Class: Fisk::UnresolvedInstruction

Inherits:
Object
  • Object
show all
Defined in:
lib/fisk.rb

Instance Method Summary collapse

Constructor Details

#initialize(insn, form, operand) ⇒ UnresolvedInstruction

Returns a new instance of UnresolvedInstruction.



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# File 'lib/fisk.rb', line 181

def initialize insn, form, operand
  @insn      = insn
  @form      = form
  @operand   = operand
  @saved_pos = nil
end

Instance Method Details

#encode(buffer, labels) ⇒ Object 



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# File 'lib/fisk.rb', line 188

def encode buffer, labels
  # Estimate by using a rel32 offset
  form          = find_form "rel32"
  encoding      = form.encodings.first
  operand_klass = Rel32

  if labels.key? @operand.name
    if @saved_pos
      # Only use rel32 if we saved the position
      buffer.seek @saved_pos, IO::SEEK_SET
    else
      estimated_offset = labels[@operand.name] - (buffer.pos + encoding.bytesize)

      if estimated_offset >= -128 && estimated_offset <= 127
        # fits in a rel8
        operand_klass = Rel8
        form          = find_form "rel8"
        encoding      = form.encodings.first
      end
    end

    jump_len = -(buffer.pos + encoding.bytesize - labels[@operand.name])
    encoding.encode buffer, [operand_klass.new(jump_len)]
    true
  else
    # We've hit a label that doesn't exist yet
    # Save the buffer position so we can seek back to it later
    @saved_pos = buffer.pos
    # Write 5 bytes to reserve our spot
    encoding.bytesize.times { buffer.putc 0 }
    false
  end
end

#label? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/fisk.rb', line 222

def label?; false; end