Merge MessageHdr into Message and make Ipv6Address a BasePrimitive

The former makes setting payload_length sensibly much easier, with
no drawbacks that I can see, while the latter lets us override
assign to make comparisons between instances sane.

All good.

lib/btc_wire_proto.rb

@@ -4,41 +4,58 @@ require 'ipaddress'
 # Wraps the IPAddress::IPv6 class found in the ipaddress gem to provide easier
 # handling of binary-format IP addresses
 # @author Nick Thomas <nick@lupine.me.uk>
-class Ipv6Address < BinData::Primitive
-  endian :big
-
-  uint128 :address
+class Ipv6Address < BinData::BasePrimitive
+  register_self if BinData::VERSION < "1.3.2"
   
-  def get
-    if address
-      if address >= 0xffff00000000 && address <= 0xffffffffffff # v6-mapped v4
-        IPAddress::IPv6::Mapped.parse_u128(address)
-      else # v6
-        IPAddress::IPv6.parse_u128(address)
-      end
-    else
-      nil # Nothing set
-    end  
+  def value_to_binary_string(v)
+    ip = any_to_ipaddress(v)
+    raise ArgumentError.new("Can't convert #{v.class} to Ipv6Address") unless ip
+    ip.data
+  end
+  
+  def read_and_return_value(io)
+    address = read_uint128(io)
+    if address >= 0xffff00000000 && address <= 0xffffffffffff # v6-mapped v4
+      IPAddress::IPv6::Mapped.parse_u128(address)
+    else # v6
+      IPAddress::IPv6.parse_u128(address)
+    end
+  end
+  
+  def sensible_default
+    IPAddress("::")
+  end
+  
+  def assign(v)
+    super(any_to_ipaddress(v))
   end
 
-  def set(v)
+  protected
+  
+  def any_to_ipaddress(v)
     v = IPAddress(v) if v.is_a?(String)
-    v = IPAddress::IPv6::Mapped.new(v.to_s) if v.is_a?(IPAddress::IPv4)
-    if v.is_a?(Fixnum) || v.is_a?(Bignum)
-      v = if v < 2**32
-        IPAddress::IPv6::Mapped.parse_u128(v)
-      else
-        IPAddress::IPv6::parse_u128(v)
-      end
-    end
-      
 
-    if v.respond_to?(:to_u128)
-      self.address = v.to_u128
+    if v.is_a?(IPAddress::IPv4)
+      IPAddress::IPv6::Mapped.new("::ffff:#{v.to_s}")
+    elsif v.is_a?(IPAddress::IPv6)
+      v
+    elsif v.is_a?(Fixnum) || v.is_a?(Bignum) || v.respond_to?(:to_u128)
+      v = v.to_u128 if v.respond_to?(:to_u128)
+      if v < 2**32
+        IPAddress::IPv6::Mapped.new("::ffff:#{IPAddress::IPv4.parse_u32(v).to_s}")
+      else
+        IPAddress::IPv6.parse_u128(v)      
+      end
     else
-      raise ArgumentError.new("Can't set #{v.class} to an IPv6Address")      
-    end  
-  end  
+      nil
+    end
+  end
+
+  def read_uint128(io)
+    top, middle1, middle2, bottom = io.readbytes(16).unpack("NNNN")
+    (top << 96) | (middle1 << 64) | (middle2 << 32) | (bottom)
+  end
+
 end
 
 # Implementation of the BitCoin wire protocol, written using bindata.
@@ -395,30 +412,6 @@ module BtcWireProto
 
   ## Top-level message format ##
   
-  # Found at the start of all Bitcoin messages.
-  # @author Nick Thomas <nick@lupine.me.uk>
-  class MessageHdr < BinData::Record
-    endian :little
-    uint32 :magic
-    string :command, :length => 12
-    uint32 :payload_len
-    uint32 :checksum, :onlyif => :has_checksum?
-    
-    def cmd_sym
-      c = command.strip
-      c == "" ? nil : c.to_sym
-    end
-    
-    protected
-    
-    # version and verack messages don't have a checksum. The rest do.
-    # @return[Boolean] does this message header have a checksum field or not?
-    def has_checksum?
-      !%w|version verack|.include?(command.strip)
-    end 
-  end
-
-
   # Everything on the wire is a Message.
   # @author Nick Thomas <nick@lupine.me.uk>
   class Message < BinData::Record
@@ -430,11 +423,11 @@ module BtcWireProto
       @version = v || ::BtcWireProto::CURRENT_VERSION(:main)
     end
 
-    message_hdr :header
-    
-    def cmd_sym
-      header ? header.cmd_sym : nil
-    end
+    endian :little
+    uint32 :magic
+    string :command, :length => 12
+    uint32 :payload_len, :value => lambda { payload.num_bytes }
+    uint32 :checksum, :onlyif => :has_checksum?
     
     choice :payload, :selection => :payload_choice do
       version         "version"
@@ -453,10 +446,20 @@ module BtcWireProto
       null_payload    "null"
     end
 
+    def cmd_sym
+      c = command.strip
+      c == "" ? nil : c.to_sym
+    end
+    # version and verack messages don't have a checksum. The rest do.
+    # @return[Boolean] does this message header have a checksum field or not?
+    def has_checksum?
+      !%w|version verack|.include?(command.to_s.strip)
+    end
+
     # Works out what the payload looks like based on the MessageHdr struct
     # and (potentially) the version
     def payload_choice
-      cmd = header.command.to_s.strip
+      cmd = command.to_s.strip
       return cmd if %w{
         version inv getdata getblocks getheaders tx block headers alert
       }.include?(cmd)