adds first version of the expanded as assembler from mikko

lib/asm/arm/builder_d.rb

@@ -0,0 +1,52 @@
+module Asm
+  module Arm
+    # ADDRESSING MODE 4
+    class BuilderD
+      include Asm::ARM::InstructionTools
+
+      def initialize
+        @cond = 0b1110
+        @inst_class = Asm::ARM::Instruction::OPC_STACK
+        @pre_post_index = 0
+        @up_down = 0
+        @s = 0
+        @write_base = 0
+        @store_load = 0
+        @rn = 0
+        @operand = 0
+      end
+      attr_accessor :cond, :inst_class, :pre_post_index, :up_down,
+                    :s, :write_base, :store_load, :rn, :operand
+
+      def self.make(pre_post, up_down, write, store_load)
+        a = new
+        a.pre_post_index = pre_post
+        a.up_down = up_down
+        a.write_base = write
+        a.store_load = store_load
+        a
+      end
+
+      # Build representation for source value
+      def build_operand(arg)
+        if (arg.is_a?(Asm::Parser::RegisterListArgNode))
+          @operand = 0
+          arg.registers.each do |reg_node|
+            reg = reg_ref(reg_node)
+            @operand |= (1 << reg)
+          end
+        else
+          raise Asm::AssemblyError.new(Asm::ERRSTR_INVALID_ARG, arg)
+        end
+      end
+
+      def write(io, as)
+        val = operand | (rn << 16) | (store_load << 16+4) | 
+              (write_base << 16+4+1) | (s << 16+4+1+1) | (up_down << 16+4+1+1+1) |
+              (pre_post_index << 16+4+1+1+1+1) | (inst_class << 16+4+1+1+1+1+2) |
+              (cond << 16+4+1+1+1+1+2+2)
+        io.write_uint32 val
+      end
+    end
+  end
+end