//
// Copyright:     Copyright 2003 Craig Stuart Sapp
// Programmer:    Craig Stuart Sapp <craig@ccrma.stanford.edu>
// Creation Date: Tue Mar 11 08:27:27 PST 2003
// Last Modified: Tue Mar 11 08:33:43 PST 2003
// Filename:      dcblock.c
// Web Address:   http://peabody.sapp.org/class/dmp2/lab/dcblock/dcblock.c
// Syntax:        C; Max4/MSP2 External Object; CodeWarrior 6.0
// OS:            Mac OS 9; PPC
//
// Description:   A DC blocking filter to remove unwanted bias from a signal.
//

#include "ext.h"
#include "z_dsp.h"

typedef struct {
   t_pxobject msp_data;   // must always be the first field; used by MSP
   float      lastinput;  // the last signal value to come into the filter.
   float      lastoutput; // the last signal value to go out of the filter.
   float      gain;       // will be set to 0.995 for best 44.1 srate behavior.
} MyObject;

void* object_data;     // pointer to data for object (created in setup());

// function declarations:
void   main            (void);
void*  create_object   (void);
void   MessageDSP      (MyObject* mo, t_signal** signal, short* count);
void   MessageClear    (MyObject* mo);
t_int* Perform         (t_int *parameters);


//////////////////////////////////////////////////////////////////////////
//
// Initialization functions:
//


void main(void) {
   setup((t_messlist**)&object_data, // the pointer for object data
         (method)create_object,      // your function that initializes object
         (method)dsp_free,           // your function that deinitializes object
         (short)sizeof(MyObject),    // size of your object data struct
         NULL,                       // your menu function
         A_NOTHING);                 // A list of default parameters types
                                     // ending with A_NOTHING

   addmess((method)MessageDSP,   "dsp",   A_CANT, A_NOTHING);
   addmess((method)MessageClear, "clear", A_NOTHING);
   dsp_initclass();
}



//////////////////////////////
//
// create_object -- object initializing function.  This function is
//    called by the setup() function inside of main().  Place code
//    here which will be used to initialized your data structure,
//    as well as the actual creation of the data storage itself.
//    The setup function will cause the pointer object_data to point
//    to the created data storage.
//

void* create_object(void) {
   MyObject *mo = (MyObject*)newobject(object_data);  
   dsp_setup((t_pxobject*)mo, 1);           // 1 signal input
   outlet_new((t_pxobject*)mo, "signal");   // outlet 1
   mo->gain = 0.995;                        // set gain for dcblock filter.
   MessageClear(mo);
   return mo;                               
}


//////////////////////////////////////////////////////////////////////////
//
// Behavior functions:
//


//////////////////////////////
//
// MessageDSP -- What to do when a "dsp" message arrives into the object.
//

void MessageDSP(MyObject* mo, t_signal** signal, short* count) {
   #pragma unused(count)
   dsp_add(Perform, 5, 5, mo, signal[0]->s_vec, signal[1]->s_vec, signal[0]->s_n);
}



//////////////////////////////
//
// MessageClear -- clear the memory of the past signal value (set it to 0).
//

void MessageClear(MyObject *mo) {
   mo->lastinput  = 0.0;
   mo->lastoutput = 0.0;
}



//////////////////////////////
//
// Perform -- do the calculations for one sample group.
//

t_int* Perform(t_int *parameters) {
   long      pcount = (long)     (parameters[1]);
   MyObject *mo     = (MyObject*)(parameters[2]);
   t_float  *input  = (t_float*) (parameters[3]);
   t_float  *output = (t_float*) (parameters[4]);
   long      count  = (long)     (parameters[5]);
   long      i;

   for (i=0; i<count; i++) {
      output[i] = input[i] - mo->lastinput + mo->gain * mo->lastoutput;
      mo->lastinput  = input[i];
      mo->lastoutput = output[i];
   }

   return parameters+pcount+1;   
}