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/buffer-view.hpp>
   9 #include <common/dynamic-buffer.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 size_t round_to_power_of_2(size_t val)
  17 {
  18         size_t rounded;
  19         const int order = utils_get_count_order_u64(val);
  20
  21         LTTNG_ASSERT(order >= 0);
  22         rounded = (1ULL << order);
  23         LTTNG_ASSERT(rounded >= val);
  24
  25         return rounded;
  26 }
  27
  28 void lttng_dynamic_buffer_init(struct lttng_dynamic_buffer *buffer)
  29 {
  30         LTTNG_ASSERT(buffer);
  31         memset(buffer, 0, sizeof(*buffer));
  32 }
  33
  34 int lttng_dynamic_buffer_append(struct lttng_dynamic_buffer *buffer, const void *buf, size_t len)
  35 {
  36         int ret = 0;
  37
  38         if (!buffer || (!buf && len)) {
  39                 ret = -1;
  40                 goto end;
  41         }
  42
  43         if (len == 0) {
  44                 /* Not an error, no-op. */
  45                 goto end;
  46         }
  47
  48         LTTNG_ASSERT(buffer->_capacity >= buffer->size);
  49         if (buffer->_capacity < (len + buffer->size)) {
  50                 ret = lttng_dynamic_buffer_set_capacity(
  51                         buffer, buffer->_capacity + (len - (buffer->_capacity - buffer->size)));
  52                 if (ret) {
  53                         goto end;
  54                 }
  55         }
  56
  57         memcpy(buffer->data + buffer->size, buf, len);
  58         buffer->size += len;
  59 end:
  60         return ret;
  61 }
  62
  63 int lttng_dynamic_buffer_append_buffer(struct lttng_dynamic_buffer *dst_buffer,
  64                                        const struct lttng_dynamic_buffer *src_buffer)
  65 {
  66         int ret;
  67
  68         if (!dst_buffer || !src_buffer) {
  69                 ret = -1;
  70                 goto end;
  71         }
  72
  73         ret = lttng_dynamic_buffer_append(dst_buffer, src_buffer->data, src_buffer->size);
  74 end:
  75         return ret;
  76 }
  77
  78 int lttng_dynamic_buffer_append_view(struct lttng_dynamic_buffer *buffer,
  79                                      const struct lttng_buffer_view *src)
  80 {
  81         int ret;
  82
  83         if (!buffer || !src) {
  84                 ret = -1;
  85                 goto end;
  86         }
  87
  88         ret = lttng_dynamic_buffer_append(buffer, src->data, src->size);
  89 end:
  90         return ret;
  91 }
  92
  93 int lttng_dynamic_buffer_set_size(struct lttng_dynamic_buffer *buffer, size_t new_size)
  94 {
  95         int ret = 0;
  96
  97         if (!buffer) {
  98                 goto end;
  99         }
 100
 101         if (new_size == buffer->size) {
 102                 goto end;
 103         }
 104
 105         if (new_size > buffer->_capacity) {
 106                 ret = lttng_dynamic_buffer_set_capacity(buffer, new_size);
 107                 if (ret) {
 108                         goto end;
 109                 }
 110
 111                 memset(buffer->data + buffer->size, 0, new_size - buffer->size);
 112         } else if (new_size > buffer->size) {
 113                 memset(buffer->data + buffer->size, 0, new_size - buffer->size);
 114         } else {
 115                 /*
 116                  * Shrinking size. There is no need to zero-out the newly
 117                  * released memory as it will either be:
 118                  *   - overwritten by lttng_dynamic_buffer_append,
 119                  *   - expanded later, which will zero-out the memory
 120                  *
 121                  * Users of external APIs are encouraged to set the buffer's
 122                  * size _before_ making such calls.
 123                  */
 124         }
 125
 126         buffer->size = new_size;
 127 end:
 128         return ret;
 129 }
 130
 131 int lttng_dynamic_buffer_set_capacity(struct lttng_dynamic_buffer *buffer, size_t demanded_capacity)
 132 {
 133         int ret = 0;
 134         void *new_buf;
 135         size_t new_capacity = demanded_capacity ? round_to_power_of_2(demanded_capacity) : 0;
 136
 137         if (!buffer || demanded_capacity < buffer->size) {
 138                 /*
 139                  * Shrinking a buffer's size by changing its capacity is
 140                  * unsupported.
 141                  */
 142                 ret = -1;
 143                 goto end;
 144         }
 145
 146         if (new_capacity == buffer->_capacity) {
 147                 goto end;
 148         }
 149
 150         /* Memory is initialized by the size increases. */
 151         new_buf = realloc(buffer->data, new_capacity);
 152         if (!new_buf) {
 153                 ret = -1;
 154                 goto end;
 155         }
 156
 157         buffer->data = (char *) new_buf;
 158         buffer->_capacity = new_capacity;
 159 end:
 160         return ret;
 161 }
 162
 163 /* Release any memory used by the dynamic buffer. */
 164 void lttng_dynamic_buffer_reset(struct lttng_dynamic_buffer *buffer)
 165 {
 166         if (!buffer) {
 167                 return;
 168         }
 169
 170         buffer->size = 0;
 171         buffer->_capacity = 0;
 172         free(buffer->data);
 173         buffer->data = nullptr;
 174 }
 175
 176 size_t lttng_dynamic_buffer_get_capacity_left(struct lttng_dynamic_buffer *buffer)
 177 {
 178         if (!buffer) {
 179                 return 0;
 180         }
 181
 182         return buffer->_capacity - buffer->size;
 183 }