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/* tempomap.c -- used by midifile reader to record and lookup time maps */
/*
* This module is designed to provide tempo change list insert and
* lookup facilities. The exact interpretation of beat and tempo are
* defined in one function, elapsed_time, which takes a tempo and a
* number of beats, and returns time.
*/
#include "cext.h"
#include "midifns.h"
#include "timebase.h"
#include "moxc.h"
#include "seq.h"
#include "tempomap.h"
static time_type elapsed_time();
/* tempomap_create -- create a tempomap */
/**/
tempomap_type tempomap_create()
{
tempochange_type tempochange = tempochange_alloc();
tempomap_type tempomap = tempomap_alloc();
tempomap->hint = tempomap->entries = tempochange;
tempochange->beat = 0L;
/* default tempo is 120 (= 50000microsec/beat) and 24 divisions/quarter */
/* this may be overridden by a tempomap_insert */
tempochange->tempo = 500000L / 24;
tempochange->rtime = 0L;
tempochange->next = NULL;
return tempomap;
}
/* tempomap_free -- deallocate storage for tempo map */
/**/
void tempomap_free(tm)
tempomap_type tm;
{
while (tm->entries) {
tempochange_type tc = tm->entries;
tm->entries = tc->next;
tempochange_free(tc);
}
memfree(tm, sizeof(tempomap_node));
}
/* tempomap_insert -- insert a tempo change into the map */
/**/
void tempomap_insert(tempomap, beat, tempo)
tempomap_type tempomap;
long beat; /* beat division number */
long tempo; /* microseconds per beat division */
{
tempochange_type tempochange = tempochange_alloc();
register tempochange_type prev;
register tempochange_type next;
tempochange->tempo = tempo;
tempochange->beat = beat;
if ((!(tempomap->hint->next)) ||
(tempomap->hint->beat > beat))
tempomap->hint = tempomap->entries;
/* find the insert point */
for (prev = tempomap->hint;
(next = prev->next) && (next->beat <= beat);
prev = next);
/* make the insert */
tempochange->next = next;
prev->next = tempochange;
tempomap->hint = prev;
/* update the real time of each change */
for (tempochange = prev;
tempochange->next;
tempochange = tempochange->next) {
tempochange->next->rtime =
tempochange->rtime +
elapsed_time(tempochange->tempo,
tempochange->next->beat - tempochange->beat);
}
}
/* tempomap_lookup -- convert beat to 4us time */
/*
* The returned time is real time in units of 4us.
*/
time_type tempomap_lookup(tempomap, beat)
tempomap_type tempomap;
long beat;
{
register tempochange_type prev;
register tempochange_type next;
if ((!(tempomap->hint->next)) ||
(tempomap->hint->beat > beat))
tempomap->hint = tempomap->entries;
/* find the last inflection point */
for (prev = tempomap->hint;
(next = prev->next) && (next->beat <= beat);
prev = next);
/* interpolate */
return prev->rtime +
elapsed_time(prev->tempo, beat - prev->beat);
}
/* elapsed_time -- compute the real elapsed time at a given tempo */
/*
* the time returned is in units of 4us.
*/
static time_type elapsed_time(tempo, beat)
long tempo;
long beat;
{
return (time_type)((tempo * beat) >> 2);
}
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