| Passing Structures with Pointers with Call_External [message #40471] |
Tue, 10 August 2004 13:06 |
MajorSetback
Messages: 9
Registered: August 2004
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Junior Member |
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I am using IDL Version 6.0 (linux x86 m32) on Red Hat Linux release 9.
I declare an array of structures thus.
function MakeFloatPlane,numrows,numcolumns
temp={Rows:long(numrows),Columns:long(numcolumns),Data:fltar r(numrows,numcolumns)}
return,temp
end
Planes=replicate(MakeFloatPlane(nY1,nX1),sNumberOfPlanes)
I then pass the array to C code through Call_External thus.
Result=Call_External('SharedLibrary.so','CFunction_cw',sNumb erOfPlanes,Planes,/unload)
The C code is as follows.
typedef struct FloatPlane_Struct
{
long Rows;
long Columns;
float **Data;
} FloatPlane;
extern "C" long CFunction_cw(int argc, void *argv[])
{
long lNumberOfPlanes;
FloatPlane *fppPlanes;
float *fpData;
lNumberOfPlanes=*((long *)(argv[0]));
fppPlanes=((FloatPlane *)(argv[1]));
fpData=((float *)(argv[3]));
fprintf(stderr, "lNumberOfPlanes=%d\n", lNumberOfPlanes);
fprintf(stderr, "fppPlanes->Rows=%d\n", fppPlanes->Rows);
fprintf(stderr, "fppPlanes->Columns=%d\n",
fppPlanes->Columns);
fprintf(stderr, "fppPlanes->Data=%d\n", fppPlanes->Data);
fprintf(stderr, "fpData=%d\n", fpData);
fprintf(stderr, "*fpData=%f\n", *fpData);
return 1;
}
I get the expected values for lNumberOfPlanes, fppPlanes->Rows,
fppPlanes->Columns, fpData and *fpData. However, I cannot interpret
the result I get for fppPlanes->Data.
If I add
fprintf(stderr, "fppPlanes->Data[0]=%d\n", fppPlanes->Data[0]);
idlde crashes, presumably due to a memory write error in the C code.
Is there any way to stop idlde crashing under such circumstances?
My main question is this. Is there a way to retrieve the IDL variable
Planes[i].Data within CFunction_cw?
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