Re: [NSE] Optimize stdnse.format_output()

[David Fifield <david () bamsoftware com>]

On Tue, Aug 23, 2011 at 03:29:22AM +0100, Djalal Harouni wrote:
> I've attached a patch that will make the format_output_sub() function
> used by the stdnse.format_output() to store results in a table and to
> call table.concat() when returning instead of doing classic
> concatenations. This will prevent stressing the Lua garbage-collector,
> and it will speed up the process.
>
> The table.concat() will first create a stack of strings, then it will
> concat them using the Tower of Hanoi [1].
>
>
> This is the output (end of the output) of a simple post-processing test
> script (after patch applied):
> |   Host:  (10.0.2.22)
> |   Vuln X 341
> |   Vulnerability Reported by: vulns-test-1
> |     State: VULNERABLE
> |     IDs:  NMAP:341
> |     Description:
> |       Generated vulnerability
> |     References:
> |       http://scanme.org/id?341
> |   
> |_  printed:  64320 entry
> No data files read.
> Nmap done: 64 IP addresses (64 hosts up) scanned in 279.33 seconds
>
> During the scan some test scripts have added multiple vulnerabilities
> entries, one of them was adding 1000 vulnerability entry for each host.
>
> Without the patch if we specify '/28' mask then the current
> implementation can eat all the memory when reporting all the
> post-processing results (I've tested and confirmed this in a guest running
> under Qemu). So I would like to commit the patch since it can have a huge
> performance boost.

Good job, commit it.

David Fifield
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