nesemu/src/native_core/test_support.rs

use crate::native_core::cpu::{Cpu6502, CpuBus};
use crate::native_core::ines::{InesHeader, InesRom, Mirroring};

pub(crate) struct TestRamBus(pub [u8; 0x10000]);

impl TestRamBus {
    pub(crate) fn new() -> Self {
        Self([0; 0x10000])
    }

    pub(crate) fn load(&mut self, start: u16, bytes: &[u8]) {
        for (i, b) in bytes.iter().copied().enumerate() {
            self.0[start as usize + i] = b;
        }
    }
}

impl CpuBus for TestRamBus {
    fn read(&mut self, addr: u16) -> u8 {
        self.0[addr as usize]
    }

    fn write(&mut self, addr: u16, value: u8) {
        self.0[addr as usize] = value;
    }
}

pub(crate) fn cpu_setup_with_reset(prog: &[u8]) -> (Cpu6502, TestRamBus) {
    let mut bus = TestRamBus::new();
    bus.load(0x8000, prog);
    bus.0[0xFFFC] = 0x00;
    bus.0[0xFFFD] = 0x80;
    let mut cpu = Cpu6502::default();
    cpu.reset(&mut bus);
    (cpu, bus)
}

pub(crate) struct MapperRomBuilder {
    mapper: u16,
    submapper: u8,
    prg_banks_16k: u16,
    chr_banks_8k: u16,
    mirroring: Mirroring,
}

impl MapperRomBuilder {
    pub(crate) fn new(mapper: u16) -> Self {
        Self {
            mapper,
            submapper: 0,
            prg_banks_16k: 1,
            chr_banks_8k: 1,
            mirroring: Mirroring::Horizontal,
        }
    }

    pub(crate) fn submapper(mut self, submapper: u8) -> Self {
        self.submapper = submapper;
        self
    }

    pub(crate) fn prg_banks_16k(mut self, banks: u16) -> Self {
        self.prg_banks_16k = banks;
        self
    }

    pub(crate) fn chr_banks_8k(mut self, banks: u16) -> Self {
        self.chr_banks_8k = banks;
        self
    }

    pub(crate) fn mirroring(mut self, mirroring: Mirroring) -> Self {
        self.mirroring = mirroring;
        self
    }

    pub(crate) fn build(self) -> InesRom {
        let prg_rom_len = self.prg_banks_16k as usize * 16 * 1024;
        let chr_len = if self.chr_banks_8k == 0 {
            8 * 1024
        } else {
            self.chr_banks_8k as usize * 8 * 1024
        };
        let chr_data = if self.chr_banks_8k == 0 {
            vec![0; chr_len]
        } else {
            (0..chr_len).map(|v| (v & 0xFF) as u8).collect()
        };
        InesRom {
            header: InesHeader {
                mapper: self.mapper,
                submapper: self.submapper,
                is_nes2: false,
                prg_rom_banks_16k: self.prg_banks_16k,
                chr_rom_banks_8k: self.chr_banks_8k,
                has_trainer: false,
                has_battery: false,
                mirroring: self.mirroring,
                prg_ram_shift: 0,
                prg_nvram_shift: 0,
                chr_ram_shift: 0,
                chr_nvram_shift: 0,
                cpu_ppu_timing_mode: 0,
                vs_hardware_type: 0,
                vs_ppu_type: 0,
                misc_rom_count: 0,
                default_expansion_device: 0,
            },
            prg_rom: (0..prg_rom_len).map(|v| (v & 0xFF) as u8).collect(),
            chr_data,
            chr_is_ram: self.chr_banks_8k == 0,
        }
    }
}