shithub: sox

ref: dd448e56da071aebba7572eb6ea81788038133e8
dir: /src/skeleff.c/

/*
 * skeleff - Skeleton Effect.  Use as sample for new effects.
 *
 * Copyright 1999 Chris Bagwell And Sundry Contributors
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library. If not, write to the Free Software
 * Foundation, Fifth Floor, 51 Franklin Street, Boston, MA 02111-1301,
 * USA.  */

#include "st_i.h"

/* Private data for effect */
typedef struct skeleff {
  int  localdata;
} *skeleff_t;

assert_static(sizeof(struct skeleff) <= ST_MAX_EFFECT_PRIVSIZE, 
              /* else */ skeleff_PRIVSIZE_too_big);

/*
 * Process command-line options
 *
 * Don't do initialization now.
 * The 'info' fields are not yet filled in.
 */
static int getopts(eff_t effp, int n, char **argv)
{
  skeleff_t skeleff = (skeleff_t)effp->priv;

  if (n && n != 1) {
    st_fail(effp->h->usage);
    return ST_EOF;
  }

  return ST_SUCCESS;
}

/*
 * Prepare processing.
 * Do all initializations.
 */
static int start(eff_t effp)
{
  if (effp->outinfo.channels == 1) {
    st_fail("Can't run skeleff on mono data.");
    return ST_EOF;
  }

  return ST_SUCCESS;
}

/*
 * Processed signed long samples from ibuf to obuf.
 * Return number of samples processed.
 */
static int flow(eff_t effp, const st_sample_t *ibuf, st_sample_t *obuf, 
                           st_size_t *isamp, st_size_t *osamp)
{
  skeleff_t skeleff = (skeleff_t)effp->priv;
  st_size_t len, done;

  switch (effp->outinfo.channels) {
  case 2:
    /* Length to process will be buffer length / 2 since we
     * work with two samples at a time.
     */
    len = min(*isamp, *osamp) / 2;
    for (done = 0; done < len; done++)
      {
        obuf[0] = ibuf[0];
        obuf[1] = ibuf[1];
        /* Advance buffer by 2 samples */
        ibuf += 2;
        obuf += 2;
      }
        
    *isamp = len * 2;
    *osamp = len * 2;
        
    break;
  }

  return ST_SUCCESS;
}

/*
 * Drain out remaining samples if the effect generates any.
 */
static int drain(eff_t effp, st_sample_t *obuf, st_size_t *osamp)
{
  *osamp = 0;
  /* Help out application and return ST_EOF when drain
   * will not return any mre information.  *osamp == 0
   * also indicates that.
   */
  return ST_EOF;
}

/*
 * Do anything required when you stop reading samples.  
 */
static int stop(eff_t effp)
{
  return ST_SUCCESS;
}

/*
 * Do anything required when you delete an effect.  
 *      (free allocated memory, etc.)
 */
static int delete(eff_t effp)
{
  return ST_SUCCESS;
}


/*
 * Effect descriptor.
 * If no specific processing is needed for any of
 * the 6 functions, then the function can be deleted
 * and 0 used in place of the its name below.
 */
static st_effect_t st_skel_effect = {
  "skel",
  "Usage: skel [option]",
  ST_EFF_MCHAN,
  getopts,
  start,
  flow,
  drain,
  stop,
  delete,
};

/*
 * Function returning effect descriptor. This should be the only
 * externally visible object.
 */
const st_effect_t *st_skel_effect_fn(void)
{
  return &st_skel_effect;
}