A number of parameters (macro constants) are necessary when calling
functions in the CDF library from a C program.
These parameters are defined in cdf.h
. When calling the
CDF functions/procedures in IDL, local variables are used to accomplish the
same thing. An IDL batch
file,
cdf.pro, is provided that
creates/initializes the necessary local variables. cdf.pro is
executed automatically by the startup file when you run IDL.
All necessary CDF parameters will be available including the status
codes commonly used (CDF_OK and CDF_WARN).
Most users will not need the other status codes since the CDFerror
function can be used to determine the explanation of a status code.
If you do require the other status codes, execute the batch file
cdf1.pro (the IDL internal path will know where to find it).
If you are using the Internal Interface (CDFlib), you will also
need the parameters (local variables) defined in cdf2.pro.
IDL limits the number of local variables that may be defined in any one function/procedure. This limit might be reached if you have to include one or more of the CDF ``include'' files. If that happens you will have to use one or more of the ``mapping'' functions provided with the CDF/IDL interface. The use of these ``mapping'' functions eliminates the need to include the corresponding `include' file.
+--------------------------------------------------------------+ | Include File Mapping Function Purpose | +--------------------------------------------------------------+ | cdf.pro mcp.pro Map CDF parameters | | cdf1.pro msc.pro Map status codes | | cdf2.pro mii.pro Map Internal Interface | +--------------------------------------------------------------+
Each function returns the longword value that corresponds to the parameter passed in as a character string. For example, the status code value for NO_SUCH_CDF would be retrieved as follows...
IDL> status = CDFopen ('test1', id)
IDL> if (status eq MSC('NO_SUCH_CDF')) ...
In this case the batch file cdf1.pro would not have to be included.