
 137                  * size _before_ making such calls.
 138                  */
 139         }
 140         buffer->size = new_size;
 141 end:
 142         return ret;
 143 }
 144
 145 LTTNG_HIDDEN
 146 int lttng_dynamic_buffer_set_capacity(struct lttng_dynamic_buffer *buffer,
 147                 size_t demanded_capacity)
 148 {
 149         int ret = 0;
 150         void *new_buf;
 151         size_t new_capacity = round_to_power_of_2(demanded_capacity);
 152
 153         if (!buffer || demanded_capacity < buffer->size) {
 154                 /*
 155                  * Shrinking a buffer's size by changing its capacity is
 156                  * unsupported.
 157                  */
 158                 ret = -1;
 159                 goto end;
 160         }
 161
 162         if (new_capacity == buffer->_capacity) {
 163                 goto end;
 164         }
 165
 166         /* Memory is initialized by the size increases. */
 167         new_buf = realloc(buffer->data, new_capacity);
 168         if (!new_buf) {
 169                 ret = -1;
 170                 goto end;
 171         }
 172         buffer->data = new_buf;
 173         buffer->_capacity = new_capacity;
 174 end:
 175         return ret;
 176 }
 177
 178 /* Release any memory used by the dynamic buffer. */
 179 LTTNG_HIDDEN
 180 void lttng_dynamic_buffer_reset(struct lttng_dynamic_buffer *buffer)
 181 {
 182         if (!buffer) {
 183                 return;
 184         }
 185         buffer->size = 0;
 186         buffer->_capacity = 0;
 187         free(buffer->data);
 188 }