Implement Sisimai::RFC791.is_ipv4address #319, imported from https://…

…github.com/sisimai/go-sisimai/blob/master/sisimai/rfc791/lib.go

lib/sisimai/fact.rb

@@ -2,6 +2,7 @@ module Sisimai
   # Sisimai::Fact generate the list of decoded bounce data
   class Fact
     require 'sisimai/message'
+    require 'sisimai/rfc791'
     require 'sisimai/rfc1123'
     require 'sisimai/rfc1894'
     require 'sisimai/rfc5322'
@@ -246,7 +247,7 @@ def self.rise(**argvs)
             ee.each do |w|
               # get a hostname from the string like "127.0.0.1 x109-20.example.com 192.0.2.20"
               # or "mx.sp.example.jp 192.0.2.135"
-              next if w =~ /\A\d{1,3}[.]\d{1,3}[.]\d{1,3}[.]\d{1,3}\z/; # Skip if it is an IPv4 address
+              next if Sisimai::RFC791.is_ipv4address(w)
               piece[v] = w
               break
             end

lib/sisimai/rfc791.rb

@@ -2,6 +2,22 @@ module Sisimai
   # Sisimai::RFC791 is a class related to the Internet host
   module RFC791
     class << self
+      # Returns 1 if the argument is an IPv4 address
+      # @param    [String] argv1  IPv4 address like "192.0.2.25"
+      # @return   [Bool]          1: is an IPv4 address
+      # @since v5.2.0
+      def is_ipv4address(argv0)
+        return false if argv0.nil? || argv0.size < 7
+        octet = argv0.split(/[.]/); return false if octet.size != 4
+
+        octet.each do |e|
+          # Check each octet is between 0 and 255
+          return false unless e =~ /\A[0-9]{1,3}\z/
+          v = e.to_i
+          return false if v < 0 || v > 255
+        end
+        return true
+      end
       # Find an IPv4 address from the given string
       # @param    [String] argv1  String including an IPv4 address
       # @return   [Array]         List of IPv4 addresses

test/public/rfc791-test.rb

@@ -2,9 +2,21 @@
 require 'sisimai/rfc791'
 
 class RFC791Test < Minitest::Test
-  Methods = { class: %w[find] }
+  Methods = { class: %w[is_ipv4address find] }
 
-  def test_ipv4
+  def test_is_upv4address
+    addr0 = ["123.456.78.9"]
+    addr1 = ["192.0.2.22"]
+
+    addr0.each do |e|
+      assert_equal false, Sisimai::RFC791.is_ipv4address(e)
+    end
+    addr1.each do |e|
+      assert_equal true,  Sisimai::RFC791.is_ipv4address(e)
+    end
+  end
+
+  def test_find
     ip4address = [
       ['host smtp.example.jp 127.0.0.4 SMTP error from remote mail server', '127.0.0.4'],
       ['mx.example.jp (192.0.2.2) reason: 550 5.2.0 Mail rejete.', '192.0.2.2'],