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15 What’s Present, What’s Missing, and Calling CFITSIO 29
}
return 0;
15 What’s Present, What’s Missing, and Calling CFITSIO
Most of the functionality of cfitsio described in Chapter 5 of the cfitsio manual is
present, although CCfits is designed to provide atomic read/write operations rather
than primitive file manipulation. For example, opening and creating FITS files are private
operations which are called by reading and writing constructors. Similarly, errors
are treated by C++ exception handling rather than returning status codes, and moving
between HDUs within a file is a primitive rather than an atomic operation [in CCfits,
operations typically call an internal HDU::makeThisCurrent() call on a specific table
or image extension, and then perform the requested read/write operation].
Read/Write operations for keys (in the HDU class) are provided; these implement calls
to fits_read_key and fits_update_key respectively. In the case of keywords, which
have one of five data types (Integer, Logical, String, Floating and Complex) CCfits
will handle certain type conversions between the keyword value and the data type of
the user-supplied variable. This is described in detail in the Keyword class reference
page. In reading image and table data, intrinsic type conversions are performed as
in cfitsio with the exception that reading numeric data into character data is not supported.
There is an extensive set of member functions supporting equivalents of most of
cfitsio’s read/write operations: the classes PHDU [primary HDU] and ExtHDU [with
subclasses template ImageExt], provide multiple overloaded versions
of read and write functions. The Column class, instances of which can be held in
Table instances [with subclasses AsciiTable and BinTable] has also an extensive set of
read/write operations.
A special constructor is provided which creates a new file with the Primary HDU of
a source file. A FITS::copy(const HDU&) function copies HDUs from one file into
another. Support for filtering table rows by expression is provided by a FITS::filter( ...
) call which may be used to create a new filtered file or overwrite an existing HDU (see
cfitsio manual section 5.6.4).
Functions are provided for adding and deleting columns, and inserting and deleting
rows in tables.
HDU objects also have functions to implement writing of history, comment and date
keys.
Extended file name syntax (chapter 10 of the cfitsio manual) is supported in general,
though not the feature which allows the opening of a particular image stored in the row
of a table.
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