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      1 /*
      2  * Copyright (C) 2016 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 CHUNK_H_
     18 #define CHUNK_H_
     19 
     20 #include "android-base/logging.h"
     21 #include "android-base/macros.h"
     22 #include "utils/ByteOrder.h"
     23 
     24 #ifdef _WIN32
     25 #ifdef ERROR
     26 #undef ERROR
     27 #endif
     28 #endif
     29 
     30 #include "androidfw/ResourceTypes.h"
     31 
     32 namespace android {
     33 
     34 // Helpful wrapper around a ResChunk_header that provides getter methods
     35 // that handle endianness conversions and provide access to the data portion
     36 // of the chunk.
     37 class Chunk {
     38  public:
     39   explicit Chunk(const ResChunk_header* chunk) : device_chunk_(chunk) {}
     40 
     41   // Returns the type of the chunk. Caller need not worry about endianness.
     42   inline int type() const { return dtohs(device_chunk_->type); }
     43 
     44   // Returns the size of the entire chunk. This can be useful for skipping
     45   // over the entire chunk. Caller need not worry about endianness.
     46   inline size_t size() const { return dtohl(device_chunk_->size); }
     47 
     48   // Returns the size of the header. Caller need not worry about endianness.
     49   inline size_t header_size() const { return dtohs(device_chunk_->headerSize); }
     50 
     51   template <typename T, size_t MinSize = sizeof(T)>
     52   inline const T* header() const {
     53     if (header_size() >= MinSize) {
     54       return reinterpret_cast<const T*>(device_chunk_);
     55     }
     56     return nullptr;
     57   }
     58 
     59   inline const void* data_ptr() const {
     60     return reinterpret_cast<const uint8_t*>(device_chunk_) + header_size();
     61   }
     62 
     63   inline size_t data_size() const { return size() - header_size(); }
     64 
     65  private:
     66   const ResChunk_header* device_chunk_;
     67 };
     68 
     69 // Provides a Java style iterator over an array of ResChunk_header's.
     70 // Validation is performed while iterating.
     71 // The caller should check if there was an error during chunk validation
     72 // by calling HadError() and GetLastError() to get the reason for failure.
     73 // Example:
     74 //
     75 //   ChunkIterator iter(data_ptr, data_len);
     76 //   while (iter.HasNext()) {
     77 //     const Chunk chunk = iter.Next();
     78 //     ...
     79 //   }
     80 //
     81 //   if (iter.HadError()) {
     82 //     LOG(ERROR) << iter.GetLastError();
     83 //   }
     84 //
     85 class ChunkIterator {
     86  public:
     87   ChunkIterator(const void* data, size_t len)
     88       : next_chunk_(reinterpret_cast<const ResChunk_header*>(data)),
     89         len_(len),
     90         last_error_(nullptr) {
     91     CHECK(next_chunk_ != nullptr) << "data can't be nullptr";
     92     VerifyNextChunk();
     93   }
     94 
     95   Chunk Next();
     96   inline bool HasNext() const { return !HadError() && len_ != 0; };
     97   // Returns whether there was an error and processing should stop
     98   inline bool HadError() const { return last_error_ != nullptr; }
     99   inline std::string GetLastError() const { return last_error_; }
    100   // Returns whether there was an error and processing should stop. For legacy purposes,
    101   // some errors are considered "non fatal". Fatal errors stop processing new chunks and
    102   // throw away any chunks already processed. Non fatal errors also stop processing new
    103   // chunks, but, will retain and use any valid chunks already processed.
    104   inline bool HadFatalError() const { return HadError() && last_error_was_fatal_; }
    105 
    106  private:
    107   DISALLOW_COPY_AND_ASSIGN(ChunkIterator);
    108 
    109   // Returns false if there was an error.
    110   bool VerifyNextChunk();
    111   // Returns false if there was an error. For legacy purposes.
    112   bool VerifyNextChunkNonFatal();
    113 
    114   const ResChunk_header* next_chunk_;
    115   size_t len_;
    116   const char* last_error_;
    117   bool last_error_was_fatal_ = true;
    118 };
    119 
    120 }  // namespace android
    121 
    122 #endif /* CHUNK_H_ */
    123