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List: gnuradio-discuss
Subject: Re: [Discuss-gnuradio] Custom GRC block not accepting derived class objects
From: "Perez, Tracie R" <tracie.perez () mavs ! uta ! edu>
Date: 2015-02-24 22:04:34
Message-ID: FF5695CB-8677-45C8-9FEA-D05488EABB04 () mavs ! uta ! edu
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On Feb 23, 2015, at 9:30 AM, Tom Rondeau <tom@trondeau.com<mailto:tom@trondeau.com>> \
wrote:
On Mon, Feb 23, 2015 at 4:06 AM, Perez, Tracie R \
<tracie.perez@mavs.uta.edu<mailto:tracie.perez@mavs.uta.edu>> wrote: I'm hoping for \
suggestions from the GRC and swig savvy folks on the list.
I am trying to add LDPC functionality to gr-fec [1]. I made a GRC block for a decoder \
class. The decoder class constructor accepts a base class called fec_mtrx. In GRC, I \
am trying to give the decoder block an input of an object of a class derived from \
fec_mtrx, called ldpc_R_U_mtrx. The issue is that swig is giving an error that it \
expects the base class as the argument.
From the swig documentation, this type of inheritance and type checking seems to be \
fully supported and handled by swig. Is there something else I need to consider in \
either the block's cheetah template for the make call, or the swig files?
The organization of the classes is like:
class FEC_API ldpc_R_U_mtrx : public fec_mtrx { };
class FEC_API ldpc_bit_flip_decoder_impl : public ldpc_bit_flip_decoder
{
public:
ldpc_bit_flip_decoder_impl(fec_mtrx *mtrx_obj, unsigned int max_iter=100);
}
And then in variable_ldpc_bit_flip_decoder.xml I've got: self.$(id) = $(id) = \
fec.ldpc_bit_flip_decoder.make($matrix_object, $max_iterations)
In my flowgraph, I provide the decoder block an input of a ldpc_R_U_mtrx variable, \
and swig throws:
TypeError: in method 'ldpc_bit_flip_decoder_make', argument 1 of type \
'gr::fec::code::fec_mtrx *
So to me, it seems like swig is not recognizing that the ldpc_R_U_mtrx class derives \
from fec_mtrx. Not sure what to do about that except to try and "un-inherit" the \
classes and overload the decoder constructor...
Thanks for any tips,
tracie
[1] github.com/tracierenea/gnuradio/tree/ldpc_mods<http://github.com/tracierenea/gnuradio/tree/ldpc_mods>
Hey Tracie,
Unfortunately, I don't have a good, easy answer for you. It does seem like this \
should work fine. I'm trying to think of examples where we've done this before. The \
closest that I know of is with the constellation objects and something like the \
constellation_receiver that takes in just the base class. All of the function calls \
required are implemented in that base class, but overloaded by the child class. It \
also has a function ".base()" that returns the pointer to the child object as the \
base class so we can pass it through.
Figuring out how to get swig to work with the child class would probably be the \
better solution, but maybe you can use the constellation class model to get things \
going.
Tom
Thanks very much Tom for the feedback. I spent many more hours trying to get swig to \
work directly with the child class and could never figure out how, or find any clues \
about this issue in the swig documentation. So as a workaround, I've added a \
get_base_ptr() function to the child classes as you described that the constellation \
objects do.
I updated the xml file for the decoder to call the make function as: self.$(id) = \
$(id) = fec.ldpc_bit_flip_decoder.make(${matrix_object}.get_base_ptr(), \
$max_iterations)
Now everything is swig'ing and working great.
Thanks again,
tracie
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<blockquote type="cite" class="">
<div class="">On Feb 23, 2015, at 9:30 AM, Tom Rondeau <<a \
href="mailto:tom@trondeau.com" class="">tom@trondeau.com</a>> wrote:</div> <br \
class="Apple-interchange-newline"> <div class="">
<div dir="ltr" class="">
<div class="gmail_extra">
<div class="gmail_quote">On Mon, Feb 23, 2015 at 4:06 AM, Perez, Tracie R <span \
dir="ltr" class=""> <<a href="mailto:tracie.perez@mavs.uta.edu" target="_blank" \
class="">tracie.perez@mavs.uta.edu</a>></span> wrote:<br class=""> <blockquote \
class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc \
solid;padding-left:1ex"> I'm hoping for suggestions from the GRC and swig savvy folks \
on the list.<br class=""> <br class="">
I am trying to add LDPC functionality to gr-fec [1]. I made a GRC block for a decoder \
class. The decoder class constructor accepts a base class called fec_mtrx. In GRC, I \
am trying to give the decoder block an input of an object of a class derived from \
fec_mtrx, called ldpc_R_U_mtrx. The issue is that swig is giving an error that it \
expects the base class as the argument.<br class=""> <br class="">
From the swig documentation, this type of inheritance and type checking seems to be \
fully supported and handled by swig. Is there something else I need to consider in \
either the block's cheetah template for the make call, or the swig files?<br \
class=""> <br class="">
The organization of the classes is like:<br class="">
<br class="">
class FEC_API ldpc_R_U_mtrx : public fec_mtrx { };<br class="">
<br class="">
class FEC_API ldpc_bit_flip_decoder_impl : public ldpc_bit_flip_decoder<br class="">
{<br class="">
public:<br class="">
ldpc_bit_flip_decoder_impl(fec_mtrx *mtrx_obj, unsigned int \
max_iter=100);<br class=""> }<br class="">
<br class="">
And then in variable_ldpc_bit_flip_decoder.xml I've got: self.$(id) = $(id) = \
fec.ldpc_bit_flip_decoder.make($matrix_object, $max_iterations)<br class=""> <br \
class=""> In my flowgraph, I provide the decoder block an input of a ldpc_R_U_mtrx \
variable, and swig throws:<br class="">
TypeError: in method 'ldpc_bit_flip_decoder_make', argument 1 of type \
'gr::fec::code::fec_mtrx *<br class=""> <br class="">
So to me, it seems like swig is not recognizing that the ldpc_R_U_mtrx class derives \
from fec_mtrx. Not sure what to do about that except to try and "un-inherit" the \
classes and overload the decoder constructor...<br class=""> <br class="">
Thanks for any tips,<br class="">
tracie<br class="">
<br class="">
<br class="">
[1] <a href="http://github.com/tracierenea/gnuradio/tree/ldpc_mods" target="_blank" \
class=""> github.com/tracierenea/gnuradio/tree/ldpc_mods</a></blockquote>
<div class=""><br class="">
</div>
<div class="">Hey Tracie,</div>
<div class=""><br class="">
</div>
<div class="">Unfortunately, I don't have a good, easy answer for you. It does seem \
like this should work fine. I'm trying to think of examples where we've done this \
before. The closest that I know of is with the constellation objects and something \
like the constellation_receiver that takes in just the base class. All of the \
function calls required are implemented in that base class, but overloaded by the \
child class. It also has a function ".base()" that returns the pointer to \
the child object as the base class so we can pass it through.</div>
<div class=""><br class="">
</div>
<div class="">Figuring out how to get swig to work with the child class would \
probably be the better solution, but maybe you can use the constellation class model \
to get things going.</div> <div class=""><br class="">
</div>
<div class="">Tom</div>
<div class=""><br class="">
</div>
<div class=""><br class="">
</div>
</div>
</div>
</div>
</div>
</blockquote>
<br class="">
</div>
<div>Thanks very much Tom for the feedback. I spent many more hours trying to get \
swig to work directly with the child class and could never figure out how, or find \
any clues about this issue in the swig documentation. So as a workaround, I've added \
a get_base_ptr() function to the child classes as you described that the \
constellation objects do.</div> <div><br class="">
</div>
<div>I updated the xml file for the decoder to call the make function as: self.$(id) \
= $(id) = fec.ldpc_bit_flip_decoder.make($<span class="x x-first \
x-last">{</span>matrix_object<span class="x x-first x-last">}.get_base_ptr()</span>, \
$max_iterations)</div> <div><br class="">
</div>
<div>Now everything is swig'ing and working great. </div>
<div><br class="">
</div>
<div>Thanks again,</div>
<div>tracie</div>
<br class="">
</body>
</html>
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