Implement clock override plugin support

[lttng-ust.git] / doc / examples / clock-override / lttng-ust-clock-override-example.c

diff --git a/doc/examples/clock-override/lttng-ust-clock-override-example.c b/doc/examples/clock-override/lttng-ust-clock-override-example.c
new file mode 100644 (file)
index 0000000..766e66c
--- /dev/null
+++ b/doc/examples/clock-override/lttng-ust-clock-override-example.c
@@ -0,0 +1,125 @@
+/*
+ * lttng-clock-override-example.c
+ *
+ * Copyright (c) 2014 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include <stdlib.h>
+#include <time.h>
+#include <string.h>
+#include <stdio.h>
+#include <lttng/ust-clock.h>
+
+static
+uint64_t plugin_read64(void)
+{
+       struct timespec ts;
+
+       clock_gettime(CLOCK_MONOTONIC, &ts);
+       /*
+        * This is a rather dumb example, but it illustrates the plugin
+        * mechanism: we take the monotonic clock, and transform it into
+        * a very coarse clock, which increment only at 1KHz frequency.
+        */
+       return ((uint64_t) ts.tv_sec * 1000ULL) + (ts.tv_nsec / 1000000ULL);
+}
+
+static
+uint64_t plugin_freq(void)
+{
+       return 1000;    /* 1KHz clock (very coarse!) */
+}
+
+static
+int plugin_uuid(char *uuid)
+{
+       const char myuuid[] = "123456789012345678901234567890123456";
+
+       /*
+        * Should read some unique identifier for this clock shared
+        * across all components of the system using this clock for
+        * tracing.
+        */
+       memcpy(uuid, myuuid, LTTNG_UST_UUID_STR_LEN);
+       return 0;
+}
+
+static
+const char *plugin_name(void)
+{
+       return "my_example_clock";
+}
+
+static
+const char *plugin_description(void)
+{
+       return "Coarse monotonic clock at 1KHz";
+}
+
+void lttng_ust_clock_plugin_init(void)
+{
+       int ret;
+
+       ret = lttng_ust_trace_clock_set_read64_cb(plugin_read64);
+       if (ret) {
+               fprintf(stderr, "Error setting clock override read64 callback: %s\n",
+                       strerror(-ret));
+               goto error;
+       }
+       ret = lttng_ust_trace_clock_set_freq_cb(plugin_freq);
+       if (ret) {
+               fprintf(stderr, "Error setting clock override freq callback: %s\n",
+                       strerror(-ret));
+               goto error;
+       }
+       ret = lttng_ust_trace_clock_set_uuid_cb(plugin_uuid);
+       if (ret) {
+               fprintf(stderr, "Error setting clock override uuid callback: %s\n",
+                       strerror(-ret));
+               goto error;
+       }
+
+       ret = lttng_ust_trace_clock_set_name_cb(plugin_name);
+       if (ret) {
+               fprintf(stderr, "Error setting clock override name callback: %s\n",
+                       strerror(-ret));
+               goto error;
+       }
+
+       ret = lttng_ust_trace_clock_set_description_cb(plugin_description);
+       if (ret) {
+               fprintf(stderr, "Error setting clock override description callback: %s\n",
+                       strerror(-ret));
+               goto error;
+       }
+
+       ret = lttng_ust_enable_trace_clock_override();
+       if (ret) {
+               fprintf(stderr, "Error enabling clock override: %s\n",
+                       strerror(-ret));
+               goto error;
+       }
+
+       return;
+
+error:
+       exit(EXIT_FAILURE);
+}