Class: N65::Bytes

Inherits:
InstructionBase show all
Defined in:
lib/n65/directives/bytes.rb

Overview

This directive to include bytes

Defined Under Namespace

Classes: InvalidByteValue

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from InstructionBase

#unresolved_symbols?

Constructor Details

#initialize(bytes_array) ⇒ Bytes

Initialize with filename



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# File 'lib/n65/directives/bytes.rb', line 50

def initialize(bytes_array)
  @bytes_array = bytes_array
end

Class Method Details

.parse(line) ⇒ Object

Try to parse an incbin directive



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# File 'lib/n65/directives/bytes.rb', line 17

def self.parse(line)
  match_data = line.match(/^\.bytes\s+(.+)$/)
  return nil if match_data.nil?

  bytes_array = match_data[1].split(',').map do |byte_string|

    ##  Does byte_string represent a numeric literal, or is it a symbol?
    ##  In numeric captures $2 is always binary, $1 is always hex

    case byte_string.strip
    when Regexp.new("^#{Regexes::Num8}$")
      $2.nil? ? $1.to_i(16) : $2.to_i(2)

    when Regexp.new("^#{Regexes::Num16}$")
      value = $2.nil? ? $1.to_i(16) : $2.to_i(2)

      ##  Break value up into two bytes
      high = (0xff00 & value) >> 8
      low  = (0x00ff & value)
      [low, high]
    when Regexp.new("^#{Regexes::Sym}$")
      $1
    else
      fail(InvalidByteValue, byte_string)
    end
  end.flatten

  Bytes.new(bytes_array)
end

Instance Method Details

#exec(assembler) ⇒ Object

Execute on the assembler



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# File 'lib/n65/directives/bytes.rb', line 57

def exec(assembler)

  promise = assembler.with_saved_state do |saved_assembler|
    @bytes_array.map! do |byte|
      case byte
      when Fixnum
        byte
      when String
        value = saved_assembler.symbol_table.resolve_symbol(byte)
      else
        fail(InvalidByteValue, byte)
      end
    end
    saved_assembler.write_memory(@bytes_array)
  end

  begin
    promise.call
  rescue SymbolTable::UndefinedSymbol
    ##  Write the bytes but assume a zero page address for all symbols
    ##  And just write 0xDE for a placeholder
    placeholder_bytes = @bytes_array.map do |byte|
      case bytes
      when Fixnum
        byte
      when String
        0xDE
      else
        fail(InvalidByteValue, byte)
      end
    end
    assembler.write_memory(placeholder_bytes)
    return promise
  end
end

#to_s ⇒ Object

Display, I don’t want to write all these out



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# File 'lib/n65/directives/bytes.rb', line 96

def to_s
  ".bytes (#{@bytes_array.length})"
end