[Swig-user] Controlling getter/setter generation for structs

[Gibbs, S. <Sol...@sr...>]

Hello,
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I hope this isn't an obvious question, but I have looked through the
docs and I can't figure it out.
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I'm exporting an existing C library to Java. I have a C struct along the
lines of:
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   struct {
      char* next_in;
      unsigned int avail_in;
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      char* next_out;
      unsigned int avail_out;
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   } bz_stream;
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bz_stream gets wrapped with a Java proxy class, and I can specify a
C-method for backing the constructor with the %extend directive. Since
the library functions as a stream filter, I allocate heap space in Java
using two direct Java NIO Buffers and override %typemap(in) char* and
%typemap(memberin) char* so that the setter method on the bz_stream
proxy class sets the bz_stream->next_in and next_out as the address of
the direct Buffer.
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There are two problems with this: Because the proxy class only retains a
reference to the underlying array and not the actual Java Buffer object,
there is the potential for the Buffer to be garbage collected
prematurely. In addition, the getter generated for the bz_stream proxy
makes no sense, because it cannot return the Buffer object.
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How do I modify the proxy code for the setters to retain a reference to
the Buffer object and the code for the getters to return that reference?

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As a matter of style and productivity, is it better to spend time fixing
up the proxy classes to present a clean interface, or should I just plan
on having a somewhat messy boundary layer between Java and C and try to
smooth it out by adding a layer of abstraction in Java?
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- Solomon