use crate::cartridge::base_mapper::BaseMapper;
use crate::cartridge::common::ChrMemory;
use crate::cartridge::mapper::{Mapper, MapperCapabilities};
const MAPPER_NUMBER: u16 = 340;
const PRG_BANK_SIZE_BYTES: usize = 16 * 1024;
const CHR_BANK_SIZE_BYTES: usize = 8 * 1024;
const PRG_WRITE_START: u16 = 0x8000;
const OUTER_PRG_MASK: u8 = 0x1F;
const INNER_PRG_MASK: u8 = 0x07;
const MODE_NROM_128_BIT: u16 = 0x20;
const HORIZONTAL_MIRROR_BITS: u16 = 0x25;
const UNROM_FIXED_INNER_BANK: i16 = 0x07;
const REGISTERS_SNAPSHOT_LEN: usize = 4;
pub struct Mapper340 {
base: BaseMapper,
outer_prg_bank: u8,
inner_prg_bank: u8,
nrom_128_mode: bool,
mirroring_horizontal: bool,
}
impl Mapper340 {
pub fn new(ctx: super::mapper::MapperContext) -> Self {
let chr_seed = ctx.chr_rom.clone();
let capabilities = MapperCapabilities {
has_dynamic_mirroring: true,
prg_bank_size_kb: 16,
chr_bank_size_kb: 8,
max_prg_ram_kb: 0,
..Default::default()
};
let mut base = BaseMapper::new(&ctx, capabilities);
base.configure_prg_banking(PRG_BANK_SIZE_BYTES);
base.configure_chr_banking(CHR_BANK_SIZE_BYTES);
let mut chr_ram = ChrMemory::new_ram(CHR_BANK_SIZE_BYTES);
if !chr_seed.is_empty() {
chr_ram.load_snapshot(&chr_seed);
}
base.set_chr_memory(chr_ram);
let mut mapper = Self {
base,
outer_prg_bank: 0,
inner_prg_bank: 0,
nrom_128_mode: false,
mirroring_horizontal: false,
};
mapper.update_banks();
mapper
}
fn update_banks(&mut self) {
let bank_8000 = self.prg_bank_8000();
let bank_c000 = self.prg_bank_c000();
self.base.select_prg_page(0, bank_8000);
self.base.select_prg_page(1, bank_c000);
self.base.select_chr_page(0, 0);
self.base.set_mirroring_hv(self.mirroring_horizontal);
}
fn prg_bank_8000(&self) -> i16 {
let outer = self.outer_prg_bank as i16;
if self.nrom_128_mode {
outer
} else {
outer | self.inner_prg_bank as i16
}
}
fn prg_bank_c000(&self) -> i16 {
let outer = self.outer_prg_bank as i16;
if self.nrom_128_mode {
outer
} else {
outer | UNROM_FIXED_INNER_BANK
}
}
fn apply_state(
&mut self,
outer_prg_bank: u8,
inner_prg_bank: u8,
nrom_128_mode: bool,
mirroring_horizontal: bool,
) {
self.outer_prg_bank = outer_prg_bank;
self.inner_prg_bank = inner_prg_bank;
self.nrom_128_mode = nrom_128_mode;
self.mirroring_horizontal = mirroring_horizontal;
self.update_banks();
}
fn decode_mirroring_horizontal(addr: u16) -> bool {
(addr & HORIZONTAL_MIRROR_BITS) == HORIZONTAL_MIRROR_BITS
}
}
impl Mapper for Mapper340 {
fn base(&self) -> &BaseMapper {
&self.base
}
fn base_mut(&mut self) -> &mut BaseMapper {
&mut self.base
}
fn mapper_number(&self) -> u16 {
MAPPER_NUMBER
}
fn write_prg(&mut self, addr: u16, value: u8) {
if addr < PRG_WRITE_START {
return;
}
self.apply_state(
(addr as u8) & OUTER_PRG_MASK,
value & INNER_PRG_MASK,
(addr & MODE_NROM_128_BIT) != 0,
Self::decode_mirroring_horizontal(addr),
);
}
fn registers_snapshot(&self) -> Vec<u8> {
vec![
self.outer_prg_bank,
self.inner_prg_bank,
self.nrom_128_mode as u8,
self.mirroring_horizontal as u8,
]
}
fn restore_registers(&mut self, data: &[u8]) {
if data.len() < REGISTERS_SNAPSHOT_LEN {
return;
}
self.apply_state(
data[0] & OUTER_PRG_MASK,
data[1] & INNER_PRG_MASK,
data[2] != 0,
data[3] != 0,
);
}
fn reset(&mut self) {
self.apply_state(0, 0, false, false);
}
}
#[cfg(test)]
mod tests {
use super::*;
use crate::cartridge::NametableLayout;
use crate::cartridge::mapper::{MapperContext, create_mapper};
use crate::cartridge::test_helpers::banked_data;
const PRG_BANKS_16K: usize = 48;
fn make_mapper() -> Mapper340 {
Mapper340::new(MapperContext::new_for_test(
MAPPER_NUMBER,
banked_data(PRG_BANK_SIZE_BYTES, PRG_BANKS_16K),
vec![],
NametableLayout::Vertical,
))
}
#[test]
fn mapper_340_is_registered() {
let result = create_mapper(MapperContext::new_for_test(
MAPPER_NUMBER,
banked_data(PRG_BANK_SIZE_BYTES, PRG_BANKS_16K),
vec![],
NametableLayout::Vertical,
));
assert!(result.is_ok(), "Mapper 340 must be registered in factory");
}
#[test]
fn unrom_mode_uses_outer_or_inner_for_8000_and_outer_or_7_for_c000() {
let mut mapper = make_mapper();
mapper.write_prg(0x8018, 0x03);
assert_eq!(mapper.read_prg(0x8000), 27);
assert_eq!(mapper.read_prg(0xC000), 31);
}
#[test]
fn nrom_128_mode_mirrors_outer_bank_in_both_windows() {
let mut mapper = make_mapper();
mapper.write_prg(0x8025, 0x07);
assert_eq!(mapper.read_prg(0x8000), 5);
assert_eq!(mapper.read_prg(0xC000), 5);
}
#[test]
fn horizontal_mirroring_requires_exact_a5_a2_a0_pattern() {
let mut mapper = make_mapper();
mapper.write_prg(0x8025, 0x00);
assert_eq!(mapper.get_mirroring(), NametableLayout::Horizontal);
mapper.write_prg(0x8005, 0x00);
assert_eq!(mapper.get_mirroring(), NametableLayout::Vertical);
}
#[test]
fn chr_ram_is_unbanked_and_writable() {
let mut mapper = make_mapper();
mapper.write_chr(0x0123, 0x5A);
assert_eq!(mapper.read_chr(0x0123), 0x5A);
}
#[test]
fn snapshot_restore_preserves_mode_bank_and_mirroring() {
let mut mapper = make_mapper();
mapper.write_prg(0x8025, 0x04);
let snapshot = mapper.registers_snapshot();
let mut restored = make_mapper();
restored.restore_registers(&snapshot);
assert_eq!(restored.read_prg(0x8000), 5);
assert_eq!(restored.read_prg(0xC000), 5);
assert_eq!(restored.get_mirroring(), NametableLayout::Horizontal);
}
#[test]
fn capabilities_match_k3036_baseline() {
let mapper = make_mapper();
let caps = mapper.capabilities();
assert!(!caps.has_irq);
assert!(!caps.has_expansion_audio);
assert!(!caps.has_chr_banking);
assert!(caps.has_dynamic_mirroring);
assert_eq!(caps.prg_bank_size_kb, 16);
assert_eq!(caps.chr_bank_size_kb, 8);
assert_eq!(caps.max_prg_ram_kb, 0);
}
}