OLD | NEW |
| (Empty) |
1 // Copyright 2014 The Chromium Authors. All rights reserved. | |
2 // Use of this source code is governed by a BSD-style license that can be | |
3 // found in the LICENSE file. | |
4 | |
5 // Functions to help with verifying various |Mojo...Options| structs from the | |
6 // (public, C) API. These are "extensible" structs, which all have |struct_size| | |
7 // as their first member. All fields (other than |struct_size|) are optional, | |
8 // but any |flags| specified must be known to the system (otherwise, an error of | |
9 // |MOJO_RESULT_UNIMPLEMENTED| should be returned). | |
10 | |
11 #ifndef MOJO_EDK_SYSTEM_OPTIONS_VALIDATION_H_ | |
12 #define MOJO_EDK_SYSTEM_OPTIONS_VALIDATION_H_ | |
13 | |
14 #include <stddef.h> | |
15 #include <stdint.h> | |
16 | |
17 #include <algorithm> | |
18 | |
19 #include "base/logging.h" | |
20 #include "base/macros.h" | |
21 #include "mojo/edk/system/memory.h" | |
22 #include "mojo/edk/system/system_impl_export.h" | |
23 #include "mojo/public/c/system/types.h" | |
24 | |
25 namespace mojo { | |
26 namespace system { | |
27 | |
28 template <class Options> | |
29 class UserOptionsReader { | |
30 public: | |
31 // Constructor from a |UserPointer<const Options>| (which it checks -- this | |
32 // constructor has side effects!). | |
33 // Note: We initialize |options_reader_| without checking, since we do a check | |
34 // in |GetSizeForReader()|. | |
35 explicit UserOptionsReader(UserPointer<const Options> options) | |
36 : options_reader_(UserPointer<const char>::Reader::NoCheck(), | |
37 options.template ReinterpretCast<const char>(), | |
38 GetSizeForReader(options)) { | |
39 static_assert(offsetof(Options, struct_size) == 0, | |
40 "struct_size not first member of Options"); | |
41 // TODO(vtl): Enable when MSVC supports this (C++11 extended sizeof): | |
42 // static_assert(sizeof(Options::struct_size) == sizeof(uint32_t), | |
43 // "Options::struct_size not a uint32_t"); | |
44 // (Or maybe assert that its type is uint32_t?) | |
45 } | |
46 | |
47 bool is_valid() const { return !!options_reader_.GetPointer(); } | |
48 | |
49 const Options& options() const { | |
50 DCHECK(is_valid()); | |
51 return *reinterpret_cast<const Options*>(options_reader_.GetPointer()); | |
52 } | |
53 | |
54 // Checks that the given (variable-size) |options| passed to the constructor | |
55 // (plausibly) has a member at the given offset with the given size. You | |
56 // probably want to use |OPTIONS_STRUCT_HAS_MEMBER()| instead. | |
57 bool HasMember(size_t offset, size_t size) const { | |
58 DCHECK(is_valid()); | |
59 // We assume that |offset| and |size| are reasonable, since they should come | |
60 // from |offsetof(Options, some_member)| and |sizeof(Options::some_member)|, | |
61 // respectively. | |
62 return options().struct_size >= offset + size; | |
63 } | |
64 | |
65 private: | |
66 static inline size_t GetSizeForReader(UserPointer<const Options> options) { | |
67 uint32_t struct_size = | |
68 options.template ReinterpretCast<const uint32_t>().Get(); | |
69 if (struct_size < sizeof(uint32_t)) | |
70 return 0; | |
71 | |
72 // Check the full requested size. | |
73 // Note: Use |MOJO_ALIGNOF()| here to match the exact macro used in the | |
74 // declaration of Options structs. | |
75 internal::CheckUserPointerWithSize<MOJO_ALIGNOF(Options)>(options.pointer_, | |
76 struct_size); | |
77 options.template ReinterpretCast<const char>().CheckArray(struct_size); | |
78 // But we'll never look at more than |sizeof(Options)| bytes. | |
79 return std::min(static_cast<size_t>(struct_size), sizeof(Options)); | |
80 } | |
81 | |
82 UserPointer<const char>::Reader options_reader_; | |
83 | |
84 DISALLOW_COPY_AND_ASSIGN(UserOptionsReader); | |
85 }; | |
86 | |
87 // Macro to invoke |UserOptionsReader<Options>::HasMember()| parametrized by | |
88 // member name instead of offset and size. | |
89 // | |
90 // (We can't just give |HasMember()| a member pointer template argument instead, | |
91 // since there's no good/strictly-correct way to get an offset from that.) | |
92 // | |
93 // TODO(vtl): With C++11, use |sizeof(Options::member)| instead of (the | |
94 // contortion below). We might also be able to pull out the type |Options| from | |
95 // |reader| (using |decltype|) instead of requiring a parameter. | |
96 #define OPTIONS_STRUCT_HAS_MEMBER(Options, member, reader) \ | |
97 reader.HasMember(offsetof(Options, member), sizeof(reader.options().member)) | |
98 | |
99 } // namespace system | |
100 } // namespace mojo | |
101 | |
102 #endif // MOJO_EDK_SYSTEM_OPTIONS_VALIDATION_H_ | |
OLD | NEW |