G_J
2nd October 2003 12:15 UTC

Buggy CRCCheck?
Hi,

I'm using NSIS 2 Modern UI, and in my installer the CRC Check is configured on. I believe this leads to the initial status dialog "Verifying installer", right? Anyway, I believe the implementation of this CRC check may be flawed, not from a functionality perspective but a performance perspective. If running the installer from a CD, the process may take up to a minute for a 10MB installer, whereas it's instantaneous from the hard disk. This is a showstopper for shrinkwrapped software. I believe the implementation bug probably lies in that file I/O (reading from the file) is done in pathetic little chunks (e.g. 100 bytes each) instead of loading the file in generous chunks of dozens of K in each gulp. This is a typical developer mistake - reading a file byte-by-byte in numerous i/o calls takes many orders of magnitude longer than reading it at once or in a few calls. Please review the implementation of the CRC check and let me know if my suspicions are correct. As it stands now, I unfortunately have to cancel it in my installer because it takes too long when installing from CD.

Regards,
GJ

kichik
2nd October 2003 12:32 UTC

It reads chunks of 512 bytes so it can easily find the header. I'll see what can be done.

G_J
2nd October 2003 23:32 UTC

Thanks. Unfortunately, my suspicions were correct. Reading in 512-byte chunks is very bad. It means NSIS is doing about 20000 separate i/o calls to verify my 10MB installer.
I've no doubt that you'll set about fixing it, but my question is whether I can obtain or apply a fix without getting all the new NSIS files - this will completely break my currently stable installer. How can I go about applying just this isolated fix if/when it becomes available?

Shalom,
GJ

kichik
3rd October 2003 13:17 UTC

That code has already been changed a lot. It'll probably be possible to implement in b3 too though. I will know better when it's ready.

kichik
28th November 2003 17:58 UTC

Fixed in latest CVS version.