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Re: Simple Resolver Function

by dakkar (Hermit)
on Mar 20, 2003 at 18:28 UTC ( #244674=note: print w/replies, xml ) Need Help??


in reply to Simple Resolver Function

You only resolve addresses in 4-number dotted decimal notation. What about addresses like 0177.1, better known as 127.0.0.1? OK, they are not very frequent, but still...

Moreover, an address is numeric if its last part is numeric, not the first. That is, all TLD are non-numeric.

To formalize:

  • an address (name or number) is made up of a number of components separated by dots
  • If the last component is a number (matches \d+), the address is numeric
  • the components of a non-numeric address match [a-zA-Z0-9-] (no, you can't have an 'underscore' in your domain names) (and this might change once non-ASCII-7 characters are allowed in names)
  • each component of a numeric address is to be interpreted as a base-16 number if it matches /^0x/i, as a base-8 number if it matches /^0/, otherwise as a base-10 number
  • a numeric address is composed of 1,2,3 or 4 components:
    • if it's one component, it must be withit the range 0...(2^32-1), and represents the entire address
    • if it's two components, the first must be in the range 0..255, and the second in 0..(2^24-1), and the address is $1<<24+$2 (I use $1, $2, and so on for the various components, left-to-right)
    • if it's three components, the first and the second must be in 0..255, and the third in 0..(2^16-1), and the address is $1<<4+$2<<16+$3
    • If it's four components, each must be in the range 0..255, and the address is $1<<24+$2<<16+$3<<8+$4

Hope this clears up the notation.

-- 
        dakkar - Mobilis in mobile

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