1 /* -*- Mode: C++; tab-width: 4; c-basic-offset: 4; indent-tabs-mode: nil -*- */
2 /*
3  *     Copyright 2017 Couchbase, Inc
4  *
5  *   Licensed under the Apache License, Version 2.0 (the "License");
6  *   you may not use this file except in compliance with the License.
7  *   You may obtain a copy of the License at
8  *
9  *       http://www.apache.org/licenses/LICENSE-2.0
10  *
11  *   Unless required by applicable law or agreed to in writing, software
12  *   distributed under the License is distributed on an "AS IS" BASIS,
13  *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14  *   See the License for the specific language governing permissions and
15  *   limitations under the License.
16  */
17 
18 #pragma once
19 
20 #include <gsl_p/span.h>
21 
22 namespace phosphor {
23 
24 /**
25  * Pure virtual base class for receiving stats from phosphor internals
26  *
27  * Methods on this class will be called with the key and value of each stat.
28  * Callback implementations MUST NOT re-enter the TraceLog or TraceBuffer
29  * upon which it used as locks may be held when the callback is invoked.
30  *
31  * Example usage:
32  *
33  *     class MyStatsCallback : public phosphor::StatsCallback {
34  *          // Implement callback methods
35  *     } callback;
36  *
37  *     phosphor::TraceLog::getInstance().getStats(callback);
38  *
39  *     // Stash data as required for application
40  *     auto data = callback.getData();
41  *
42  * Implementations should note that phosphor makes no guarantees about
43  * atomicity of the stats with respect to each other.
44  */
45 class StatsCallback {
46 public:
47     /**
48      * Utility template method for passing a string literal as the first
49      * argument instead of a string span
50      * @param s String to convert to a span
51      * @param value Value to forward
52      */
53     template <size_t N, typename T>
operator ()(const char (&s)[N], T&& value)54     void operator()(const char (&s)[N], T&& value) {
55         this->operator()(gsl_p::make_span(s), std::forward<T>(value));
56     }
57 
58     virtual void operator()(gsl_p::cstring_span key,
59                             gsl_p::cstring_span value) = 0;
60     virtual void operator()(gsl_p::cstring_span key, bool value) = 0;
61     virtual void operator()(gsl_p::cstring_span key, size_t value) = 0;
62     virtual void operator()(gsl_p::cstring_span key, ssize_t value) = 0;
63     virtual void operator()(gsl_p::cstring_span key, double value) = 0;
64 };
65 
66 }
67