How to convert wchar_t array to byte array for java using swig?

Question

I have created the following helper function but I am unable to get it to generate a java interface that accepts a byte array as the input.

size_t get_p_wchar_t_bytes(wchar_t *wstr, char * bytes, size_t len)
{
    size_t wlen,cpylen;
    wlen = count_p_wchar_t_bytes(wstr);
    cpylen = len > wlen ? wlen : len;
    memcpy(bytes, wstr, cpylen);
    return cpylen;
}

size_t count_p_wchar_t_bytes(wchar_t *wstr)
{
    return wcslen(wstr) * sizeof(wchar_t);
}

I have the following defined in my template

%include "arrays_java.i"
%apply int[] {int *};
%include "wchar.i"

The problem with this is that the char * is being converted to a "String" instead of a byte array which isn't helpful.

public static long get_p_wchar_t_bytes(SWIGTYPE_p_wchar_t wstr, String bytes, long len)

What I want as the output from swig is this...

public static long get_p_wchar_t_bytes(SWIGTYPE_p_wchar_t wstr, byte[] bytes, long len)

So how can I do this? Ultimately I simply need a way to pass a w_char_t array to java in a format it can work with without creating any memory leaks.

Why do you want to do wchar_t to byte? Sounds like you're trying to solve the wrong problem. — Flexo - Save the data dump
– Flexo - Save the data dump ♦, Commented Apr 23, 2014 at 6:26
Flexo I have another function which returns sizeof(wchar_t) so with that information I can determine if the encoding is UTF-16 or UTF-32 for conversion of a byte array into a Java String. — Ralph Ritoch
– Ralph Ritoch, Commented Apr 23, 2014 at 7:05
If you just want to make it work properly as a Java string you're making this far more complicated than needed. — Flexo - Save the data dump
– Flexo - Save the data dump ♦, Commented Apr 23, 2014 at 7:07

Ralph Ritoch · Accepted Answer · 2014-04-23 07:24:25Z

1

I was able to solve this problem by changing my template to the following which is a solution I found at http://swig.10945.n7.nabble.com/Converting-char-to-byte-String-in-Java-td276.html

// knows about things like int *OUTPUT:
%include "typemaps.i"
// knows about int32_t
%include "stdint.i"
%include "arrays_java.i"
%apply int[] {int *};

// convert char * to byte array
%apply signed char[] {char* pchar}; 

%include "wchar.i"

answered Apr 23, 2014 at 7:24

Ralph Ritoch

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