1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
|
/*
* Copyright (c) 2022 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#ifndef API_FIELD_TRIALS_H_
#define API_FIELD_TRIALS_H_
#include <memory>
#include <string>
#include <utility>
#include "absl/base/nullability.h"
#include "absl/strings/string_view.h"
#include "api/field_trials_registry.h"
#include "rtc_base/containers/flat_map.h"
namespace webrtc {
// The FieldTrials class is used to inject field trials into webrtc.
//
// Field trials allow webrtc clients (such as Chromium) to turn on feature code
// in binaries out in the field and gather information with that.
//
// They are designed to be easy to use with Chromium field trials and to speed
// up developers by reducing the need to wire up APIs to control whether a
// feature is on/off.
//
// The field trials are injected into objects that use them at creation time.
class FieldTrials : public FieldTrialsRegistry {
public:
// Creates field trials from a valid field trial string.
// Returns nullptr if the string is invalid.
// E.g., valid string:
// "WebRTC-ExperimentFoo/Enabled/WebRTC-ExperimentBar/Enabled100kbps/"
// Assigns to group "Enabled" on WebRTC-ExperimentFoo trial
// and to group "Enabled100kbps" on WebRTC-ExperimentBar.
//
// E.g., invalid string:
// "WebRTC-experiment1/Enabled" (note missing / separator at the end).
static absl_nullable std::unique_ptr<FieldTrials> Create(absl::string_view s);
// Creates field trials from a string.
// It is an error to call the constructor with an invalid field trial string.
explicit FieldTrials(absl::string_view s);
FieldTrials(const FieldTrials&) = default;
FieldTrials(FieldTrials&&) = default;
FieldTrials& operator=(const FieldTrials&) = default;
FieldTrials& operator=(FieldTrials&&) = default;
~FieldTrials() override = default;
template <typename Sink>
friend void AbslStringify(Sink& sink, const FieldTrials& self);
// Merges field trials from the `other` into this.
//
// If a key (trial) exists twice with conflicting values (groups), the value
// in `other` takes precedence.
void Merge(const FieldTrials& other);
// Sets value (`group`) for an indvidual `trial`.
// It is an error to call this function with an invalid `trial` or `group`.
// Setting empty `group` is valid and removes the `trial`.
void Set(absl::string_view trial, absl::string_view group);
// TODO: bugs.webrtc.org/42220378 - Deprecate and inline once no longer used
// within webrtc.
static std::unique_ptr<FieldTrials> CreateNoGlobal(absl::string_view s) {
return std::make_unique<FieldTrials>(s);
}
private:
explicit FieldTrials(flat_map<std::string, std::string> key_value_map)
: key_value_map_(std::move(key_value_map)) {}
std::string GetValue(absl::string_view key) const override;
flat_map<std::string, std::string> key_value_map_;
};
template <typename Sink>
void AbslStringify(Sink& sink, const FieldTrials& self) {
for (const auto& [trial, group] : self.key_value_map_) {
sink.Append(trial);
sink.Append("/");
sink.Append(group);
// Intentionally output a string that is not a valid field trial string.
// Stringification is intended only for human readable logs, and is not
// intended for reusing as `FieldTrials` construction parameter.
sink.Append("//");
}
}
} // namespace webrtc
#endif // API_FIELD_TRIALS_H_
|
