FieldWriter.h

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#pragma once
 
#include <memory>
#include <string>
#include <utility>  // std::pair
#include <vector>
 
#include "../global/global.h"
#include "../grid/field_info.h"
#include "../grid/grid3D.h"
#include "../io/FnameTemplate.h"  // define FnameTemplate
#include "../io/LazyScratchBuf.h"
#include "../io/ParameterMap.h"      // define ParameterMap
#include "../io/WriterManager.h"     // declare WriterFn
#include "../utils/basic_structs.h"  // VectorXYZ
 
namespace io
{
 
inline std::optional<std::string> lookup_legacy_short_name_(std::string_view field_name, bool for_text_file = true)
{
  if (field_name == "density") {
    const char *name = for_text_file ? "rho" : "d";
    return {std::string(name)};
  } else if (field_name == "momentum_x") {
    return {std::string("mx")};
  } else if (field_name == "momentum_y") {
    return {std::string("my")};
  } else if (field_name == "momentum_z") {
    return {std::string("mz")};
  } else if (field_name == "Energy") {
    return {std::string("E")};
  } else if (field_name == "GasEnergy") {
    const char *name = for_text_file ? "ge" : "GE";
    return {std::string(name)};
  } else {
    return std::nullopt;
  }
}
 
enum struct FileFormat { TEXT, H5_NATIVE_PRECISION, H5_F32 };
 
enum struct WriteCond { ALWAYS, REQUIRE_COMPLETE_DATA };
 
struct DatasetSpecEntry {
  int field_id;
  std::string name;
  field::IOBuf io_buf;
  WriteCond condition;
 
  // the following constructor is defined in order to make this type work with
  // std::vector::emplace_back. Delete it, once we require C++20 or newer
#if __cpp_aggregate_paren_init < 201902L
  DatasetSpecEntry(int field_id, std::string name, field::IOBuf io_buf, WriteCond condition)
      : field_id{field_id}, name{std::move(name)}, io_buf{io_buf}, condition{condition}
  {
  }
#endif
};
 
struct DatasetSpec {
  std::vector<DatasetSpecEntry> cc_dataset_entries;
  hydro_utilities::VectorXYZ<bool> write_mag = {false, false, false};
};
 
class FieldWriter
{
  FileFormat file_format_;
  DatasetSpec dataset_spec_;
  std::shared_ptr<LazyScratchBuf> lazy_scratch_buf_;
 
  // this has been made private to force the usage of the factory method
  FieldWriter(FileFormat file_format, ParameterMap &pmap, const FieldInfo &field_info);
 
 public:
  FieldWriter() = delete;
 
  static std::pair<WriterFn, std::string> try_create(int ndim, ParameterMap &pmap, const FieldInfo &field_info,
                                                     bool write_h5_f32)
  {
    // construct a payload denoting an error
    auto prep_err = [](const std::string &msg) -> std::pair<WriterFn, std::string> {
      return std::pair<WriterFn, std::string>{WriterFn(), msg};
    };
 
#ifdef HDF5
    FileFormat file_format = (write_h5_f32) ? FileFormat::H5_F32 : FileFormat::H5_NATIVE_PRECISION;
#else
    if (write_h5_f32) return prep_err("h5_f32 outputs require compilation with hdf5");
    FileFormat file_format = FileFormat::TEXT;
#endif
 
    if (file_format == FileFormat::TEXT and ndim != 1) {
      return prep_err("can only write Fields to text files for 1D simulations");
    } else if (file_format == FileFormat::H5_F32 and ndim != 3) {
      return prep_err("can only write Fields to h5_f32 files for 3D simulations");
    }
    std::pair<WriterFn, std::string> out{WriterFn(FieldWriter(file_format, pmap, field_info)), ""};
    return out;
  }
 
  void operator()(Grid3D &G, Parameters P, int nfile, const FnameTemplate &fname_template) const;
};
 
}  // namespace io