How to read from a binary file and load the data into a 3d vector in C++?

Ziggy1209 0
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I currently have some .bin files, each of which contains a matrix of size AxBxC. I would like to load it into a 3d vector vector<vector<vector<float>>> in C++, but encountered some problems.

I tried to flatten the matrix and load it into a buffer first, but the size of the buffer was weird so I got stuck there.

My code was:

vector<vector<vector<float>>> load_3d_bin(const std::string& path){
    vector<vector<vector<float>>> r;
    std::ifstream binary_feat(path.c_str(),std::ios::in | std::ios::binary);
    std::vector<float> flattened_feat((std::istream_iterator<char>(binary_feat)),std::istream_iterator<char>());
    for(auto i: flattened_feat){
        int value = i;
    }
    std::cout<<flattened_feat.size()<<endl;

// code to be written

   return r;
}

Ideally r would be a 3d vector, but I am stuck at the iterator part as the .size() outputs differently from total length = AxBxC, which was what I expected...

Any solution or feedback? Thanks in advance!

istream-iterator istream binaryfiles vector c++
1 Answers

Assuming your bin files just contain a flat concatenation of floats in binary format, in row-major order:

vector<vector<vector<float>>> load_3d_bin(const std::string& path){
  vector<vector<vector<float>>> ret(A, vector<vector<float>>(B));
  std::ifstream binary_feat(path.c_str(),std::ios::in | std::ios::binary);

  for (int i = 0; i < A; i++) {
    for (int j = 0; j < B; j++) {
      for (int k = 0; k < C; k++) {
        auto& row = ret[i][j].emplace_back(C);
        binary_feat.read(row.data(), row.size() * sizeof(float));
      }
    }
  }
  return ret;
}

Alternatively, you could use the fantastic armadillo library:

fcube c;
c.load(path.c_str(), raw_binary);
c.reshape(A, B, C);
Botje0
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