Modified saved data to be more future-compatible.

Core/gb.c

@@ -208,113 +208,134 @@ int gb_load_rom(GB_gameboy_t *gb, const char *path)
     return 0;
 }
 
+static bool dump_section(FILE *f, const void *src, uint32_t size)
+{
+    if (fwrite(&size, 1, sizeof(size), f) != sizeof(size)) {
+        return false;
+    }
+
+    if (fwrite(src, 1, size, f) != size) {
+        return false;
+    }
+
+    return true;
+}
+
+#define DUMP_SECTION(gb, f, section) dump_section(f, GB_GET_SECTION(gb, section), GB_SECTION_SIZE(section))
+
 /* Todo: we need a sane and protable save state format. */
 int gb_save_state(GB_gameboy_t *gb, const char *path)
 {
-    GB_gameboy_t save;
-    memcpy(&save, gb, offsetof(GB_gameboy_t, first_unsaved_data));
-    save.cartridge_type = NULL; // Kept from load_rom
-    save.rom = NULL; // Kept from load_rom
-    save.rom_size = 0; // Kept from load_rom
-    save.mbc_ram = NULL;
-    save.ram = NULL;
-    save.vram = NULL;
-    save.screen = NULL; // Kept from user
-    save.audio_buffer = NULL; // Kept from user
-    save.buffer_size = 0; // Kept from user
-    save.sample_rate = 0; // Kept from user
-    save.audio_position = 0; // Kept from previous state
-    save.vblank_callback = NULL;
-    save.user_data = NULL;
-    memset(save.keys, 0, sizeof(save.keys)); // Kept from user
-
     FILE *f = fopen(path, "w");
     if (!f) {
         return errno;
     }
 
-    if (fwrite(&save, 1, offsetof(GB_gameboy_t, first_unsaved_data), f) != offsetof(GB_gameboy_t, first_unsaved_data)) {
+    if (fwrite(GB_GET_SECTION(gb, header), 1, GB_SECTION_SIZE(header), f) != GB_SECTION_SIZE(header)) goto error;
-        fclose(f);
+    if (!DUMP_SECTION(gb, f, core_state)) goto error;
-        return EIO;
+    if (!DUMP_SECTION(gb, f, hdma      )) goto error;
-    }
+    if (!DUMP_SECTION(gb, f, mbc       )) goto error;
+    if (!DUMP_SECTION(gb, f, hram      )) goto error;
+    if (!DUMP_SECTION(gb, f, timing    )) goto error;
+    if (!DUMP_SECTION(gb, f, apu       )) goto error;
+    if (!DUMP_SECTION(gb, f, rtc       )) goto error;
+    if (!DUMP_SECTION(gb, f, video     )) goto error;
+
 
     if (fwrite(gb->mbc_ram, 1, gb->mbc_ram_size, f) != gb->mbc_ram_size) {
-        fclose(f);
+        goto error;
-        return EIO;
     }
 
     if (fwrite(gb->ram, 1, gb->ram_size, f) != gb->ram_size) {
-        fclose(f);
+        goto error;
-        return EIO;
     }
 
     if (fwrite(gb->vram, 1, gb->vram_size, f) != gb->vram_size) {
-        fclose(f);
+        goto error;
-        return EIO;
     }
 
     errno = 0;
+
+error:
     fclose(f);
     return errno;
 }
 
+/* Best-effort read function for maximum future compatibility. */
+static bool read_section(FILE *f, void *dest, uint32_t size)
+{
+    uint32_t saved_size = 0;
+    if (fread(&saved_size, 1, sizeof(size), f) != sizeof(size)) {
+        return false;
+    }
+
+    if (saved_size <= size) {
+        if (fread(dest, 1, saved_size, f) != saved_size) {
+            return false;
+        }
+    }
+    else {
+        if (fread(dest, 1, size, f) != size) {
+            return false;
+        }
+        fseek(f, saved_size - size, SEEK_CUR);
+    }
+
+    return true;
+}
+
+#define READ_SECTION(gb, f, section) read_section(f, GB_GET_SECTION(gb, section), GB_SECTION_SIZE(section))
+
 int gb_load_state(GB_gameboy_t *gb, const char *path)
 {
     GB_gameboy_t save;
 
+    /* Every unread value should be kept the same. */
+    memcpy(&save, gb, sizeof(save));
+
     FILE *f = fopen(path, "r");
     if (!f) {
         return errno;
     }
 
-    if (fread(&save, 1, offsetof(GB_gameboy_t, first_unsaved_data), f) != offsetof(GB_gameboy_t, first_unsaved_data)) {
+    if (fread(GB_GET_SECTION(&save, header), 1, GB_SECTION_SIZE(header), f) != GB_SECTION_SIZE(header)) goto error;
-        fclose(f);
+    if (!READ_SECTION(&save, f, core_state)) goto error;
-        return EIO;
+    if (!READ_SECTION(&save, f, hdma      )) goto error;
-    }
+    if (!READ_SECTION(&save, f, mbc       )) goto error;
-
+    if (!READ_SECTION(&save, f, hram      )) goto error;
-    save.cartridge_type = gb->cartridge_type;
+    if (!READ_SECTION(&save, f, timing    )) goto error;
-    save.rom = gb->rom;
+    if (!READ_SECTION(&save, f, apu       )) goto error;
-    save.rom_size = gb->rom_size;
+    if (!READ_SECTION(&save, f, rtc       )) goto error;
-    save.mbc_ram = gb->mbc_ram;
+    if (!READ_SECTION(&save, f, video     )) goto error;
-    save.ram = gb->ram;
-    save.vram = gb->vram;
-    save.screen = gb->screen;
-    save.audio_buffer = gb->audio_buffer;
-    save.buffer_size = gb->buffer_size;
-    save.sample_rate = gb->sample_rate;
-    save.audio_position = gb->audio_position;
-    save.vblank_callback = gb->vblank_callback;
-    save.user_data = gb->user_data;
-    memcpy(save.keys, gb->keys, sizeof(save.keys));
 
     if (gb->magic != save.magic) {
         gb_log(gb, "File is not a save state, or is from an incompatible operating system.\n");
-        fclose(f);
+        errno = -1;
-        return -1;
+        goto error;
     }
 
     if (gb->version != save.version) {
         gb_log(gb, "Save state is for a different version of SameBoy.\n");
-        fclose(f);
+        errno = -1;
-        return -1;
+        goto error;
     }
 
     if (gb->mbc_ram_size != save.mbc_ram_size) {
         gb_log(gb, "Save state has non-matching MBC RAM size.\n");
-        fclose(f);
+        errno = -1;
-        return -1;
+        goto error;
     }
 
     if (gb->ram_size != save.ram_size) {
         gb_log(gb, "Save state has non-matching RAM size. Try changing emulated model.\n");
-        fclose(f);
+        errno = -1;
-        return -1;
+        goto error;
     }
 
     if (gb->vram_size != save.vram_size) {
         gb_log(gb, "Save state has non-matching VRAM size. Try changing emulated model.\n");
-        fclose(f);
+        errno = -1;
-        return -1;
+        goto error;
     }
 
     if (fread(gb->mbc_ram, 1, gb->mbc_ram_size, f) != gb->mbc_ram_size) {
@@ -332,8 +353,9 @@ int gb_load_state(GB_gameboy_t *gb, const char *path)
         return EIO;
     }
 
-    memcpy(gb, &save, offsetof(GB_gameboy_t, first_unsaved_data));
+    memcpy(gb, &save, sizeof(save));
     errno = 0;
+error:
     fclose(f);
     return errno;
 }

Core/gb.h

@@ -5,8 +5,10 @@
 #include <stdio.h>
 #include <time.h>
 #include "apu.h"
+#include "save_struct.h"
 
-#define GB_STRUCT_VERSION 7
+
+#define GB_STRUCT_VERSION 8
 
 enum {
     GB_REGISTER_AF,
@@ -168,14 +170,23 @@ typedef struct {
     bool has_rumble;
 } GB_cartridge_t;
 
-typedef struct GB_gameboy_s{
+/* When state saving, each section is dumped independently of other sections.
+   This allows adding data to the end of the section without worrying about future compatibility.
+   Some other changes might be "safe" as well. */
+
+typedef struct GB_gameboy_s {
+    GB_SECTION(header,
         uintptr_t magic; // States are currently platform dependent
         int version; // and version dependent
+    );
+
+    GB_SECTION(core_state,
         /* Registers */
         unsigned short pc;
         unsigned short registers[GB_REGISTERS_16_BIT];
         bool ime;
         unsigned char interrupt_enable;
+        unsigned char cgb_ram_bank;
 
         /* CPU and General Hardware Flags*/
         bool cgb_mode;
@@ -183,77 +194,51 @@ typedef struct GB_gameboy_s{
         bool cgb_double_speed;
         bool halted;
         bool stopped;
+        bool bios_finished;
+    );
 
     /* HDMA */
+    GB_SECTION(hdma,
         bool hdma_on;
         bool hdma_on_hblank;
         unsigned char hdma_steps_left;
         unsigned short hdma_cycles;
         unsigned short hdma_current_src, hdma_current_dest;
+    );
     
-    /* Memory */
+    /* MBC */
-    unsigned char *rom;
+    GB_SECTION(mbc,
-    size_t rom_size;
         unsigned short mbc_rom_bank;
-
-    const GB_cartridge_t *cartridge_type;
-    unsigned char *mbc_ram;
         unsigned char mbc_ram_bank;
         size_t mbc_ram_size;
         bool mbc_ram_enable;
         bool mbc_ram_banking;
+    );
 
-    unsigned char *ram;
-    unsigned long ram_size; // Different between CGB and DMG
-    unsigned char cgb_ram_bank;
 
+    /* HRAM and HW Registers */
+    GB_SECTION(hram,
         unsigned char hram[0xFFFF - 0xFF80];
         unsigned char io_registers[0x80];
-
+    );
-    /* Video Display */
-    unsigned char *vram;
-    unsigned long vram_size; // Different between CGB and DMG
-    unsigned char cgb_vram_bank;
-    unsigned char oam[0xA0];
-    unsigned char background_palletes_data[0x40];
-    unsigned char sprite_palletes_data[0x40];
-    uint32_t background_palletes_rgb[0x20];
-    uint32_t sprite_palletes_rgb[0x20];
-    bool ly144_bug_oam;
-    bool ly144_bug_hblank;
-    signed short previous_lcdc_x;
-    signed short line_x_bias;
-    bool effective_window_enabled;
-    unsigned char effective_window_y;
-    bool stat_interrupt_line;
-
-    unsigned char bios[0x900];
-    bool bios_finished;
 
     /* Timing */
+    GB_SECTION(timing,
         signed long last_vblank;
         unsigned long display_cycles;
         unsigned long div_cycles;
         unsigned long tima_cycles;
         unsigned long dma_cycles;
         double apu_cycles;
+    );
 
     /* APU */
+    GB_SECTION(apu,
         GB_apu_t apu;
-    GB_sample_t *audio_buffer;
+    );
-    unsigned int buffer_size;
-    unsigned int sample_rate;
-    unsigned int audio_position;
-    volatile bool audio_copy_in_progress;
-    bool audio_stream_started; // detects first copy request to minimize lag
-    
-    /* I/O */
-    uint32_t *screen;
-    GB_vblank_callback_t vblank_callback;
-
-    bool keys[8];
 
     /* RTC */
+    GB_SECTION(rtc,
         union {
             struct {
                 unsigned char rtc_seconds;
@@ -265,23 +250,72 @@ typedef struct GB_gameboy_s{
             unsigned char rtc_data[5];
         };
         time_t last_rtc_second;
+    );
 
-    /* Unsaved User */
+    /* Video Display */
-    struct {} first_unsaved_data;
+    GB_SECTION(video,
-    bool turbo;
+        unsigned long vram_size; // Different between CGB and DMG
-    bool debug_stopped;
+        unsigned char cgb_vram_bank;
+        unsigned char oam[0xA0];
+        unsigned char background_palletes_data[0x40];
+        unsigned char sprite_palletes_data[0x40];
+        uint32_t background_palletes_rgb[0x20];
+        uint32_t sprite_palletes_rgb[0x20];
+        bool ly144_bug_oam;
+        bool ly144_bug_hblank;
+        signed short previous_lcdc_x;
+        unsigned char padding;
+        bool effective_window_enabled;
+        unsigned char effective_window_y;
+        bool stat_interrupt_line;
+        signed char line_x_bias;
+    );
+
+    /* Unsaved data. This includes all pointers, as well as everything that shouldn't be on a save state */
+
+    /* ROM */
+    unsigned char *rom;
+    size_t rom_size;
+    const GB_cartridge_t *cartridge_type;
+
+    /* Various RAMs */
+    unsigned char *ram;
+    unsigned char *vram;
+    unsigned char *mbc_ram;
+
+    /* I/O */
+    uint32_t *screen;
+    GB_sample_t *audio_buffer;
+    bool keys[8];
+
+    /* Audio Specific */
+    unsigned int buffer_size;
+    unsigned int sample_rate;
+    unsigned int audio_position;
+    bool audio_stream_started; // detects first copy request to minimize lag
+    volatile bool audio_copy_in_progress;
+
+    /* Callbacks */
+    void *user_data;
     GB_log_callback_t log_callback;
     GB_input_callback_t input_callback;
     GB_rgb_encode_callback_t rgb_encode_callback;
-    void *user_data;
+    GB_vblank_callback_t vblank_callback;
+
+    /* Debugger */
     int debug_call_depth;
     bool debug_fin_command, debug_next_command;
     unsigned short n_breakpoints;
     unsigned short *breakpoints;
-
     bool stack_leak_detection;
     unsigned short sp_for_call_depth[0x200]; /* Should be much more than enough */
     unsigned short addr_for_call_depth[0x200];
+    bool debug_stopped;
+
+    /* Misc */
+    bool turbo;
+    unsigned long ram_size; // Different between CGB and DMG
+    unsigned char bios[0x900];
 
 } GB_gameboy_t;
 

Core/save_struct.h

@@ -0,0 +1,12 @@
+/* Macros to make the GB_gameboy_t struct more future compatible when state saving */
+#ifndef save_struct_h
+#define save_struct_h
+
+#define GB_PADDING(type, old_usage) type old_usage##__do_not_use
+
+#define GB_SECTION(name, ...) __attribute__ ((aligned (sizeof(void*)))) struct {} name##_section_start; __VA_ARGS__; struct {} name##_section_end
+#define GB_SECTION_OFFSET(name) (offsetof(GB_gameboy_t, name##_section_start))
+#define GB_SECTION_SIZE(name) (offsetof(GB_gameboy_t, name##_section_end) - offsetof(GB_gameboy_t, name##_section_start))
+#define GB_GET_SECTION(gb, name) ((void*)&((gb)->name##_section_start))
+
+#endif /* save_struct_h */