Class: Amaterasu::GameBoy::Cpu::Instructions::CbRes

Inherits:
Base
  • Object
show all
Includes:
Utils::BitOps
Defined in:
lib/amaterasu/game_boy/cpu/instructions/cb_res.rb,
sig/akane/game_boy/cpu/instructions/cb_res.rbs

Overview

Holds the logic of all the RES instructions.

Instance Attribute Summary

Attributes inherited from Base

#mnemonic

Instance Method Summary collapse

Methods included from Utils::BitOps

bit, clear_bit, #self?.bit, #self?.clear_bit, #self?.set_bit, set_bit

Methods inherited from Base

#execute, #format_operand

Constructor Details

#initialize(cpu:, bit_pos:, target:) ⇒ CbRes

Creates a new CbRes object containing the mnemonic (String) and logic (Proc).

Parameters:

  • cpu: (Cpu)
  • bit_pos: (Integer)
  • target: (Symbol) 


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# File 'lib/amaterasu/game_boy/cpu/instructions/cb_res.rb', line 12

def initialize(cpu:, bit_pos:, target:)
  super(cpu:)

  @mnemonic = "RES #{bit_pos}, #{format_operand(target)}"
  @logic    = build_logic(bit_pos, target)
end

Instance Method Details

#build_logic(bit_pos, target) ⇒ Proc

Returns Logic to be executed by the Cpu.

Parameters:

  • bit_pos (Integer) —

    Integer between 0 and 7.

  • target (Symbol) —

    Either a 8-bit register (:a, :b, :c, ...) or :mem_hl.

Returns:

  • (Proc) —

    Logic to be executed by the Cpu.



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# File 'lib/amaterasu/game_boy/cpu/instructions/cb_res.rb', line 26

def build_logic(bit_pos, target)
  case target
  when :a      then -> { @registers.a = clear_bit(@registers.a, bit_pos) }
  when :b      then -> { @registers.b = clear_bit(@registers.b, bit_pos) }
  when :c      then -> { @registers.c = clear_bit(@registers.c, bit_pos) }
  when :d      then -> { @registers.d = clear_bit(@registers.d, bit_pos) }
  when :e      then -> { @registers.e = clear_bit(@registers.e, bit_pos) }
  when :h      then -> { @registers.h = clear_bit(@registers.h, bit_pos) }
  when :l      then -> { @registers.l = clear_bit(@registers.l, bit_pos) }
  when :mem_hl
    lambda do
      value_at_mem_hl = @cpu.bus_read(address: @registers.hl)
      result = clear_bit(value_at_mem_hl, bit_pos)
      @cpu.bus_write(address: @registers.hl, value: result)
    end
  else
    raise ArgumentError, 'Unknown CbRes target'
  end
end