| Re: IDL calling C [message #33065 is a reply to message #32814] |
Mon, 25 November 2002 01:33   |
rmlongfield
Messages: 68
Registered: August 1998
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Member |
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nrk5@cornell.edu (Nidhi Kalra) wrote in message news:<6c4c9ef3.0211071158.2eea6820@posting.google.com>...
> Hi,
>
> I was wondering if anybody could point me to some resources for
> calling C functions from IDL. I have never done this before myself and
> am quite unfamiliar with C. I have somebody else's .h and .c files and
> need to call their functions from IDL, but have little understanding
> of the internals of their stuff. Thanks!
>
> Nidhi
Hi Nidhi (and everyone),
This is a bit late but I can help you with the C and IDL
interface using CALL_EXTERNAL. I have some sample files that I
need to make a little more user friendly and then I can send them
to you. They are written for SGI and Linux (with some necessary
keywords).
Below is a sample IDL code, I use it to call a C program
to call a Fortran program. Let me know if this is what you need
and I can send the rest.
Rose
PRO idl_rtau
;+
; NAME:
; IDL_RTAU
;
; PURPOSE: Demonstrate how one can run FORTRAN code from an IDL
session.
; AUTHOR: Rose
; CATEGORY: CALL_EXTERNAL
; PROCEDURE: IDL_RTAU does two things.
; 1) Runs a UNIX shell program through a SPAWN procedure.
; This compiles the C and Fortran programs which will
; be used later in the CALL_EXTERNAL.
; If compilation has already been done, no need to recompile
; This might save time for large compilation times.
; Set compile_flag to zero.
; 2) Calls IDL Procedure, CALL_EXTERNAL, which accepts DOUBLE
; input and returns DOUBLE output. All variables must be
; pre-defined.
; CALLING SEQUENCE: idl_rtau
; MAJOR FUNCTIONS and PROCEDURES:
; SPAWN
; CALL_EXTERNAL
; NOTES: If there are ANY modifications to the C or FORTRAN programs
; one must exit IDL and then return to run new executables.
; Debugging should be done using accompanying wrapper routines.
; MODIFICATION HISTORY: 26 October 1999
;
; COMMON BLOCKS: none
;
print,'In idl_rtau: '
compile_flag = 1
IF(compile_flag GT 0) THEN BEGIN
;
;-- Run make command which produces rtauc.o,rtauf.o,rtauc.so,
so_locations
;
sh_command = 'idl_rtau.sh'
SPAWN,sh_command
ENDIF ELSE BEGIN
;
print,'File is ok'
;
ENDELSE
; *** DEFINE variables for CALL_EXTERNAL ***
; Must be Type double
;
surface_reflectivity = DOUBLE(.1)
nbcloud=14
tau = DBLARR(nbcloud)
reflectivity = DBLARR(nbcloud)
result_rtau = CALL_EXTERNAL('rtauc.so','rtauc',surface_reflectivity,tau,re flectivity)
print,'Returned values from rtau: ',result_rtau
; Check results
IF(result_rtau EQ 0) THEN BEGIN
FOR i = 0,N_ELEMENTS(tau)-1 DO BEGIN
print,tau[i],reflectivity[i],FORMAT='(f6.2,1x,f6.2)'
ENDFOR
ENDIF ELSE BEGIN
print, ' Well, something did not work'
ENDELSE
end
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