tools/aapt2/unflatten/ResChunkPullParser.h

/*
 * Copyright (C) 2015 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef AAPT_RES_CHUNK_PULL_PARSER_H
#define AAPT_RES_CHUNK_PULL_PARSER_H

#include "util/Util.h"

#include <androidfw/ResourceTypes.h>
#include <string>

namespace aapt {

/**
 * A pull parser, modeled after XmlPullParser, that reads
 * android::ResChunk_header structs from a block of data.
 *
 * An android::ResChunk_header specifies a type, headerSize,
 * and size. The pull parser will verify that the chunk's size
 * doesn't extend beyond the available data, and will iterate
 * over each chunk in the given block of data.
 *
 * Processing nested chunks is done by creating a new ResChunkPullParser
 * pointing to the data portion of a chunk.
 */
class ResChunkPullParser {
 public:
  enum class Event {
    StartDocument,
    EndDocument,
    BadDocument,

    Chunk,
  };

  /**
   * Returns false if the event is EndDocument or BadDocument.
   */
  static bool isGoodEvent(Event event);

  /**
   * Create a ResChunkPullParser to read android::ResChunk_headers
   * from the memory pointed to by data, of len bytes.
   */
  ResChunkPullParser(const void* data, size_t len);

  ResChunkPullParser(const ResChunkPullParser&) = delete;

  Event getEvent() const;
  const std::string& getLastError() const;
  const android::ResChunk_header* getChunk() const;

  /**
   * Move to the next android::ResChunk_header.
   */
  Event next();

 private:
  Event mEvent;
  const android::ResChunk_header* mData;
  size_t mLen;
  const android::ResChunk_header* mCurrentChunk;
  std::string mLastError;
};

template <typename T>
inline static const T* convertTo(const android::ResChunk_header* chunk) {
  if (util::deviceToHost16(chunk->headerSize) < sizeof(T)) {
    return nullptr;
  }
  return reinterpret_cast<const T*>(chunk);
}

inline static const uint8_t* getChunkData(
    const android::ResChunk_header* chunk) {
  return reinterpret_cast<const uint8_t*>(chunk) +
         util::deviceToHost16(chunk->headerSize);
}

inline static uint32_t getChunkDataLen(const android::ResChunk_header* chunk) {
  return util::deviceToHost32(chunk->size) -
         util::deviceToHost16(chunk->headerSize);
}

//
// Implementation
//

inline bool ResChunkPullParser::isGoodEvent(ResChunkPullParser::Event event) {
  return event != Event::EndDocument && event != Event::BadDocument;
}

inline ResChunkPullParser::ResChunkPullParser(const void* data, size_t len)
    : mEvent(Event::StartDocument),
      mData(reinterpret_cast<const android::ResChunk_header*>(data)),
      mLen(len),
      mCurrentChunk(nullptr) {}

inline ResChunkPullParser::Event ResChunkPullParser::getEvent() const {
  return mEvent;
}

inline const std::string& ResChunkPullParser::getLastError() const {
  return mLastError;
}

inline const android::ResChunk_header* ResChunkPullParser::getChunk() const {
  return mCurrentChunk;
}

}  // namespace aapt

#endif  // AAPT_RES_CHUNK_PULL_PARSER_H