Binary table data classes

Detailed Description

Binary table data unit containers and tools.

ColumnInfo

ColumnInfo is the simple structure which stores the column metadata:

• The value type as a template parameter;
• The name;
• The unit;
• The field shape (column entries can be multidimensional).

Column, PtrColumn, VecColumn

A Column is an abstract class composed of a ColumnInfo and some contiguous data. Analogously to Raster, two specializations are provided, and others can be user-defined:

• PtrColumn is the lightest structure: it just knows a pointer to the first element of the column;
• VecColumn owns the data as a std::vector and is compatible with the move semantics.

To write a column, any Column implementation works: you can even provide your own, e.g. some EigenColumn. Columns are generally read as VecColumn instances. If you want to give or steal the data to or from a VecColumn, you can exploit move semantics, as shown in the Tutorial:

 
  /* Initialize and later fill a column */
 
  Fits::VecColumn<std::string> string_column({"STRING", "unit", 3}, 100);
  // String columns must be wide-enough to hold each character.
  for (long i = 0; i < string_column.row_count(); ++i) {
    string_column(i) = std::to_string(i);
  }
  // operator() takes two parameters: the row index, and repeat index (=0 by default)
 
  /* Create a column from a vector */
 
  std::vector<std::int32_t> int32_vec(100);
  // ... do what you have to do with the vector, and then move it to the column ...
  Fits::VecColumn<std::int32_t> int32_column({"INT32", "", 1}, std::move(int32_vec));
  // Analogously to rasters, columns can be managed with the lightweight PtrColumn classe.
 
  /* Generate a random column */
 
  auto float_column = Fits::Test::RandomVectorColumn<float>(8, 100);
 

Segment, ColumnKey, TypedKey

The following helpers are defined:

• Segment is just a pair of longs used to specify a chunk of a Column, e.g. for partial reading and writing of binary table HDUs;
• ColumnKey is a minimal structure which basically means long or std::string and is responsible for backward indexing resolution;
• TypedKey is a typed wrapper used to specify which column to read, as well as the desired return type; Maker function as() is provided to simplify usage (see below).

For example, to read several columns of different types, do:

columns.read_n(as<int>(1), as<float>(3), as<std::string>(8));

instead of:

columns.read_n<int, float, std::string>({1, 3, 8}); // Error-prone and illegal!

which would be error-prone when reading many columns.

Typedefs
template<typename T , long N = 1>
using	PtrColumn = Column< T, N, DataContainerHolder< T, T * > >
	Column which points to some external data (THolder = T*).
template<typename T , long N = 1>
using	VecColumn = Column< T, N, DataContainerHolder< T, std::vector< T > > >
	Column which owns a data vector (THolder = std::vector<T>).

Classes
class	Column< T, N, THolder >
	Binary table column data and metadata. More...
struct	ColumnInfo< T, N >
	Column informations, i.e. name, unit, field shape and value type. More...
struct	Segment
	Bounds of a closed index interval. More...

Macros
#define	ELEFITS_FOREACH_COLUMN_TYPE(MACRO)
	Loop over supported column types. More...