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 "util/Util.h"
21
22#include <androidfw/ResourceTypes.h>
23#include <string>
24
25namespace aapt {
26
27/**
28 * A pull parser, modeled after XmlPullParser, that reads
29 * android::ResChunk_header structs from a block of data.
30 *
31 * An android::ResChunk_header specifies a type, headerSize,
32 * and size. The pull parser will verify that the chunk's size
33 * doesn't extend beyond the available data, and will iterate
34 * over each chunk in the given block of data.
35 *
36 * Processing nested chunks is done by creating a new ResChunkPullParser
37 * pointing to the data portion of a chunk.
38 */
39class ResChunkPullParser {
40public:
41    enum class Event {
42        StartDocument,
43        EndDocument,
44        BadDocument,
45
46        Chunk,
47    };
48
49    /**
50     * Returns false if the event is EndDocument or BadDocument.
51     */
52    static bool isGoodEvent(Event event);
53
54    /**
55     * Create a ResChunkPullParser to read android::ResChunk_headers
56     * from the memory pointed to by data, of len bytes.
57     */
58    ResChunkPullParser(const void* data, size_t len);
59
60    ResChunkPullParser(const ResChunkPullParser&) = delete;
61
62    Event getEvent() const;
63    const std::string& getLastError() const;
64    const android::ResChunk_header* getChunk() const;
65
66    /**
67     * Move to the next android::ResChunk_header.
68     */
69    Event next();
70
71private:
72    Event mEvent;
73    const android::ResChunk_header* mData;
74    size_t mLen;
75    const android::ResChunk_header* mCurrentChunk;
76    std::string mLastError;
77};
78
79template <typename T>
80inline static const T* convertTo(const android::ResChunk_header* chunk) {
81    if (util::deviceToHost16(chunk->headerSize) < sizeof(T)) {
82        return nullptr;
83    }
84    return reinterpret_cast<const T*>(chunk);
85}
86
87inline static const uint8_t* getChunkData(const android::ResChunk_header* chunk) {
88    return reinterpret_cast<const uint8_t*>(chunk) + util::deviceToHost16(chunk->headerSize);
89}
90
91inline static uint32_t getChunkDataLen(const android::ResChunk_header* chunk) {
92    return util::deviceToHost32(chunk->size) - util::deviceToHost16(chunk->headerSize);
93}
94
95//
96// Implementation
97//
98
99inline bool ResChunkPullParser::isGoodEvent(ResChunkPullParser::Event event) {
100    return event != Event::EndDocument && event != Event::BadDocument;
101}
102
103inline ResChunkPullParser::ResChunkPullParser(const void* data, size_t len) :
104        mEvent(Event::StartDocument),
105        mData(reinterpret_cast<const android::ResChunk_header*>(data)),
106        mLen(len),
107        mCurrentChunk(nullptr) {
108}
109
110inline ResChunkPullParser::Event ResChunkPullParser::getEvent() const {
111    return mEvent;
112}
113
114inline const std::string& ResChunkPullParser::getLastError() const {
115    return mLastError;
116}
117
118inline const android::ResChunk_header* ResChunkPullParser::getChunk() const {
119    return mCurrentChunk;
120}
121
122} // namespace aapt
123
124#endif // AAPT_RES_CHUNK_PULL_PARSER_H
125