Re: Java char *INOUT doesn't OUT

William,

Thanks for the input.  For clarification, the char* are basically strings (not 
single chars) that are passed back and forth with this DLL.

Does the signed char * properly handle null terminating the Strings?

Thanks,

Gary


At 04:06 PM 9/22/2004, William S Fulton wrote:
>Gary Nissen wrote:
>
>>Hi,
>>I'm using SWIG-1.3.22 on Windows with Java JDK 1.4.2.
>>I'm trying to wrap a C DLL.  All parameters are passed as pointers (int *, 
>>double *, and char *).  Most parameters are *INPUT, but some are *INOUT.  The 
>>int *INOUT and double *INOUT work as expected by turning the parameter into a 
>>single dimensional array.  But a char *INOUT turns the parameter into a 
>>String, basically making it a char *INPUT.
>>I expected the char *INOUT to allow me to pass Strings back and forth via a 
>>1-dimensional array just like int *INOUT.  Am I off track?  Is there a better 
>>method to do this?
>>Through my struggles I also tried the *SBUF and *BYTE methods.  Unfortunately 
>>neither worked for me.  
>>The *SBUF caused Access Violations because the char array was a different 
>>length than the string contained in the StringBuffer.  It was using the 
>>capacity of a StringBuffer instead of the length of the String contained in 
>>it.  I tried changing the typemap to use length.  Then I received Access 
>>Violations when the resulting string was being appended back to the 
>>StringBuffer.  I wasn't able to figure out why that was failing.
>>The *BYTE caused garbage to be pasted back into my String.  I was using the 
>>BYTE method this way:
>>String s = "0123456789";
>>byte[] b = s.toByteArray();
>>int r = DLLWrapper.getResult(b);
>>s = new String(b);
>>System.out.println(s);
>>This resulted in garbage printouts.
>>Any advice on the best/easiest way to do this?  
>
>SWIG wraps char* as a string, that is well documented. To change the behaviour 
>of char* to a pointer to an in/out single char character, apply the 'signed 
>char *' typemaps.
>
>%include "typemaps.i"
>%apply signed char *INOUT {char *pnum};
>%typemap(freearg) char *pnum "";
>
>void foo(char *pnum);
>
>Unfortunately the default char* typemaps require a freearg typemap and this is 
>still picked up, thus the extra typemap above to clear the freearg typemap. 
>I'll change this so it won't be necessary in the future.
>
>William
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