Class: Gruesome::Z::Memory

Inherits:
Object
  • Object
show all
Defined in:
lib/gruesome/z/memory.rb

Overview

This class holds the memory for the virtual machine

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(contents, save_file_name) ⇒ Memory

Returns a new instance of Memory.



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# File 'lib/gruesome/z/memory.rb', line 43

def initialize(contents, save_file_name)
  @call_stack = []
  @save_file_name = save_file_name
  @stack = []
  @memory = contents
  @num_locals = 0

  # Get the header information
  @header = Header.new(@memory)
  @program_counter = @header.entry

  # With the header info, discover the bounds of each memory region
  @dyn_base = 0x0
  @dyn_limit = @header.static_mem_base

  # Cannot Write to Static Memory
  @static_base = @header.static_mem_base
  @static_limit = @memory.length

  # Cannot Access High Memory
  @high_base = @header.high_mem_base
  @high_limit = @memory.length

  # Error if high memory overlaps dynamic memory
  if @high_base < @dyn_limit
    # XXX: ERROR
  end

  # Check machine endianess
  @endian = [1].pack('S')[0] == 1 ? 'little' : 'big'
end

Instance Attribute Details

#num_locals ⇒ Object (readonly)

Returns the value of attribute num_locals.



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# File 'lib/gruesome/z/memory.rb', line 41

def num_locals
  @num_locals
end

#program_counter ⇒ Object

Returns the value of attribute program_counter.



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# File 'lib/gruesome/z/memory.rb', line 40

def program_counter
  @program_counter
end

Instance Method Details

#contents ⇒ Object 



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# File 'lib/gruesome/z/memory.rb', line 208

def contents
  @memory
end

#force_readb(address) ⇒ Object 



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# File 'lib/gruesome/z/memory.rb', line 154

def force_readb(address)
  if address < @memory.size
    @memory.getbyte(address)
  else
    # XXX: Access Violation
    raise "Major Access Violation accessing $" + sprintf("%04x", address)
    nil
  end
end

#force_readw(address) ⇒ Object 



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# File 'lib/gruesome/z/memory.rb', line 164

def force_readw(address)
  if (address + 1) < @memory.size
    if @endian == 'little'
      (@memory.getbyte(address+1) << 8) | @memory.getbyte(address)
    else
      (@memory.getbyte(address) << 8) | @memory.getbyte(address+1)
    end
  else
    # XXX: Access Violation
    raise "Major Access Violation accessing $" + sprintf("%04x", address)
    nil
  end
end

#force_readzstr(index, max_len = -1)) ⇒ Object 



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# File 'lib/gruesome/z/memory.rb', line 243

def force_readzstr(index, max_len = -1)
  chrs = []
  continue = true
  orig_index = index

  until continue == false do
    if max_len != -1 and (index + 2 - orig_index) > max_len
      break
    end

    byte1 = force_readb(index)
    byte2 = force_readb(index+1)

    index += 2

    chrs << ((byte1 >> 2) & 0b11111)
    chrs << (((byte1 & 0b11) << 3) | (byte2 >> 5))
    chrs << (byte2 & 0b11111)

    continue = (byte1 & 0b10000000) == 0
  end

  return [index - orig_index, chrs]
end

#force_writeb(address, value) ⇒ Object 



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# File 'lib/gruesome/z/memory.rb', line 178

def force_writeb(address, value)
  if address < @memory.size
    @memory.setbyte(address, (value & 255))
  else
    # XXX: Access Violation
    raise "Major Access (W) Violation accessing $" + sprintf("%04x", address)
    nil
  end
end

#force_writew(address, value) ⇒ Object 



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# File 'lib/gruesome/z/memory.rb', line 188

def force_writew(address, value)
  if (address + 1) < @memory.size
    low_byte = value & 255
    high_byte = (value >> 8) & 255

    if @endian == 'little'
      tmp = high_byte
      high_byte = low_byte
      low_byte = tmp
    end

    @memory.setbyte(address, high_byte)
    @memory.setbyte(address+1, low_byte)
  else
    # XXX: Access Violation
    raise "Major Access (W) Violation accessing $" + sprintf("%04x", address)
    nil
  end
end

#packed_address_to_byte_address(address) ⇒ Object 



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# File 'lib/gruesome/z/memory.rb', line 75

def packed_address_to_byte_address(address)
  if @header.version <=3
    address * 2
  else
  end
end

#pop_routine ⇒ Object

Tears down the environment for the current routine



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# File 'lib/gruesome/z/memory.rb', line 104

def pop_routine()
  # return the return address
  return_addr = @stack[0]
  @stack = @call_stack.pop
  destination = @call_stack.pop
  @num_locals = @call_stack.pop

  {:destination => destination, :return_address => return_addr}
end

#push_routine(return_addr, num_locals, destination) ⇒ Object

Sets up the environment for a new routine



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# File 'lib/gruesome/z/memory.rb', line 83

def push_routine(return_addr, num_locals, destination)
  # pushes the stack onto the call stack
  @call_stack.push @num_locals
  @call_stack.push destination
  @call_stack.push @stack

  # empties the current stack
  @stack = Array.new()

  # pushes the return address onto the stack
  @stack.push(return_addr)

  # push locals
  num_locals.times do
    @stack.push 0
  end

  @num_locals = num_locals
end

#readb(address) ⇒ Object 



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# File 'lib/gruesome/z/memory.rb', line 114

def readb(address)
  if address < @high_base
    force_readb(address)
  else
    # XXX: Access violation
    raise "Access Violation accessing $" + sprintf("%04x", address)
    nil
  end
end

#readv(index) ⇒ Object

Read from variable number index



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# File 'lib/gruesome/z/memory.rb', line 213

def readv(index)
  if index == 0
    # pop from stack
    @stack.pop
  elsif index >= 16
    index -= 16
    readw(@header.global_var_addr + (index*2))
  elsif index <= @num_locals
    @stack[index]
  else
    # XXX: Error
  end
end

#readw(address) ⇒ Object 



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# File 'lib/gruesome/z/memory.rb', line 124

def readw(address)
  if (address + 1) < @high_base
    force_readw(address)
  else
    # XXX: Access violation
    raise "Access Violation accessing $" + sprintf("%04x", address)
    nil
  end
end

#restore ⇒ Object 



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# File 'lib/gruesome/z/memory.rb', line 297

def restore
  # Restore, if it can, the contents of memory from disk
  File.open(@save_file_name, "rb") do |f|
    @call_stack = []

    @program_counter = f.readline.to_i
    call_stack_size = f.readline.to_i

    call_stack_size.times do
      num_locals = f.readline.to_i
      destination = f.readline.to_i
      stack_size = f.readline.to_i

      stack = []
      stack_size.times do |i|
        stack.push f.readline.to_i
      end

      @call_stack.push num_locals
      @call_stack.push destination
      @call_stack.push stack
    end

    @num_locals = f.readline.to_i
    stack_size = f.readline.to_i

    @stack = []
    stack_size.times do |i|
      @stack.push f.readline.to_i
    end

    i = 0
    f.read.each_byte do |b|
      force_writeb(i, b)
      i += 1
    end
  end
end

#save ⇒ Object 



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# File 'lib/gruesome/z/memory.rb', line 268

def save
  # Save contents of dynamic memory to disk
  File.open(@save_file_name, "wb+") do |f|
    f.puts @program_counter
    f.puts (@call_stack.size / 3)
    @call_stack.each_with_index do |call_stack, i|
      if (i % 3) == 0 or (i % 3) == 1
        f.puts call_stack
      else
        # this is stack
        stack = call_stack
        f.puts stack.size
        stack.each do |stack_entry|
          f.puts stack_entry
        end
      end
    end
    f.puts @num_locals
    f.puts @stack.size
    @stack.each do |stack_entry|
      f.puts stack_entry
    end

    @dyn_limit.times do |i|
      f.write force_readb(i).chr
    end
  end
end

#writeb(address, value) ⇒ Object 



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# File 'lib/gruesome/z/memory.rb', line 134

def writeb(address, value)
  if address < @static_base
    force_writeb(address, value)
  else
    # XXX: Access violation
    raise "Access Violation (W) accessing $" + sprintf("%04x", address)
    nil
  end
end

#writev(index, value) ⇒ Object

Write value to variable number index



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# File 'lib/gruesome/z/memory.rb', line 228

def writev(index, value)
  value &= 65535
  if index == 0
    # push to stack
    @stack.push value
  elsif index >= 16
    index -= 16
    writew(@header.global_var_addr + (index*2), value)
  elsif index <= @num_locals
    @stack[index] = value
  else
    # XXX: Error
  end
end

#writew(address, value) ⇒ Object 



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# File 'lib/gruesome/z/memory.rb', line 144

def writew(address, value)
  if (address + 1) < @static_base
    force_writew(address, value)
  else
    # XXX: Access violation
    raise "Access Violation (W) accessing $" + sprintf("%04x", address)
    nil
  end
end