Date: Sat, 12 Feb 2011 10:48:37 +0000 From: Matthew Seaman <m.seaman@infracaninophile.co.uk> To: Devin Teske <dteske@vicor.com> Cc: freebsd-hackers@freebsd.org, Ian Smith <smithi@nimnet.asn.au> Subject: Re: [RELEASE] host-setup(1): a dialog(1)-based utility for configuring FreeBSD Message-ID: <4D566585.7020802@infracaninophile.co.uk> In-Reply-To: <1297447687.9144.6.camel@dt.vicor.com> References: <20110211120031.9D37510656E5@hub.freebsd.org> <20110212015155.I96449@sola.nimnet.asn.au> <1297447687.9144.6.camel@dt.vicor.com>
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On 11/02/2011 18:08, Devin Teske wrote:
> $ time blen2netmask 26
> 255.255.255.192
>=20
> real 0m0.004s
> user 0m0.001s
> sys 0m0.004s
>=20
> That's pretty fast, I'd say ^_^ (faster than the other implementations
> -- especially considering that it doesn't have to fork anything).
There are only 33 possible netmasks -- did you evaluate simply
enumerating them all and simply looking up the result?
Hmmm...
blen2netmask() {
local nbits=3D$1
case $nbits in
0) echo '0.0.0.0' ;;
1) echo '128.0.0.0' ;;
2) echo '192.0.0.0' ;;
3) echo '224.0.0.0' ;;
4) echo '240.0.0.0' ;;
5) echo '248.0.0.0' ;;
6) echo '252.0.0.0' ;;
7) echo '254.0.0.0' ;;
8) echo '255.0.0.0' ;;
9) echo '255.128.0.0' ;;
10) echo '255.192.0.0' ;;
11) echo '255.224.0.0' ;;
12) echo '255.240.0.0' ;;
13) echo '255.248.0.0' ;;
14) echo '255.252.0.0' ;;
15) echo '255.254.0.0' ;;
16) echo '255.255.0.0' ;;
17) echo '255.255.128.0' ;;
18) echo '255.255.192.0' ;;
19) echo '255.255.224.0' ;;
20) echo '255.255.240.0' ;;
21) echo '255.255.248.0' ;;
22) echo '255.255.252.0' ;;
23) echo '255.255.254.0' ;;
24) echo '255.255.255.0' ;;
25) echo '255.255.255.128' ;;
26) echo '255.255.255.192' ;;
27) echo '255.255.255.224' ;;
28) echo '255.255.255.240' ;;
29) echo '255.255.255.248' ;;
30) echo '255.255.255.252' ;;
31) echo '255.255.255.254' ;;
32) echo '255.255.255.255' ;;
*) echo "$nbits -- not a valid IPv4 netmask length"
return -1 ;;
esac
return 0
}
Cheers,
Matthew
--=20
Dr Matthew J Seaman MA, D.Phil. 7 Priory Courtyard
Flat 3
PGP: http://www.infracaninophile.co.uk/pgpkey Ramsgate
JID: matthew@infracaninophile.co.uk Kent, CT11 9PW
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