base.exe

compiler.rb

# -*- coding: utf-8 -*-

class String
  # offset 文字目から val の長さぶん val で置き換える
  def write(offset, val)
    self[offset, val.length] = val
  end
end

def compile(lines)
  lines << "exit" unless lines.last == "exit"

  ret = ""
  lines.each_with_index do |line, i|
    line.strip!
    case line
    when /^let eax (.+)$/
      ret << [0xb8, $1.to_i].pack("CI")
    when /^exit$/
      ret << [0xc3].pack("C")
    else
      puts "can't compile(line #{i+1}): #{line}"
      exit 1
    end
  end
  ret
end

source = [
  "let eax 123",
]

base = File.open("base.exe", "rb").read
text = compile(source)
base.write(0x180, [text.length].pack("I"))
base.write(0x200, text)

File.open("output.exe", "wb").write(base)