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astChannelData - Return a pointer to user-supplied data stored with a Channel

Description:
This macro is intended to be used within the source or sink functions associated with a Channel. It returns any pointer previously stored in the Channel (that is, the Channel that has invoked the source or sink function) using astPutChannelData.

This mechanism is a thread-safe alternative to passing file descriptors, etc, via static global variables.

Synopsis:
void $*$astChannelData
Class Applicability:
Channel
This macro applies to all Channels.
Returned Value:
astChannelData
The pointer previously stored with the Channel using astPutChannelData. A NULL pointer will be returned if no such pointer has been stored with the Channel.
Notes:
  • This routine is not available in the Fortran 77 interface to the AST library.


next up previous 264
Next: astCircle - Create a Circle
Up: AST Function Descriptions
Previous: astChannel - Create a Channel

AST A Library for Handling World Coordinate Systems in Astronomy
Starlink User Note 211
R.F. Warren-Smith & D.S. Berry
24th May 2011
E-mail:ussc@star.rl.ac.uk

Copyright (C) 2009 Science \& Technology Facilities Council