Add lttng_dynamic_buffer util

[lttng-tools.git] / src / common / dynamic-buffer.c

diff --git a/src/common/dynamic-buffer.c b/src/common/dynamic-buffer.c
new file mode 100644 (file)
index 0000000..ea26a51
--- /dev/null
+++ b/src/common/dynamic-buffer.c
@@ -0,0 +1,181 @@
+/*
+ * Copyright (C) 2017 - Jérémie Galarneau <jeremie.galarneau@efficios.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU Lesser General Public License, version 2.1 only,
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License
+ * for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <common/dynamic-buffer.h>
+#include <common/macros.h>
+#include <common/utils.h>
+#include <assert.h>
+
+static
+size_t round_to_power_of_2(size_t val)
+{
+       int order;
+       size_t rounded;
+
+       order = utils_get_count_order_u64(val);
+       assert(order >= 0);
+       rounded = (1ULL << order);
+       assert(rounded >= val);
+
+       return rounded;
+}
+
+void lttng_dynamic_buffer_init(struct lttng_dynamic_buffer *buffer)
+{
+       assert(buffer);
+       memset(buffer, 0, sizeof(*buffer));
+}
+
+int lttng_dynamic_buffer_append(struct lttng_dynamic_buffer *buffer,
+               const void *buf, size_t len)
+{
+       int ret = 0;
+
+       if (!buffer || (!buf && len)) {
+               ret = -1;
+               goto end;
+       }
+
+       if (len == 0) {
+               /* Not an error, no-op. */
+               goto end;
+       }
+
+       if ((buffer->capacity - buffer->size) < len) {
+               ret = lttng_dynamic_buffer_set_capacity(buffer,
+                               buffer->capacity +
+                               (len - (buffer->capacity - buffer->size)));
+               if (ret) {
+                       goto end;
+               }
+       }
+
+       memcpy(buffer->data + buffer->size, buf, len);
+       buffer->size += len;
+end:
+       return ret;
+}
+
+int lttng_dynamic_buffer_append_buffer(struct lttng_dynamic_buffer *dst_buffer,
+               struct lttng_dynamic_buffer *src_buffer)
+{
+       int ret;
+
+       if (!dst_buffer || !src_buffer) {
+               ret = -1;
+               goto end;
+       }
+
+       ret = lttng_dynamic_buffer_append(dst_buffer, src_buffer->data,
+                       src_buffer->size);
+end:
+       return ret;
+}
+
+int lttng_dynamic_buffer_set_size(struct lttng_dynamic_buffer *buffer,
+               size_t new_size)
+{
+       int ret = 0;
+
+       if (!buffer) {
+               goto end;
+       }
+
+       if (new_size == buffer->size) {
+               goto end;
+       }
+
+       if (new_size > buffer->capacity) {
+               ret = lttng_dynamic_buffer_set_capacity(buffer, new_size);
+               if (ret) {
+                       goto end;
+               }
+       } else if (new_size > buffer->size) {
+               memset(buffer->data + buffer->size, 0, new_size - buffer->size);
+       } else {
+               /*
+                * Shrinking size. There is no need to zero-out the newly
+                * released memory as it will either be:
+                *   - overwritten by lttng_dynamic_buffer_append,
+                *   - expanded later, which will zero-out the memory
+                *
+                * Users of external APIs are encouraged to set the buffer's
+                * size _before_ making such calls.
+                */
+       }
+       buffer->size = new_size;
+end:
+       return ret;
+}
+
+int lttng_dynamic_buffer_set_capacity(struct lttng_dynamic_buffer *buffer,
+               size_t new_capacity)
+{
+       int ret = 0;
+       size_t rounded_capacity = round_to_power_of_2(new_capacity);
+
+       if (!buffer || new_capacity < buffer->size) {
+               ret = -1;
+               goto end;
+       }
+
+       if (rounded_capacity == buffer->capacity) {
+               goto end;
+       }
+
+       if (!buffer->data) {
+               buffer->data = zmalloc(rounded_capacity);
+               if (!buffer->data) {
+                       ret = -1;
+                       goto end;
+               }
+       } else {
+               void *new_buf;
+
+               new_buf = realloc(buffer->data, rounded_capacity);
+               if (new_buf) {
+                       if (rounded_capacity > buffer->capacity) {
+                               memset(new_buf + buffer->capacity, 0,
+                                               rounded_capacity - buffer->capacity);
+                       }
+               } else {
+                       /* Realloc failed, try to acquire a new block. */
+                       new_buf = zmalloc(rounded_capacity);
+                       if (!new_buf) {
+                               ret = -1;
+                               goto end;
+                       }
+                       memcpy(new_buf, buffer->data, buffer->size);
+                       free(buffer->data);
+               }
+               buffer->data = new_buf;
+       }
+       buffer->capacity = rounded_capacity;
+end:
+       return ret;
+}
+
+/* Release any memory used by the dynamic buffer. */
+void lttng_dynamic_buffer_reset(struct lttng_dynamic_buffer *buffer)
+{
+       if (!buffer) {
+               return;
+       }
+       buffer->size = 0;
+       buffer->capacity = 0;
+       free(buffer->data);
+}