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audio/vocdec: handle non type 1 blocks better

* skip over unrecognized blocks
* correct improper read for reserved field in block 9
* read block type 2 correctly

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

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

@@ -80,9 +80,10 @@

 main(int argc, char **argv)

 {

 	Block b;

-	uchar buf[20];

+	static uchar buf[2048];

 	char fmt[32], size[32];

 	ushort chksum, ver;

+	int n;

 	ARGBEGIN{

 	default:

@@ -99,9 +100,10 @@

 	if(~ver + 0x1234 != chksum)

 		sysfatal("invalid checksum");

+	memset(&b, 0, sizeof b);

 	for(;;){

-		b.type = get();

-		if(b.type == 0)

+		/* files may end without a proper block */

+		if(read(0, &b.type, 1) != 1 || b.type == 0)

 			break;

 		b.size = get3();

@@ -112,16 +114,27 @@

 			b.chan = 1;

 			b.size -= 2;

 			break;

+		case 2:

+			if(b.freq == 0)

+				sysfatal("block 2 without defined codec");

+			break;

 		case 9:

 			b.freq = get4();

 			b.bits = get();

 			b.chan = get();

 			b.codec = get2();

-			get(); /* reserved */

-			b.size -= 4+1+1+2+1;

+			get4(); /* reserved */

+			b.size -= 4+1+1+2+4;

 			break;

 		default:

-			sysfatal("unsupported blocktype");

+			while(b.size != 0){

+				n = b.size;

+				if(n > sizeof buf)

+					n = sizeof buf;

+				if(readn(0, buf, n) != n)

+					break;

+				b.size -= n;

+			}

 			break;

 		}