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1 /*
2  * Copyright (C) 2015 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 <map>
20 #include <string>
21 #include <vector>
22 
23 #include "result.h"
24 
25 namespace android {
26 namespace init {
27 
28 // Every init builtin, init service option, and ueventd option has a minimum and maximum number of
29 // arguments.  These must be checked both at run time for safety and also at build time for
30 // correctness in host_init_verifier.  Instead of copying and pasting the boiler plate code that
31 // does this check into each function, it is abstracted in KeywordMap<>.  This class maps keywords
32 // to functions and checks that the number of arguments provided falls in the correct range or
33 // returns an error otherwise.
34 
35 // Value is the return value of Find(), which is typically either a single function or a struct with
36 // additional information.
37 template <typename Value>
38 class KeywordMap {
39   public:
40     struct MapValue {
41         size_t min_args;
42         size_t max_args;
43         Value value;
44     };
45 
KeywordMap()46     KeywordMap() {}
KeywordMap(std::initializer_list<std::pair<const std::string,MapValue>> init)47     KeywordMap(std::initializer_list<std::pair<const std::string, MapValue>> init) : map_(init) {}
48 
Find(const std::vector<std::string> & args)49     Result<Value> Find(const std::vector<std::string>& args) const {
50         if (args.empty()) return Error() << "Keyword needed, but not provided";
51 
52         auto& keyword = args[0];
53         auto num_args = args.size() - 1;
54 
55         auto result_it = map_.find(keyword);
56         if (result_it == map_.end()) {
57             return Errorf("Invalid keyword '{}'", keyword);
58         }
59 
60         auto result = result_it->second;
61 
62         auto min_args = result.min_args;
63         auto max_args = result.max_args;
64         if (min_args == max_args && num_args != min_args) {
65             return Errorf("{} requires {} argument{}", keyword, min_args,
66                           (min_args > 1 || min_args == 0) ? "s" : "");
67         }
68 
69         if (num_args < min_args || num_args > max_args) {
70             if (max_args == std::numeric_limits<decltype(max_args)>::max()) {
71                 return Errorf("{} requires at least {} argument{}", keyword, min_args,
72                               min_args > 1 ? "s" : "");
73             } else {
74                 return Errorf("{} requires between {} and {} arguments", keyword, min_args,
75                               max_args);
76             }
77         }
78 
79         return result.value;
80     }
81 
82   private:
83     std::map<std::string, MapValue> map_;
84 };
85 
86 }  // namespace init
87 }  // namespace android
88