Interface WideFits

All Known Implementing Classes:
AbstractWideFits

public interface WideFits
Defines a convention for storing extended column data in a FITS BINTABLE extension. The general idea assumes storing the BINTABLE data as if there were no 999 column limit, with a container column containing the byte data for all the extended columns and some non-standard way to record column metadata for the columns beyond the container. For practical purposes it only makes sense to use a container column index of 999, the maximum allowed standard column index allowed by FITS BINTABLE. But the interface provides the option to use a smaller value, perhaps for testing purposes.

There are various options for filling in the details, in particular how the metadata for the extended columns is stored in the FITS headers. These are defined by the implementation(s) in the AbstractWideFits class.

This convention is based on an idea suggested by William Pence on the FITSBITS list in June 2012, and by Francois-Xavier Pineau (CDS) in 2016. It was discussed at some length on the FITSBITS mailing list in July 2017 in the thread BINTABLE convention for >999 columns

Since:
27 Jul 2017
Author:
Mark Taylor
  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final WideFits
    Default WideFits instance; currently TFORMaaa using column 999.
    static final int
    Maximum number of standard columns, imposed by FITS standard (999).
  • Method Summary

    Modifier and Type
    Method
    Description
    createExtendedHeader(int icolContainer, int jcol)
    Creates a BintableColumnHeader instance suitable for use with the extended column convention defined by this class.
    getContainerColumnCards(long nbyteExt, long nslice)
    Returns an array of per-HDU header cards that describe the single container column (with index icolContainer) used to implement this convention in a BINTABLE HDU.
    int
    Returns the index of the column used (if any) by this specification for extended column data.
    int
    Maximum extended number of columns that can be represented by this convention.
    int
    Returns the total number of columns, including extended ones, described by a FITS header according to this convention.
    getExtensionCards(int ncolExt)
    Returns an array of per-HDU header cards that announce the operation of this convention in a BINTABLE HDU.
  • Field Details

    • MAX_NCOLSTD

      static final int MAX_NCOLSTD
      Maximum number of standard columns, imposed by FITS standard (999).
      See Also:
    • DEFAULT

      static final WideFits DEFAULT
      Default WideFits instance; currently TFORMaaa using column 999.
  • Method Details

    • getContainerColumnIndex

      int getContainerColumnIndex()
      Returns the index of the column used (if any) by this specification for extended column data. The result is the FITS column index, so the first column in the table is 1. This value is equal to the number of standard columns if extended columns are included.

      Under normal circumstances, this returns 999 (MAX_NCOLSTD).

      Returns:
      1-based index of container column
    • getExtColumnMax

      int getExtColumnMax()
      Maximum extended number of columns that can be represented by this convention. This value includes the standard columns.
      Returns:
      maximum extended column count
    • getExtensionCards

      CardImage[] getExtensionCards(int ncolExt)
      Returns an array of per-HDU header cards that announce the operation of this convention in a BINTABLE HDU.
      Parameters:
      ncolExt - total column count including extended
      Returns:
      cards to append to BINTABLE header
    • getContainerColumnCards

      CardImage[] getContainerColumnCards(long nbyteExt, long nslice)
      Returns an array of per-HDU header cards that describe the single container column (with index icolContainer) used to implement this convention in a BINTABLE HDU.
      Parameters:
      nbyteExt - number of bytes per row in container column
      nslice - if >0 this will result in a TDIMnnn header that gives a 2-element shape, with the supplied value being the second element; if you don't want TDIMnnn, use 0
      Returns:
      cards to append to BINTABLE header
    • getExtendedColumnCount

      int getExtendedColumnCount(FitsHeader hdr, int ncolStd)
      Returns the total number of columns, including extended ones, described by a FITS header according to this convention.
      Parameters:
      hdr - FITS header
      ncolStd - number of 'standard' BINTABLE columns, got from TFIELDS header
      Returns:
      extended number of columns, includes standard ones
    • createExtendedHeader

      BintableColumnHeader createExtendedHeader(int icolContainer, int jcol)
      Creates a BintableColumnHeader instance suitable for use with the extended column convention defined by this class.
      Parameters:
      icolContainer - 1-based index of container column used for storing extended column data
      jcol - 1-based column index for an extended column
      Returns:
      new column header instance