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#include "cart.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
static const char *mbc_name(MbcType m) {
switch (m) {
case MBC_NONE: return "ROM-only";
case MBC_1: return "MBC1";
case MBC_2: return "MBC2";
case MBC_3: return "MBC3";
case MBC_5: return "MBC5";
}
return "?";
}
// Decode cartridge type byte (0x0147) into MBC + feature flags.
static void decode_type(Cart *c, u8 t) {
c->mbc = MBC_NONE;
c->has_ram = false;
c->has_battery = false;
c->has_rtc = false;
switch (t) {
case 0x00: c->mbc = MBC_NONE; break;
case 0x01: c->mbc = MBC_1; break;
case 0x02: c->mbc = MBC_1; c->has_ram = true; break;
case 0x03: c->mbc = MBC_1; c->has_ram = true; c->has_battery = true; break;
case 0x05: c->mbc = MBC_2; break;
case 0x06: c->mbc = MBC_2; c->has_battery = true; break;
case 0x08: c->mbc = MBC_NONE; c->has_ram = true; break;
case 0x09: c->mbc = MBC_NONE; c->has_ram = true; c->has_battery = true; break;
case 0x0F: c->mbc = MBC_3; c->has_rtc = true; c->has_battery = true; break;
case 0x10: c->mbc = MBC_3; c->has_rtc = true; c->has_ram = true; c->has_battery = true; break;
case 0x11: c->mbc = MBC_3; break;
case 0x12: c->mbc = MBC_3; c->has_ram = true; break;
case 0x13: c->mbc = MBC_3; c->has_ram = true; c->has_battery = true; break;
case 0x19: c->mbc = MBC_5; break;
case 0x1A: c->mbc = MBC_5; c->has_ram = true; break;
case 0x1B: c->mbc = MBC_5; c->has_ram = true; c->has_battery = true; break;
case 0x1C: c->mbc = MBC_5; break;
case 0x1D: c->mbc = MBC_5; c->has_ram = true; break;
case 0x1E: c->mbc = MBC_5; c->has_ram = true; c->has_battery = true; break;
default:
fprintf(stderr, "warning: unknown cart type 0x%02X, assuming MBC1\n", t);
c->mbc = MBC_1; c->has_ram = true;
break;
}
}
static size_t ram_size_bytes(u8 code) {
switch (code) {
case 0x00: return 0;
case 0x01: return 2 * 1024; // unofficial
case 0x02: return 8 * 1024;
case 0x03: return 32 * 1024;
case 0x04: return 128 * 1024;
case 0x05: return 64 * 1024;
default: return 0;
}
}
int cart_load(Cart *c, const char *path) {
memset(c, 0, sizeof(*c));
FILE *f = fopen(path, "rb");
if (!f) { perror("fopen rom"); return -1; }
fseek(f, 0, SEEK_END);
long sz = ftell(f);
fseek(f, 0, SEEK_SET);
if (sz < 0x150) { fprintf(stderr, "rom too small\n"); fclose(f); return -1; }
c->rom = malloc(sz);
if (fread(c->rom, 1, sz, f) != (size_t)sz) { fclose(f); return -1; }
fclose(f);
c->rom_size = sz;
memcpy(c->title, c->rom + 0x134, 16);
c->title[16] = 0;
for (int i = 0; i < 16; i++)
if ((u8)c->title[i] < 0x20 || (u8)c->title[i] > 0x7e) c->title[i] = 0;
u8 cgb_flag = c->rom[0x143];
c->cgb = (cgb_flag == 0x80 || cgb_flag == 0xC0);
decode_type(c, c->rom[0x147]);
c->rom_banks = 2 << c->rom[0x148];
if ((size_t)c->rom_banks * 0x4000 > c->rom_size) {
// trust the file size
c->rom_banks = c->rom_size / 0x4000;
if (c->rom_banks < 2) c->rom_banks = 2;
}
c->ram_size = ram_size_bytes(c->rom[0x149]);
if (c->mbc == MBC_2) c->ram_size = 512; // built-in 512x4 bit
if (c->has_ram && c->ram_size == 0) c->ram_size = 8 * 1024;
if (c->ram_size) {
c->ram = calloc(1, c->ram_size);
c->ram_banks = c->ram_size / 0x2000;
if (c->ram_banks < 1) c->ram_banks = 1;
}
c->rom_bank = 1;
c->rom_bank_hi = 0;
c->ram_bank = 0;
// battery save path: rom path with .sav
snprintf(c->save_path, sizeof(c->save_path), "%s.sav", path);
if (c->has_battery && c->ram) {
FILE *sf = fopen(c->save_path, "rb");
if (sf) {
fread(c->ram, 1, c->ram_size, sf);
fclose(sf);
}
}
fprintf(stderr, "Loaded '%s' | %s | %d ROM banks (%zuKB) | %zuKB RAM | %s%s\n",
c->title, mbc_name(c->mbc), c->rom_banks, c->rom_size / 1024,
c->ram_size / 1024, c->cgb ? "CGB " : "DMG ",
c->has_battery ? "battery" : "");
return 0;
}
void cart_save(Cart *c) {
if (!c->has_battery || !c->ram) return;
FILE *sf = fopen(c->save_path, "wb");
if (sf) {
fwrite(c->ram, 1, c->ram_size, sf);
fclose(sf);
}
}
void cart_free(Cart *c) {
cart_save(c);
free(c->rom);
free(c->ram);
c->rom = c->ram = NULL;
}
// ---- Bank math helpers ----
static u8 read_rom(Cart *c, u32 bank, u16 off) {
if (c->rom_banks) bank %= (u32)c->rom_banks;
size_t idx = (size_t)bank * 0x4000 + off;
if (idx >= c->rom_size) return 0xFF;
return c->rom[idx];
}
u8 cart_read(Cart *c, u16 addr) {
if (addr < 0x4000) {
// bank 0 region (MBC1 mode1 can remap, handle simply)
if (c->mbc == MBC_1 && c->bank_mode == 1) {
u32 bank = (c->rom_bank_hi << 5);
return read_rom(c, bank, addr);
}
return read_rom(c, 0, addr);
}
if (addr < 0x8000) {
u32 bank;
switch (c->mbc) {
case MBC_1: {
bank = (c->rom_bank & 0x1F) | (c->rom_bank_hi << 5);
if ((bank & 0x1F) == 0) bank |= 1;
break;
}
case MBC_2:
bank = c->rom_bank & 0x0F;
if (bank == 0) bank = 1;
break;
case MBC_3:
bank = c->rom_bank & 0x7F;
if (bank == 0) bank = 1;
break;
case MBC_5:
bank = c->rom_bank | (c->rom_bank_hi << 8);
break;
default:
bank = 1;
break;
}
return read_rom(c, bank, addr - 0x4000);
}
if (addr >= 0xA000 && addr < 0xC000) {
if (!c->ram_enabled) return 0xFF;
if (c->mbc == MBC_2) {
return 0xF0 | (c->ram[(addr - 0xA000) & 0x1FF] & 0x0F);
}
if (c->mbc == MBC_3 && c->ram_bank >= 0x08) {
// RTC register read
if (c->ram_bank <= 0x0C) return c->rtc_reg[c->ram_bank - 0x08];
return 0xFF;
}
if (!c->ram) return 0xFF;
u32 bank = c->ram_bank;
if (c->mbc == MBC_1 && c->bank_mode == 0) bank = 0;
if (c->ram_banks) bank %= (u32)c->ram_banks;
size_t idx = bank * 0x2000 + (addr - 0xA000);
if (idx >= c->ram_size) return 0xFF;
return c->ram[idx];
}
return 0xFF;
}
void cart_write(Cart *c, u16 addr, u8 val) {
switch (c->mbc) {
case MBC_NONE:
break;
case MBC_1:
if (addr < 0x2000) c->ram_enabled = (val & 0x0F) == 0x0A;
else if (addr < 0x4000) c->rom_bank = val & 0x1F;
else if (addr < 0x6000) c->rom_bank_hi = val & 0x03;
else if (addr < 0x8000) c->bank_mode = val & 1;
break;
case MBC_2:
if (addr < 0x4000) {
if (addr & 0x0100) c->rom_bank = val & 0x0F;
else c->ram_enabled = (val & 0x0F) == 0x0A;
}
break;
case MBC_3:
if (addr < 0x2000) c->ram_enabled = (val & 0x0F) == 0x0A;
else if (addr < 0x4000) c->rom_bank = val & 0x7F;
else if (addr < 0x6000) c->ram_bank = val; // 0-3 ram, 8-C rtc
else if (addr < 0x8000) {
if (c->rtc_latch == 0 && val == 1) { /* latch clock (stub) */ }
c->rtc_latch = val;
}
break;
case MBC_5:
if (addr < 0x2000) c->ram_enabled = (val & 0x0F) == 0x0A;
else if (addr < 0x3000) c->rom_bank = val;
else if (addr < 0x4000) c->rom_bank_hi = val & 1;
else if (addr < 0x6000) c->ram_bank = val & 0x0F;
break;
}
if (addr >= 0xA000 && addr < 0xC000) {
if (!c->ram_enabled) return;
if (c->mbc == MBC_2) {
c->ram[(addr - 0xA000) & 0x1FF] = val & 0x0F;
return;
}
if (c->mbc == MBC_3 && c->ram_bank >= 0x08) {
if (c->ram_bank <= 0x0C) c->rtc_reg[c->ram_bank - 0x08] = val;
return;
}
if (!c->ram) return;
u32 bank = c->ram_bank;
if (c->mbc == MBC_1 && c->bank_mode == 0) bank = 0;
if (c->ram_banks) bank %= (u32)c->ram_banks;
size_t idx = bank * 0x2000 + (addr - 0xA000);
if (idx < c->ram_size) c->ram[idx] = val;
}
}
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