/*
 * atari_sb.c - DOS Sound Blaster sound port code
 *
 * Copyright (c) 1998-2000 Matthew Conte
 * Copyright (c) 2000-2005 Atari800 development team (see DOC/CREDITS)
 *
 * This file is part of the Atari800 emulator project which emulates
 * the Atari 400, 800, 800XL, 130XE, and 5200 8-bit computers.
 *
 * Atari800 is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * Atari800 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 General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with Atari800; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
*/

/*
 * Note: the information in this file has been gathered from many
 * Internet documents, and from source code written by Ethan Brodsky.
*/

#include "config.h"
#ifdef SOUND

#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <dos.h>
#include <go32.h>
#include <dpmi.h>

#ifdef DJGPP_USE_NEARPTR
#include <sys/nearptr.h>
#endif /* DJGPP_USE_NEARPTR */

#include "atari.h"

/* customize this logging routine as needed */
#include "log.h"
#define  log_printf  Log_print

#include "dos_sb.h"
#include "dos_ints.h"

typedef  char     int8;
typedef  short    int16;
typedef  int      int32;

typedef  unsigned char  uint8;
typedef  unsigned short uint16;
typedef  unsigned int   uint32;

typedef  uint8    boolean;

/* General defines */
#define  LOW_BYTE(x)          ((uint8) (x))
#define  HIGH_BYTE(x)         ((uint8) ((x) >> 8))

#define  INVALID              0xFFFFFFFF
#define  DEFAULT_TIMEOUT      20000

#define  DETECT_POLL_REPS     1000

#define  DSP_VERSION_SB_15    0x0200
#define  DSP_VERSION_SB_20    0x0201
#define  DSP_VERSION_SB_PRO   0x0300
#define  DSP_VERSION_SB16     0x0400

/* Sample format bitfields */
#define  SB_FORMAT_8BIT       0x00
#define  SB_FORMAT_16BIT      0x01
#define  SB_FORMAT_MONO       0x00
#define  SB_FORMAT_STEREO     0x02

/* DSP register offsets */
#define  MIXER_REGISTER       0x04
#define  MIXER_DATA           0x05
#define  DSP_RESET            0x06
#define  DSP_READ             0x0A
#define  DSP_READ_READY       0x0E
#define  DSP_WRITE            0x0C
#define  DSP_WRITE_BUSY       0x0C
#define  DSP_DMA_ACK_8BIT     0x0E
#define  DSP_DMA_ACK_16BIT    0x0F

/* SB 1.0 commands */
#define  DSP_DMA_TIME_CONST   0x40
#define  DSP_DMA_DAC_8BIT     0x14
#define  DSP_DMA_PAUSE_8BIT   0xD0
#define  DSP_DMA_CONT_8BIT    0xD4
#define  DSP_SPEAKER_ON       0xD1
#define  DSP_SPEAKER_OFF      0xD3
#define  DSP_GET_VERSION      0xE1

/* SB 1.5 - Pro commands */
#define  MIXER_OUTPUT_STEREO  0x0E
#define  MIXER_OUTPUT_STEREO_MONO    0x11
#define  MIXER_OUTPUT_STEREO_STEREO  0x13
#define  DSP_DMA_BLOCK_SIZE   0x48
#define  DSP_DMA_DAC_AI_8BIT  0x1C  /* low-speed autoinit */
#define  DSP_DMA_DAC_HS_8BIT  0x90  /* high-speed autoinit */

/* SB16 commands */
#define  DSP_DMA_DAC_RATE     0x41
#define  DSP_DMA_START_16BIT  0xB0
#define  DSP_DMA_START_8BIT   0xC0
#define  DSP_DMA_DAC_MODE     0x06
#define  DSP_DMA_PAUSE_16BIT  0xD5
#define  DSP_DMA_CONT_16BIT   0xD6
#define  DSP_DMA_STOP_8BIT    0xDA

/* DMA flags */
#define  DSP_DMA_UNSIGNED     0x00
#define  DSP_DMA_SIGNED       0x10
#define  DSP_DMA_MONO         0x00
#define  DSP_DMA_STEREO       0x20

/* DMA address/port/command defines */
#define  DMA_MASKPORT_16BIT   0xD4
#define  DMA_MODEPORT_16BIT   0xD6
#define  DMA_CLRPTRPORT_16BIT 0xD8
#define  DMA_ADDRBASE_16BIT   0xC0
#define  DMA_COUNTBASE_16BIT  0XC2
#define  DMA_MASKPORT_8BIT    0x0A
#define  DMA_MODEPORT_8BIT    0x0B
#define  DMA_CLRPTRPORT_8BIT  0x0C
#define  DMA_ADDRBASE_8BIT    0x00
#define  DMA_COUNTBASE_8BIT   0x01
#define  DMA_STOPMASK_BASE    0x04
#define  DMA_STARTMASK_BASE   0x00
#define  DMA_AUTOINIT_MODE    0x58
#define  DMA_ONESHOT_MODE     0x48

/* centerline */
#define  SILENCE_SIGNED       0x00
#define  SILENCE_UNSIGNED     0x80


/* DOS low-memory buffer info */
static struct
{
   _go32_dpmi_seginfo buffer;
   uint32 bufaddr; /* linear address */
   uint32 offset;
   uint32 page;
} dos;

/* Interrupt stuff */
static struct
{
   _go32_dpmi_seginfo old_interrupt;
   _go32_dpmi_seginfo new_interrupt;
   uint32 irq_vector;
   uint8 pic_rotateport;
   uint8 pic_maskport;
   uint8 irq_stopmask;
   uint8 irq_startmask;
} intr;

/* DMA information */
static struct
{
   boolean autoinit;
   volatile int count;
   uint16 addrport;
   uint16 ackport;
} dma;

/* 8 and 16 bit DMA ports */
static const uint8 dma8_ports[4] =  { 0x87, 0x83, 0x81, 0x82 };
static const uint8 dma16_ports[4] = { 0xFF, 0x8B, 0x89, 0x8A };

/* Sound Blaster context */
static struct
{
   boolean initialized;

   uint16 baseio;
   uint16 dsp_version;

   uint32 sample_rate;
   uint8 format;

   uint8 irq, dma, dma16;

   void *buffer;
   uint32 buf_size;
   uint32 buf_chunk;

   sbmix_t callback;
} sb;


/*
** Basic DSP routines
*/
static void dsp_write(uint8 value)
{
   int timeout = DEFAULT_TIMEOUT;

   /* wait until DSP is ready... */
   while (timeout-- && (inportb(sb.baseio + DSP_WRITE_BUSY) & 0x80))
      ; /* loop */

   outportb(sb.baseio + DSP_WRITE, value);
}

static uint8 dsp_read(void)
{
   int timeout = DEFAULT_TIMEOUT;

   while (timeout-- && (0 == (inportb(sb.baseio + DSP_READ_READY) & 0x80)))
      ; /* loop */

   return inportb(sb.baseio + DSP_READ);
}

/* returns TRUE if DSP found and successfully reset, FALSE otherwise */
static boolean dsp_reset(void)
{
   outportb(sb.baseio + DSP_RESET, 1); /* reset command */
   delay(5);                           /* 5 usec delay */
   outportb(sb.baseio + DSP_RESET, 0); /* clear */
   delay(5);                           /* 5 usec delay */

   if (0xAA == dsp_read())
      return TRUE;

   /* BLEH, we failed */
   return FALSE;
}

/* return DSP version in 8:8 major:minor format */
static uint16 dsp_getversion(void)
{
   uint16 major, minor;

   dsp_write(DSP_GET_VERSION);

   major = dsp_read();
   minor = dsp_read();

   return ((major << 8) + minor);
}

/*
** BLASTER environment variable parsing
*/
static boolean get_env_item(char *env, void *ptr, char find, int base, int width)
{
   char *item;
   int value;

   item = strrchr(env, find);
   if (NULL == item)
      return FALSE;

   item++;
   value = strtol(item, NULL, base);

   switch (width) {
   case 32:
      *(uint32 *) ptr = value;
      break;
   case 16:
      *(uint16 *) ptr = value;
      break;
   case 8:
      *(uint8 *) ptr = value;
      break;
   default:
      break;
   }

   return TRUE;
}

/* parse the BLASTER environment variable */
static boolean parse_blaster_env(void)
{
   char blaster[256], *penv;

   penv = getenv("BLASTER");

   /* bail out if we can't find it... */
   if (NULL == penv)
      return FALSE;

   /* copy it, normalize case */
   strcpy(blaster, penv);
   strupr(blaster);

   if (FALSE == get_env_item(blaster, &sb.baseio, 'A', 16, 16))
      return FALSE;
   if (FALSE == get_env_item(blaster, &sb.irq, 'I', 10, 8))
      return FALSE;
   if (FALSE == get_env_item(blaster, &sb.dma, 'D', 10, 8))
      return FALSE;
   get_env_item(blaster, &sb.dma16, 'H', 10, 8);

   return TRUE;
}

/*
** Brute force autodetection code
*/

/* detect the base IO by attempting to
** reset the DSP at known addresses
*/
static uint16 detect_baseio(void)
{
   int i;
   static uint16 port_val[] =
   {
      0x210, 0x220, 0x230, 0x240,
      0x250, 0x260, 0x280, (uint16) INVALID
   };

   for (i = 0; (uint16) INVALID != port_val[i]; i++) {
      sb.baseio = port_val[i];
      if (dsp_reset())
         break;
   }

   /* will return INVALID if not found */
   return port_val[i];
}

/* stop all DSP activity */
static void dsp_stop(void)
{
   /* pause 8/16 bit DMA mode digitized sound IO */
   dsp_reset();
   dsp_write(DSP_DMA_PAUSE_8BIT);
   dsp_write(DSP_DMA_PAUSE_16BIT);
}

/* return number of set bits in byte x */
static int bitcount(uint8 x)
{
   int i, set_count = 0;

   for (i = 0; i < 8; i++)
      if (x & (1 << i))
         set_count++;

   return set_count;
}

/* returns position of lowest bit set in byte x (INVALID if none) */
static int bitpos(uint8 x)
{
   int i;

   for (i = 0; i < 8; i++)
      if (x & (1 << i))
         return i;

   return INVALID;
}

static uint8 detect_dma(boolean high_dma)
{
   uint8 dma_maskout, dma_mask;
   int i;

   /* stop DSP activity */
   dsp_stop();

   dma_maskout = ~0x10; /* initially mask only DMA4 */

   /* poll to find out which dma channels are in use */
   for (i = 0; i < DETECT_POLL_REPS; i++)
      dma_maskout &= ~(inportb(0xD0) & 0xF0) | (inportb(0x08) >> 4);

   /* TODO: this causes a pretty nasty sound */
   /* program card, see whch channel becomes active */
   if (FALSE == high_dma) {
      /* 8 bit */
      dsp_write(DSP_DMA_DAC_8BIT);
      dsp_write(0xF0);
      dsp_write(0xFF);
   }
   else {
      dsp_write(DSP_DMA_START_16BIT); /* 16-bit, D/A, S/C, FIFO off */
      dsp_write(DSP_DMA_SIGNED | DSP_DMA_MONO); /* 16-bit mono signed PCM */
      dsp_write(0xF0);
      dsp_write(0xFF);
   }

   /* poll to find out which DMA channels are in use with sound */
   dma_mask = 0; /* dma channels active during audio, minus masked out */
   for (i = 0; i < DETECT_POLL_REPS; i++)
      dma_mask |= (((inportb(0xD0) & 0xF0) | (inportb(0x08) >> 4)) & dma_maskout);

   /* stop all DSP activity */
   dsp_stop();

   if (1 == bitcount(dma_mask))
      return (uint8) bitpos(dma_mask);
   else
      return (uint8) INVALID;
}

static void dsp_transfer(uint8 dma)
{
   outportb(DMA_MASKPORT_8BIT, DMA_STOPMASK_BASE | dma);

   /* write DMA mode: single-cycle read transfer */
   outportb(DMA_MODEPORT_8BIT, DMA_ONESHOT_MODE | dma);
   outportb(DMA_CLRPTRPORT_8BIT, 0x00);

   /* one transfer */
   outportb(DMA_COUNTBASE_8BIT + (2 * dma), 0x00); /* low */
   outportb(DMA_COUNTBASE_8BIT + (2 * dma), 0x00); /* high */

   /* address */
   outportb(DMA_ADDRBASE_8BIT + (2 * dma), 0x00);
   outportb(DMA_ADDRBASE_8BIT + (2 * dma), 0x00);
   outportb(dma8_ports[dma], 0x00);

   /* unmask DMA channel */
   outportb(DMA_MASKPORT_8BIT, DMA_STARTMASK_BASE | dma);

   /* 8-bit single cycle DMA mode */
   dsp_write(DSP_DMA_DAC_8BIT);
   dsp_write(0x00);
   dsp_write(0x00);
}

#define  MAX_IRQS    11
static _go32_dpmi_seginfo old_handler[MAX_IRQS];
static _go32_dpmi_seginfo new_handler[MAX_IRQS];
static volatile boolean irq_hit[MAX_IRQS];

static void irq2_handler(void)  { irq_hit[2]  = TRUE; }
END_OF_STATIC_FUNCTION(irq2_handler)
static void irq3_handler(void)  { irq_hit[3]  = TRUE; }
END_OF_STATIC_FUNCTION(irq3_handler)
static void irq5_handler(void)  { irq_hit[5]  = TRUE; }
END_OF_STATIC_FUNCTION(irq5_handler)
static void irq7_handler(void)  { irq_hit[7]  = TRUE; }
END_OF_STATIC_FUNCTION(irq7_handler)
static void irq10_handler(void) { irq_hit[10] = TRUE; }
END_OF_STATIC_FUNCTION(irq10_handler)

static void set_handler(int handler, int irq, int vector)
{
   new_handler[irq].pm_offset = (int) handler;
   new_handler[irq].pm_selector = _go32_my_cs();
   _go32_dpmi_get_protected_mode_interrupt_vector(vector, &old_handler[irq]);
   _go32_dpmi_chain_protected_mode_interrupt_vector(vector, &new_handler[irq]);
}

static void ack_interrupt(uint8 irq)
{
   /* acknowledge the interrupts! */
   inportb(sb.baseio + 0x0E);
   if (irq > 7)
      outportb(0xA0, 0x20);
   outportb(0x20, 0x20);
}

static uint8 detect_irq(void)
{
   int pic1_oldmask, pic2_oldmask;
   boolean irq_mask[MAX_IRQS];
   uint8 irq = (uint8) INVALID;
   int i;

   LOCK_FUNCTION(irq2_handler);
   LOCK_FUNCTION(irq3_handler);
   LOCK_FUNCTION(irq5_handler);
   LOCK_FUNCTION(irq7_handler);
   LOCK_FUNCTION(irq10_handler);
   LOCK_VARIABLE(irq_hit);

   /* install temp handlers */
   set_handler((int) irq2_handler, 2, 0x0A);
   set_handler((int) irq3_handler, 3, 0x0B);
   set_handler((int) irq5_handler, 5, 0x0D);
   set_handler((int) irq7_handler, 7, 0x0F);
   set_handler((int) irq10_handler, 10, 0x72);

   for (i = 0; i < MAX_IRQS; i++)
      irq_hit[i] = FALSE;

   /* save old IRQ mask and unmask IRQs */
   pic1_oldmask = inportb(0x21);
   outportb(0x21, pic1_oldmask & 0x53);
   pic2_oldmask = inportb(0xA1);
   outportb(0xA1, pic1_oldmask & 0xFB);

   /* wait to see what interrupts are triggered without sound */
   delay(100);

   /* mask out any interrupts triggered without sound */
   for (i = 0; i < MAX_IRQS; i++) {
      irq_mask[i] = irq_hit[i];
      irq_hit[i] = FALSE;
   }

   /* try to trigger an interrupt using DSP command F2 */
   dsp_write(0xF2);

   delay(100);

   /* detect triggered interrupts */
   for (i = 0; i < MAX_IRQS; i++) {
      if (TRUE == irq_hit[i] && FALSE == irq_mask[i]) {
         irq = i;
         ack_interrupt(irq);
      }
   }

   /* if F2 fails to trigger an int, run a short transfer */
   if ((uint8) INVALID == irq) {
      dsp_reset();
      dsp_transfer(sb.dma);

      delay(100);

      /* detect triggered interrupts */
      for (i = 0; i < MAX_IRQS; i++) {
         if (TRUE == irq_hit[i] && FALSE == irq_mask[i]) {
            irq = i;
            ack_interrupt(irq);
         }
      }
   }

   /* reset DSP just in case */
   dsp_reset();

   /* remask IRQs */
   outportb(0x21, pic1_oldmask);
   outportb(0xA1, pic2_oldmask);

   /* uninstall handlers */
   _go32_dpmi_set_protected_mode_interrupt_vector(0x0A, &old_handler[2]);
   _go32_dpmi_set_protected_mode_interrupt_vector(0x0B, &old_handler[3]);
   _go32_dpmi_set_protected_mode_interrupt_vector(0x0D, &old_handler[5]);
   _go32_dpmi_set_protected_mode_interrupt_vector(0x0F, &old_handler[7]);
   _go32_dpmi_set_protected_mode_interrupt_vector(0x72, &old_handler[10]);

   return irq;
}

/* try and detect an SB without environment variables */
static boolean sb_detect(void)
{
   sb.baseio = detect_baseio();
   if ((uint16) INVALID == sb.baseio)
      return FALSE;

   sb.dma = detect_dma(FALSE);
   if ((uint8) INVALID == sb.dma)
      return FALSE;

   sb.dma16 = detect_dma(TRUE);
   if ((uint8) INVALID == sb.dma16)
      return FALSE;

   sb.irq = detect_irq();
   if ((uint8) INVALID == sb.irq)
      return FALSE;

   return TRUE;
}

/*
** Probe for an SB
*/
static boolean sb_probe(void)
{
   boolean success = FALSE;
   int probe;

   for (probe = 0; probe < 2; probe++)
   {
      /* first time look for BLASTER=,
      ** second time, probe the hardware
      */
      if (0 == probe)
         success = parse_blaster_env();
      else
         success = sb_detect();

      if (FALSE == success)
         continue;

      if (FALSE == dsp_reset()) {
         log_printf("could not reset SB DSP: check BLASTER= variable\n");
      }
      else {
         sb.dsp_version = dsp_getversion();
         return TRUE;
      }
   }

   return FALSE;
}

/* copy data to DOS memory buffer */
#ifdef DJGPP_USE_NEARPTR
#define  DOS_PUTBUFFER(dest, src, len)
#else /* !DJGPP_USE_NEARPTR */
#define  DOS_PUTBUFFER(dest, src, len) dosmemput((src), (len), (dest))
#endif /* !DJGPP_USE_NEARPTR */

/*
** Interrupt handler for 8/16-bit audio
*/

static void sb_isr(void)
{
   uint32 address;

   /* maybe needed for slow machines? */
   /*DISABLE_INTS();*/

   dma.count++;

   /* NOTE: this only works with 8-bit, as one-shot mode
   ** does not seem to work with 16-bit transfers
   */
   if (FALSE == dma.autoinit) {
      dsp_write(DSP_DMA_DAC_8BIT);
      dsp_write(LOW_BYTE(sb.buf_size - 1));
      dsp_write(HIGH_BYTE(sb.buf_size - 1));
   }

   /* indicate we got the interrupt */
   inportb(dma.ackport);

   /* determine the current playback position */
   address = inportb(dma.addrport);
   address |= (inportb(dma.addrport) << 8);
   address -= dos.offset;

   if (address < sb.buf_size) {
      sb.callback((uint8 *) sb.buffer + sb.buf_chunk, sb.buf_size);
      DOS_PUTBUFFER(dos.bufaddr + sb.buf_chunk, (uint8 *) sb.buffer + sb.buf_chunk, sb.buf_chunk);
   }
   else {
      sb.callback(sb.buffer, sb.buf_size);
      DOS_PUTBUFFER(dos.bufaddr, sb.buffer, sb.buf_chunk);
   }

   /* acknowledge interrupt was taken */
   if (sb.irq > 7)
      outportb(0xA0, 0x20);
   outportb(0x20, 0x20);

   /* maybe needed for slow machines? */
   /*ENABLE_INTS();*/
}
END_OF_STATIC_FUNCTION(sb_isr)


/* install the SB ISR */
static void sb_setisr(void)
{
   /* lock variables, routines */
   LOCK_VARIABLE(dma);
   LOCK_VARIABLE(dos);
   LOCK_VARIABLE(sb);
   LOCK_FUNCTION(sb_isr);

   if (sb.format & SB_FORMAT_16BIT) {
      dma.ackport = sb.baseio + DSP_DMA_ACK_16BIT;
      dma.addrport = DMA_ADDRBASE_16BIT + (4 * (sb.dma16 - 4));
   }
   else {
      dma.ackport = sb.baseio + DSP_DMA_ACK_8BIT;
      dma.addrport = DMA_ADDRBASE_8BIT + (2 * sb.dma);
   }

   if (sb.irq < 8) {
      /* PIC 1 */
      intr.irq_vector = 0x08 + sb.irq;
      intr.pic_rotateport = 0x20;
      intr.pic_maskport = 0x21;
   }
   else {
      /* PIC 2 */
      intr.irq_vector = 0x70 + (sb.irq - 8);
      intr.pic_rotateport = 0xA0;
      intr.pic_maskport = 0xA1;
   }

   intr.irq_stopmask = 1 << (sb.irq % 8);
   intr.irq_startmask = ~intr.irq_stopmask;

   /* reset DMA count */
   dma.count = 0;

   DISABLE_INTS();

   outportb(intr.pic_maskport, inportb(intr.pic_maskport) | intr.irq_stopmask);

   _go32_dpmi_get_protected_mode_interrupt_vector(intr.irq_vector, &intr.old_interrupt);
   intr.new_interrupt.pm_offset = (int) sb_isr;
   intr.new_interrupt.pm_selector = _go32_my_cs();
   _go32_dpmi_allocate_iret_wrapper(&intr.new_interrupt);
   _go32_dpmi_set_protected_mode_interrupt_vector(intr.irq_vector, &intr.new_interrupt);

   /* unmask the PIC, get things ready to roll */
   outportb(intr.pic_maskport, inportb(intr.pic_maskport) & intr.irq_startmask);

   ENABLE_INTS();
}

/* remove SB ISR, restore old */
static void sb_resetisr(void)
{
   DISABLE_INTS();

   outportb(intr.pic_maskport, inportb(intr.pic_maskport) | intr.irq_stopmask);

   _go32_dpmi_set_protected_mode_interrupt_vector(intr.irq_vector, &intr.old_interrupt);
   _go32_dpmi_free_iret_wrapper(&intr.new_interrupt);

   ENABLE_INTS();
}

/* allocate sound buffers */
static boolean sb_allocate_buffers(int buf_size)
{
   int double_bufsize;

   /* TODO: I don't like this. */
   if (sb.format & SB_FORMAT_16BIT) {
      sb.buf_size = 2 * buf_size;
      sb.buf_chunk = sb.buf_size * sizeof(uint16);
   }
   else {
      sb.buf_size = buf_size;
      sb.buf_chunk = sb.buf_size * sizeof(uint8);
   }

   double_bufsize = 2 * sb.buf_chunk;

   dos.buffer.size = (double_bufsize + 15) >> 4;
   if (_go32_dpmi_allocate_dos_memory(&dos.buffer))
      return FALSE;

   /* calc linear address */
   dos.bufaddr = dos.buffer.rm_segment << 4;
   if (sb.format & SB_FORMAT_16BIT)
   {
      dos.page = (dos.bufaddr >> 16) & 0xFF;
      /* bleh! thanks, creative! */
      dos.offset = (dos.bufaddr >> 1) & 0xFFFF;
   }
   else
   {
      dos.page = (dos.bufaddr >> 16) & 0xFF;
      dos.offset = dos.bufaddr & 0xFFFF;
   }

#ifdef DJGPP_USE_NEARPTR
   sb.buffer = (uint8 *) dos.bufaddr + __djgpp_conventional_base;
#else /* !DJGPP_USE_NEARPTR */
   sb.buffer = malloc(double_bufsize);
   if (NULL == sb.buffer)
      return FALSE;
#endif /* !DJGPP_USE_NEARPTR */

   /* clear out the buffers */
   if (sb.format & SB_FORMAT_16BIT)
      memset(sb.buffer, SILENCE_SIGNED, double_bufsize);
   else
      memset(sb.buffer, SILENCE_UNSIGNED, double_bufsize);

   DOS_PUTBUFFER(dos.bufaddr, sb.buffer, double_bufsize);

   return TRUE;
}

/* free them buffers */
static void sb_free_buffers(void)
{
   sb.callback = NULL;

   _go32_dpmi_free_dos_memory(&dos.buffer);

#ifndef DJGPP_USE_NEARPTR
   free(sb.buffer);
#endif /* !DJGPP_USE_NEARPTR */

   sb.buffer = NULL;
}

/* get rid of all things SB */
void sb_shutdown(void)
{
   if (TRUE == sb.initialized) {
      sb.initialized = FALSE;

      dsp_reset();
      sb_resetisr();
      sb_free_buffers();
   }
}

/* initialize sound bastard */
int sb_init(int *sample_rate, int *bps, int *buf_size, int *stereo)
{
#define  CLAMP_RATE(in_rate, min_rate, max_rate) \
                    (in_rate < min_rate ? min_rate : \
                    (in_rate > max_rate ? max_rate : in_rate))

   /* don't init twice! */
   if (TRUE == sb.initialized)
      return 0;

   memset(&sb, 0, sizeof(sb));

   if (FALSE == sb_probe())
      return -1;

   log_printf("\nSB DSP version: %d.%d baseio: %X IRQ: %d DMA: %d High: %d\n",
              sb.dsp_version >> 8, sb.dsp_version & 0xFF,
              sb.baseio, sb.irq, sb.dma, sb.dma16);

   /* try autoinit DMA first */
   dma.autoinit = TRUE;
   sb.format = (16 == *bps) ? SB_FORMAT_16BIT : SB_FORMAT_8BIT;
   sb.format |= *stereo ? SB_FORMAT_STEREO : SB_FORMAT_MONO;

   /* determine which SB model we have, and act accordingly */
   if (sb.dsp_version < DSP_VERSION_SB_15) {
      /* SB 1.0 */
      sb.sample_rate = CLAMP_RATE(*sample_rate, 4000, 22050);
      sb.format &= ~(SB_FORMAT_16BIT | SB_FORMAT_STEREO);
      dma.autoinit = FALSE;
   }
   else if (sb.dsp_version < DSP_VERSION_SB_20) {
      /* SB 1.5 */
      sb.sample_rate = CLAMP_RATE(*sample_rate, 5000, 22050);
      sb.format &= ~(SB_FORMAT_16BIT | SB_FORMAT_STEREO);
   }
   else if (sb.dsp_version < DSP_VERSION_SB_PRO) {
      /* SB 2.0 */
      sb.sample_rate = CLAMP_RATE(*sample_rate, 5000, 44100);
      sb.format &= ~(SB_FORMAT_16BIT | SB_FORMAT_STEREO);
   }
   else if (sb.dsp_version < DSP_VERSION_SB16) {
      /* SB Pro */
      if (sb.format & SB_FORMAT_STEREO)
         sb.sample_rate = CLAMP_RATE(*sample_rate, 5000, 22050);
      else
         sb.sample_rate = CLAMP_RATE(*sample_rate, 5000, 44100);
      sb.format &= ~SB_FORMAT_16BIT;
   }
   else {
      /* SB 16 */
      sb.sample_rate = CLAMP_RATE(*sample_rate, 5000, 44100);
   }

   /* sanity check for 16-bit */
   if ((sb.format & SB_FORMAT_16BIT) && ((uint8) INVALID == sb.dma16)) {
      sb.format &= ~SB_FORMAT_16BIT;
      log_printf("16-bit DMA channel not available, dropping to 8-bit\n");
   }

   /* allocate buffer / DOS memory */
   if (FALSE == sb_allocate_buffers(*buf_size))
      return -1;

   /* set the new IRQ vector! */
   sb_setisr();

   sb.initialized = TRUE;

   /* return the actual values */
   *sample_rate = sb.sample_rate;
   *buf_size = sb.buf_size;
   *bps = (sb.format & SB_FORMAT_16BIT) ? 16 : 8;
   *stereo = (sb.format & SB_FORMAT_STEREO) ? TRUE : FALSE;
   return 0;
}

void sb_stopoutput(void)
{
   if (TRUE == sb.initialized) {
      if (sb.format & SB_FORMAT_16BIT) {
         dsp_write(DSP_DMA_PAUSE_16BIT);  /* pause 16-bit DMA */
         dsp_write(DSP_DMA_STOP_8BIT);
         dsp_write(DSP_DMA_PAUSE_16BIT);
      }
      else {
         dsp_write(DSP_DMA_PAUSE_8BIT);  /* pause 8-bit DMA */
         dsp_write(DSP_SPEAKER_OFF);
      }
   }
}

/* return time constant for older sound bastards */
static uint8 get_time_constant(int rate)
{
   return ((65536 - (256000000L / rate)) >> 8);
}

static void init_samplerate(int rate)
{
   if ((sb.format & SB_FORMAT_STEREO))
      rate *= 2;
   if ((sb.format & SB_FORMAT_16BIT) || sb.dsp_version >= DSP_VERSION_SB16) {
      dsp_write(DSP_DMA_DAC_RATE);
      dsp_write(HIGH_BYTE(rate));
      dsp_write(LOW_BYTE(rate));
   }
   else {
      dsp_write(DSP_DMA_TIME_CONST);
      dsp_write(get_time_constant(rate));
   }
}

/* set the sample rate */
void sb_setrate(int rate)
{
   if (sb.format & SB_FORMAT_16BIT) {
      dsp_write(DSP_DMA_PAUSE_16BIT);  /* pause 16-bit DMA */
      init_samplerate(rate);
      dsp_write(DSP_DMA_CONT_16BIT);   /* continue 16-bit DMA */
   }
   else {
      dsp_write(DSP_DMA_PAUSE_8BIT);   /* pause 8-bit DMA */
      init_samplerate(rate);
      dsp_write(DSP_DMA_CONT_8BIT);    /* continue 8-bit DMA */
   }

   sb.sample_rate = rate;
}

/* start SB DMA transfer */
static void start_transfer(void)
{
   uint8 dma_mode, start_command, mode_command;
   int dma_length;

   dma.count = 0;

   dma_length = sb.buf_size << 1;

   if (TRUE == dma.autoinit) {
      start_command = DSP_DMA_DAC_MODE;   /* autoinit DMA */
      dma_mode = DMA_AUTOINIT_MODE;
   }
   else {
      start_command = 0;
      dma_mode = DMA_ONESHOT_MODE;
   }

   /* things get a little bit nasty here, look out */
   if (sb.format & SB_FORMAT_16BIT) {
      uint8 dma_base = sb.dma16 - 4;

      dma_mode |= dma_base;
      start_command |= DSP_DMA_START_16BIT;
      mode_command = DSP_DMA_SIGNED;

      outportb(DMA_MASKPORT_16BIT, DMA_STOPMASK_BASE | dma_base);
      outportb(DMA_MODEPORT_16BIT, dma_mode);
      outportb(DMA_CLRPTRPORT_16BIT, 0x00);
      outportb(DMA_ADDRBASE_16BIT + (4 * dma_base), LOW_BYTE(dos.offset));
      outportb(DMA_ADDRBASE_16BIT + (4 * dma_base), HIGH_BYTE(dos.offset));
      outportb(DMA_COUNTBASE_16BIT + (4 * dma_base), LOW_BYTE(dma_length - 1));
      outportb(DMA_COUNTBASE_16BIT + (4 * dma_base), HIGH_BYTE(dma_length - 1));
      outportb(dma16_ports[dma_base], dos.page);
      outportb(DMA_MASKPORT_16BIT, DMA_STARTMASK_BASE | dma_base);
   }
   else {
      dma_mode |= sb.dma;
      start_command |= DSP_DMA_START_8BIT;
      mode_command = DSP_DMA_UNSIGNED;

      outportb(DMA_MASKPORT_8BIT, DMA_STOPMASK_BASE + sb.dma);
      outportb(DMA_MODEPORT_8BIT, dma_mode);
      outportb(DMA_CLRPTRPORT_8BIT, 0x00);
      outportb(DMA_ADDRBASE_8BIT + (2 * sb.dma), LOW_BYTE(dos.offset));
      outportb(DMA_ADDRBASE_8BIT + (2 * sb.dma), HIGH_BYTE(dos.offset));
      outportb(DMA_COUNTBASE_8BIT + (2 * sb.dma), LOW_BYTE(dma_length - 1));
      outportb(DMA_COUNTBASE_8BIT + (2 * sb.dma), HIGH_BYTE(dma_length - 1));
      outportb(dma8_ports[sb.dma], dos.page);
      outportb(DMA_MASKPORT_8BIT, DMA_STARTMASK_BASE + sb.dma);
   }

   /* check stereo */
   if (sb.format & SB_FORMAT_STEREO)
      mode_command |= DSP_DMA_STEREO;
   else
      mode_command |= DSP_DMA_MONO;

   init_samplerate(sb.sample_rate);

   /* start things going */
   if ((sb.format & SB_FORMAT_16BIT) || sb.dsp_version >= DSP_VERSION_SB16) {
      dsp_write(start_command);
      dsp_write(mode_command);
      dsp_write(LOW_BYTE(sb.buf_size - 1));
      dsp_write(HIGH_BYTE(sb.buf_size - 1));
   }
   else {
      /* turn on speaker */
      dsp_write(DSP_SPEAKER_ON);

      if (TRUE == dma.autoinit) {
         dsp_write(DSP_DMA_BLOCK_SIZE);  /* set buffer size */
         dsp_write(LOW_BYTE(sb.buf_size - 1));
         dsp_write(HIGH_BYTE(sb.buf_size - 1));

         if (sb.dsp_version < DSP_VERSION_SB_20)
            dsp_write(DSP_DMA_DAC_AI_8BIT); /* low speed autoinit */
         else
            dsp_write(DSP_DMA_DAC_HS_8BIT);
      }
      else
      {
         dsp_write(DSP_DMA_DAC_8BIT);
         dsp_write(LOW_BYTE(sb.buf_size - 1));
         dsp_write(HIGH_BYTE(sb.buf_size - 1));
      }
   }
}

/* start playing the output buffer */
int sb_startoutput(sbmix_t fillbuf)
{
   int count;

   /* make sure we really should be here... */
   if (FALSE == sb.initialized || NULL == fillbuf)
      return -1;

   /* stop any current processing */
   sb_stopoutput();

   /* set the callback routine */
   sb.callback = fillbuf;

   /* XXX: is this all MIXER stuff necessary? */
   /* outportb(sb.baseio, 0); */
   outportb(sb.baseio + MIXER_REGISTER, MIXER_OUTPUT_STEREO);
   outportb(sb.baseio + MIXER_DATA, (sb.format & SB_FORMAT_STEREO) ? MIXER_OUTPUT_STEREO_STEREO : MIXER_OUTPUT_STEREO_MONO);

   /* get the transfer going */
   start_transfer();

   /* this ugly bit of code checks to see we really have
   ** interrupts firing at this point...
   */
   count = clock();
   while (((clock() - count) < CLOCKS_PER_SEC / 2) && (dma.count < 2))
      ; /* loop */

   if (dma.count < 2) {
      if (TRUE == dma.autoinit) {
         log_printf("Autoinit DMA failed, trying one-shot mode.\n");
         dsp_reset();
         dma.autoinit = FALSE;
         dma.count = 0;
         return (sb_startoutput(fillbuf));
      }
      else {
         log_printf("One-shot DMA mode failed, sound will not be heard.\n");
         log_printf("%d counts\n", dma.count);
         return -1;
      }
   }
   else
      return 0;
}

#endif /* SOUND */
