Add IPAddr#+/-

[taketo1113]

Add +/- methods to get an ipaddr instance greater/less than the original address by offset.
the current IPAddr#succ only return next address, this IPAddr#+ return any address with offset.

addr = IPAddr.new("192.168.1.10")

addr + 10
=> #<IPAddr: IPv4:192.168.1.20/255.255.255.255>


(addr + 10).to_s
=> "192.168.1.20"

[olleolleolle]

I logged the build failure as #73

EDIT: I merged fixes to the CI, so @taketo1113, if you rebase this on top of latest, it ought to run tests right.

[taketo1113]

@olleolleolle Thanks for fixing ci build error.
It passed CI :-)

[knu]

If this effectively introduces the concept of delta of IP addresses, does ipaddr1 - ipaddr2 make sense if they share the address family?

[taketo1113]

@knu No. I think it is not an introduction to the concept of delta.

The use case I was thinking of is a human friendly calculation of addresses.
When a network operator reserved a few addresses (upper/downer) such as VRRP (virtual/primary/secondary), a network user can't use reserved addresses.
It needs to calculate available addresses, to indicate available addresses for network user.

addr = IPAddr.new("192.168.1.1")
addr + 10
=> #<IPAddr: IPv4:192.168.1.11/255.255.255.255>


addr = IPAddr.new("192.168.1.255")
addr - 10
=> #<IPAddr: IPv4:192.168.1.245/255.255.255.255>

[knu]

One more question: should IPAddr.new("192.168.0.255/24" ) + 1 be considered a valid operation? The resulted address will break out of the network.

[taketo1113]

I think it should be valid operation, because it just calculates the IP Address (which is not address block or network mask) like the bitwise operator of >> or <<.
If needs to detect breaking out of the network, I think it could use #include? or #to_range.

addr = IPAddr.new("192.168.0.0/24") + 255
=> #<IPAddr: IPv4:192.168.0.255/255.255.255.0>

# `"192.168.0.255/24" + 1` just return next ip address
addr + 1
=> #<IPAddr: IPv4:192.168.1.0/255.255.255.0>