nese/src/map/nrom.c

#include <stdlib.h>

#include "map.h"


typedef struct {
    uint8_t* prg_rom;
    int prg_rom_banks;
    uint8_t* chr_rom;
    int chr_rom_banks;
    uint8_t mirror;
    uint8_t vram[nes_vram_page_size * 2];
    uint8_t wram[nes_mem_wram_size];
} nrom_mapper;


static void nrom_reset(nes_mapper* nes_map) {}

static int nrom_init(nes_mapper* nes_map, nes_cart* cart) {
    nrom_mapper* map = calloc(1, sizeof(nrom_mapper));
    nes_map->data = map;
    if (NULL != map) {
        map->prg_rom       = cart->prg_rom;
        map->prg_rom_banks = cart->prg_rom_banks;
        map->chr_rom       = cart->chr_rom;
        map->chr_rom_banks = cart->chr_rom_banks;
        map->mirror = (cart->flags & Cart_Flag_Horizontal) ? 0 : 1;
    }
    return (NULL == map ? -1 : 0);
}

static void nrom_done(nes_mapper* nes_map) {
    free(nes_map->data);
}

static inline uint8_t* nrom_prg_addr(nrom_mapper* map,
                                     uint16_t addr) {
    addr &= 0x7FFFU;
    if (map->prg_rom_banks == 1) {
        addr &= 0x3FFF;
    }
    return &(map->prg_rom[addr]);
}

static inline uint8_t* nrom_wram_addr(nrom_mapper* map,
                                     uint16_t addr) {
    return &(map->wram[addr & 0x1FFFU]);
}

static uint8_t nrom_read(nes_mapper* map, uint16_t addr) {
    uint8_t val = 0;
    if (addr >= nes_mem_rom_start) {
        val = *(nrom_prg_addr((nrom_mapper*)map->data, addr));
    } else if (addr >= nes_mem_wram_start) {
        val = *(nrom_wram_addr((nrom_mapper*)map->data, addr));
    }
    return val;
}

static void nrom_write(nes_mapper* map,
                       uint16_t addr, uint8_t val) {
    if (addr < nes_mem_rom_start && addr >= nes_mem_wram_start) {
        *(nrom_wram_addr((nrom_mapper*)map->data, addr)) = val;
    }
}

static uint8_t* nrom_chr_addr(nes_mapper* nes_map,
                              uint16_t addr) {
    return &(((nrom_mapper*)nes_map->data)->chr_rom[addr]);
}

static uint8_t* nrom_vram_addr(nes_mapper* nes_map,
                               uint16_t addr) {
    nrom_mapper* map = (nrom_mapper*)nes_map->data;
    int page = addr >> 10U;
    page >>= map->mirror;
    addr = ((page & 1) << 10U) | (addr & 0x3FFU);
    return &map->vram[addr];
}

static void nrom_chr_write(nes_mapper* map,
                           uint16_t addr, uint8_t val) {
    // ROM only.
    printf("CHR ROM Write: $%04x < %02x\n", addr, val);
}

nes_mapper mapper_nrom = {
    .name = "NROM",
    .init = nrom_init,
    .reset = nrom_reset,
    .done = nrom_done,
    .read = nrom_read,
    .write = nrom_write,
    .chr_addr = nrom_chr_addr,
    .vram_addr = nrom_vram_addr,
    .chr_write = nrom_chr_write,
};