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#ifndef AAPT_RES_CHUNK_PULL_PARSER_H
18#define AAPT_RES_CHUNK_PULL_PARSER_H
19
20#include <androidfw/ResourceTypes.h>
21#include <string>
22
23namespace aapt {
24
25/**
26 * A pull parser, modeled after XmlPullParser, that reads
27 * android::ResChunk_header structs from a block of data.
28 *
29 * An android::ResChunk_header specifies a type, headerSize,
30 * and size. The pull parser will verify that the chunk's size
31 * doesn't extend beyond the available data, and will iterate
32 * over each chunk in the given block of data.
33 *
34 * Processing nested chunks is done by creating a new ResChunkPullParser
35 * pointing to the data portion of a chunk.
36 */
37class ResChunkPullParser {
38public:
39    enum class Event {
40        StartDocument,
41        EndDocument,
42        BadDocument,
43
44        Chunk,
45    };
46
47    /**
48     * Returns false if the event is EndDocument or BadDocument.
49     */
50    static bool isGoodEvent(Event event);
51
52    /**
53     * Create a ResChunkPullParser to read android::ResChunk_headers
54     * from the memory pointed to by data, of len bytes.
55     */
56    ResChunkPullParser(const void* data, size_t len);
57
58    ResChunkPullParser(const ResChunkPullParser&) = delete;
59
60    Event getEvent() const;
61    const std::string& getLastError() const;
62    const android::ResChunk_header* getChunk() const;
63
64    /**
65     * Move to the next android::ResChunk_header.
66     */
67    Event next();
68
69private:
70    Event mEvent;
71    const android::ResChunk_header* mData;
72    size_t mLen;
73    const android::ResChunk_header* mCurrentChunk;
74    std::string mLastError;
75};
76
77template <typename T>
78inline static const T* convertTo(const android::ResChunk_header* chunk) {
79    if (chunk->headerSize < sizeof(T)) {
80        return nullptr;
81    }
82    return reinterpret_cast<const T*>(chunk);
83}
84
85inline static const uint8_t* getChunkData(const android::ResChunk_header& chunk) {
86    return reinterpret_cast<const uint8_t*>(&chunk) + chunk.headerSize;
87}
88
89inline static size_t getChunkDataLen(const android::ResChunk_header& chunk) {
90    return chunk.size - chunk.headerSize;
91}
92
93//
94// Implementation
95//
96
97inline bool ResChunkPullParser::isGoodEvent(ResChunkPullParser::Event event) {
98    return event != Event::EndDocument && event != Event::BadDocument;
99}
100
101inline ResChunkPullParser::ResChunkPullParser(const void* data, size_t len) :
102        mEvent(Event::StartDocument),
103        mData(reinterpret_cast<const android::ResChunk_header*>(data)),
104        mLen(len),
105        mCurrentChunk(nullptr) {
106}
107
108inline ResChunkPullParser::Event ResChunkPullParser::getEvent() const {
109    return mEvent;
110}
111
112inline const std::string& ResChunkPullParser::getLastError() const {
113    return mLastError;
114}
115
116inline const android::ResChunk_header* ResChunkPullParser::getChunk() const {
117    return mCurrentChunk;
118}
119
120} // namespace aapt
121
122#endif // AAPT_RES_CHUNK_PULL_PARSER_H
123