Index: src/resolver.cr
==================================================================
--- src/resolver.cr
+++ src/resolver.cr
@@ -29,49 +29,39 @@
       def initialize(@query : Query, @id : UInt16, @settings : Settings,
                      @block : Response | Error ->)
         @ns_index = 0
         @attempt = 0
         @used_ns = nil
-        @raw_data = Bytes.new(512)
 
         # Header
 
-        i = 0
-        @raw_data[i] = (@id >> 8).to_u8; i += 1
-        @raw_data[i] = (@id & 0xFF).to_u8; i += 1
+        io = IO::Memory.new(512)
+        io.write_bytes(@id, IO::ByteFormat::BigEndian)
         # RD
-        @raw_data[i] = 1; i += 1
-        i += 1
+        io.write_bytes(0x100_u16, IO::ByteFormat::BigEndian)
         # QDCOUNT
-        i += 1
-        @raw_data[i] = 1; i += 1
+        io.write_bytes(1_u16, IO::ByteFormat::BigEndian)
         # ANCOUNT, NSCOUNT and ARCOUNT
-        i += 6
+        3.times { io.write_bytes(0_u16) }
 
         # Question
 
         # QNAME
         @query.domain.split('.').each do |component|
-          if component.bytesize > 63 || i + component.bytesize > 512
+          if component.bytesize > 63 || io.size + component.bytesize > 512
             raise ArgumentError.new("Domain component too long")
           end
 
-          raw_component = component.to_slice
-          @raw_data[i] = raw_component.bytesize.to_u8; i += 1
-          @raw_data[i, raw_component.bytesize].copy_from(raw_component)
-          i += raw_component.bytesize
+          io << component
         end
 
         # QTYPE
-        qtype = @query.rr_type.to_i
-        @raw_data[i] = (qtype >> 8).to_u8; i += 1
-        @raw_data[i] = (qtype & 0xFF).to_u8; i+= 1
-
+        io.write_bytes(@query.rr_type.to_u16, IO::ByteFormat::BigEndian)
         # QCLASS
-        qclass = @query.dns_class.to_i
-        @raw_data[i] = (qclass >> 8).to_u8; i += 1
-        @raw_data[i] = (qclass & 0xFF).to_u8; i += 1
+        io.write_bytes(@query.dns_class.to_u16, IO::ByteFormat::BigEndian)
+
+        @raw_data = io.to_slice
       end
     end
 
     def initialize
       @settings = Settings.new