It must be defined inside the context of a function!

GNU Radio
1

Dear Sir,

Below code will produce compilation error: ‘input_sizes’ does not name
a
type.
This is because input_sizes must be assigned inside a context of a
function
in c++, right ?

std::vector input_sizes;
input_sizes.push_back(sizeof(float));
input_sizes.push_back(sizeof(double));
gr_sync_block(“my block”, gr_make_io_signaturev(2, 2, input_sizes),
gr_make_io_signature(1, 1, sizeof(float)))

Source:
http://gnuradio.org/redmine/projects/gnuradio/wiki/BlocksCodingGuide#IO-signatures

My code (which produce error) is below.

/* -*- c++ -*- */

#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include <gr_io_signature.h>
#include <vector>
#include <complex>
#include "sample_and_hold_cc_impl.h"

namespace gr {
  namespace howto {

    sample_and_hold_cc::sptr
    sample_and_hold_cc::make()
    {
      return gnuradio::get_initial_sptr
        (new sample_and_hold_cc_impl());
    }

    /*
     * The private constructor
     */

    std::vector <int> xx;
    xx.push_back(25);
    xx.push_back( sizeof( float ) );
    xx.push_back( sizeof( std::complex<float> ) );

    sample_and_hold_cc_impl::sample_and_hold_cc_impl()
      : gr_sync_block("sample_and_hold_cc",
              gr_make_io_signature(<+MIN_IN+>, <+MAX_IN+>,
sizeof(<+ITYPE+>)),
              gr_make_io_signature(<+MIN_OUT+>, <+MAX_OUT+>,
sizeof(<+OTYPE+>)))
    {}

    /*
     * Our virtual destructor.
     */
    sample_and_hold_cc_impl::~sample_and_hold_cc_impl()
    {
    }

    int
    sample_and_hold_cc_impl::work(int noutput_items,
              gr_vector_const_void_star &input_items,
              gr_vector_void_star &output_items)
    {
        const <+ITYPE+> *in = (const <+ITYPE+> *) input_items[0];
        <+OTYPE+> *out = (<+OTYPE+> *) output_items[0];

        // Do <+signal processing+>

        // Tell runtime system how many output items we produced.
        return noutput_items;
    }

  } /* namespace howto */
} /* namespace gr */
2

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Hi Activecat,

you’re right. Method calls (or function calls in general) such us
push_back can only take place in functions. That’s why constructors
exist! Please refer to your favourite C++ literature for more
information. As you understood correctly, this is a C++ problem, and
not really GR-related.
Your code won’t compile even after moving these calls into a function,
because you yet have to replace the <+ +> placeholders.

Then: Working in namespace gr::howto is really deprecated. To get a
working, correctly named module infrastructure fitting your
installation of GR (which hopefully is either v3.6.5 or 3.7.X), please
use gr_modtool.

Greetings,
Marcus

On 16.01.2014 08:46, Activecat wrote:

1, sizeof(float)))
#ifdef HAVE_CONFIG_H #include “config.h” #endif

sample_and_hold_cc_impl::~sample_and_hold_cc_impl() { }

} /* namespace howto / } / namespace gr */ [/code]

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3

On Thu, Jan 16, 2014 at 10:13 AM, Activecat [email protected] wrote:

Dear Sir,

Is this a good alternative?
gr_make_io_signature2 (2, 2, sizeof(float), sizeof(double))

c++ - How to define a block with 2 inputs? - Stack Overflow

Dear Activecat,

yes, you must specify the input size as you have done, so
gr_make_io_signature2 (2, 2, sizeof(float), sizeof(double)) is a valid
signature.

Is this considered a correct answer?

Re: [Discuss-gnuradio] A block with 2 inputs

It would work, but for reasons of readability I suggest you use the
other
form.

Then: Working in namespace gr::howto is really deprecated. To get a

working, correctly named module infrastructure fitting your
installation of GR (which hopefully is either v3.6.5 or 3.7.X), please
use gr_modtool.

modtool does use these namespaces! If you generate a module called
‘howto’,
it will put blocks in the gr::howto namespace.

MB

4

Dear Sir,

Is this a good alternative?
gr_make_io_signature2 (2, 2, sizeof(float), sizeof(double))

Is this considered a correct answer?
Re: [Discuss-gnuradio] A block with 2 inputs

Regards.