sfc_famicom.c

#include "sfc_famicom.h"
#include <assert.h>
#include <string.h>

// 加载新的ROM
static sfc_ecode sfc_load_new_rom(sfc_famicom_t* famicom);
// 加载mapper
extern sfc_ecode sfc_load_mapper(sfc_famicom_t* famicom, uint8_t);

// 默认加载释放ROM
static sfc_ecode sfc_loadfree_rom(void* arg, sfc_rom_info_t* info) { return SFC_ERROR_FAILED; }

// 默认音频事件
static void sfc_audio_changed(void*a, uint32_t b, enum sfc_channel_index c) {}
// 默认SRAM读写事件
static void sfc_save_load_sram(void*a, const sfc_rom_info_t*b, const sfc_data_set_t*c, uint32_t l) {}
// 默认状态读写事件
static void sfc_sl_stream(void*a, const uint8_t* b, uint32_t c) {}

// 声明一个随便(SB)的函数指针类型
typedef void(*sfc_funcptr_t)();

// VRC7 初始化 LUT
extern void sfc_vrc7_init_lut(void);
// FME7 初始化 LUT
extern void sfc_fme7_init_lut(void);


/// <summary>
/// StepFC: 初始化famicom
/// </summary>
/// <param name="famicom">The famicom.</param>
/// <param name="argument">The argument.</param>
/// <param name="interfaces">The interfaces.</param>
/// <returns></returns>
sfc_ecode sfc_famicom_init(
    sfc_famicom_t* famicom, 
    void* argument, 
    const sfc_interface_t* interfaces) {
    assert(famicom && "bad famicom");
    // 清空数据
    memset(famicom, 0, sizeof(sfc_famicom_t));
    // 生成VRC7用LUT
    sfc_vrc7_init_lut();
    // 生成FME7用LUT
    sfc_fme7_init_lut();
    // 保留参数
    famicom->argument = argument;
    // 载入默认接口
    famicom->interfaces.load_rom = sfc_loadfree_rom;
    famicom->interfaces.free_rom = sfc_loadfree_rom;
    famicom->interfaces.audio_change = sfc_audio_changed;
    famicom->interfaces.load_sram = sfc_save_load_sram;
    famicom->interfaces.save_sram = sfc_save_load_sram;
    famicom->interfaces.sl_write_stream = sfc_sl_stream;
    famicom->interfaces.sl_read_stream = sfc_sl_stream;
    // 初步BANK
    famicom->prg_banks[0] = famicom->main_memory;
    famicom->prg_banks[1] = famicom->main_memory;
    famicom->prg_banks[4] = famicom->bus_memory;
    famicom->prg_banks[6] = famicom->save_memory;
    famicom->prg_banks[7] = famicom->save_memory + 4*1024;
    // 提供了接口
    if (interfaces) {
        const int count = sizeof(*interfaces) / sizeof(interfaces->load_rom);
        // 复制有效的函数指针
        // UB: C标准并不一定保证sizeof(void*)等同sizeof(fp) (非冯体系)
        //     所以这里声明了一个sfc_funcptr_t
        sfc_funcptr_t* const func_src = (sfc_funcptr_t*)interfaces;
        sfc_funcptr_t* const func_des = (sfc_funcptr_t*)&famicom->interfaces;
        for (int i = 0; i != count; ++i) if (func_src[i]) func_des[i] = func_src[i];
    }
    // 默认是NTSC制式
    famicom->config = SFC_CONFIG_NTSC;
    // 一开始载入测试ROM
    return sfc_load_new_rom(famicom);
    return SFC_ERROR_OK;
}


/// <summary>
/// SFCs the check save sram.
/// </summary>
/// <param name="famicom">The famicom.</param>
static void sfc_check_saveload_sram(
    void(*func)(void*, const sfc_rom_info_t*, const sfc_data_set_t*, uint32_t),
    sfc_famicom_t* famicom) {
    // 检测标志位
    const uint8_t flags = famicom->rom_info.save_ram_flags;
    if (flags & SFC_ROMINFO_SRAM_HasSRAM) {
        sfc_data_set_t sets[16];
        // [0] ------------------------------ SRAM
        // 使用扩展SRAM
        if (flags & SFC_ROMINFO_SRAM_More8KiB) {
            sets[0].address = famicom->expansion_ram32;
            sets[0].length = sizeof(famicom->expansion_ram32);
        }
        // 使用标准SRAM
        else {
            sets[0].address = famicom->save_memory;
            sets[0].length = sizeof(famicom->save_memory);
        }
        uint32_t count = 1;
        // [1] ------------------------------ N163-IRAM
        if (flags & SFC_ROMINFO_SRAM_M128_Of8) {
            sets[1].address = famicom->expansion_ram32 + 8 * 1024;
            sets[1].length = 128;
            count++;
        }
        // 调用接口
        func(famicom->argument, &famicom->rom_info, sets, count);
    }
}

/// <summary>
/// StepFC: 反初始化famicom
/// </summary>
/// <param name="famicom">The famicom.</param>
void sfc_famicom_uninit(sfc_famicom_t* famicom) {
    // 检测SRAM
    sfc_check_saveload_sram(famicom->interfaces.save_sram, famicom);
    // 释放ROM
    famicom->interfaces.free_rom(famicom->argument, &famicom->rom_info);
}


/// <summary>
/// SFCs the switch nametable mirroring.
/// </summary>
/// <param name="famicom">The famicom.</param>
/// <param name="mode">The mode.</param>
void sfc_switch_nametable_mirroring(sfc_famicom_t* famicom, sfc_nametable_mirroring_mode mode) {
    switch (mode)
    {
    case SFC_NT_MIR_SingleLow:
        famicom->ppu.banks[0x8] = famicom->video_memory + 0x400 * 0;
        famicom->ppu.banks[0x9] = famicom->video_memory + 0x400 * 0;
        famicom->ppu.banks[0xa] = famicom->video_memory + 0x400 * 0;
        famicom->ppu.banks[0xb] = famicom->video_memory + 0x400 * 0;
        break;
    case SFC_NT_MIR_SingleHigh:
        famicom->ppu.banks[0x8] = famicom->video_memory + 0x400 * 1;
        famicom->ppu.banks[0x9] = famicom->video_memory + 0x400 * 1;
        famicom->ppu.banks[0xa] = famicom->video_memory + 0x400 * 1;
        famicom->ppu.banks[0xb] = famicom->video_memory + 0x400 * 1;
        break;
    case SFC_NT_MIR_Vertical:
        famicom->ppu.banks[0x8] = famicom->video_memory + 0x400 * 0;
        famicom->ppu.banks[0x9] = famicom->video_memory + 0x400 * 1;
        famicom->ppu.banks[0xa] = famicom->video_memory + 0x400 * 0;
        famicom->ppu.banks[0xb] = famicom->video_memory + 0x400 * 1;
        break;
    case SFC_NT_MIR_Horizontal:
        famicom->ppu.banks[0x8] = famicom->video_memory + 0x400 * 0;
        famicom->ppu.banks[0x9] = famicom->video_memory + 0x400 * 0;
        famicom->ppu.banks[0xa] = famicom->video_memory + 0x400 * 1;
        famicom->ppu.banks[0xb] = famicom->video_memory + 0x400 * 1;
        break;
    case SFC_NT_MIR_FourScreen:
        famicom->ppu.banks[0x8] = famicom->video_memory + 0x400 * 0;
        famicom->ppu.banks[0x9] = famicom->video_memory + 0x400 * 1;
        famicom->ppu.banks[0xa] = famicom->video_memory_ex + 0x400 * 0;
        famicom->ppu.banks[0xb] = famicom->video_memory_ex + 0x400 * 1;
        break;
    default:
        assert(!"BAD ACTION");
    }
    // 镜像
    famicom->ppu.banks[0xc] = famicom->ppu.banks[0x8];
    famicom->ppu.banks[0xd] = famicom->ppu.banks[0x9];
    famicom->ppu.banks[0xe] = famicom->ppu.banks[0xa];
    famicom->ppu.banks[0xf] = famicom->ppu.banks[0xb];
}



/// <summary>
/// StepFC: 设置名称表用仓库
/// </summary>
/// <param name="famicom">The famicom.</param>
static inline void sfc_setup_nametable_bank(sfc_famicom_t* famicom) {
    sfc_switch_nametable_mirroring(famicom,
        famicom->rom_info.four_screen ? (SFC_NT_MIR_FourScreen) :
        (famicom->rom_info.vmirroring ? SFC_NT_MIR_Vertical : SFC_NT_MIR_Horizontal)
    );
}

// 重置VRC7
extern void sfc_vrc7_reset(sfc_famicom_t* famicom);

/// <summary>
/// StepFC: 重置famicom
/// </summary>
/// <param name="famicom">The famicom.</param>
/// <returns></returns>
sfc_ecode sfc_famicom_reset(sfc_famicom_t* famicom) {
    // 清空PPU数据
    memset(&famicom->ppu, 0, sizeof(famicom->ppu));
    // 重置mapper
    sfc_ecode ecode = famicom->mapper.reset(famicom);
    if (ecode) return ecode;
    famicom->registers.accumulator = 0;
    famicom->registers.x_index = 0;
    famicom->registers.y_index = 0;
    famicom->registers.stack_pointer = 0xfd;
    famicom->registers.status = 0x34
        | SFC_FLAG_R    //  一直为1
        ;
    // NSF
    if (famicom->rom_info.song_count) {
        const uint8_t index = famicom->rom_info.start_play - 1;
        const uint8_t count = famicom->rom_info.song_count;
        sfc_famicom_nsf_init(famicom, index >= count ? 0 : index, 0);
    }
    // NES
    else {
        // 初始化寄存器
        const uint8_t pcl = sfc_read_cpu_address(SFC_VERCTOR_RESET + 0, famicom);
        const uint8_t pch = sfc_read_cpu_address(SFC_VERCTOR_RESET + 1, famicom);
        famicom->registers.program_counter = (uint16_t)pcl | (uint16_t)pch << 8;
    }
    // 调色板
    // 名称表
    sfc_setup_nametable_bank(famicom);
    // 重置APU
    sfc_apu_on_reset(&famicom->apu);
    // 重置VRC7
    sfc_vrc7_reset(famicom);
    return SFC_ERROR_OK;
}


// CRC32-b HASH
extern uint32_t sfc_crc32b(uint32_t input, const void *buf, size_t bufLen);

/// <summary>
/// StepFC: 加载ROM
/// </summary>
/// <param name="famicom">The famicom.</param>
/// <returns></returns>
sfc_ecode sfc_load_new_rom(sfc_famicom_t* famicom) {
    // 先释放旧的ROM
    sfc_ecode code = famicom->interfaces.free_rom(
        famicom->argument,
        &famicom->rom_info
    );
    // 清空数据
    memset(&famicom->rom_info, 0, sizeof(famicom->rom_info));
    // 载入ROM
    if (code == SFC_ERROR_OK) {
        code = famicom->interfaces.load_rom(
            famicom->argument,
            &famicom->rom_info
        );
    }
    // 载入新的Mapper
    if (code == SFC_ERROR_OK) {
        code = sfc_load_mapper(
            famicom,
            famicom->rom_info.mapper_number
        );
    }
    // 载入ROM后处理
    if (code == SFC_ERROR_OK) {
        // 计算HASH
        sfc_rom_info_t* const info = &famicom->rom_info;
        info->prgrom_crc32b = sfc_crc32b(0, info->data_prgrom, info->size_prgrom);
        info->chrrom_crc32b = sfc_crc32b(0, info->data_chrrom, info->size_chrrom);
        // 载入SRAM
        sfc_check_saveload_sram(famicom->interfaces.load_sram, famicom);
    }
    // 首次重置
    if (code == SFC_ERROR_OK) {
        code = sfc_famicom_reset(famicom);
    }
    return code;
}


/// <summary>
/// uint8_t x2
/// </summary>
typedef struct { uint8_t a, b; } u8x2_t;

/// <summary>
/// SFCs the NSF swap endian u16.
/// </summary>
/// <param name="data">The data.</param>
static inline void sfc_nsf_swap_endian_u16(uint16_t* data) {
    u8x2_t* const ptr = (u8x2_t*)data;
    const uint8_t c = ptr->a;
    ptr->a = ptr->b;
    ptr->b = c;
}

/// <summary>
/// SFCs the NSF swap endian.
/// </summary>
/// <param name="header">The header.</param>
void sfc_nsf_swap_endian(sfc_nsf_header_t* header) {
    sfc_nsf_swap_endian_u16(&header->load_addr_le);
    sfc_nsf_swap_endian_u16(&header->init_addr_le);
    sfc_nsf_swap_endian_u16(&header->play_addr_le);
    sfc_nsf_swap_endian_u16(&header->play_speed_ntsc_le);
    sfc_nsf_swap_endian_u16(&header->play_speed__pal_le);
}