Hi Mark,
many thanks for your help. I tried your code in my program and it worked.
I would like to understand what the code is doing and I have some questions
to it.
> Are you passing in these values, or are they being returned? To me the
> depth of the pointer references implies numVars, varNames, and varTypes
> are out parameters. I'll assume that for now. If they are in/out
> parameters let me know.
Your exactly right: the parameters numVars, varNames and VarTypes are out
paramters.
> I mocked up a DLL to test returning values of these types. I used VS2008
> and compiled with "cl /LD func.c":
>
> --- func.c -------------------------------
> #include <stdlib.h>
> #define FUNCDLL
> #include "func.h"
>
> static char* g_data[] = {"one","two","three"};
> static int g_types[] = {1,2,3};
>
> FUNCAPI int func (int handle, int *numVars, char ***varNames, int
> **varTypes)
> {
> *numVars = _countof(g_data);
> *varNames = g_data;
> *varTypes = g_types;
> return handle + 1;
> }
What does the signature FUNCAPI do in this context?
>
>
> --- func.h -------------------------------
> #ifdef FUNCDLL
> # define FUNCAPI __declspec(dllexport)
> #else
> # define FUNCAPI __declspec(dllimport)
> #endif
>
> FUNCAPI int func (int handle, int *numVars, char ***varNames, int
> **varTypes);
>
Do I need to wrap the compiled DLL file this way? I can load the DLL with
the CDLL method, make calls to simple functions, e.g. no parameters,
returning stirng and get the right values.
I added all the code from your func.py module to the code I already had.
And -- it works fine and delivers the expected results.
> --- func.py -------------------------------
... cut ...
>
> # int func (int handle, int *numVars, char ***varNames, int **varTypes)
> func = c.CDLL('func').func
> func.restype = INT
> func.argtypes = [INT,PINT,PPPCHAR,PPINT]
I added this part to my program.
> # allocate storage for the out parameters
> numVars = INT()
> varNames = PPCHAR()
> varTypes = PINT()
I added this part also.
> print func(5,c.byref(numVars),c.byref(varNames),c.byref(varTypes))
I called the library routine.
> # numVars contains size of returned arrays. Recast to access.
> varNamesArray = c.cast(varNames,c.POINTER(PCHAR * numVars.value))
> varTypesArray = c.cast(varTypes,c.POINTER(INT * numVars.value))
What does this cast? How do I know how I have to cast the objects returned
from the library function?
What kind of objects do I get? I learned that the values of objects created
by the ctypes module are accessed using object.value?
Best regards
Georg
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