From: b.candler@...
Date: 2007-03-21T19:11:10+09:00
Subject: Extensions to ipaddr.rb

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I'd like to contribute the following extensions to ipaddr.rb 

They allow the following constructs: 

 puts IPAddr.new("192.168.0.0") + 1          # => 192.168.0.1
 puts IPAddr.new("192.168.0.0") - 1          # => 192.167.255.255
 puts IPAddr.new("192.168.0.0/24").netmask   # => 255.255.255.0
 puts IPAddr.new("192.168.0.0/24").prefixlen # => 24
 puts IPAddr.new("192.168.0.0/24").size      # => 256 

Regards, 

Brian Candler. 



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--- /usr/lib/ruby/1.8/ipaddr.rb	2006-08-04 23:00:21.000000000 +0100
+++ ipaddr.rb	2007-03-21 10:11:55.000000000 +0000
@@ -125,6 +125,16 @@
     return self.clone.set(addr_mask(@addr << num))
   end
 
+  # Returns a new ipaddr built by addition.
+  def +(other)
+    return self.clone.set(@addr + other.to_i)
+  end
+
+  # Returns a new ipaddr built by subtraction.
+  def -(other)
+    return self.clone.set(@addr - other.to_i)
+  end
+
   # Returns a new ipaddr built by bitwise negation.
   def ~
     return self.clone.set(addr_mask(~@addr))
@@ -331,6 +341,37 @@
 		   af, _to_string(@addr), _to_string(@mask_addr))
   end
 
+  # Return just the netmask.
+  def netmask
+    _to_string(@mask_addr)
+  end
+
+  # Return just the prefix length.
+  def prefixlen
+    m = case @family
+    when Socket::AF_INET
+      IN4MASK
+    when Socket::AF_INET6
+      IN6MASK
+    else
+      raise "unsupported address family"
+    end
+    return $1.length if /\A(1*)(0*)\z/ =~ (@mask_addr & m).to_s(2)
+    raise "bad addr_mask format"
+  end
+
+  # Return the number of IP addresses in the block.
+  def size
+    case @family
+    when Socket::AF_INET
+      ((~@mask_addr) & IN4MASK) + 1
+    when Socket::AF_INET6
+      ((~@mask_addr) & IN6MASK) + 1
+    else
+      raise "unsupported address family"
+    end
+  end
+
   protected
 
   def set(addr, *family)
@@ -547,6 +588,9 @@
     a = IPAddr.new("0123:4567:89ab:cdef:0ABC:DEF0:1234:5678")
     assert_equal("123:4567:89ab:cdef:abc:def0:1234:5678", a.to_s)
     assert_equal("0123:4567:89ab:cdef:0abc:def0:1234:5678", a.to_string)
+    assert_equal("ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff", a.netmask)
+    assert_equal(128, a.prefixlen)
+    assert_equal(1, a.size)
     assert_equal(Socket::AF_INET6, a.family)
 
     a = IPAddr.new("3ffe:505:2::/48")
@@ -556,6 +600,9 @@
     assert_equal(false, a.ipv4?)
     assert_equal(true, a.ipv6?)
     assert_equal("#<IPAddr: IPv6:3ffe:0505:0002:0000:0000:0000:0000:0000/ffff:ffff:ffff:0000:0000:0000:0000:0000>", a.inspect)
+    assert_equal("ffff:ffff:ffff:0000:0000:0000:0000:0000", a.netmask)
+    assert_equal(48, a.prefixlen)
+    assert_equal(1 << 80, a.size)
 
     a = IPAddr.new("3ffe:505:2::/ffff:ffff:ffff::")
     assert_equal("3ffe:505:2::", a.to_s)
@@ -566,6 +613,16 @@
     assert_equal("0.0.0.0", a.to_s)
     assert_equal("0.0.0.0", a.to_string)
     assert_equal(Socket::AF_INET, a.family)
+    assert_equal("#<IPAddr: IPv4:0.0.0.0/255.255.255.255>", a.inspect)
+    assert_equal("255.255.255.255", a.netmask)
+    assert_equal(32, a.prefixlen)
+    assert_equal(1, a.size)
+
+    a = IPAddr.new("0.0.0.0/0")
+    assert_equal("#<IPAddr: IPv4:0.0.0.0/0.0.0.0>", a.inspect)
+    assert_equal("0.0.0.0", a.netmask)
+    assert_equal(0, a.prefixlen)
+    assert_equal(1 << 32, a.size)
 
     a = IPAddr.new("192.168.1.2")
     assert_equal("192.168.1.2", a.to_s)
@@ -579,11 +636,17 @@
     assert_equal("192.168.1.0", a.to_string)
     assert_equal(Socket::AF_INET, a.family)
     assert_equal("#<IPAddr: IPv4:192.168.1.0/255.255.255.0>", a.inspect)
+    assert_equal("255.255.255.0", a.netmask)
+    assert_equal(24, a.prefixlen)
+    assert_equal(256, a.size)
 
     a = IPAddr.new("192.168.1.2/255.255.255.0")
     assert_equal("192.168.1.0", a.to_s)
     assert_equal("192.168.1.0", a.to_string)
     assert_equal(Socket::AF_INET, a.family)
+    assert_equal("255.255.255.0", a.netmask)
+    assert_equal(24, a.prefixlen)
+    assert_equal(256, a.size)
 
     assert_equal("0:0:0:1::", IPAddr.new("0:0:0:1::").to_s)
     assert_equal("2001:200:300::", IPAddr.new("2001:200:300::/48").to_s)
@@ -728,6 +791,16 @@
     assert_equal("3ffe:505:2::", @a.to_s)
   end
 
+  def test_add
+    a = IPAddr.new("3ffe:505:2:1:ffff:ffff:ffff:fffd")
+    assert_equal("3ffe:505:2:1:ffff:ffff:ffff:fffe", (a + 1).to_s)
+    assert_equal("3ffe:505:2:2::", (a + 3).to_s)
+  end
+
+  def test_sub
+    assert_equal("3ffe:505:1:ffff:ffff:ffff:ffff:ffff", (@a - 1).to_s)
+  end
+
   def test_carrot
     a = ~@in6_addr_any
     assert_equal(IN6MASK128, a.to_s)

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