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dmid: add support for midi streams

tested with a usb midi keyboard and a midi->usb adaptor

--- a/sys/man/1/dmid

+++ b/sys/man/1/dmid

@@ -4,7 +4,7 @@

 .SH SYNOPSIS

 .B dmid

 [

-.B -2

+.B -2s

 ] [

 .B -i

 .I bank

@@ -33,6 +33,13 @@

 .B -i

 command line option.

 .PP

+The

+.B -s

+flag enables streaming mode,

+in which the input file is a stream of MIDI events.

+The file needn't provide any timing information such as MIDI tics.

+This is suitable for MIDI instruments.

+.PP

 In

 .SM GENMIDI

 lumps, two voices are defined per instrument.

@@ -55,6 +62,14 @@

 createfile SW18_7: file already exists

 % games/mus /mnt/wad/d_doom | games/dmid | games/opl3 >/dev/audio

 .EE

+.PP

+Play a MIDI stream from a USB device (see

+.BR usb (3)):

+.IP

+.EX

+% games/wadfs /sys/games/lib/doom/doom2.wad >[2]/dev/null

+% games/dmid -s /dev/usb/ep10.1/data | games/opl3 >/dev/audio

+.EE

 .SH SOURCE

 .B /sys/src/games/dmid.c

 .SH "SEE ALSO"

@@ -62,6 +77,7 @@

 .IR mus (1) ,

 .IR opl3 (1) ,

 .IR audio (3) ,

+.IR usb (3) ,

 .IR wadfs (4)

 .SH HISTORY

 .I Dmid

--- a/sys/src/games/dmid.c

+++ b/sys/src/games/dmid.c

@@ -1,6 +1,7 @@

 #include <u.h>

 #include <libc.h>

 #include <bio.h>

+#include <thread.h>

 typedef struct Inst Inst;

 typedef struct Opl Opl;

@@ -82,8 +83,9 @@

 Trk *tr;

 double freq[128];

-int mfmt, ntrk, div, tempo, opl2;

+int mfmt, ntrk, div = 1, tempo, opl2, stream;

 uvlong T;

+Channel *echan;

 Biobuf *ib, *ob;

 void *

@@ -436,6 +438,29 @@

 }

 void

+tproc(void *)

+{

+	vlong t, Δt;

+	uchar u[4];

+	Trk x;

+

+	x.e = u + sizeof u;

+	t = nsec();

+	for(;;){

+		if(nbrecv(echan, u) > 0){

+			u[0] = 0;

+			x.p = u;

+			ev(&x);

+		}

+		putcmd(0, 0, 1);

+		t += 10000000 / (Rate / 100);

+		Δt = (t - nsec()) / 1000000;

+		if(Δt > 0)

+			sleep(Δt);

+	}

+}

+

+void

 readinst(char *file)

 {

 	int n;

@@ -475,6 +500,8 @@

 	Trk *x;

 	ib = file != nil ? bopen(file, OREAD) : bfdopen(0, OREAD);

+	if(stream)

+		return;

 	if(get32(nil) != 0x4d546864 || get32(nil) != 6)

 		sysfatal("invalid header");

 	mfmt = get16(nil);

@@ -501,16 +528,17 @@

 void

 usage(void)

 {

-	fprint(2, "usage: %s [-2] [-i inst] [mid]\n", argv0);

+	fprint(2, "usage: %s [-2s] [-i inst] [mid]\n", argv0);

 	exits("usage");

 }

 void

-main(int argc, char **argv)

+threadmain(int argc, char **argv)

 {

 	int n, t, mint;

 	char *i;

 	double f;

+	uchar u[4];

 	Chan *c;

 	Opl *o;

 	Trk *x, *minx;

@@ -519,6 +547,7 @@

 	ARGBEGIN{

 	case '2': opl2 = 1; ople = opl + 9; break;

 	case 'i': i = EARGF(usage()); break;

+	case 's': stream = 1; break;

 	default: usage();

 	}ARGEND

 	readinst(i);

@@ -538,6 +567,18 @@

 	tempo = 500000;

 	putcmd(Rwse, Mwse, 0);

 	putcmd(Rop3, 1, 0);

+	if(stream){

+		if(proccreate(tproc, nil, mainstacksize) < 0)

+			sysfatal("proccreate: %r");

+		if((echan = chancreate(sizeof u, 0)) == nil)

+			sysfatal("chancreate: %r");

+		for(;;){

+			if((n = Bread(ib, u, sizeof u)) != sizeof u)

+				break;

+			send(echan, u);

+		}

+		threadexitsall(n < 0 ? "read: %r" : nil);

+	}

 	for(;;){

 		minx = nil;

 		mint = 0;