A StcsChan is a specialised form of Channel which supports STC-S I/O operations. Writing an Object to an StcsChan (using astWrite) will, if the Object is suitable, generate an STC-S description of that Object, and reading from an StcsChan will create a new Object from its STC-S description.
Normally, when you use an StcsChan, you should provide "source" and "sink" functions which connect it to an external data store by reading and writing the resulting text. These functions should perform any conversions needed between external character encodings and the internal ASCII encoding. If no such functions are supplied, a Channel will read from standard input and write to standard output.
If "source" is NULL, the Channel will read from standard input instead.
If "sink" is NULL, the StcsChan will write to standard output instead.
AST A Library for Handling World Coordinate Systems in Astronomy