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NetBSD/usr.bin/midiplay/midiplay.c

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/* $NetBSD: midiplay.c,v 1.25 2006/07/01 11:05:42 he Exp $ */
/*
* Copyright (c) 1998, 2002 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Lennart Augustsson (augustss@NetBSD.org).
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the NetBSD
* Foundation, Inc. and its contributors.
* 4. Neither the name of The NetBSD Foundation nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
* ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*/
#include <sys/cdefs.h>
#ifndef lint
__RCSID("$NetBSD: midiplay.c,v 1.25 2006/07/01 11:05:42 he Exp $");
#endif
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <err.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/ioctl.h>
#include <sys/midiio.h>
#define DEVMUSIC "/dev/music"
struct track {
struct track *indirect; /* for fast swaps in heap code */
u_char *start, *end;
u_long delta;
u_char status;
};
#define MIDI_META 0xff
#define META_SEQNO 0x00
#define META_TEXT 0x01
#define META_COPYRIGHT 0x02
#define META_TRACK 0x03
#define META_INSTRUMENT 0x04
#define META_LYRIC 0x05
#define META_MARKER 0x06
#define META_CUE 0x07
#define META_CHPREFIX 0x20
#define META_EOT 0x2f
#define META_SET_TEMPO 0x51
#define META_KEY 0x59
#define META_SMPTE 0x54
#define META_TIMESIGN 0x58
char *metanames[] = {
"", "Text", "Copyright", "Track", "Instrument",
"Lyric", "Marker", "Cue",
};
static int midi_lengths[] = { 2,2,2,2,1,1,2,0 };
/* Number of bytes in a MIDI command */
#define MIDI_LENGTH(d) (midi_lengths[((d) >> 4) & 7])
void usage(void);
void send_event(seq_event_t *);
void dometa(u_int, u_char *, u_int);
void midireset(void);
void send_sysex(u_char *, u_int);
u_long getvar(struct track *);
u_long getlen(struct track *);
void playfile(FILE *, char *);
void playdata(u_char *, u_int, char *);
int main(int argc, char **argv);
void Heapify(struct track *, int, int);
void BuildHeap(struct track *, int);
int ShrinkHeap(struct track *, int);
/*
* This sample plays at an apparent tempo of 120 bpm when the BASETEMPO is 150
* bpm, because the quavers are 5 divisions (4 on 1 off) rather than 4 total.
*/
#define P(c) 1,0x90,c,0x7f,4,0x80,c,0
#define PL(c) 1,0x90,c,0x7f,8,0x80,c,0
#define C 0x3c
#define D 0x3e
#define E 0x40
#define F 0x41
u_char sample[] = {
'M','T','h','d', 0,0,0,6, 0,1, 0,1, 0,8,
'M','T','r','k', 0,0,0,4+13*8,
P(C), P(C), P(C), P(E), P(D), P(D), P(D),
P(F), P(E), P(E), P(D), P(D), PL(C),
0, 0xff, 0x2f, 0
};
#undef P
#undef PL
#undef C
#undef D
#undef E
#undef F
#define MARK_HEADER "MThd"
#define MARK_TRACK "MTrk"
#define MARK_LEN 4
#define RMID_SIG "RIFF"
#define RMID_MIDI_ID "RMID"
#define RMID_DATA_ID "data"
#define SIZE_LEN 4
#define HEADER_LEN 6
#define GET8(p) ((p)[0])
#define GET16(p) (((p)[0] << 8) | (p)[1])
#define GET24(p) (((p)[0] << 16) | ((p)[1] << 8) | (p)[2])
#define GET32(p) (((p)[0] << 24) | ((p)[1] << 16) | ((p)[2] << 8) | (p)[3])
#define GET32_LE(p) (((p)[3] << 24) | ((p)[2] << 16) | ((p)[1] << 8) | (p)[0])
void
usage(void)
{
printf("usage: %s [-d unit] [-f file] [-l] [-m] [-p pgm] [-q] "
"[-t %%tempo] [-v] [-x] [file ...]\n",
getprogname());
exit(1);
}
int showmeta = 0;
int verbose = 0;
#define BASETEMPO 400000 /* us/beat(=24 clks or qn) (150 bpm) */
u_int tempo_set = 0;
u_int tempo_abs = 0;
u_int ttempo = 100;
int unit = 0;
int play = 1;
int fd = -1;
int sameprogram = 0;
int insysex = 0;
int svsysex = 0; /* number of sysex bytes saved internally */
void
send_event(seq_event_t *ev)
{
/*
printf("%02x %02x %02x %02x %02x %02x %02x %02x\n",
ev->arr[0], ev->arr[1], ev->arr[2], ev->arr[3],
ev->arr[4], ev->arr[5], ev->arr[6], ev->arr[7]);
*/
if (play)
write(fd, ev, sizeof *ev);
}
u_long
getvar(struct track *tp)
{
u_long r, c;
r = 0;
do {
c = *tp->start++;
r = (r << 7) | (c & 0x7f);
} while ((c & 0x80) && tp->start < tp->end);
return r;
}
u_long
getlen(struct track *tp)
{
u_long len;
len = getvar(tp);
if (tp->start + len > tp->end)
errx(1, "bogus item length exceeds remaining track size");
return len;
}
void
dometa(u_int meta, u_char *p, u_int len)
{
static char const * const keys[] = {
"Cb", "Gb", "Db", "Ab", "Eb", "Bb", "F",
"C",
"G", "D", "A", "E", "B", "F#", "C#",
"G#", "D#", "A#" /* for minors */
};
seq_event_t ev;
uint32_t usperbeat;
switch (meta) {
case META_TEXT:
case META_COPYRIGHT:
case META_TRACK:
case META_INSTRUMENT:
case META_LYRIC:
case META_MARKER:
case META_CUE:
if (showmeta) {
printf("%s: ", metanames[meta]);
fwrite(p, len, 1, stdout);
printf("\n");
}
break;
case META_SET_TEMPO:
usperbeat = GET24(p);
ev = SEQ_MK_TIMING(TEMPO,
.bpm=(60000000. / usperbeat) * (ttempo / 100.) + 0.5);
if (showmeta)
printf("Tempo: %u us/'beat'(24 midiclks)"
" at %u%%; adjusted bpm = %u\n",
usperbeat, ttempo, ev.t_TEMPO.bpm);
if (tempo_abs)
warnx("tempo event ignored"
" in absolute-timed MIDI file");
else {
send_event(&ev);
if (!tempo_set) {
tempo_set = 1;
send_event(&SEQ_MK_TIMING(START));
}
}
break;
case META_TIMESIGN:
ev = SEQ_MK_TIMING(TIMESIG,
.numerator=p[0], .lg2denom=p[1],
.clks_per_click=p[2], .dsq_per_24clks=p[3]);
if (showmeta) {
printf("Time signature: %d/%d."
" Click every %d midiclk%s"
" (24 midiclks = %d 32nd note%s)\n",
ev.t_TIMESIG.numerator,
1 << ev.t_TIMESIG.lg2denom,
ev.t_TIMESIG.clks_per_click,
1 == ev.t_TIMESIG.clks_per_click ? "" : "s",
ev.t_TIMESIG.dsq_per_24clks,
1 == ev.t_TIMESIG.dsq_per_24clks ? "" : "s");
}
/* send_event(&ev); not implemented in sequencer */
break;
case META_KEY:
if (showmeta)
printf("Key: %s %s\n",
keys[((char)p[0]) + p[1] ? 10 : 7],
p[1] ? "minor" : "major");
break;
default:
break;
}
}
void
midireset(void)
{
/* General MIDI reset sequence */
send_event(&SEQ_MK_SYSEX(unit,[0]=0x7e, 0x7f, 0x09, 0x01, 0xf7));
}
#define SYSEX_CHUNK 6
void
send_sysex(u_char *p, u_int l)
{
seq_event_t event;
static u_char bf[6];
if ( 0 == l ) {
warnx("zero-length system-exclusive event");
return;
}
/*
* This block is needed only to handle the possibility that a sysex
* message is broken into multiple events in a MIDI file that do not
* have length six; the /dev/music sequencer assumes a sysex message is
* finished with the first SYSEX event carrying fewer than six bytes,
* even if the last is not MIDI_SYSEX_END. So, we need to be careful
* not to send a short sysex event until we have seen the end byte.
* Instead, save some straggling bytes in bf, and send when we have a
* full six (or an end byte). Note bf/saved/insysex should be per-
* device, if we supported output to more than one device at a time.
*/
if ( svsysex > 0 ) {
if ( l > sizeof bf - svsysex ) {
memcpy(bf + svsysex, p, sizeof bf - svsysex);
l -= sizeof bf - svsysex;
p += sizeof bf - svsysex;
send_event(&SEQ_MK_SYSEX(unit,[0]=
bf[0],bf[1],bf[2],bf[3],bf[4],bf[5]));
svsysex = 0;
} else {
memcpy(bf + svsysex, p, l);
svsysex += l;
p += l;
if ( MIDI_SYSEX_END == bf[svsysex-1] ) {
event = SEQ_MK_SYSEX(unit);
memcpy(event.sysex.buffer, bf, svsysex);
send_event(&event);
svsysex = insysex = 0;
} else
insysex = 1;
return;
}
}
/*
* l > 0. May as well test now whether we will be left 'insysex'
* after processing this event.
*/
insysex = ( MIDI_SYSEX_END != p[l-1] );
/*
* If not for multi-event sysexes and chunk-size weirdness, this
* function could pretty much start here. :)
*/
while ( l >= SYSEX_CHUNK ) {
send_event(&SEQ_MK_SYSEX(unit,[0]=
p[0],p[1],p[2],p[3],p[4],p[5]));
p += SYSEX_CHUNK;
l -= SYSEX_CHUNK;
}
if ( l > 0 ) {
if ( insysex ) {
memcpy(bf, p, l);
svsysex = l;
} else { /* a <6 byte chunk is ok if it's REALLY the end */
event = SEQ_MK_SYSEX(unit);
memcpy(event.sysex.buffer, p, l);
send_event(&event);
}
}
}
void
playfile(FILE *f, char *name)
{
u_char *buf, *nbuf;
u_int tot, n, size, nread;
/*
* We need to read the whole file into memory for easy processing.
* Using mmap() would be nice, but some file systems do not support
* it, nor does reading from e.g. a pipe. The latter also precludes
* finding out the file size without reading it.
*/
size = 1000;
buf = malloc(size);
if (buf == 0)
errx(1, "malloc() failed");
nread = size;
tot = 0;
for (;;) {
n = fread(buf + tot, 1, nread, f);
tot += n;
if (n < nread)
break;
/* There must be more to read. */
nread = size;
nbuf = realloc(buf, size * 2);
if (nbuf == NULL)
errx(1, "realloc() failed");
buf = nbuf;
size *= 2;
}
playdata(buf, tot, name);
free(buf);
}
void
playdata(u_char *buf, u_int tot, char *name)
{
int format, ntrks, divfmt, ticks, t;
u_int len, mlen, status, chan;
u_char *p, *end, byte, meta, *msg;
struct track *tracks;
struct track *tp;
end = buf + tot;
if (verbose)
printf("Playing %s (%d bytes) ... \n", name, tot);
if (tot < MARK_LEN + 4) {
warnx("Not a MIDI file, too short");
return;
}
if (memcmp(buf, RMID_SIG, MARK_LEN) == 0) {
u_char *eod;
/* Detected a RMID file, let's just check if it's
* a MIDI file */
if (GET32_LE(buf + MARK_LEN) != tot - 8) {
warnx("Not a RMID file, bad header");
return;
}
buf += MARK_LEN + 4;
if (memcmp(buf, RMID_MIDI_ID, MARK_LEN) != 0) {
warnx("Not a RMID file, bad ID");
return;
}
/* Now look for the 'data' chunk, which contains
* MIDI data */
buf += MARK_LEN;
/* Test against end-8 since we must have at least 8 bytes
* left to read */
while(buf < end-8 && memcmp(buf, RMID_DATA_ID, MARK_LEN))
buf += GET32_LE(buf+4) + 8; /* MARK_LEN + 4 */
if (buf >= end-8) {
warnx("Not a valid RMID file, no data chunk");
return;
}
buf += MARK_LEN; /* "data" */
eod = buf + 4 + GET32_LE(buf);
if (eod >= end) {
warnx("Not a valid RMID file, bad data chunk size");
return;
}
end = eod;
buf += 4;
}
if (memcmp(buf, MARK_HEADER, MARK_LEN) != 0) {
warnx("Not a MIDI file, missing header");
return;
}
if (GET32(buf + MARK_LEN) != HEADER_LEN) {
warnx("Not a MIDI file, bad header");
return;
}
format = GET16(buf + MARK_LEN + SIZE_LEN);
ntrks = GET16(buf + MARK_LEN + SIZE_LEN + 2);
divfmt = GET8(buf + MARK_LEN + SIZE_LEN + 4);
ticks = GET8(buf + MARK_LEN + SIZE_LEN + 5);
p = buf + MARK_LEN + SIZE_LEN + HEADER_LEN;
/*
* Set the timebase (or timebase and tempo, for absolute-timed files).
* PORTABILITY: some sequencers actually check the timebase against
* available timing sources and may adjust it accordingly (storing a
* new value in the ioctl arg) which would require us to compensate
* somehow. That possibility is ignored for now, as NetBSD's sequencer
* currently synthesizes all timebases, for better or worse, from the
* system clock.
*
* For a non-absolute file, if timebase is set to the file's divisions
* value, and tempo set in the obvious way, then the timing deltas in
* the MTrks require no scaling. A downside to this approach is that
* the sequencer API wants tempo in (integer) beats per minute, which
* limits how finely tempo can be specified. That might be got around
* in some cases by frobbing tempo and timebase more obscurely, but this
* player is meant to be simple and clear.
*/
if ((divfmt & 0x80) == 0) {
ticks |= divfmt << 8;
if (ioctl(fd, SEQUENCER_TMR_TIMEBASE, &(int){ticks}) < 0)
err(1, "SEQUENCER_TMR_TIMEBASE");
} else {
tempo_abs = tempo_set = 1;
divfmt = -(int8_t)divfmt;
/*
* divfmt is frames per second; multiplying by 60 to set tempo
* in frames per minute could exceed sequencer's (arbitrary)
* tempo limits, so factor 60 as 12*5, set tempo in frames per
* 12 seconds, and account for the 5 in timebase.
*/
send_event(&SEQ_MK_TIMING(TEMPO,
.bpm=(12*divfmt) * (ttempo/100.) + 0.5));
if (ioctl(fd, SEQUENCER_TMR_TIMEBASE, &(int){5*ticks}) < 0)
err(1, "SEQUENCER_TMR_TIMEBASE");
}
if (verbose > 1)
printf(tempo_abs ?
"format=%d ntrks=%d abs fps=%u subdivs=%u\n" :
"format=%d ntrks=%d divisions=%u\n",
format, ntrks, tempo_abs ? divfmt : ticks, ticks);
if (format != 0 && format != 1) {
warnx("Cannot play MIDI file of type %d", format);
return;
}
if (ntrks == 0)
return;
tracks = malloc(ntrks * sizeof(struct track));
if (tracks == NULL)
errx(1, "malloc() tracks failed");
for (t = 0; t < ntrks; ) {
if (p >= end - MARK_LEN - SIZE_LEN) {
warnx("Cannot find track %d", t);
goto ret;
}
len = GET32(p + MARK_LEN);
if (len > 1000000) { /* a safe guard */
warnx("Crazy track length");
goto ret;
}
if (memcmp(p, MARK_TRACK, MARK_LEN) == 0) {
tracks[t].start = p + MARK_LEN + SIZE_LEN;
tracks[t].end = tracks[t].start + len;
tracks[t].delta = getvar(&tracks[t]);
tracks[t].indirect = &tracks[t]; /* -> self for now */
t++;
}
p += MARK_LEN + SIZE_LEN + len;
}
/*
* Force every channel to the same patch if requested by the user.
*/
if (sameprogram) {
for(t = 0; t < 16; t++) {
send_event(&SEQ_MK_CHN(PGM_CHANGE, .device=unit,
.channel=t, .program=sameprogram-1));
}
}
/*
* Play MIDI events by selecting the track with the lowest
* delta. Execute the event, update the delta and repeat.
*
* The ticks variable is the number of ticks that make up a beat
* (beat: 24 MIDI clocks always, a quarter note by usual convention)
* and is used as a reference value for the delays between
* the MIDI events.
*/
BuildHeap(tracks, ntrks); /* tracks[0].indirect is always next */
for (;;) {
tp = tracks[0].indirect;
if ((verbose > 2 && tp->delta > 0) || verbose > 3) {
printf("DELAY %4ld TRACK %2td%s",
tp->delta, tp - tracks, verbose>3?" ":"\n");
fflush(stdout);
}
if (tp->delta > 0) {
if (!tempo_set) {
if (verbose || showmeta)
printf("No initial tempo;"
" defaulting:\n");
dometa(META_SET_TEMPO, (u_char[]){
BASETEMPO >> 16,
(BASETEMPO >> 8) & 0xff,
BASETEMPO & 0xff},
3);
}
send_event(&SEQ_MK_TIMING(WAIT_REL,
.divisions=tp->delta));
}
byte = *tp->start++;
if (byte == MIDI_META) {
meta = *tp->start++;
mlen = getlen(tp);
if (verbose > 3)
printf("META %02x (%d)\n", meta, mlen);
dometa(meta, tp->start, mlen);
tp->start += mlen;
} else {
if (MIDI_IS_STATUS(byte))
tp->status = byte;
else
tp->start--;
mlen = MIDI_LENGTH(tp->status);
msg = tp->start;
if (verbose > 3) {
if (mlen == 1)
printf("MIDI %02x (%d) %02x\n",
tp->status, mlen, msg[0]);
else
printf("MIDI %02x (%d) %02x %02x\n",
tp->status, mlen, msg[0], msg[1]);
}
if (insysex && tp->status != MIDI_SYSEX_END) {
warnx("incomplete system exclusive message"
" aborted");
svsysex = insysex = 0;
}
status = MIDI_GET_STATUS(tp->status);
chan = MIDI_GET_CHAN(tp->status);
switch (status) {
case MIDI_NOTEOFF:
send_event(&SEQ_MK_CHN(NOTEOFF, .device=unit,
.channel=chan, .key=msg[0], .velocity=msg[1]));
break;
case MIDI_NOTEON:
send_event(&SEQ_MK_CHN(NOTEON, .device=unit,
.channel=chan, .key=msg[0], .velocity=msg[1]));
break;
case MIDI_KEY_PRESSURE:
send_event(&SEQ_MK_CHN(KEY_PRESSURE,
.device=unit, .channel=chan,
.key=msg[0], .pressure=msg[1]));
break;
case MIDI_CTL_CHANGE:
send_event(&SEQ_MK_CHN(CTL_CHANGE,
.device=unit, .channel=chan,
.controller=msg[0], .value=msg[1]));
break;
case MIDI_PGM_CHANGE:
if (!sameprogram)
send_event(&SEQ_MK_CHN(PGM_CHANGE,
.device=unit, .channel=chan,
.program=msg[0]));
break;
case MIDI_CHN_PRESSURE:
send_event(&SEQ_MK_CHN(CHN_PRESSURE,
.device=unit, .channel=chan, .pressure=msg[0]));
break;
case MIDI_PITCH_BEND:
send_event(&SEQ_MK_CHN(PITCH_BEND,
.device=unit, .channel=chan,
.value=(msg[0] & 0x7f) | ((msg[1] & 0x7f)<<7)));
break;
case MIDI_SYSTEM_PREFIX:
mlen = getlen(tp);
if (tp->status == MIDI_SYSEX_START) {
send_sysex(tp->start, mlen);
break;
} else if (tp->status == MIDI_SYSEX_END) {
/* SMF uses SYSEX_END as CONTINUATION/ESCAPE */
if (insysex) { /* CONTINUATION */
send_sysex(tp->start, mlen);
} else { /* ESCAPE */
for ( ; mlen > 0 ; -- mlen ) {
send_event(
&SEQ_MK_EVENT(putc,
SEQOLD_MIDIPUTC,
.device=unit,
.byte=*(tp->start++)
));
}
}
break;
}
/* Sorry, can't do this yet; FALLTHROUGH */
default:
if (verbose)
printf("MIDI event 0x%02x ignored\n",
tp->status);
}
tp->start += mlen;
}
if (tp->start >= tp->end) {
ntrks = ShrinkHeap(tracks, ntrks); /* track gone */
if (0 == ntrks)
break;
} else
tp->delta = getvar(tp);
Heapify(tracks, ntrks, 0);
}
if (ioctl(fd, SEQUENCER_SYNC, 0) < 0)
err(1, "SEQUENCER_SYNC");
ret:
free(tracks);
}
int
main(int argc, char **argv)
{
int ch;
int listdevs = 0;
int example = 0;
int nmidi;
const char *file = DEVMUSIC;
const char *sunit;
struct synth_info info;
FILE *f;
if ((sunit = getenv("MIDIUNIT")))
unit = atoi(sunit);
while ((ch = getopt(argc, argv, "?d:f:lmp:qt:vx")) != -1) {
switch(ch) {
case 'd':
unit = atoi(optarg);
break;
case 'f':
file = optarg;
break;
case 'l':
listdevs++;
break;
case 'm':
showmeta++;
break;
case 'p':
sameprogram = atoi(optarg);
break;
case 'q':
play = 0;
break;
case 't':
ttempo = atoi(optarg);
break;
case 'v':
verbose++;
break;
case 'x':
example++;
break;
case '?':
default:
usage();
}
}
argc -= optind;
argv += optind;
if (!play)
goto output;
fd = open(file, O_WRONLY);
if (fd < 0)
err(1, "%s", file);
if (ioctl(fd, SEQUENCER_NRMIDIS, &nmidi) < 0)
err(1, "ioctl(SEQUENCER_NRMIDIS) failed, ");
if (nmidi == 0)
errx(1, "Sorry, no MIDI devices available");
if (listdevs) {
for (info.device = 0; info.device < nmidi; info.device++) {
if (ioctl(fd, SEQUENCER_INFO, &info) < 0)
err(1, "ioctl(SEQUENCER_INFO) failed, ");
printf("%d: %s\n", info.device, info.name);
}
exit(0);
}
output:
if (example)
while (example--)
playdata(sample, sizeof sample, "<Gubben Noa>");
else if (argc == 0)
playfile(stdin, "<stdin>");
else
while (argc--) {
f = fopen(*argv, "r");
if (f == NULL)
err(1, "%s", *argv);
else {
playfile(f, *argv);
fclose(f);
}
argv++;
}
exit(0);
}
/*
* relative-time priority queue (min-heap). Properties:
* 1. The delta time at a node is relative to the node's parent's time.
* 2. When an event is dequeued from a track, the delta time of the new head
* event is relative to the time of the event just dequeued.
* Therefore:
* 3. After dequeueing the head event from the track at heap root, the next
* event's time is directly comparable to the root's children.
* These properties allow the heap to be maintained with delta times throughout.
* Insert is also implementable, but not needed: all the tracks are present
* at first; they just go away as they end.
*/
#define PARENT(i) ((i-1)>>1)
#define LEFT(i) ((i<<1)+1)
#define RIGHT(i) ((i+1)<<1)
#define DTIME(i) (t[i].indirect->delta)
#define SWAP(i,j) do { \
struct track *_t = t[i].indirect; \
t[i].indirect = t[j].indirect; \
t[j].indirect = _t; \
} while ( /*CONSTCOND*/ 0 )
void
Heapify(struct track *t, int ntrks, int node)
{
int lc, rc, mn;
lc = LEFT(node);
rc = RIGHT(node);
if (rc >= ntrks) { /* no right child */
if (lc >= ntrks) /* node is a leaf */
return;
if (DTIME(node) > DTIME(lc))
SWAP(node,lc);
DTIME(lc) -= DTIME(node);
return; /* no rc ==> lc is a leaf */
}
mn = lc;
if (DTIME(lc) > DTIME(rc))
mn = rc;
if (DTIME(node) <= DTIME(mn)) {
DTIME(rc) -= DTIME(node);
DTIME(lc) -= DTIME(node);
return;
}
SWAP(node,mn);
DTIME(rc) -= DTIME(node);
DTIME(lc) -= DTIME(node);
Heapify(t, ntrks, mn); /* gcc groks tail recursion */
}
void
BuildHeap(struct track *t, int ntrks)
{
int node;
for ( node = PARENT(ntrks-1); node --> 0; )
Heapify(t, ntrks, node);
}
/*
* Make the heap 1 item smaller by discarding the track at the root. Move the
* rightmost bottom-level leaf to the root and decrement ntrks. It remains to
* run Heapify, which the caller is expected to do. Returns the new ntrks.
*/
int
ShrinkHeap(struct track *t, int ntrks)
{
int ancest;
-- ntrks;
for ( ancest = PARENT(ntrks); ancest > 0; ancest = PARENT(ancest) )
DTIME(ntrks) += DTIME(ancest);
t[0].indirect = t[ntrks].indirect;
return ntrks;
}
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