CCfits Documentation

2.2

CCfits-2.2 requires cfitsio version 3.08 or later Return To CCfits Home Page

Introduction

CCfits is an object oriented interface to the cfitsio library. cfitsio is a widely used library for manipulating FITS (Flexible Image Transport System) formatted files. This following documentation assumes prior knowledge of the FITS format and some knowledge of the use of the cfitsio library, which is in wide use, well developed, and available on many platforms.

For information about FITS and cfitsio, refer to:

• Details about the FITS format and the current standard
• Home page for the cfitsio library

The CCfits library provides an interface that allows the user to manipulate FITS format data through the high-level building blocks of FITS files and Header-Data Units (HDUs). The implementation is designed to hide the details of performing FITS I/O from the user, who will write calls that manipulate FITS objects by passing filenames and lists of strings that represent HDUs, keywords, image data and data columns. Unlike cfitsio, which typically requires several calls to access data (e.g. open file, move to correct header, determine column containing table data, read data) CCfits is designed to make reading data atomic. For example, it exploits internally existing optimization techniques for FITS I/O, choosing the optimal reading strategy as available [see the cfitsio manual, Chapter 13] when data are read on initialization. Data written by CCfits will also be compliant with the FITS standard by specification of class constructors representing FITS dataset elements.

CCfits necessarily works in a fundamentally different way than cfitsio. The general pattern of usage for CCfits is: create a FITS object, which either opens a disk file or creates a new disk file, create references to existing or new HDU objects within it, and manipulated the data through the references. For files with Write access the library is designed to keep the FITS object on disk in sync with the memory copy. The additional memory copy increases the resources required by a calling program in return for some flexibility in accessing the data.

About this Manual

This document lays out the specification for the CCfits library.

The hyperlinks below document the installation procedure, and the demonstration program cookbook which gives examples of usage with comments.

• Installing the Package
• Getting Started
• What's Present, What's Missing, and Calling CFITSIO
• Implementation Notes

Release Notes For Version 2.2 Sep 2009

Enhancements to CCfits:

• Added an auto-generated pkg-config file to the stand-alone distribution.
• Added an option for case-insensitive searching in the ExtHDU and Table Column get-by-name functions.
• The public functions column() and numCols() have been added to the ExtHDU interface. They were previously available only in the derived Table class.
• New resetRead and getNullValue functions for Column class.
• Improved the documentation for the nullValue versions of the Column read/write member functions.

Bug Fixes:

• Converted non-standard calls to vector and valarray end iterators. These were causing runtime exceptions when built with Microsoft Visual C++ v9.0.
• The Column addNullValue function now works for cases where the null value argument is of a type that requires casting to match the type of data stored in the Column.
• Fix to the Column writeArrays function for the case where valarrays of varying length were sent to fixed-width columns. It was previously sending along a default null value even when the user did not request one.
• Fix for reading and writing complex data types to scalar columns. The first "firstRow" complex values were not being written or read.
• Renamed private FITS::extension() function to extensionMap(). This is to prevent user from having to explicitly declare a const FITS pointer in order to use the public const FITS::extension*() function.

Backwards Compatibility Issue:

• To prevent overloading ambiguity resulting from the new flag added to ExtHDU/Table get-by-name Column functions for case-insensitive searches, the protected column(string,Column*) function has been renamed to setColumn. As this is a protected function, the change should not affect standard usage of CCfits.

Release Notes For Version 2.1 Nov 2008

• Modified several FITS constructors and FITS::open function to allow proper handling of CFITSIO extended filename syntax.
• Extended filename syntax example added to cookbook.
• Fix made to FITS::read function for case of missing EXTVER keyword when searching for HDU with extver > 1.
• Removed inclusion of the internal-only CFITSIO fitsio2.h file from Column.cxx. LONGLONG limits definitions are now found in fitsio.h.

For a more complete listing, see the CHANGES file distributed with the software. For earlier versions, see Previous Release Notes.

Authors and Acknowledgements

CCfits was written as part of a re-engineering effort for the X-Ray data analysis program, XSPEC. It was designed using Rational Rose and originally implemented on a Solaris platform by Ben Dorman to whom blame should be attached. Sandhia Bansal worked on part of the implementation and, and Paul Kunz (pfkeb@slac.stanford.edu) wrote the configuration scheme and dispensed helpful advice: both are also thanked profusely for the port to Windows2000/VC++.net. Thanks to R. Mathar (MPIA) and Patrik Jonsson (Lick Obs.) for contributing many helpful suggestions and bug reports, and ports to HP-UX and AIX respectively.

CCfits is currently maintained by Craig Gordon and Bryan Irby (ccfits@heasarc.gsfc.nasa.gov). Suggestions and bug reports are welcome, as are offers to fill out parts of the implementation that are missing. We are also interested in knowing which parts of cfitsio that are not currently supported should be the highest priority for future extensions.