Public bug reported:
Binary package hint: zsync
Ubuntu 8.04, i386
zsync 0.5
zsyncmake is utility to create files with metadata information for zsync
client. It has several parameter, one of them is blocksize, -b.
Blocksize value has to be power of 2; this is checked by zsyncmake;
exmaple:
# zsyncmake -b 2000
blocksize must be a power of 2 (512, 1024, 2048, ...)
There is other limit, the largest blocksize possible; limited by zsync
client design. This value is not checked and zsyncmake utility can
create "zsync" file that cannot be processed by client. For example,
blocksize 65536 is power by 2 but too big to be processed by zsync
client.
Two issues here:
1) zsync client doesn't exit with error when it get zsync file with blocksize
bigger that it can process (by sw design limits). When client get file with big
blocksize it finish in some never-ending loop... The value in zsync file has to
be checked by zsync client.
2) zsyncmake doesn't check blocksize well and warn user that he creates file
that cannot be used by zsync client as blocksize is too big.
I think the same could be written about minimum value of blocksize.
I tested values of blocksize 1024, 2048, 4096, 8096 and 16384, these are
working well. blocksize value 32768 is too big.
About blocksize from zsyncmake man page:
-b blocksize
Specify the blocksize to the underlying rsync algorithm. A
smaller blocksize may be more efficient for files where there
are likely to be lots of small, scattered changes between down‐
loads; a larger blocksize is more efficient for files with fewer
or less scattered changes. This blocksize must be a power of
two. If not specified, zsyncmake chooses one which it thinks is
best for this file (currently either 2048 or 4096 depending on
file size) - so normally you should not need to override the
default.
** Affects: zsync (Ubuntu)
Importance: Undecided
Status: New
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zsyncmake doesn't check blocksize parameter well
https://bugs.launchpad.net/bugs/421044
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