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tapefs/^(v6fs 32vfs): fix read errors (thanks Lyssa)

We were always returning the start of the block when
doing unaligned reads.

Additionally the logical to physical block translation
for 32vfs was not correct for files over 512 bytes.
This code was tested with the 32V dumps from TUHS.

--- a/sys/src/cmd/tapefs/32vfs.c

+++ b/sys/src/cmd/tapefs/32vfs.c

@@ -131,7 +131,7 @@

 		bno++;

 		i++;

 	}

-	return buf;

+	return buf+off;

 }

 void

@@ -208,10 +208,12 @@

 	if (bno < VNADDR-3)

 		return ((long*)r->data)[bno];

 	if (bno < VNADDR*LNINDIR) {

-		seek(tapefile, ((long *)r->data)[(bno-(VNADDR-3))/LNINDIR]*BLSIZE, 0);

+		seek(tapefile, ((long *)r->data)[(bno-(VNADDR-3))/LNINDIR+(VNADDR-3)]*BLSIZE, 0);

 		if (read(tapefile, (char *)indbuf, BLSIZE) != BLSIZE)

 			return 0;

-		return ((indbuf[bno%LNINDIR][1]<<8) + indbuf[bno%LNINDIR][0]);

+

+		return ((indbuf[(bno-(VNADDR-3))%LNINDIR][2]<<16) + (indbuf[(bno-(VNADDR-3))%LNINDIR][1]<<8)

+			+ indbuf[(bno-(VNADDR-3))%LNINDIR][0]);

 	}

 	return 0;

 }

--- a/sys/src/cmd/tapefs/v6fs.c

+++ b/sys/src/cmd/tapefs/v6fs.c

@@ -123,7 +123,7 @@

 		bno++;

 		i++;

 	}

-	return buf;

+	return buf+off;

 }

 void