[PD-dev] Help with own external

[thewade]

Hello list,

I need some help understanding whats going on with my external, and I havent coded in a long time. I appologize if I do newbie things, All I do is try to make the errors go away by trying things. For example I try to cast (t_float *) to (float) for truncf but I get errors unless I make *(t_float *)...

Problem 1, Basic functionality. I want to return the Nth sample from a block of samples. Is others have pointed out there may be other ways of doing this using other externals and combonations of objects, but I want to write my own object, in order to both learn more about writing externals, and to have a cleaner solution.

Problem 2, Weird errors. I get a werid warning: implicit declaration of function `truncf\' when using a simple math.h function, and if I connect my external to fft~ while enabling a small piece of code I color the FFT~ output. When I then disconnect my object, the fft~ stops putting output out.

Problem 1: a closer look.
Ive included my code at the bottom of this email. I really appreciate if someone could point out what Im doing wrong. Ive looked at snapshot~ and tried to adopt some of its methods, but it doesnt seem to work when compaired to print~ output.

Problem 2: a closer look.
The peice of code:
int      n      = (int)(w[3]);
t_float *bin    = (t_float *)(w[4]);
  *bin = truncf(*bin);
  if (*bin > n) *bin = n;
  if (*bin < 0) *bin = 0;
Gives me the error: warning: implicit declaration of function `truncf\'. Im not redefining the function...
Also when this piece of code is enabled, and I connect to FFT~ real output I get colored output, then when I break the connection, FFT~ doesnt output anything, it seems.
w[3]=sp[0]->s_n - 1
w[4]=&ref->x_bin
t_float x_bin;

-------------The Code-----------------
#include <m_pd.h>
#include <math.h>

/*-------------------------------------------------------*/
/*fftbin~                                                */
/* A tool to extract specific bins from the output of    */
/* fft~. Inlets are (from left to right):                */
/* The output of fft~ and bang, the bin number to        */
/* capture.                                              */
/* The outlet is a control rate float equal to the value */
/* of the bin in question.                               */
/*-------------------------------------------------------*/

static t_class *fftbin_tilde_class;

typedef struct _fftbin {
  t_object  x_obj;
  t_float x_n;
  t_float x_bin;
  t_float x_binval;
  float x_f;
} t_fftbin;

void *fftbin_tilde_new(t_floatarg f)
{
  t_fftbin *ref = (t_fftbin *)pd_new(fftbin_tilde_class);
  ref->x_bin = f;
  ref->x_binval=0;
  ref->x_f = 0;
  ref->x_n=64;                     //Signal inlet exists by default
  outlet_new(&ref->x_obj, &s_float);             //bin value outlet
  floatinlet_new(&ref->x_obj, &ref->x_bin);      //bin number inlet
  return (void *)ref;
}

t_int *fftbin_tilde_perform(t_int *w)
{
  t_float *in1    = (t_float *)(w[1]);            //fft~ output
  t_float *binval = (t_float *)(w[2]);            //value requested
  int      n      = (int)(w[3]);                  //block size
  t_float *bin    = (t_float *)(w[4]);            //bin request

//make sure bin requested is within block, and an integer
  *bin = truncf(*bin);
  if (*bin > n) *bin = n;
  if (*bin < 0) *bin = 0;

  *binval = *in1;

  return (w+5);
}

void fftbin_tilde_dsp(t_fftbin *ref, t_signal **sp)
{
  dsp_add(fftbin_tilde_perform, 4,
   sp[0]->s_vec + (int)ref->x_bin, &ref->x_binval, sp[0]->s_n - 1, &ref->x_bin);
}

void fftbin_tilde_set(t_fftbin *ref, t_floatarg f)
{
  ref->x_bin = f;
}

void fftbin_tilde_bang(t_fftbin *ref)
{
  outlet_float(ref->x_obj.ob_outlet, ref->x_binval);
}

void fftbin_tilde_setup(void) {
  fftbin_tilde_class = class_new(gensym(\"fftbin~\"),
        (t_newmethod)fftbin_tilde_new,
        0, sizeof(t_fftbin),
        CLASS_DEFAULT,
        A_DEFFLOAT, 0);

  class_addmethod(fftbin_tilde_class,
        (t_method)fftbin_tilde_dsp, gensym(\"dsp\"), 0);
  class_addmethod(fftbin_tilde_class,
        (t_method)fftbin_tilde_set, gensym(\"set\"), A_DEFFLOAT, 0);
  class_addbang(fftbin_tilde_class, fftbin_tilde_bang);

  CLASS_MAINSIGNALIN(fftbin_tilde_class, t_fftbin, x_f);
  post(\"fftbin~: written by thewade with help from the PD list\");
}