cpp-package/include/mxnet-cpp/io.h

/*!
*  Copyright (c) 2016 by Contributors
* \file operator.h
* \brief definition of io, such as DataIter
* \author Zhang Chen
*/
#ifndef CPP_PACKAGE_INCLUDE_MXNET_CPP_IO_H_
#define CPP_PACKAGE_INCLUDE_MXNET_CPP_IO_H_

#include <map>
#include <string>
#include <vector>
#include <sstream>
#include "mxnet-cpp/base.h"
#include "mxnet-cpp/ndarray.h"
#include "dmlc/logging.h"

namespace mxnet {
namespace cpp {
/*!
* \brief Default object for holding a mini-batch of data and related
* information.
*/
class DataBatch {
 public:
  NDArray data;
  NDArray label;
  int pad_num;
  std::vector<int> index;
};
class DataIter {
 public:
  virtual void BeforeFirst(void) = 0;
  virtual bool Next(void) = 0;
  virtual NDArray GetData(void) = 0;
  virtual NDArray GetLabel(void) = 0;
  virtual int GetPadNum(void) = 0;
  virtual std::vector<int> GetIndex(void) = 0;

  DataBatch GetDataBatch() {
    return DataBatch{GetData(), GetLabel(), GetPadNum(), GetIndex()};
  }
  void Reset() { BeforeFirst(); }
};

class MXDataIterMap {
 public:
  inline MXDataIterMap() {
    mx_uint num_data_iter_creators = 0;
    DataIterCreator *data_iter_creators = nullptr;
    int r = MXListDataIters(&num_data_iter_creators, &data_iter_creators);
    CHECK_EQ(r, 0);
    for (mx_uint i = 0; i < num_data_iter_creators; i++) {
      const char *name;
      const char *description;
      mx_uint num_args;
      const char **arg_names;
      const char **arg_type_infos;
      const char **arg_descriptions;
      r = MXDataIterGetIterInfo(data_iter_creators[i], &name, &description,
                                &num_args, &arg_names, &arg_type_infos,
                                &arg_descriptions);
      CHECK_EQ(r, 0);
      mxdataiter_creators_[name] = data_iter_creators[i];
    }
  }
  inline DataIterCreator GetMXDataIterCreator(const std::string &name) {
    return mxdataiter_creators_[name];
  }

 private:
  std::map<std::string, DataIterCreator> mxdataiter_creators_;
};

struct MXDataIterBlob {
 public:
  MXDataIterBlob() : handle_(nullptr) {}
  explicit MXDataIterBlob(DataIterHandle handle) : handle_(handle) {}
  ~MXDataIterBlob() { MXDataIterFree(handle_); }
  DataIterHandle handle_;

 private:
  MXDataIterBlob &operator=(const MXDataIterBlob &);
};

class MXDataIter : public DataIter {
 public:
  explicit MXDataIter(const std::string &mxdataiter_type);
  MXDataIter(const MXDataIter &other) {
    creator_ = other.creator_;
    params_ = other.params_;
    blob_ptr_ = other.blob_ptr_;
  }
  void BeforeFirst();
  bool Next();
  NDArray GetData();
  NDArray GetLabel();
  int GetPadNum();
  std::vector<int> GetIndex();
  MXDataIter CreateDataIter();
  /*!
   * \brief set config parameters
   * \param name name of the config parameter
   * \param value value of the config parameter
   * \return reference of self
   */
  template <typename T>
  MXDataIter &SetParam(const std::string &name, const T &value) {
    std::string value_str;
    std::stringstream ss;
    ss << value;
    ss >> value_str;

    params_[name] = value_str;
    return *this;
  }

 private:
  DataIterCreator creator_;
  std::map<std::string, std::string> params_;
  std::shared_ptr<MXDataIterBlob> blob_ptr_;
  static MXDataIterMap*& mxdataiter_map();
};
}  // namespace cpp
}  // namespace mxnet

#endif  // CPP_PACKAGE_INCLUDE_MXNET_CPP_IO_H_