/* libSoX effect: swap pairs of audio channels * * First version written 01/2012 by Ulrich Klauer. * Replaces an older swap effect originally written by Chris Bagwell * on March 16, 1999. * * Copyright 2012 Chris Bagwell and SoX 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 2.1 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, * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA */ #include "sox_i.h" static int start(sox_effect_t *effp){  return effp->in_signal.channels >= 2 ? SOX_SUCCESS : SOX_EFF_NULL;} static int flow(sox_effect_t *effp, const sox_sample_t *ibuf,    sox_sample_t *obuf, size_t *isamp, size_t *osamp){  size_t len = min(*isamp, *osamp);  size_t channels = effp->in_signal.channels;  len /= channels;  *isamp = *osamp = len * channels;   while (len--) {    size_t i;    for (i = 0; i + 1 < channels; i += 2) {      *obuf++ = ibuf[1];      *obuf++ = ibuf[0];      ibuf += 2;    }    if (channels % 2)      *obuf++ = *ibuf++;  }   return SOX_SUCCESS;} sox_effect_handler_t const *lsx_swap_effect_fn(void){  static sox_effect_handler_t handler = {    "swap", NULL,    SOX_EFF_MCHAN | SOX_EFF_MODIFY,    NULL, start, flow, NULL, NULL, NULL,    0  };  return &handler;}