#!/usr/bin/env tclsh
# Martin Heinrich <martin.heinrich@frequentis.com>
package require ip
namespace eval ::ip {
   # XXX fix toInteger to return ipv4 in range 0 through 4294967295 in any architecture
   # two possible fixes:
   # * scan wide (as implemented below)
   # * format wide (original code, but %lu instead of %u)
   proc toInteger {ip} {
      binary scan \0\0\0\0[Normalize4 $ip] W out
      return [format %u $out]
   }
   # calculate the integer distance from ip1 to ip2, i.e. $ip2-$ip1
   proc distance1 {ip1 ip2} {
      # use package ip for normalization
      # XXX does not support ipv6 --> could use faster distance2 instead
      expr {[toInteger $ip2]-[toInteger $ip1]}
   }
   proc distance2 {ip1 ip2} {
      # calculate with small numbers, but undefined for invalid IPv4
      lassign [split $ip1 .] ip11 ip12 ip13 ip14
      lassign [split $ip2 .] ip21 ip22 ip23 ip24
      expr {(((
         $ip21-$ip11)*256+
         $ip22-$ip12)*256+
         $ip23-$ip13)*256+
         $ip24-$ip14
      }
   }
   # calculate the ip address at an offset from a given address, i.e. $ip2 == [nextIp $ip1 [distance $ip1 $ip2]]
   proc nextIp {ip {offset 1}} {
      set int [toInteger $ip]
      incr int $offset
      set prot {}
      # TODO if ipv4 then set prot -ipv4, but
      # XXX intToString has -ipv4, but never returns ipv6
      intToString $int {*}$prot
   }
   proc nextIp2 {ipVar {offset 1}} {
      upvar 1 $ipVar ip
      lassign [split $ip .] ip1 ip2 ip3 ip4
      incr $ip4 $offset
      if {0 > $ip4} {

      }
      set ip "$ip1.$ip2.$ip3.$ip4"
   }
}
puts ===nextIp===
foreach {ip1 ip2} {
   0.0.0.0         255.255.255.255
   255.255.255.255 0.0.0.0
   10.11.12.13     10.11.42.42
   10.11.42.42     10.11.12.13
   54.229.115.42   173.194.116.195
   173.194.116.195 54.229.115.42
} {
   puts "$ip2 - $ip1 == [::ip::distance1 $ip1 $ip2]; test: [expr {$ip2 == [::ip::nextIp $ip1 [::ip::distance1 $ip1 $ip2]]}]"
}
puts ===distance===
set t1 [time {::ip::distance1 10.11.12.13 10.11.42.42} 10000]
set t2 [time {::ip::distance2 10.11.12.13 10.11.42.42} 10000]
puts "robust + code reuse: $t1"
puts "no arg checks:       $t2"
lassign $t1 t1
lassign $t2 t2
puts "no arg checks is [format %0.0f [expr {100-100.0*$t2/$t1}]]% faster,\
      robustness costs [format %0.0f [expr {100.0*$t1/$t2-100}]]%"
************
in my VM:
===nextIp===
255.255.255.255 - 0.0.0.0 == 4294967295; test: 1
0.0.0.0 - 255.255.255.255 == -4294967295; test: 1
10.11.42.42 - 10.11.12.13 == 7709; test: 1
10.11.12.13 - 10.11.42.42 == -7709; test: 1
173.194.116.195 - 54.229.115.42 == 1994195353; test: 1
54.229.115.42 - 173.194.116.195 == -1994195353; test: 1
===distance===
robust + code reuse: 11.574 microseconds per iteration
no arg checks:       3.0491 microseconds per iteration
no arg checks is 74% faster, robustness costs 280%