1 /*
2 * Copyright (C) 2018 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 // Utility functions for working with FlatBuffers.
18
19 #ifndef LIBTEXTCLASSIFIER_UTILS_FLATBUFFERS_FLATBUFFERS_H_
20 #define LIBTEXTCLASSIFIER_UTILS_FLATBUFFERS_FLATBUFFERS_H_
21
22 #include <string>
23
24 #include "annotator/model_generated.h"
25 #include "flatbuffers/flatbuffers.h"
26
27 namespace libtextclassifier3 {
28
29 // Loads and interprets the buffer as 'FlatbufferMessage' and verifies its
30 // integrity.
31 template <typename FlatbufferMessage>
LoadAndVerifyFlatbuffer(const void * buffer,int size)32 const FlatbufferMessage* LoadAndVerifyFlatbuffer(const void* buffer, int size) {
33 const FlatbufferMessage* message =
34 flatbuffers::GetRoot<FlatbufferMessage>(buffer);
35 if (message == nullptr) {
36 return nullptr;
37 }
38 flatbuffers::Verifier verifier(reinterpret_cast<const uint8_t*>(buffer),
39 size);
40 if (message->Verify(verifier)) {
41 return message;
42 } else {
43 return nullptr;
44 }
45 }
46
47 // Same as above but takes string.
48 template <typename FlatbufferMessage>
LoadAndVerifyFlatbuffer(const std::string & buffer)49 const FlatbufferMessage* LoadAndVerifyFlatbuffer(const std::string& buffer) {
50 return LoadAndVerifyFlatbuffer<FlatbufferMessage>(buffer.c_str(),
51 buffer.size());
52 }
53
54 // Loads and interprets the buffer as 'FlatbufferMessage', verifies its
55 // integrity and returns its mutable version.
56 template <typename FlatbufferMessage>
57 std::unique_ptr<typename FlatbufferMessage::NativeTableType>
LoadAndVerifyMutableFlatbuffer(const void * buffer,int size)58 LoadAndVerifyMutableFlatbuffer(const void* buffer, int size) {
59 const FlatbufferMessage* message =
60 LoadAndVerifyFlatbuffer<FlatbufferMessage>(buffer, size);
61 if (message == nullptr) {
62 return nullptr;
63 }
64 return std::unique_ptr<typename FlatbufferMessage::NativeTableType>(
65 message->UnPack());
66 }
67
68 // Same as above but takes string.
69 template <typename FlatbufferMessage>
70 std::unique_ptr<typename FlatbufferMessage::NativeTableType>
LoadAndVerifyMutableFlatbuffer(const std::string & buffer)71 LoadAndVerifyMutableFlatbuffer(const std::string& buffer) {
72 return LoadAndVerifyMutableFlatbuffer<FlatbufferMessage>(buffer.c_str(),
73 buffer.size());
74 }
75
76 template <typename FlatbufferMessage>
FlatbufferFileIdentifier()77 const char* FlatbufferFileIdentifier() {
78 return nullptr;
79 }
80
81 template <>
82 inline const char* FlatbufferFileIdentifier<Model>() {
83 return ModelIdentifier();
84 }
85
86 // Packs the mutable flatbuffer message to string.
87 template <typename FlatbufferMessage>
PackFlatbuffer(const typename FlatbufferMessage::NativeTableType * mutable_message)88 std::string PackFlatbuffer(
89 const typename FlatbufferMessage::NativeTableType* mutable_message) {
90 flatbuffers::FlatBufferBuilder builder;
91 builder.Finish(FlatbufferMessage::Pack(builder, mutable_message),
92 FlatbufferFileIdentifier<FlatbufferMessage>());
93 return std::string(reinterpret_cast<const char*>(builder.GetBufferPointer()),
94 builder.GetSize());
95 }
96
97 // A convenience flatbuffer object with its underlying buffer.
98 template <typename T, typename B = flatbuffers::DetachedBuffer>
99 class OwnedFlatbuffer {
100 public:
OwnedFlatbuffer(B && buffer)101 explicit OwnedFlatbuffer(B&& buffer) : buffer_(std::move(buffer)) {}
102
103 // Cast as flatbuffer type.
get()104 const T* get() const { return flatbuffers::GetRoot<T>(buffer_.data()); }
105
buffer()106 const B& buffer() const { return buffer_; }
107
108 const T* operator->() const {
109 return flatbuffers::GetRoot<T>(buffer_.data());
110 }
111
112 private:
113 B buffer_;
114 };
115
116 } // namespace libtextclassifier3
117
118 #endif // LIBTEXTCLASSIFIER_UTILS_FLATBUFFERS_FLATBUFFERS_H_
119