/*
** Nofrendo (c) 1998-2000 Matthew Conte (matt@conte.com)
**
**
** This program is free software; you can redistribute it and/or
** modify it under the terms of version 2 of the GNU Library General 
** Public License as published by the Free Software Foundation.
**
** This program 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 
** Library General Public License for more details.  To obtain a 
** copy of the GNU Library General Public License, write to the Free 
** Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
**
** Any permitted reproduction of these routines, in whole or in part,
** must bear this legend.
**
**
** vrcvisnd.c
**
** VRCVI sound hardware emulation
** $Id$
*/

#include "types.h"
#include "vrcvisnd.h"
#include "nes_apu.h"


static vrcvisnd_t vrcvi;
static int32 vrcvi_incsize;

/* VRCVI rectangle wave generation */
static int32
vrcvi_rectangle (vrcvirectangle_t * chan)
{
  /* reg0: 0-3=volume, 4-6=duty cycle
   ** reg1: 8 bits of freq
   ** reg2: 0-3=high freq, 7=enable
   */

  chan->phaseacc -= vrcvi_incsize;      /* # of clocks per wave cycle */
  while (chan->phaseacc < 0) {
    chan->phaseacc += chan->freq;
    chan->adder = (chan->adder + 1) & 0x0F;
  }

  /* return if not enabled */
  if (FALSE == chan->enabled)
    return 0;

  if (chan->adder < chan->duty_flip)
    return -(chan->volume);
  else
    return chan->volume;
}

/* VRCVI sawtooth wave generation */
static int32
vrcvi_sawtooth (vrcvisawtooth_t * chan)
{
  /* reg0: 0-5=phase accumulator bits
   ** reg1: 8 bits of freq
   ** reg2: 0-3=high freq, 7=enable
   */

  chan->phaseacc -= vrcvi_incsize;      /* # of clocks per wav cycle */
  while (chan->phaseacc < 0) {
    chan->phaseacc += chan->freq;
    chan->output_acc += chan->volume;

    if (7 == ++chan->adder) {
      chan->adder = 0;
      chan->output_acc = 0;
    }
  }

  /* return if not enabled */
  if (FALSE == chan->enabled)
    return 0;
  else
    return (chan->output_acc >> 3) << 9;
}

/* mix vrcvi sound channels together */
static int32
vrcvi_process (void)
{
  int32 output;

  output = vrcvi_rectangle (&vrcvi.rectangle[0]);
  output += vrcvi_rectangle (&vrcvi.rectangle[1]);
  output += vrcvi_sawtooth (&vrcvi.saw);

  return output;
}

/* write to registers */
static void
vrcvi_write (uint32 address, uint8 value)
{
  int chan;

  switch (address & 0xB003) {
    case 0x9000:
    case 0xA000:
      chan = (address >> 12) - 9;
      vrcvi.rectangle[chan].reg[0] = value;
      vrcvi.rectangle[chan].volume = (value & 0x0F) << 8;
      vrcvi.rectangle[chan].duty_flip = (value >> 4) + 1;
      break;
    case 0x9001:
    case 0xA001:
      chan = (address >> 12) - 9;
      vrcvi.rectangle[chan].reg[1] = value;
      vrcvi.rectangle[chan].freq =
          APU_TO_FIXED (((vrcvi.rectangle[chan].reg[2] & 0x0F) << 8) + value +
          1);
      break;
    case 0x9002:
    case 0xA002:
      chan = (address >> 12) - 9;
      vrcvi.rectangle[chan].reg[2] = value;
      vrcvi.rectangle[chan].freq =
          APU_TO_FIXED (((value & 0x0F) << 8) + vrcvi.rectangle[chan].reg[1] +
          1);
      vrcvi.rectangle[chan].enabled = (value & 0x80) ? TRUE : FALSE;
      break;
    case 0xB000:
      vrcvi.saw.reg[0] = value;
      vrcvi.saw.volume = value & 0x3F;
      break;
    case 0xB001:
      vrcvi.saw.reg[1] = value;
      vrcvi.saw.freq =
          APU_TO_FIXED ((((vrcvi.saw.reg[2] & 0x0F) << 8) + value + 1) << 1);
      break;
    case 0xB002:
      vrcvi.saw.reg[2] = value;
      vrcvi.saw.freq =
          APU_TO_FIXED ((((value & 0x0F) << 8) + vrcvi.saw.reg[1] + 1) << 1);
      vrcvi.saw.enabled = (value & 0x80) ? TRUE : FALSE;
      break;
    default:
      break;
  }
}

/* reset state of vrcvi sound channels */
static void
vrcvi_reset (void)
{
  int i;

  /* preload regs */
  for (i = 0; i < 3; i++) {
    vrcvi_write (0x9000 + i, 0);
    vrcvi_write (0xA000 + i, 0);
    vrcvi_write (0xB000 + i, 0);
  }

  /* get the phase period from the apu */
  vrcvi_incsize = apu_getcyclerate ();
}

static void
vrcvi_dummy (void)
{
}

static apu_memwrite vrcvi_memwrite[] = {
  /*   { 0x4040, 0x4092, ext_write }, *//* FDS sound regs */
  {0x9000, 0x9002, vrcvi_write},        /* vrc6 */
  {0xA000, 0xA002, vrcvi_write},
  {0xB000, 0xB002, vrcvi_write},
  {-1, -1, NULL}
};

apuext_t vrcvi_ext = {
  vrcvi_dummy,                  /* no init */
  vrcvi_dummy,                  /* no shutdown */
  vrcvi_reset,
  vrcvi_process,
  NULL,                         /* no reads */
  vrcvi_memwrite
};

/*
** $Log$
** Revision 1.3  2008/03/25 15:56:13  slomo
** Patch by: Andreas Henriksson <andreas at fatal dot set>
** * gst/nsf/Makefile.am:
** * gst/nsf/dis6502.h:
** * gst/nsf/fds_snd.c:
** * gst/nsf/fds_snd.h:
** * gst/nsf/fmopl.c:
** * gst/nsf/fmopl.h:
** * gst/nsf/gstnsf.c:
** * gst/nsf/log.c:
** * gst/nsf/log.h:
** * gst/nsf/memguard.c:
** * gst/nsf/memguard.h:
** * gst/nsf/mmc5_snd.c:
** * gst/nsf/mmc5_snd.h:
** * gst/nsf/nes6502.c:
** * gst/nsf/nes6502.h:
** * gst/nsf/nes_apu.c:
** * gst/nsf/nes_apu.h:
** * gst/nsf/nsf.c:
** * gst/nsf/nsf.h:
** * gst/nsf/osd.h:
** * gst/nsf/types.h:
** * gst/nsf/vrc7_snd.c:
** * gst/nsf/vrc7_snd.h:
** * gst/nsf/vrcvisnd.c:
** * gst/nsf/vrcvisnd.h:
** Update our internal nosefart to nosefart-2.7-mls to fix segfaults
** on some files. Fixes bug #498237.
** Remove some // comments, fix some compiler warnings and use pow()
** instead of a slow, selfmade implementation.
**
** Revision 1.1  2003/04/08 20:53:01  ben
** Adding more files...
**
** Revision 1.9  2000/07/04 04:51:41  matt
** cleanups
**
** Revision 1.8  2000/07/03 02:18:53  matt
** much better external module exporting
**
** Revision 1.7  2000/06/20 04:06:16  matt
** migrated external sound definition to apu module
**
** Revision 1.6  2000/06/20 00:08:58  matt
** changed to driver based API
**
** Revision 1.5  2000/06/09 16:49:02  matt
** removed all floating point from sound generation
**
** Revision 1.4  2000/06/09 15:12:28  matt
** initial revision
**
*/