[Discuss-gnuradio] Problem with gr_vector_float type

[address@hidden]

Hi all,

I'm having a problem trying to use gr_vector_float type. 
I don't have 
any problem to work with streams, but when I try to create a block that takes a 
vector of float numbers on its input and produces a vector of float numbers on 
its output (N:N) I always receive this error: 

ValueError: itemsize mismatch: 
stream_to_vector(2):0 using 4096, xcor_ff(4):0 using 4

I understood this error 
is caused by different vectors' size, but I don't understand what I did wrong 
in my code.

This is c++ source of my block (I'm trying to create a block that 
compute the autocorrelation of its input vector):


############################################################################################################

/* -*- c++ -*- */
/*
 * Copyright 2005 Free Software Foundation, Inc.
 * 
 * 
This file is part of GNU Radio
 * 
 * GNU Radio is free software; you can 
redistribute it and/or modify
 * it under the terms of the GNU General Public 
License as published by
 * the Free Software Foundation; either version 3, or 
(at your option)
 * any later version.
 * 
 * GNU Radio is distributed in the 
hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the 
implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  
See the
 * GNU General Public License for more details.
 * 
 * You should have 
received a copy of the GNU General Public License
 * along with GNU Radio; see 
the file COPYING.  If not, write to
 * the Free Software Foundation, Inc., 51 
Franklin Street,
 * Boston, MA 02110-1301, USA.
 */

#ifdef HAVE_CONFIG_H

#include "config.h"
#endif

#include <howto_xcor_ff.h>
#include 
<gr_io_signature.h>
#include <gri_fft.h>
#include <math.h>
#include <stdexcept>

#include <cstdio>
#include <iostream>
#include <string.h>
#include <gr_types.h>


howto_xcor_ff_sptr howto_make_xcor_ff (int fftsize)
{
  return 
howto_xcor_ff_sptr (new howto_xcor_ff (fftsize));
}


howto_xcor_ff::
howto_xcor_ff (int fftsize)
  : gr_sync_block ("xcor_ff",
                       
gr_make_io_signature (1, 1, sizeof (float)),
                       gr_make_io_signature (1, 
1, sizeof (float)))
{
  d_fftsize = fftsize;
  d_fwdfft = new gri_fft_real_fwd
(d_fftsize);
  d_invfft = new gri_fft_real_rev(d_fftsize);
  
}

howto_xcor_ff::
~howto_xcor_ff ()
{
  delete d_fwdfft;
  delete d_invfft;
}

int
howto_xcor_ff::
work (int noutput_items,
                         gr_vector_const_void_star &input_items,
                         
gr_vector_void_star &output_items)
{

  const gr_vector_float *in = (const 
gr_vector_float *) input_items[0];
  gr_vector_float *out = (gr_vector_float *) 
output_items[0];

  unsigned int input_data_size = input_signature()-
>sizeof_stream_item (0);
  unsigned int output_data_size = output_signature()-
>sizeof_stream_item (0);

  int j,i=0;
    
  while (i++ < noutput_items)
 {

    memcpy(d_fwdfft->get_inbuf(), in, input_data_size);
    
    memcpy
(d_invfft->get_inbuf(), in, input_data_size);   

    d_fwdfft->execute();        // 
compute fwd xform

    float scale = 1.0 / d_fftsize;
    for (j = 0; j < 
d_fftsize; j++)
    d_invfft->get_inbuf()[j] = d_invfft->get_outbuf()[j] * 
scale;

    d_invfft->execute();        // compute inv xform    


    for (j = 0; j < 
d_fftsize; j++) 
      d_invfft->get_inbuf()[j] = d_fwdfft->get_outbuf()[j] * 
d_invfft->get_outbuf()[j];
    
    d_invfft->execute();        // compute inv xform


    // copy result to output
        
   memcpy(out, d_invfft->get_outbuf(), 
output_data_size);

   out += d_fftsize;
   in  += d_fftsize;
 } 
  return 
noutput_items;
}


######################################################################################################


I'm a beginner, so probably my code is full of errors.


Thank you for your 
help.


Elettra