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playlib.c
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playlib.c
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/*
** PLAYLIB.C
**
** Public domain for TC only by Lynn R. Lively
** Modified by Bob Stout
*/
#include <dos.h>
#include <stdlib.h>
#include "pchwio.h"
#include "sound.h"
#ifndef __ZTC__
static void (INTERRUPT FAR *n_oldtmint) (void);
#endif
#define TIMER_TICK_INTR 0x1c
static NOTE * n_buff;
static unsigned n_buff_sz;
static NOTE * n_head;
static NOTE * n_tail;
static unsigned play_duration;
static unsigned play_freq;
/*
** Add note to note buff. Return = 1 (note added), 0 (Out of note buff)
*/
int playb_note (unsigned freq, unsigned duration)
{
if (++n_tail == (n_buff + n_buff_sz))
n_tail = n_buff;
if (n_tail == n_head)
{
--n_tail;
return (0);
}
n_tail->freq = freq;
n_tail->duration = duration;
return (1);
}
/*
** ISR for background music.
*/
#ifndef __ZTC__
static void INTERRUPT FAR play_intr (void)
#else
static int play_intr (struct INT_DATA *idp)
#endif
{
int_off ();
#ifndef __ZTC__
(*n_oldtmint) (); /* Call Old timer interrupt. */
#else
int_prev(idp);
#endif
if (play_duration == 0)
{
soundoff ();
if (++n_head == (n_buff + n_buff_sz))
n_head = n_buff;
if (n_head == n_tail)
{
--n_head;
int_on ();
return;
}
play_duration = n_head->duration;
if (0 != (play_freq = n_head->freq))
soundon();
dosound (play_freq);
}
else --play_duration;
int_on ();
#ifdef __ZTC__
return 1; /* Don't chain */
#endif
}
/*
** Call this function to init background music. buff_sz is number of
** notes in the note buffer. Returns pointer to buff or NULL if
** out of heap space.
*/
NOTE * playb_open (unsigned buff_sz)
{
n_buff =
n_head =
n_tail = (NOTE *) calloc (buff_sz, sizeof (NOTE));
if (n_buff != (NOTE *) NULL)
{
n_buff_sz = buff_sz;
play_duration =
play_freq = 0;
#ifdef __ZTC__
int_intercept(TIMER_TICK_INTR, play_intr, 256);
#else
n_oldtmint = getvect (TIMER_TICK_INTR);
setvect (TIMER_TICK_INTR, play_intr);
#endif
}
return (n_buff);
}
/*
** Return things to normal and free allocated space.
*/
void playb_close (void)
{
soundoff ();
#ifndef __ZTC__
setvect (TIMER_TICK_INTR, n_oldtmint);
#else
int_restore(TIMER_TICK_INTR);
#endif
free (n_buff);
}