Regexp vs Exceptions for IPAddr validation

validate_ip.rb

require 'ipaddr'

def by_exception ip
  begin
    IPAddr.new(ip, Socket::AF_INET)
    true
  rescue ArgumentError
    false
  end
end

def by_regexp ip
  !!ip.match(/\A(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\Z/)
end

# First some sanity checks
{
  "355.55.43.33" => false,
  "245.34.63.44" => true,
  "10.10.90.424" => false,
  "127.0.0.1" => true,
}.each do |ip, result|
  raise "Doesn't pass sanity check, by_exception(#{ip}) == #{result}" unless by_exception(ip) == result
  raise "Doesn't pass sanity check, by_regexp(#{ip}) == #{result}" unless by_regexp(ip) == result
end

N = 100_000
Benchmark.bm(20) do |x|
  x.report("Regexp FAIL") { N.times { by_regexp("355.55.43.43") }  }
  x.report("Exception FAIL") { N.times { by_exception("355.55.43.43") }  }

  x.report("Regexp OK") { N.times { by_regexp("10.10.0.1") }  }
  x.report("Exception OK") { N.times { by_exception("10.10.0.1") }  }
end

## RESULTS ruby 1.8.7 (2012-10-12 patchlevel 371) [x86_64-linux]
                          user     system      total        real
Regexp FAIL           0.110000   0.000000   0.110000 (  0.108501)
Exception FAIL       12.300000  16.160000  28.460000 ( 37.298097)
Regexp OK             0.210000   0.000000   0.210000 (  0.212452)
Exception OK          1.730000   0.000000   1.730000 (  1.732759)


## RESULTS ruby 1.9.2p320 (2012-04-20 revision 35421) [x86_64-linux]
                          user     system      total        real
Regexp FAIL           0.080000   0.000000   0.080000 (  0.080491)
Exception FAIL       14.550000  16.210000  30.760000 ( 39.894375)
Regexp OK             0.140000   0.000000   0.140000 (  0.151422)
Exception OK          0.810000   0.000000   0.810000 (  0.796678)


## RESULTS ruby 1.9.3p392 (2013-02-22 revision 39386) [x86_64-linux]
                           user     system      total        real
Regexp FAIL            0.090000   0.000000   0.090000 (  0.087240)
Exception FAIL         1.780000   0.010000   1.790000 (  1.791048)
Regexp OK              0.160000   0.000000   0.160000 (  0.161234)
Exception OK           0.840000   0.000000   0.840000 (  0.849894)

## RESULTS ruby 2.0.0p0 (2013-02-24 revision 39474) [x86_64-linux]
                           user     system      total        real
Regexp FAIL            0.090000   0.000000   0.090000 (  0.092935)
Exception FAIL         0.890000   0.000000   0.890000 (  0.893954)
Regexp OK              0.170000   0.000000   0.170000 (  0.170380)
Exception OK           0.970000   0.000000   0.970000 (  0.968676)