block dsl facelift

lib/asm/block.rb

@@ -9,20 +9,44 @@ module Asm
   
   # A Block is the smalles unit of code, a list of instructions as it were
   # It is also a point to jump/branch to. An address in the final stream.
-  # To allow for forward branches creation does not fix the position. Either set or assembling does that.
+  # To allow for forward branches creation does not fix the position. 
+  # Thee position is fixed in one of three ways
+  # - create the block with ruby block, signalling that the instantiation poin is the position
+  # - call block.code with the code or if you wish program.add_block (and add you code with calls)
+  # - the assmebly process will pin it if it wasn't set
+
+  # creating blocks is done by calling the blocks name/label on either a program or a block
+  #  (method missing will cathc the call and create the block)
+  # and the easiest way is to go into a ruby block and start writing instructions
+  # Example (backward jump):
+  #       program.loop do                         create a new block with label loop
+  #                 sub r1 , r1 , 1               count the r1 register down
+  #                 bne :loop                     jump back to loop when the counter is not zero
+  #       end                                    (initialization and actual code missing off course)
+  
+  # Example (forward jump)
+  #       else_block = program.else
+  #       program.if do
+  #                  test r1 , 0                  test some condition
+  #                  beq :else_block
+  #                   mov . . .. ..               do whatever the if block does
+  #       end
+  #       else_block.code do
+  #                      ldr ....                 do whatever else does
+  #       end
   
   # Blocks are also used to create instructions, and so Block has functions for every cpu instruction
   # and to make using the apu function easier, there are functions that create registers as well
   class Block < Code
-    extend Forwardable  # forward block call back to program
-    def_delegator :@program, :block
 
-    def initialize(asm)
+    def initialize(name , prog)
       super()
+      @name = name.to_sym
       @codes = []
       @position = 0
-      @program = asm
+      @program = prog
     end
+    attr_reader :name
 
     ArmMachine::REGISTERS.each do |reg , number|
       define_method(reg) { Asm::Register.new(reg , number) }
@@ -39,6 +63,9 @@ module Asm
           arg_nodes << @program.add_string(arg)
         elsif (arg.is_a?(Asm::Block))
           arg_nodes << arg
+        elsif (arg.is_a?(Symbol))
+          block = @program.get_block arg
+          arg_nodes << block
         else
           raise "Invalid argument #{arg.inspect} for instruction"
         end
@@ -84,12 +111,11 @@ module Asm
       define_instruction(inst , CallInstruction)
     end
 
-    # setting a block fixes it's position in the stream. 
+    # codeing a block fixes it's position in the stream. 
-    # For backwards jumps, positions of blocks are known at creation, but for forward off course not.
+    # You must call with a block, which is instance_eval'd and provides the actual code for the block
-    # So then one can create a block, branch to it and set it later. 
+    def code &block
-    def set!
       @program.add_block self
-      self
+      self.instance_eval block 
     end
 
     # length of the codes. In arm it would be the length * 4
@@ -111,6 +137,17 @@ module Asm
       end
     end
 
+    # this is used to create blocks. 
+    # All functions that have no args are interpreted as block names
+    # In fact the block calls are delegated to the program which then instantiates the blocks
+    def method_missing(meth, *args, &block)
+      if args.length == 0
+        @program.send(meth , *args , &block)
+      else
+        super
+      end
+    end
+
   end
 
 end

lib/asm/program.rb

@@ -53,24 +53,6 @@ module Asm
       @blocks.inject(0) {| sum  , item | sum + item.length}
     end
 
-    # call block to create a new (code) block. The simple way is to do this with a block and 
-    # use the yielded block to add code, ie something like:
-    #   prog.block do |loop|
-    #         loop.instance_eval do           #this part you can acheive with calls too
-    #                   mov r0 , 10
-    #                   subs r0 , 1
-    #                   bne block
-    #         end
-    #   end
-    # Easy, because it's a backward jump. For forward branches that doesn't work and so you have to 
-    # create the block without a ruby block. You can then jumpt to it immediately
-    # But the block is not part of the program (since we don't know where) and so you have to add it later
-    def block
-      block = Block.new(self)
-      yield block.set! if block_given? #yield the block (which set returns)
-      block
-    end
-
     # This is how you add a forward declared block. This is called automatically when you 
     # call block with ruby block, but has to be done manually if not
     def add_block block
@@ -78,6 +60,32 @@ module Asm
       @blocks << block
     end
 
+    # return the block of the given name
+    # or raise an exception, as this is meant to be called when the block is available 
+    def get_block name
+      block = @blocks.find {|b| b.name == name}
+      raise "No block found for #{name} (in #{blocks.collect{|b|b.name}.join(':')})" unless block
+      block
+    end
+    # this is used to create blocks. 
+    # All functions that have no args are interpreted as block names
+    # and if a block is provided, it is evaluated in the (ruby)blocks scope and the block added to the 
+    # program immediately. 
+    # If no block is provided (forward declaration), you must call code on it later 
+    def method_missing(meth, *args, &block)
+      if args.length == 0
+        code = Block.new(meth.to_s , self )
+        if block_given?
+          add_block code
+          code.instance_eval(&block)
+        end
+        return code
+      else
+        super
+      end
+    end
+    
+
     private
     
     def assemble(io)

test/test_small_program.rb

@@ -13,17 +13,13 @@ class TestSmallProg < MiniTest::Test
   end
 
   def test_loop
-    @program.block do |main|
+    @program.main do
-      main.instance_eval do
+      mov r0, 5                #1
-        mov r0, 5                #1
+      start do
-        main.block do |start|
+        subs r0, r0, 1       #2
-          start.instance_eval do
+        bne :start           #3
-            subs r0, r0, 1       #2
+        mov r7, 1               #4
-            bne start           #3
+      	swi 0                   #5  5 instructions
-          end
-          mov r7, 1               #4
-        	swi 0                   #5  5 instructions
-        end
       end
     end
     write( 5 , "loop" )
@@ -31,16 +27,14 @@ class TestSmallProg < MiniTest::Test
 
   def test_hello
     hello = "Hello Raisa\n"
-    @program.block do |main|
+    @program.main do 
-      main.instance_eval do
+      mov r7, 4     # 4 == write
-        mov r7, 4     # 4 == write
+      mov r0 , 1    # stdout
-        mov r0 , 1    # stdout
+      add r1 , pc , hello   # address of "hello Raisa"
-        add r1 , pc , hello   # address of "hello Raisa"
+      mov r2 , hello.length
-        mov r2 , hello.length
+    	swi 0         #software interupt, ie kernel syscall
-      	swi 0         #software interupt, ie kernel syscall
+      mov r7, 1     # 1 == exit
-        mov r7, 1     # 1 == exit
+    	swi 0
-      	swi 0
-      end
     end
     write(7 + hello.length/4 + 1 , 'hello') 
   end