decode_statsd: compat: Implement StatsD decoder

include/cmetrics/cmt_decode_statsd.h

@@ -0,0 +1,60 @@
+/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+
+/*  CMetrics
+ *  ========
+ *  Copyright 2021-2022 The CMetrics Authors
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+
+
+#ifndef CMT_DECODE_STATSD_H
+#define CMT_DECODE_STATSD_H
+
+#include <cmetrics/cmetrics.h>
+
+#define CMT_DECODE_STATSD_TYPE_COUNTER 1
+#define CMT_DECODE_STATSD_TYPE_GAUGE   2
+#define CMT_DECODE_STATSD_TYPE_TIMER   3
+#define CMT_DECODE_STATSD_TYPE_SET     4
+
+#define CMT_DECODE_STATSD_SUCCESS                  0
+#define CMT_DECODE_STATSD_ALLOCATION_ERROR         1
+#define CMT_DECODE_STATSD_UNEXPECTED_ERROR         2
+#define CMT_DECODE_STATSD_INVALID_ARGUMENT_ERROR   3
+#define CMT_DECODE_STATSD_UNEXPECTED_METRIC_TYPE   4
+#define CMT_DECODE_STATSD_DECODE_ERROR             5
+#define CMT_DECODE_STATSD_UNPACK_ERROR             6
+#define CMT_DECODE_STATSD_UNSUPPORTED_METRIC_TYPE  7
+#define CMT_DECODE_STATSD_INVALID_TAG_FORMAT_ERROR 8
+
+#define CMT_DECODE_STATSD_GAUGE_OBSERVER     1 << 0
+
+/*
+ * The "cmt_statsd_message" represents a single line in UDP packet.
+ * It's just a bunch of pointers to ephemeral buffer.
+ */
+struct cmt_statsd_message {
+    char *bucket;
+    int bucket_len;
+    char *value;
+    char *labels;
+    int value_len;
+    int type;
+    double sample_rate;
+};
+
+int cmt_decode_statsd_create(struct cmt **out_cmt, char *in_buf, size_t in_size, int flags);
+void cmt_decode_statsd_destroy(struct cmt *cmt);
+
+#endif

src/CMakeLists.txt

@@ -35,6 +35,7 @@ set(src
   cmt_encode_influx.c
   cmt_encode_msgpack.c
   cmt_decode_msgpack.c
+  cmt_decode_statsd.c
   cmt_mpack_utils.c
   external/remote.pb-c.c
   external/types.pb-c.c