Class: Amaterasu::GameBoy::Ram

Inherits:
Object
  • Object
show all
Defined in:
lib/amaterasu/game_boy/ram.rb

Overview

Models the RAM chip within the Game Boy.

Direct Known Subclasses

Oam, Vram

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(size:, offset:) ⇒ Ram

Creates a new Ram object.

Parameters:

  • size (Integer) —

    Memory size in bytes.

  • offset (Integer) —

    Address offset based on the Bus memory map.



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# File 'lib/amaterasu/game_boy/ram.rb', line 14

def initialize(size:, offset:)
  @size = size
  @offset = offset

  @data = Array.new(size, 0x00)
  @backup = nil
  @backed_up = false
end

Instance Attribute Details

#size ⇒ Object (readonly)

Memory size in bytes.



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# File 'lib/amaterasu/game_boy/ram.rb', line 8

def size
  @size
end

Instance Method Details

#disk_size ⇒ Object

Returns a readable string in B or KiB based on memory size.



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# File 'lib/amaterasu/game_boy/ram.rb', line 41

def disk_size
  return "#{@size} B" if @size < 1024

  "#{@size / 1024} KiB"
end

#read_backup(address:) ⇒ Object

Provides an interface to read backup data.



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# File 'lib/amaterasu/game_boy/ram.rb', line 34

def read_backup(address:)
  return 0xFF unless @backed_up

  @backup[address - @offset]
end

#read_byte(address:) ⇒ Object

Returns a 8-bit value from a given address in memory.



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# File 'lib/amaterasu/game_boy/ram.rb', line 24

def read_byte(address:)
  @data[address - @offset]
end

#restore_data ⇒ Object

Restores a previously backed up memory state.



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# File 'lib/amaterasu/game_boy/ram.rb', line 54

def restore_data
  @data = @backup.dup
end

#save_data ⇒ Object

Creates a copy of the current state of memory.



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# File 'lib/amaterasu/game_boy/ram.rb', line 48

def save_data
  @backup = @data.dup
  @backed_up = true
end

#wipe_backup ⇒ Object

Clears all previously set backup values.



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# File 'lib/amaterasu/game_boy/ram.rb', line 64

def wipe_backup
  @backup = Array.new
  @backed_up = false
end

#wipe_data ⇒ Object

Clears all previously set memory values.



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# File 'lib/amaterasu/game_boy/ram.rb', line 59

def wipe_data
  @data = Array.new(@size, 0x00)
end

#write_byte(address:, value:) ⇒ Object

Stores a 8-bit value into a given address in memory.



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# File 'lib/amaterasu/game_boy/ram.rb', line 29

def write_byte(address:, value:)
  @data[address - @offset] = value & 0xFF
end