1 files changed, 45 insertions, 0 deletions
diff --git a/src/lib/metrics/metrics_common.h b/src/lib/metrics/metrics_common.h
new file mode 100644
index 0000000000..c684a3ec42
--- /dev/null
+++ b/src/lib/metrics/metrics_common.h
@@ -0,0 +1,45 @@
+/* Copyright (c) 2020, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * @file metrics_common.h
+ * @brief Header for lib/metrics/metrics_common.c
+ **/
+
+#ifndef TOR_LIB_METRICS_METRICS_COMMON_H
+#define TOR_LIB_METRICS_METRICS_COMMON_H
+
+#include "lib/cc/torint.h"
+
+/** Helper macro that must be used to construct the right namespaced metrics
+ * name. A name is a string so stringify the result. */
+#define METRICS_STR(val) #val
+#define METRICS_NAME(name) METRICS_STR(tor_ ## name)
+
+/** Format output type. */
+typedef enum {
+  /** Prometheus data output format. */
+  METRICS_FORMAT_PROMETHEUS = 1,
+} metrics_format_t;
+
+/** Metric type. */
+typedef enum {
+  /* Increment only. */
+  METRICS_TYPE_COUNTER,
+  /* Can go up or down. */
+  METRICS_TYPE_GAUGE,
+} metrics_type_t;
+
+/** Metric counter object (METRICS_TYPE_COUNTER). */
+typedef struct metrics_counter_t {
+  uint64_t value;
+} metrics_counter_t;
+
+/** Metric gauge object (METRICS_TYPE_GAUGE). */
+typedef struct metrics_gauge_t {
+  int64_t value;
+} metrics_gauge_t;
+
+const char *metrics_type_to_str(const metrics_type_t type);
+
+#endif /* !defined(TOR_LIB_METRICS_METRICS_COMMON_H) */