src/common/dynamic-buffer.c

   1 /*
   2  * Copyright (C) 2017 - Jérémie Galarneau <jeremie.galarneau@efficios.com>
   3  *
   4  * This library 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 library 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 library; 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         if ((buffer->capacity - buffer->size) < len) {
  59                 ret = lttng_dynamic_buffer_set_capacity(buffer,
  60                                 buffer->capacity +
  61                                 (len - (buffer->capacity - buffer->size)));
  62                 if (ret) {
  63                         goto end;
  64                 }
  65         }
  66
  67         memcpy(buffer->data + buffer->size, buf, len);
  68         buffer->size += len;
  69 end:
  70         return ret;
  71 }
  72
  73 int lttng_dynamic_buffer_set_size(struct lttng_dynamic_buffer *buffer,
  74                 size_t new_size)
  75 {
  76         int ret = 0;
  77
  78         if (!buffer) {
  79                 goto end;
  80         }
  81
  82         if (new_size == buffer->size) {
  83                 goto end;
  84         }
  85
  86         if (new_size > buffer->capacity) {
  87                 ret = lttng_dynamic_buffer_set_capacity(buffer, new_size);
  88                 if (ret) {
  89                         goto end;
  90                 }
  91         } else if (new_size > buffer->size) {
  92                 memset(buffer->data + buffer->size, 0, new_size - buffer->size);
  93                 buffer->size = new_size;
  94         } else {
  95                 /*
  96                  * Shrinking size. There is no need to zero-out the newly
  97                  * released memory as it will either be:
  98                  *   - overwritten by lttng_dynamic_buffer_append,
  99                  *   - expanded later, which will zero-out the memory
 100                  *
 101                  * Users of external APIs are encouraged to set the buffer's
 102                  * size _before_ making such calls.
 103                  */
 104         }
 105         buffer->size = new_size;
 106 end:
 107         return ret;
 108 }
 109
 110 int lttng_dynamic_buffer_set_capacity(struct lttng_dynamic_buffer *buffer,
 111                 size_t new_capacity)
 112 {
 113         int ret = 0;
 114         size_t rounded_capacity = round_to_power_of_2(new_capacity);
 115
 116         if (!buffer || new_capacity < buffer->size) {
 117                 ret = -1;
 118                 goto end;
 119         }
 120
 121         if (rounded_capacity == buffer->capacity) {
 122                 goto end;
 123         }
 124
 125         if (!buffer->data) {
 126                 buffer->data = zmalloc(rounded_capacity);
 127                 if (!buffer->data) {
 128                         ret = -1;
 129                         goto end;
 130                 }
 131         } else {
 132                 void *new_buf;
 133
 134                 new_buf = realloc(buffer->data, rounded_capacity);
 135                 if (new_buf) {
 136                         if (rounded_capacity > buffer->capacity) {
 137                                 memset(new_buf + buffer->capacity, 0,
 138                                                 rounded_capacity - buffer->capacity);
 139                         }
 140                 } else {
 141                         /* Realloc failed, try to acquire a new block. */
 142                         new_buf = zmalloc(rounded_capacity);
 143                         if (!new_buf) {
 144                                 ret = -1;
 145                                 goto end;
 146                         }
 147                         memcpy(new_buf, buffer->data, buffer->size);
 148                         free(buffer->data);
 149                 }
 150                 buffer->data = new_buf;
 151         }
 152         buffer->capacity = rounded_capacity;
 153 end:
 154         return ret;
 155 }
 156
 157 /* Release any memory used by the dynamic buffer. */
 158 void lttng_dynamic_buffer_reset(struct lttng_dynamic_buffer *buffer)
 159 {
 160         if (!buffer) {
 161                 return;
 162         }
 163         buffer->size = 0;
 164         buffer->capacity = 0;
 165         free(buffer->data);
 166 }