xd(1) has problems when dumping with the -r option.  It prints wrong
address offsets and misses non-repeating data.

Test with xd -r -c, diff of using unpatched vs patched with
http://pcoutin.us.to/randomfs


diff unpatched patched
15,17c15,17
< 0000160  00 00 00 00 00 00 00 00 00 00 00 00 00 00  U aa
< 0000170  f0 ff ff ff 0f 00 00 00 00 00 00 00 00 00 00 00
< 0000180  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
---
> 00001f0  00 00 00 00 00 00 00 00 00 00 00 00 00 00  U aa
> 0000200  f0 ff ff ff 0f 00 00 00 00 00 00 00 00 00 00 00
> 0000210  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
19,20c19,20
< 0000a80  f0 ff ff ff 0f 00 00 00 00 00 00 00 00 00 00 00
< 0000a90  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
---
> 0001400  f0 ff ff ff 0f 00 00 00 00 00 00 00 00 00 00 00
> 0001410  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
22,26c22,26
< 0001390   A  n 00  o 00  t 00  a 00  f 00 0f 00 f8  i 00
< 00013a0   l 00  e 00 00 00 ff ff ff ff 00 00 ff ff ff ff
< 00013b0   N  O  T  A  F  I  L  E          00 00 00 00 00
< 00013c0  00 00 00 00 00 00 ac  $ 03  E 02 00 \r 00 00 00
< 00013d0  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
---
> 0002600   A  n 00  o 00  t 00  a 00  f 00 0f 00 f8  i 00
> 0002610   l 00  e 00 00 00 ff ff ff ff 00 00 ff ff ff ff
> 0002620   N  O  T  A  F  I  L  E          00 00 00 00 00
> 0002630  00 00 00 00 00 00 ac  $ 03  E 02 00 \r 00 00 00
> 0002640  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
28,30c28,33
< 00b40b0  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  9
< 00b40c0 
< 00b40c0 
---
> 0004200   h  e  l  l  o  ,     w  o  r  l  d \n 00 00 00
> 0004210  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> *
> 0167ff0  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  9
> 0168000 
> 0168000 

Note that the 'hello, world' string only shows up with the patched
xd's output.  The unpatched one misses the first 16 bytes of data when
it stops repeating.

Reference: /n/sources/patch/xd-repeating-bugfix
Date: Sun Aug  3 13:48:37 CES 2014
Signed-off-by: pcoutin@sdf.org

--- /sys/src/cmd/xd.c	Sun Aug  3 13:48:25 2014
+++ /sys/src/cmd/xd.c	Sun Aug  3 13:48:22 2014
@@ -247,6 +247,10 @@
 						break;
 				if(i == nsee){
 					addr += nsee;
+					if(nread>nsee){
+						nleft = nread - nsee;
+						memmove(data, data + nsee, nleft);
+					}
 					if(star == 0){
 						star++;
 						xprint("*\n", 0);