games/opl3: don't buffer output and simplify (thanks umbraticus)

this fixes real-time applications.

-n previously specified a rate divisor rather than the rate itself,
which was used for specific applications outside of 9front.  instead,
just set the rate directly, more useful and straightforward.

sys/man/1/opl3

@@ -4,7 +4,7 @@ opl3 \- OPL3 chip emulator
 .SH SYNOPSIS
 .B opl3
 [
-.B -n
+.B -r
 .I rate
 ] [
 .I file
@@ -44,7 +44,7 @@ It is a multiple of a command period, during which the
 chip may be sampled before processing the next command.
 The period itself is the inverse of the command rate, 44100 Hz by default.
 This rate can be set using the
-.B -n
+.B -r
 parameter.
 .SH SOURCE
 .B /sys/src/games/opl3

sys/src/games/opl3/opl3m.c

@@ -6,29 +6,25 @@ void	opl3out(uchar *, int);
 void	opl3wr(int, int);
 void	opl3init(int);
 
-enum{
-	Rate = 44100,
-};
-
 void
 usage(void)
 {
-	fprint(2, "usage: %s [-n nsamp] [file]\n", argv0);
+	fprint(2, "usage: %s [-r rate] [file]\n", argv0);
 	exits("usage");
 }
 
 void
 main(int argc, char **argv)
 {
-	int r, v, dt, nsamp, fd;
-	uchar *sb, u[5];
-	Biobuf *bi, *bo;
+	int rate, r, v, dt, fd;
+	uchar sb[65536 * 4], u[5];
+	Biobuf *bi;
 
 	fd = 0;
-	nsamp = 1;
+	rate = 44100;
 	ARGBEGIN{
-	case 'n':
-		nsamp = Rate / atoi(EARGF(usage()));
+	case 'r':
+		rate = atoi(EARGF(usage()));
 		break;
 	default:
 		usage();
@@ -37,21 +33,16 @@ main(int argc, char **argv)
 		if((fd = open(*argv, OREAD)) < 0)
 			sysfatal("open: %r");
 	bi = Bfdopen(fd, OREAD);
-	bo = Bfdopen(1, OWRITE);
-	if(bi == nil || bo == nil)
+	if(bi == nil)
 		sysfatal("Bfdopen: %r");
-	nsamp *= 4;
-	if((sb = malloc(nsamp)) == nil)
-		sysfatal("malloc: %r");
-	opl3init(Rate);
+	opl3init(rate);
 	while(Bread(bi, u, sizeof u) > 0){
 		r = u[1] << 8 | u[0];
 		v = u[2];
-		dt = u[4] << 8 | u[3];
 		opl3wr(r, v);
-		while(dt-- > 0){
-			opl3out(sb, nsamp);
-			Bwrite(bo, sb, nsamp);
+		if(dt = (u[4] << 8 | u[3]) * 4){	/* 16-bit stereo */
+			opl3out(sb, dt);
+			write(1, sb, dt);
 		}
 	}
 }