path: root/src/GBACart.cpp

/*
    Copyright 2019 Arisotura, Raphaël Zumer

    This file is part of melonDS.

    melonDS is free software: you can redistribute it and/or modify it under
    the terms of the GNU General Public License as published by the Free
    Software Foundation, either version 3 of the License, or (at your option)
    any later version.

    melonDS is distributed in the hope that it will be useful, but WITHOUT ANY
    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
    FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

    You should have received a copy of the GNU General Public License along
    with melonDS. If not, see http://www.gnu.org/licenses/.
*/

#include <stdio.h>
#include <string.h>
#include "GBACart.h"
#include "CRC32.h"
#include "Platform.h"


namespace GBACart_SRAM
{


enum SaveType {
    S_NULL,
    S_EEPROM4K,
    S_EEPROM64K,
    S_SRAM256K,
    S_FLASH512K,
    S_FLASH1M
};

struct FlashProperties
{
    u8 state;
    u8 cmd;
    u8 device;
    u8 manufacturer;
    u8 bank;
};

u8* SRAM;
u32 SRAMLength;
SaveType SRAMType;
FlashProperties SRAMFlash;

char SRAMPath[1024];

void (*WriteFunc)(u32 addr, u8 val);


void Write_Null(u32 addr, u8 val);
void Write_EEPROM(u32 addr, u8 val);
void Write_SRAM(u32 addr, u8 val);
void Write_Flash(u32 addr, u8 val);


bool Init()
{
    SRAM = NULL;
    return true;
}

void DeInit()
{
    if (SRAM) delete[] SRAM;
}

void Reset()
{
    if (SRAM) delete[] SRAM;
    SRAM = NULL;
    SRAMLength = 0;
    SRAMType = S_NULL;
    SRAMFlash = {};
}

void DoSavestate(Savestate* file)
{
    // TODO?
}

void LoadSave(const char* path)
{
    if (SRAM) delete[] SRAM;

    strncpy(SRAMPath, path, 1023);
    SRAMPath[1023] = '\0';
    SRAMLength = 0;

    FILE* f = Platform::OpenFile(path, "rb");
    if (f)
    {
        fseek(f, 0, SEEK_END);
        SRAMLength = (u32)ftell(f);
        SRAM = new u8[SRAMLength];

        fseek(f, 0, SEEK_SET);
        fread(SRAM, SRAMLength, 1, f);

        fclose(f);
    }

    switch (SRAMLength)
    {
    case 512:
        SRAMType = S_EEPROM4K;
        WriteFunc = Write_EEPROM;
        break;
    case 8192:
        SRAMType = S_EEPROM64K;
        WriteFunc = Write_EEPROM;
        break;
    case 32768:
        SRAMType = S_SRAM256K;
        WriteFunc = Write_SRAM;
        break;
    case 65536:
        SRAMType = S_FLASH512K;
        WriteFunc = Write_Flash;
        break;
    case 128*1024:
        SRAMType = S_FLASH1M;
        WriteFunc = Write_Flash;
        break;
    default:
        printf("!! BAD SAVE LENGTH %d\n", SRAMLength);
    case 0:
        SRAMType = S_NULL;
        WriteFunc = Write_Null;
        break;
    }

    if (SRAMType == S_FLASH512K)
    {
        // Panasonic 64K chip
        SRAMFlash.device = 0x1B;
        SRAMFlash.manufacturer = 0x32;
    }
    else if (SRAMType == S_FLASH1M)
    {
        // Sanyo 128K chip
        SRAMFlash.device = 0x13;
        SRAMFlash.manufacturer = 0x62;
    }
}

void RelocateSave(const char* path, bool write)
{
    if (!write)
    {
        LoadSave(path); // lazy
        return;
    }

    strncpy(SRAMPath, path, 1023);
    SRAMPath[1023] = '\0';

    FILE* f = Platform::OpenFile(path, "wb");
    if (!f)
    {
        printf("GBACart_SRAM::RelocateSave: failed to create new file. fuck\n");
        return;
    }

    fwrite(SRAM, SRAMLength, 1, f);
    fclose(f);
}

u8 Read_Flash(u32 addr)
{
    if (SRAMFlash.cmd == 0) // no cmd
    {
        return *(u8*)&SRAM[addr + 0x10000 * SRAMFlash.bank];
    }

    // TODO properly keep track of command sequences,
    // and deny unauthorized writes
    switch (SRAMFlash.cmd)
    {
        case 0x90: // chip ID
            if (addr == 0x0A000000) return SRAMFlash.manufacturer;
            if (addr == 0x0A000001) return SRAMFlash.device;
            break;
        case 0xF0: // terminate command (TODO: break if non-Macronix chip and not at the end of an ID call?)
            SRAMFlash.state = 0;
            SRAMFlash.cmd = 0;
            break;
        case 0xB0: // bank switching (128K only)
            break; // we don't track the request for now
        default:
            printf("GBACart_SRAM::Read_Flash: unknown command 0x%02X @ 0x%08X\n", SRAMFlash.cmd, addr);
            break;
    }

    return 0xFF;
}

void Write_Null(u32 addr, u8 val) {}

void Write_EEPROM(u32 addr, u8 val)
{
    // TODO: could be used in homebrew?
}

void Write_Flash(u32 addr, u8 val)
{
    // TODO: pokemen
}

void Write_SRAM(u32 addr, u8 val)
{
    *(u8*)&SRAM[addr] = val;

    // bit wasteful to do this for every written byte
    FILE* f = Platform::OpenFile(SRAMPath, "r+b");
    if (f)
    {
        fseek(f, addr, SEEK_SET);
        fwrite((u8*)&SRAM[addr], 1, 1, f);
        fclose(f);
    }
}

u8 Read8(u32 addr)
{
    if (SRAMType == S_NULL)
    {
        return 0xFF;
    }

    if (SRAMType == S_FLASH512K || SRAMType == S_FLASH1M)
    {
        return Read_Flash(addr);
    }

    return *(u8*)&SRAM[addr];
}

u16 Read16(u32 addr)
{
    if (SRAMType == S_NULL)
    {
        return 0xFFFF;
    }

    if (SRAMType == S_FLASH512K || SRAMType == S_FLASH1M)
    {
        return Read_Flash(addr) & (Read_Flash(addr + 1) << 8);
    }

    return *(u16*)&SRAM[addr];
}

u32 Read32(u32 addr)
{
    if (SRAMType == S_NULL)
    {
        return 0xFFFFFFFF;
    }

    if (SRAMType == S_FLASH512K || SRAMType == S_FLASH1M)
    {
        return Read_Flash(addr) &
            (Read_Flash(addr + 1) << 8) &
            (Read_Flash(addr + 2) << 16) &
            (Read_Flash(addr + 3) << 24);
    }

    return *(u32*)&SRAM[addr];
}

void Write8(u32 addr, u8 val)
{
    u8 prev = *(u8*)&SRAM[addr];

    if (prev != val)
    {
        WriteFunc(addr, val);
    }
}

void Write16(u32 addr, u16 val)
{
    u16 prev = *(u16*)&SRAM[addr];

    if (prev != val)
    {
        WriteFunc(addr, val & 0xFF);
        WriteFunc(addr + 1, val >> 8 & 0xFF);
    }
}

void Write32(u32 addr, u32 val)
{
    u32 prev = *(u32*)&SRAM[addr];

    if (prev != val)
    {
        WriteFunc(addr, val & 0xFF);
        WriteFunc(addr + 1, val >> 8 & 0xFF);
        WriteFunc(addr + 2, val >> 16 & 0xFF);
        WriteFunc(addr + 3, val >> 24 & 0xFF);
    }
}

}


namespace GBACart
{

bool CartInserted;
u8* CartROM;
u32 CartROMSize;
u32 CartCRC;
u32 CartID;


bool Init()
{
    if (!GBACart_SRAM::Init()) return false;

    CartROM = NULL;

    return true;
}

void DeInit()
{
    if (CartROM) delete[] CartROM;

    GBACart_SRAM::DeInit();
}

void Reset()
{
    CartInserted = false;
    if (CartROM) delete[] CartROM;
    CartROM = NULL;
    CartROMSize = 0;

    GBACart_SRAM::Reset();
}

void DoSavestate(Savestate* file)
{
    // TODO?
}

bool LoadROM(const char* path, const char* sram)
{
    FILE* f = Platform::OpenFile(path, "rb");
    if (!f)
    {
        return false;
    }

    if (CartInserted)
    {
        Reset();
    }

    fseek(f, 0, SEEK_END);
    u32 len = (u32)ftell(f);

    CartROMSize = 0x200;
    while (CartROMSize < len)
        CartROMSize <<= 1;

    u32 gamecode;
    fseek(f, 0xAC, SEEK_SET);
    fread(&gamecode, 4, 1, f);
    printf("Game code: %c%c%c%c\n", gamecode&0xFF, (gamecode>>8)&0xFF, (gamecode>>16)&0xFF, gamecode>>24);

    CartROM = new u8[CartROMSize];
    memset(CartROM, 0, CartROMSize);
    fseek(f, 0, SEEK_SET);
    fread(CartROM, 1, len, f);

    fclose(f);
    //CartROM = f;

    CartCRC = CRC32(CartROM, CartROMSize);
    printf("ROM CRC32: %08X\n", CartCRC);

    CartInserted = true;

    // save
    printf("Save file: %s\n", sram);
    GBACart_SRAM::LoadSave(sram);

    return true;
}

void RelocateSave(const char* path, bool write)
{
    // derp herp
    GBACart_SRAM::RelocateSave(path, write);
}

}