helloworld.c 2.59 KB
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/*
 * HOWTO write an External for Pure data
 * (c) 2001-2006 IOhannes m zmölnig zmoelnig[AT]iem.at
 *
 * this is the source-code for the first example in the HOWTO
 * it creates an object that prints "Hello world!" whenever it 
 * gets banged.
 *
 * for legal issues please see the file LICENSE.txt
 */



/**
 * include the interface to Pd 
 */
#include "m_pd.h"

/**
 * define a new "class" 
 */
static t_class *helloworld_class;


/**
 * this is the dataspace of our new object
 * we don't need to store anything,
 * however the first (and only) entry in this struct
 * is mandatory and of type "t_object"
 */
typedef struct _helloworld {
  t_object  x_obj;
} t_helloworld;


/**
 * this method is called whenever a "bang" is sent to the object
 * the name of this function is arbitrary and is registered to Pd in the 
 * helloworld_setup() routine
 */
void helloworld_bang(t_helloworld *x)
{
  /*
   * post() is Pd's version of printf()
   * the string (which can be formatted like with printf()) will be
   * output to wherever Pd thinks it has too (pd's console, the stderr...)
   * it automatically adds a newline at the end of the string
   */
  post("Hello world !!");
}


/**
 * this is the "constructor" of the class
 * this method is called whenever a new object of this class is created
 * the name of this function is arbitrary and is registered to Pd in the 
 * helloworld_setup() routine
 */
void *helloworld_new(void)
{
  /*
   * call the "constructor" of the parent-class
   * this will reserve enough memory to hold "t_helloworld"
   */
  t_helloworld *x = (t_helloworld *)pd_new(helloworld_class);

  /*
   * return the pointer to the class - this is mandatory
   * if you return "0", then the object-creation will fail
   */
  return (void *)x;
}


/**
 * define the function-space of the class
 * within a single-object external the name of this function is special
 */
void helloworld_setup(void) {
  /* create a new class */
  helloworld_class = class_new(gensym("helloworld"),        /* the object's name is "helloworld" */
			       (t_newmethod)helloworld_new, /* the object's constructor is "helloworld_new()" */
			       0,                           /* no special destructor */
			       sizeof(t_helloworld),        /* the size of the data-space */
			       CLASS_DEFAULT,               /* a normal pd object */
			       0);                          /* no creation arguments */

  /* attach functions to messages */
  /* here we bind the "helloworld_bang()" function to the class "helloworld_class()" -
   * it will be called whenever a bang is received
   */
  class_addbang(helloworld_class, helloworld_bang); 
}