src/common/dynamic-buffer.cpp

   1 /*
   2  * Copyright (C) 2017 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   3  *
   4  * SPDX-License-Identifier: LGPL-2.1-only
   5  *
   6  */
   7
   8 #include <common/dynamic-buffer.hpp>
   9 #include <common/buffer-view.hpp>
  10 #include <common/utils.hpp>
  11
  12 /*
  13  * Round to (upper) power of two, val is returned if it already is a power of
  14  * two.
  15  */
  16 static
  17 size_t round_to_power_of_2(size_t val)
  18 {
  19         size_t rounded;
  20         const int order = utils_get_count_order_u64(val);
  21
  22         LTTNG_ASSERT(order >= 0);
  23         rounded = (1ULL << order);
  24         LTTNG_ASSERT(rounded >= val);
  25
  26         return rounded;
  27 }
  28
  29 void lttng_dynamic_buffer_init(struct lttng_dynamic_buffer *buffer)
  30 {
  31         LTTNG_ASSERT(buffer);
  32         memset(buffer, 0, sizeof(*buffer));
  33 }
  34
  35 int lttng_dynamic_buffer_append(struct lttng_dynamic_buffer *buffer,
  36                 const void *buf, size_t len)
  37 {
  38         int ret = 0;
  39
  40         if (!buffer || (!buf && len)) {
  41                 ret = -1;
  42                 goto end;
  43         }
  44
  45         if (len == 0) {
  46                 /* Not an error, no-op. */
  47                 goto end;
  48         }
  49
  50         LTTNG_ASSERT(buffer->_capacity >= buffer->size);
  51         if (buffer->_capacity < (len + buffer->size)) {
  52                 ret = lttng_dynamic_buffer_set_capacity(buffer,
  53                                 buffer->_capacity +
  54                                 (len - (buffer->_capacity - buffer->size)));
  55                 if (ret) {
  56                         goto end;
  57                 }
  58         }
  59
  60         memcpy(buffer->data + buffer->size, buf, len);
  61         buffer->size += len;
  62 end:
  63         return ret;
  64 }
  65
  66 int lttng_dynamic_buffer_append_buffer(struct lttng_dynamic_buffer *dst_buffer,
  67                 const struct lttng_dynamic_buffer *src_buffer)
  68 {
  69         int ret;
  70
  71         if (!dst_buffer || !src_buffer) {
  72                 ret = -1;
  73                 goto end;
  74         }
  75
  76         ret = lttng_dynamic_buffer_append(dst_buffer, src_buffer->data,
  77                         src_buffer->size);
  78 end:
  79         return ret;
  80 }
  81
  82 int lttng_dynamic_buffer_append_view(struct lttng_dynamic_buffer *buffer,
  83                 const struct lttng_buffer_view *src)
  84 {
  85         int ret;
  86
  87         if (!buffer || !src) {
  88                 ret = -1;
  89                 goto end;
  90         }
  91
  92         ret = lttng_dynamic_buffer_append(buffer, src->data,
  93                         src->size);
  94 end:
  95         return ret;
  96 }
  97
  98 int lttng_dynamic_buffer_set_size(struct lttng_dynamic_buffer *buffer,
  99                 size_t new_size)
 100 {
 101         int ret = 0;
 102
 103         if (!buffer) {
 104                 goto end;
 105         }
 106
 107         if (new_size == buffer->size) {
 108                 goto end;
 109         }
 110
 111         if (new_size > buffer->_capacity) {
 112                 ret = lttng_dynamic_buffer_set_capacity(buffer, new_size);
 113                 if (ret) {
 114                         goto end;
 115                 }
 116
 117                 memset(buffer->data + buffer->size, 0, new_size - buffer->size);
 118         } else if (new_size > buffer->size) {
 119                 memset(buffer->data + buffer->size, 0, new_size - buffer->size);
 120         } else {
 121                 /*
 122                  * Shrinking size. There is no need to zero-out the newly
 123                  * released memory as it will either be:
 124                  *   - overwritten by lttng_dynamic_buffer_append,
 125                  *   - expanded later, which will zero-out the memory
 126                  *
 127                  * Users of external APIs are encouraged to set the buffer's
 128                  * size _before_ making such calls.
 129                  */
 130         }
 131
 132         buffer->size = new_size;
 133 end:
 134         return ret;
 135 }
 136
 137 int lttng_dynamic_buffer_set_capacity(struct lttng_dynamic_buffer *buffer,
 138                 size_t demanded_capacity)
 139 {
 140         int ret = 0;
 141         void *new_buf;
 142         size_t new_capacity = demanded_capacity ?
 143                         round_to_power_of_2(demanded_capacity) : 0;
 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
 165         buffer->data = (char *) new_buf;
 166         buffer->_capacity = new_capacity;
 167 end:
 168         return ret;
 169 }
 170
 171 /* Release any memory used by the dynamic buffer. */
 172 void lttng_dynamic_buffer_reset(struct lttng_dynamic_buffer *buffer)
 173 {
 174         if (!buffer) {
 175                 return;
 176         }
 177
 178         buffer->size = 0;
 179         buffer->_capacity = 0;
 180         free(buffer->data);
 181         buffer->data = NULL;
 182 }
 183
 184 size_t lttng_dynamic_buffer_get_capacity_left(
 185                 struct lttng_dynamic_buffer *buffer)
 186 {
 187         if (!buffer) {
 188                 return 0;
 189         }
 190
 191         return buffer->_capacity - buffer->size;
 192 }