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mixfs: add reading (audio loopback)

--- a/sys/src/cmd/audio/mixfs/mixfs.c

+++ b/sys/src/cmd/audio/mixfs/mixfs.c

@@ -16,6 +16,7 @@

 {

 	int	used;

 	int	run;

+	int	rd;

 	ulong	wp;

 	QLock;

 	Rendez;

@@ -23,6 +24,7 @@

 ulong	mixrp;

 int	mixbuf[NBUF][NCHAN];

+int	lbbuf[NBUF][NCHAN];

 Lock	mixlock;

 Stream	streams[16];

@@ -61,6 +63,7 @@

 			s->used = 1;

 			qunlock(s);

+			s->rd = (r->ifcall.mode&OWRITE) == 0;

 			r->fid->aux = s;

 			respond(r, nil);

 			return;

@@ -144,6 +147,7 @@

 		for(i=0; i<m; i++){

 			for(j=0; j<NCHAN; j++){

 				v = clip16(mixbuf[mixrp % NBUF][j]);

+				lbbuf[mixrp % NBUF][j] = v;

 				mixbuf[mixrp % NBUF][j] = 0;

 				*p++ = v & 0xFF;

 				*p++ = v >> 8;

@@ -155,6 +159,56 @@

 }

 void

+fsread(Req *r)

+{

+	Srv *srv;

+	int i, j, n, m, v;

+	Stream *s;

+	uchar *p;

+

+	p = (uchar*)r->ofcall.data;

+	n = r->ifcall.count;

+	n &= ~(NCHAN*2 - 1);

+	r->ofcall.count = n;

+	n /= (NCHAN*2);

+

+	srv = r->srv;

+	srvrelease(srv);

+	s = r->fid->aux;

+	qlock(s);

+	while(n > 0){

+		if(s->run == 0){

+			s->wp = mixrp;

+			s->run = 1;

+		}

+		m = NBUF-1 - (long)(s->wp - mixrp);

+		if(m <= 0){

+			s->run = 1;

+			rsleep(s);

+			continue;

+		}

+		if(m > n)

+			m = n;

+

+		lock(&mixlock);

+		for(i=0; i<m; i++){

+			for(j=0; j<NCHAN; j++){

+				v = lbbuf[s->wp % NBUF][j];

+				*p++ = v & 0xFF;

+				*p++ = v >> 8;

+			}

+			s->wp++;

+		}

+		unlock(&mixlock);

+

+		n -= m;

+	}

+	qunlock(s);

+	respond(r, nil);

+	srvacquire(srv);

+}

+

+void

 fswrite(Req *r)

 {

 	Srv *srv;

@@ -234,7 +288,7 @@

 	Stream *s;

 	for(s=streams; s < streams+nelem(streams); s++){

-		s->used = s->run = 0;

+		s->used = s->run = s->rd = 0;

 		s->Rendez.l = &s->QLock;

 	}

 	proccreate(audioproc, nil, 16*1024);

@@ -248,6 +302,7 @@

 Srv fs = {

 	.open=		fsopen,

+	.read=		fsread,

 	.write=		fswrite,

 	.stat=		fsstat,

 	.destroyfid=	fsclunk,

@@ -286,7 +341,7 @@

 		usage();

 	fs.tree = alloctree(nil, nil, DMDIR|0777, nil);

-	createfile(fs.tree->root, "audio", nil, 0222, nil);

+	createfile(fs.tree->root, "audio", nil, 0666, nil);

 	threadpostmountsrv(&fs, srv, mtpt, MREPL);

 	mtpt = smprint("%s/audio", mtpt);