uk.ac.starlink.fits

## 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

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static WideFits` | `DEFAULT` Default WideFits instance; currently TFORMaaa using column 999.
    `static int` | `MAX_NCOLSTD` Maximum number of standard columns, imposed by FITS standard (999).

  - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method and Description
    --- | ---
    `BintableColumnHeader` | `createExtendedHeader(int icolContainer, int jcol)` Creates a BintableColumnHeader instance suitable for use with the extended column convention defined by this class.
    `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.
    `int` | `getContainerColumnIndex()` Returns the index of the column used (if any) by this specification for extended column data.
    `int` | `getExtColumnMax()` Maximum extended number of columns that can be represented by this convention.
    `int` | `getExtendedColumnCount(FitsHeader hdr, int ncolStd)` Returns the total number of columns, including extended ones, described by a FITS header according to this convention.
    `CardImage[]` | `getExtensionCards(int ncolExt)` Returns an array of per-HDU header cards that announce the operation of this convention in a BINTABLE HDU.

- - ### Field Detail

    - #### MAX_NCOLSTD

          static final int MAX_NCOLSTD

      Maximum number of standard columns, imposed by FITS standard (999).
      See Also:
        Constant Field Values

    - #### DEFAULT

          static final WideFits DEFAULT

      Default WideFits instance; currently TFORMaaa using column 999.

  - ### Method Detail

    - #### 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