Assembler for DCPU-16

dcpu-assembler.rb

class Register < Struct.new(:name)
  BASIC   = %w[A B C X Y Z I J].map(&:to_sym)
  SPECIAL = %w[POP PEEK PUSH SP PC O].map(&:to_sym)
  ALL     = BASIC + SPECIAL

  attr_accessor :plus

  def value
    case name
    when *BASIC
      BASIC.index(name)
    when *SPECIAL
      SPECIAL.index(name) + 0x18
    end
  end

  def +(n)
    @plus = n
    self
  end
end

class Instruction < Struct.new(:name, :a, :b)
  BASIC = %w[SET ADD SUB MUL DIV MOD SHL SHR AND BOR XOR IFE IFN IFG IFB].map(&:to_sym)
  NON   = %w[JSR].map(&:to_sym)
  ALL   = BASIC + NON

  def basic?
    BASIC.include?(name)
  end

  def opcode
    if basic?
      BASIC.index(name) + 1
    else
      NON.index(name) + 1
    end
  end

  def to_memory(mem = [])
    if basic?
      acode, an = value(a)
      bcode, bn = value(b)
      mem << (opcode | (acode << 4) | (bcode << 10))
      mem << an if an
      mem << bn if bn
    else
      acode, an = value(a)
      mem << ((opcode << 4) | (acode << 10))
      mem << an if an
    end

    mem
  end

  def value(thing)
    case thing
    when Register
      if thing.plus
        [thing.value + 0x10, thing.plus]
      else
        thing.value
      end
    when Indirect
      thing.value
    when Fixnum
      if thing <= 0x1F
        thing + 0x20
      else
        [0x1F, thing]
      end
    else
      [0x1F, thing]
    end
  end
end

class Indirect < Struct.new(:cell)
  def value
    case cell
    when Fixnum
      [0x1E, cell]
    when Register
      0x08 + cell.value
    else
      raise "Missing: #{cell}"
    end
  end
end

class Unit
  Register::ALL.each do |name|
    define_method(name.to_s.downcase) { Register.new(name) }
  end

  Instruction::BASIC.each do |name|
    define_method(name) do |a, b|
      @ins << Instruction.new(name.to_sym, a, b)
    end
  end

  def JSR(a)
    @ins << Instruction.new(:JSR, a)
  end

  def at(t)
    Indirect.new(t)
  end

  def initialize
    @ins = []
  end

  def label(name)
    @ins << name
  end

  def memory
    labels = {}
    res = []
    @ins.each do |i|
      if i.is_a?(Symbol)
        labels[i] = res.compact.size
      else
        res.concat(i.to_memory)
      end
    end

    res.each_with_index do |x, idx|
      if x.is_a?(Symbol)
        res[idx] = labels[x]
      end
    end

    res
  end

  def dump
    memory.each_slice(8).each_with_index do |r, i|
      print "#{(i*8).to_s(16).rjust(4, '0')}: "
      puts r.map { |x| x.to_s(16).rjust(4, '0') }.join(" ")
    end
  end
end

def unit(&blk)
  Unit.new.tap { |x| x.instance_eval(&blk) }
end

if $0 == __FILE__
  unit do
    SET a, 0x30
    SET at(0x1000), 0x20
    SUB a, at(0x1000)
    IFN a, 0x10
    SET pc, :crash

    SET i, 10
    SET a, 0x2000
    label :loop
    SET (i+0x2000), at(a)
    SUB i, 1
    IFN i, 0
    SET pc, :loop

    SET x, 0x4
    JSR :testsub
    SET pc, :crash

    label :testsub
    SHL x, 0x4
    SET pc, pop

    label :crash
    SET pc, :crash
  end.dump
end

See also: https://github.com/judofyr/rcpu