1 /*
2  * Copyright 2022 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #pragma once
18 
19 #include <string>
20 #include <string_view>
21 
22 #include <ftl/optional.h>
23 
24 namespace android::utils {
25 
26 // Dumps variables by appending their name and value to the output string. A variable is formatted
27 // as "name=value". If the name or value is empty, the format is "value" or "name=", respectively.
28 // A value of user-defined type T is stringified via `std::string to_string(const T&)`, which must
29 // be defined in the same namespace as T per the rules of ADL (argument-dependent lookup).
30 //
31 // TODO(b/249828573): Consolidate with <compositionengine/impl/DumpHelpers.h>
32 class Dumper {
33 public:
Dumper(std::string & out)34     explicit Dumper(std::string& out) : mOut(out) {}
35 
eol()36     void eol() { mOut += '\n'; }
37 
out()38     std::string& out() { return mOut; }
39 
40     void dump(std::string_view name, std::string_view value = {}) {
41         using namespace std::string_view_literals;
42 
43         for (int i = mIndent; i-- > 0;) mOut += "    "sv;
44         mOut += name;
45         if (!name.empty()) mOut += '=';
46         mOut += value;
47         eol();
48     }
49 
dump(std::string_view name,const std::string & value)50     void dump(std::string_view name, const std::string& value) {
51         dump(name, static_cast<const std::string_view&>(value));
52     }
53 
dump(std::string_view name,bool value)54     void dump(std::string_view name, bool value) {
55         using namespace std::string_view_literals;
56         dump(name, value ? "true"sv : "false"sv);
57     }
58 
59     template <typename T>
dump(std::string_view name,const std::optional<T> & opt)60     void dump(std::string_view name, const std::optional<T>& opt) {
61         if (opt) {
62             dump(name, *opt);
63         } else {
64             using namespace std::string_view_literals;
65             dump(name, "nullopt"sv);
66         }
67     }
68 
69     template <typename T>
dump(std::string_view name,const ftl::Optional<T> & opt)70     void dump(std::string_view name, const ftl::Optional<T>& opt) {
71         dump(name, static_cast<const std::optional<T>&>(opt));
72     }
73 
74     template <typename T, typename... Ts>
dump(std::string_view name,const T & value,const Ts &...rest)75     void dump(std::string_view name, const T& value, const Ts&... rest) {
76         std::string string;
77 
78         constexpr bool kIsTuple = sizeof...(Ts) > 0;
79         if constexpr (kIsTuple) {
80             string += '{';
81         }
82 
83         using std::to_string;
84         string += to_string(value);
85 
86         if constexpr (kIsTuple) {
87             string += ((", " + to_string(rest)) + ...);
88             string += '}';
89         }
90 
91         dump(name, string);
92     }
93 
94     struct Indent {
IndentIndent95         explicit Indent(Dumper& dumper) : dumper(dumper) { dumper.mIndent++; }
~IndentIndent96         ~Indent() { dumper.mIndent--; }
97 
98         Dumper& dumper;
99     };
100 
101     struct Section {
SectionSection102         Section(Dumper& dumper, std::string_view heading) : dumper(dumper) {
103             dumper.dump({}, heading);
104             indent.emplace(dumper);
105         }
106 
~SectionSection107         ~Section() {
108             indent.reset();
109             dumper.eol();
110         }
111 
112         Dumper& dumper;
113         std::optional<Indent> indent;
114     };
115 
116 private:
117     std::string& mOut;
118     int mIndent = 0;
119 };
120 
121 } // namespace android::utils
122