std::variant

Detailed Description

Specialized functions to read/write a std::variant from/to HDF5.

The following code writes a std::variant to an HDF5 file, reads the same variant and outputs it to stdout:

#include <h5/h5.hpp>
#include <iostream>
#include <variant>
#include <string>
 
int main() {
  // create file in read/write mode
  h5::file file("variant.h5", 'w');
 
 // write variant
 h5::write(file, "myvariant", std::variant<double, std::string> { "Hello, World!" });
 
  // read into variant
  std::variant<double, std::string> var;
  h5::read(file, "myvariant", var);
 
  // output variant
  std::visit([](const auto& x) { std::cout << x << std::endl; }, var);
}

Output:

Hello, World!

Contents of variant.h5:

HDF5 "variant.h5" {
GROUP "/" {
   DATASET "myvariant" {
      DATATYPE  H5T_STRING {
         STRSIZE H5T_VARIABLE;
         STRPAD H5T_STR_NULLTERM;
         CSET H5T_CSET_UTF8;
         CTYPE H5T_C_S1;
      }
      DATASPACE  SCALAR
      DATA {
      (0): "Hello, World!"
      }
   }
}
}

Classes
struct	h5::hdf5_format_impl< std::variant< T... > >
	Specialization of h5::hdf5_format_impl for std::variant. More...

Functions
template<typename... Ts>
void	h5::h5_read (group g, std::string const &name, std::variant< Ts... > &v)
	Read a std::variant from an HDF5 dataset.
template<typename... Ts>
void	h5::h5_write (group g, std::string const &name, std::variant< Ts... > const &v)
	Write a std::variant to an HDF5 dataset/subgroup.

Function Documentation

h5_read()

template<typename... Ts>

void h5::h5_read	(	group	g,
		std::string const &	name,
		std::variant< Ts... > &	v )

#include <h5/stl/variant.hpp>

Read a std::variant from an HDF5 dataset.

Warning

This function only works, if name points to a dataset and not a group. Depending on the HDF5 datatype of the dataset, it calls the specialized h5_read.

Template Parameters

Ts	Variant types.

Parameters

g	h5::group containing the dataset.
name	Name of the dataset from which the std::variant is read.
v	std::variant to read into.

Definition at line 92 of file variant.hpp.

h5_write()

template<typename... Ts>

void h5::h5_write	(	group	g,
		std::string const &	name,
		std::variant< Ts... > const &	v )

#include <h5/stl/variant.hpp>

Write a std::variant to an HDF5 dataset/subgroup.

Calls the specialized h5_write for the type currently stored in the std::variant.

Template Parameters

Ts	Variant types.

Parameters

g	h5::group in which the dataset/subgroup is created.
name	Name of the dataset/subgroup to which the std::variant is written.
v	std::variant to be written.

Definition at line 58 of file variant.hpp.