code: 9ferno

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kfs64 with block checksum

--- a/appl/cmd/disk/kfs64.b

+++ b/appl/cmd/disk/kfs64.b

@@ -136,13 +136,14 @@

 #

 # disc structure:

-#	Tag:	pad[2] tag[2] path[8] TODO change pad?

-Tagsize: con 2+2+8;

+#	Tag:	pad[2] tag[2] path[8] cksum[4]

+Tagsize: con 2+2+8+4;

 Tag: adt

 {

 	tag:	int;

 	path:	big;

+	cksum:	int;

 	unpack:	fn(a: array of byte): Tag;

 	pack:	fn(t: self Tag, a: array of byte);

@@ -2141,7 +2142,7 @@

 Tag.unpack(a: array of byte): Tag

 {

-	return Tag(get2(a,2), get8(a,4));

+	return Tag(get2(a,2), get8(a,4), get4(a,12));

 }

 Tag.pack(t: self Tag, a: array of byte)

@@ -2150,6 +2151,7 @@

 	put2(a, 2, t.tag);

 	if(t.path != QPNONE)

 		put8(a, 4, t.path & ~QPDIR);

+	put4(a, 12, t.cksum);

 }

 Superb.get(dev: ref Device, flags: int): ref Superb

@@ -2922,6 +2924,12 @@

 			p.unlock();

 			return nil;

 		}

+		cksum := checksum(p.iobuf);

+		ocksum := get4(p.iobuf, RBUFSIZE-4);

+		if(cksum != ocksum){

+			eprint(sys->sprint("block %bud: checksum failed cksum 0x%bux ocksum 0x%bux", addr, big cksum, big ocksum));

+			return nil;

+		}

 	}

 	return p;

 }

@@ -2933,6 +2941,8 @@

 	if(p.flags & Bimm){

 		if(!(p.flags & Bmod))

 			eprint(sys->sprint("imm and no mod (%bd)", p.addr));

+		cksum := checksum(p.iobuf);

+		put4(p.iobuf, RBUFSIZE-4, cksum);

 		if(!wrenwrite(p.dev.fd, p.addr, p.iobuf))

 			p.flags &= ~(Bmod|Bimm);

 		else

@@ -3042,9 +3052,47 @@

 	return 0;

 }

+# using an array of big instead of int to keep it fast

+#	ignoring the last 4 bytes before tag from the checksum calculation

+# using 1's complement addition from

+#	https://barrgroup.com/embedded-systems/how-to/additive-checksums

+#uint16_t

+#NetIpChecksum(uint16_t const ipHeader[], int nWords)

+#{

+#    uint32_t  sum = 0;

+#    /*

+#     * IP headers always contain an even number of bytes.

+#     */

+#    while (nWords-- > 0)

+#    {

+#        sum += *(ipHeader++);

+#    }

+#    /*

+#     * Use carries to compute 1's complement sum.

+#     */

+#    sum = (sum >> 16) + (sum & 0xFFFF);

+#    sum += sum >> 16;

+#    /*

+#     * Return the inverted 16-bit result.

+#     */

+#    return ((unsigned short) ~sum);

+#}   /* NetIpChecksum() */

+checksum(buf: array of byte): int

+{

+	cksum := big 0;

+	for(i := 0; i<(RBUFSIZE-4); i+=4){

+		cksum += big get4(buf,i);

+	}

+	cksum = (cksum >> 32) + (cksum & big 16rFFFFFFFF);

+	cksum += cksum >> 32;

+	return int (~cksum & big 16rFFFFFFFF);

+}

+

 Iobuf.settag(p: self ref Iobuf, tag: int, qpath: big)

 {

-	Tag(tag, qpath).pack(p.iobuf[BUFSIZE:]);

+	# checksum on the tag and qpath too

+	cksum := checksum(p.iobuf);

+	Tag(tag, qpath, cksum).pack(p.iobuf[BUFSIZE:]);

 	p.flags |= Bmod;

 }