[R] INET_NTOA equivalent?

[Eberhard Lisse]

Thank you,

el

on 2014-04-24, 10:33 Martin Maechler said the following:
>>>>>> "EL" == Eberhard Lisse <nospam at lisse.NA>
>>>>>>     on Thu, 24 Apr 2014 01:21:37 +0100 writes:
> 
>     EL> In MySQL
>     EL> SELECT INET_ATON('127.0.0.1')
> 
>     EL> returns the integer 2130706433
> 
>     EL> Is there a function in R to reverse that, ie so that something like
> 
>     EL> ip <- inet_ntoa(2130706433)
> 
>     EL> would put  '127.0.0.1' into ip?
> 
> almost:
> 
>   install.packages("sfsmisc")
>   require("sfsmisc")
> 
>   # NTOA :
> 
>   > digitsBase(2130706433, base = 256)
>   Class 'basedInt'(base = 256) [1:1]
>        [,1]
>   [1,]  127
>   [2,]    0
>   [3,]    0
>   [4,]    1
> 
>   # ATON :
> 
>   > as.intBase(digitsBase(2130706433, base = 256), base = 256)
> 	   1 
>   2130706433 
>   > 
> 
> So, an easy solution seems
> 
> 
>> ip.ntoa <- function(n) paste(sfsmisc::digitsBase(n, base = 256), collapse=".")
>> ip.ntoa(2130706433)
> [1] "127.0.0.1"
>>
> 
> but that does not vectorize (work for  length(n) > 1 )
> correctly.
> 
> The correct solution then is
> 
> ip.ntoa <- function(n) 
>     apply(sfsmisc::digitsBase(n, base = 256), 2, paste, collapse=".")
> 
> and that does work nicely:
> 
>> ip.ntoa(1000000000+ (0:10))
> 
>  [1] "59.154.202.0"  "59.154.202.1"  "59.154.202.2"  "59.154.202.3"  "59.154.202.4" 
>  [6] "59.154.202.5"  "59.154.202.6"  "59.154.202.7"  "59.154.202.8"  "59.154.202.9" 
> [11] "59.154.202.10"
> 
> right ?
> 
> --
> Martin Maechler, ETH Zurich
> 
>