src/mercenary/main.c

   1 /* main routine
   2  *
   3  * (C) 2018 by Andreas Eversberg <jolly@eversberg.eu>
   4  * All Rights Reserved
   5  *
   6  * This program is free software: you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation, either version 3 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18  */
  19
  20 #include <stdio.h>
  21 #include <stdint.h>
  22 #include <stdlib.h>
  23 #include <endian.h>
  24 #include <sys/stat.h>
  25 #include <sys/types.h>
  26 #include "../libsdl/sdl.h"
  27 #include "../libsdl/opengl.h"
  28 #include "../libcpu/m68k.h"
  29 #include "../libcpu/execute.h"
  30 #include "../libvideo/video.h"
  31 #include "../libsound/sound.h"
  32 #include "../libjoystick/joystick.h"
  33 #include "../libkeyboard/keyboard.h"
  34 #include "../libdisk/disk.h"
  35 #include "mercenary.h"
  36
  37 static int config_amiga_speed = 1;
  38 static const char *config_gamesave_dir = ".mercenary";
  39 static int config_video_filter = 0;
  40 static int config_audio_filter = 1;
  41
  42 #define CPU_SPEED       7093790.0;
  43
  44 #define SOUND_SAMPLERATE 48000
  45 /* - game IRQ rate
  46  * - must be used for sound rendering chunk
  47  */
  48 #define IRQ_RATE        50
  49 /* numbe of buffer chunks to dejitter:
  50  * - SDL render interval
  51  * - sound rendering interval
  52  * - sound card interval
  53  * 4 should be minimum, if video rate is >=50 Hz
  54  */
  55 #define SOUND_CHUNKS    4
  56
  57 /* test sound to check if buffer does not overflow / underrun */
  58 //#define DEBUG_SOUND_BUFFERING
  59
  60 #define IOSIZE          0x1000 /* bytes in io space */
  61 #define MEMORY_SIZE     0x80000
  62 static uint8_t *memory = NULL;
  63 static uint8_t *image = NULL;
  64 #define SCREEN_WIDTH    (320*3)
  65 #define SCREEN_HEIGHT   (200*3)
  66 #define IMAGE_WIDTH     320
  67 #define IMAGE_HEIGHT    200
  68 #define BENSON_AT_LINE  136
  69 #define IMAGE_DIWSTART  0x2c
  70 static uint16_t *chipreg = NULL;
  71 static float *sound_buffer = NULL; /* sound buffer memory */
  72 static int sound_buffer_size; /* buffer sample size */
  73 static int sound_buffer_writep; /* write pointer at buffer */
  74 static int sound_buffer_readp; /* read pointer at buffer */
  75
  76 static const char *home_dir;
  77
  78 static int quit = 0;
  79
  80 int parse_args(int argc, char *argv[])
  81 {
  82         int i = 1;
  83
  84         while (argc > i) {
  85                 if (!strcmp(argv[i], "-h") || !strcmp(argv[i], "--help")) {
  86                         printf("Usage: %s\n", argv[0]);
  87                         printf(" -s --amiga-speed original | full\n");
  88                         printf("        Set speed of rendering to original Amiga or full speed.\n");
  89                         printf(" -v --video-filter on | off\n");
  90                         printf("        Set video filter.\n");
  91                         printf(" -a --audio-filter on | off\n");
  92                         printf("        Set audio filter.\n");
  93                         return -1;
  94                 } else
  95                 if (!strcmp(argv[i], "-s") || !strcmp(argv[i], "--amiga-speed")) {
  96                         i++;
  97                         if (argc == i) {
  98 missing_parameter:
  99                                 printf("Missing parameter, use '--help'!\n");
 100                                 return -1;
 101                         }
 102                         if (!strcmp(argv[i], "original"))
 103                                 config_amiga_speed = 1;
 104                         else
 105                         if (!strcmp(argv[i], "full"))
 106                                 config_amiga_speed = 0;
 107                         else {
 108 illegal_parameter:
 109                                 printf("Illegal parameter, use '--help'!\n");
 110                                 return -1;
 111                         }
 112                 } else
 113                 if (!strcmp(argv[i], "-v") || !strcmp(argv[i], "--video-filter")) {
 114                         i++;
 115                         if (argc == i)
 116                                 goto missing_parameter;
 117                         if (!strcmp(argv[i], "on"))
 118                                 config_video_filter = 1;
 119                         else
 120                         if (!strcmp(argv[i], "off"))
 121                                 config_video_filter = 0;
 122                         else
 123                                 goto illegal_parameter;
 124                 } else
 125                 if (!strcmp(argv[i], "-a") || !strcmp(argv[i], "--audio-filter")) {
 126                         i++;
 127                         if (argc == i)
 128                                 goto missing_parameter;
 129                         if (!strcmp(argv[i], "on"))
 130                                 config_audio_filter = 1;
 131                         else
 132                         if (!strcmp(argv[i], "off"))
 133                                 config_audio_filter = 0;
 134                         else
 135                                 goto illegal_parameter;
 136                 } else {
 137                         printf("Illegal option '%s', use '--help'!\n", argv[i]);
 138                         return -1;
 139                 }
 140                 i++;
 141         }
 142
 143         return 0;
 144 }
 145
 146 static void special_event(int event)
 147 {
 148 }
 149
 150 static void main_loop(void)
 151 {
 152         int had_first_irq = 0;
 153         static uint32_t current_time, last_time = 0, diff;
 154         int i, rc;
 155         int space, length;
 156         int cycle_count, event;
 157         double render_delay = 0.0;
 158         uint32_t palette_address;
 159         uint16_t palette[16];
 160
 161         last_time = SDL_GetTicks();
 162
 163         /* render result on window */
 164         while (!quit) {
 165                 /* STEP 1: let the CPU render/process the game */
 166                 /* don't render if we still delay */
 167                 if (!render_delay) {
 168                         /* execute until the rendered image is ready (wait for VBL) */
 169                         cycle_count = 0;
 170                         do {
 171                                 cycle_count += execute_cpu(0, mercenary_stop_at, &event);
 172                                 /* handle special events */
 173                                 if (event != STOP_AT_WAIT_VBL)
 174                                         special_event(event);
 175                         } while (event != STOP_AT_WAIT_VBL);
 176                         /* copy palette */
 177                         palette_address = mercenary_palette();
 178                         for (i = 0; i < 16; i++)
 179                                 palette[i] = m68k_read_memory_16(palette_address + i*2);
 180                         /* for amiga speed: set delay by the number of cycles */
 181                         if (config_amiga_speed)
 182                                 render_delay = (double)cycle_count / CPU_SPEED;
 183                 }
 184
 185                 /* STEP 2: render image in memory via OpenGL */
 186                 if (had_first_irq) {
 187                         /* render game view without benson
 188                          * because benson is not updated before VBL IRQ, we don't want old image from double buffer
 189                          */
 190                         emul_video(image, memory, palette, IMAGE_WIDTH, IMAGE_HEIGHT, IMAGE_DIWSTART, chipreg, 0, BENSON_AT_LINE);
 191                 }
 192                 rc = event_sdl();
 193                 if (rc)
 194                         break;
 195                 render_opengl(image, config_video_filter);
 196                 swap_sdl();
 197
 198                 /* STEP 3: execute interrupt at rate of 50Hz, render sound */
 199                 current_time = SDL_GetTicks();
 200                 diff = current_time - last_time;
 201                 /* in case of timer glitch, execute IRQ only by maximum number of SOUND_CHUNKS */
 202                 if (diff > 1000 * SOUND_CHUNKS / IRQ_RATE) {
 203                         diff = 1000 * SOUND_CHUNKS / IRQ_RATE;
 204                         last_time = current_time - 1000 * SOUND_CHUNKS / IRQ_RATE;
 205                 }
 206                 while (diff > 1000 / IRQ_RATE) {
 207                         execute_cpu(3, NULL, NULL);
 208                         execute_cpu(4, NULL, NULL);
 209                         had_first_irq = 1;
 210                         /* render benson without game view
 211                          * because we only got benson refreshed during VBL IRQ
 212                          */
 213                         emul_video(image, memory, palette, IMAGE_WIDTH, IMAGE_HEIGHT, IMAGE_DIWSTART, chipreg, BENSON_AT_LINE, IMAGE_HEIGHT);
 214                         /* render sound to sound buffer
 215                          * buffer pointer read and write is atomic, so no locking required!
 216                          */
 217                         space = (sound_buffer_readp - sound_buffer_writep - 1 + sound_buffer_size) % sound_buffer_size;
 218                         if (space < SOUND_SAMPLERATE / IRQ_RATE) {
 219 #ifdef DEBUG_SOUND_BUFFERING
 220                                 fprintf(stderr, "sound buffer overflow\n");
 221 #endif
 222                                 length = space;
 223                         } else
 224                                 length = SOUND_SAMPLERATE / IRQ_RATE;
 225 #ifdef DEBUG_SOUND_BUFFERING
 226                         printf("can write %d, write %d\n", space, length);
 227                         static int cnt = 0;
 228                         int s;
 229                         for (s = 0; s < length; s++) {
 230                                 sound_buffer[(sound_buffer_writep + s) % sound_buffer_size]
 231                                         = sin(2 * M_PI * 999 * cnt / SOUND_SAMPLERATE)
 232                                         * sin(2 * M_PI * 21 * cnt / SOUND_SAMPLERATE)
 233                                         * sin(2 * M_PI * 0.5 * cnt / SOUND_SAMPLERATE);
 234                                  cnt++;
 235                         }
 236 #else
 237                         render_sound(memory, sound_buffer, sound_buffer_size, sound_buffer_writep, length, config_audio_filter);
 238 #endif
 239                         sound_buffer_writep = (sound_buffer_writep + length) % sound_buffer_size;
 240                         diff -= 1000 / IRQ_RATE;
 241                         last_time += 1000 / IRQ_RATE;
 242
 243                         /* count down render delay */
 244                         if (render_delay) {
 245                                 render_delay -= 1.0 / (double)IRQ_RATE;
 246                                 if (render_delay < 0.0)
 247                                         render_delay = 0.0;
 248                         }
 249                 }
 250         }
 251 }
 252
 253 int main(int argc, char *argv[])
 254 {
 255         int rc;
 256         int sdl_sound_chunk;
 257
 258         home_dir = getenv("HOME");
 259         if (!home_dir)
 260                 home_dir = "";
 261
 262         rc = parse_args(argc, argv);
 263         if (rc)
 264                 return 0;
 265
 266         /* allocate image */
 267         image = calloc(IMAGE_WIDTH * IMAGE_HEIGHT, 3);
 268         if (!image) {
 269                 fprintf(stderr, "Failed to allocate image buffer\n");
 270                 goto done;
 271         }
 272
 273         if ((SOUND_SAMPLERATE % IRQ_RATE)) {
 274                 fprintf(stderr, "Sample rate must be a multiple of IRQ rate, please fix!\n");
 275                 goto done;
 276         }
 277         if ((1000 % IRQ_RATE)) {
 278                 fprintf(stderr, "1000 (Ticks per second) rate must be a multiple of IRQ rate, please fix!\n");
 279                 goto done;
 280         }
 281
 282         /* calculate SDL chunk size for audio
 283          * it must be a power of two, but not more than the chunk size for each IRQ!
 284          */
 285         for (sdl_sound_chunk = 2; sdl_sound_chunk <= (SOUND_SAMPLERATE / IRQ_RATE); sdl_sound_chunk <<= 1)
 286                 ;
 287         sdl_sound_chunk >>= 1;
 288 //      printf("samples per IRQ = %d, samples per SDL audio = %d\n", SOUND_SAMPLERATE / IRQ_RATE, sdl_sound_chunk); exit(0);
 289
 290         /* allocate sound buffers */
 291         sound_buffer_size = SOUND_SAMPLERATE / IRQ_RATE * SOUND_CHUNKS;
 292         sound_buffer = calloc(sound_buffer_size, sizeof(*sound_buffer));
 293         if (!sound_buffer) {
 294                 fprintf(stderr, "Failed to allocate image buffer\n");
 295                 goto done;
 296         }
 297
 298         /* allocate memory */
 299         memory = calloc(MEMORY_SIZE, 1);
 300         if (!memory) {
 301                 fprintf(stderr, "Failed to allocate cpu's memory\n");
 302                 goto done;
 303         }
 304         chipreg = calloc(IOSIZE, 1);
 305         if (!chipreg) {
 306                 fprintf(stderr, "Failed to allocate chip register\n");
 307                 goto done;
 308         }
 309
 310         /* init cpu code */
 311         execute_init(MEMORY_SIZE, memory, chipreg);
 312
 313         /* load binary */
 314         mercenary_load();
 315
 316         /* patch some stuff */
 317         mercenary_patch();
 318
 319         /* init SDL and OpenGL */
 320         rc = init_sdl(argv[0], SCREEN_WIDTH, SCREEN_HEIGHT, SOUND_SAMPLERATE, sdl_sound_chunk);
 321         if (rc < 0)
 322                 goto done;
 323         rc = init_opengl(IMAGE_WIDTH, IMAGE_HEIGHT);
 324         if (rc < 0)
 325                 goto done;
 326         resize_opengl(SCREEN_WIDTH, SCREEN_HEIGHT);
 327
 328         /* init audio filter */
 329         sound_init_filter(SOUND_SAMPLERATE);
 330
 331         /* start cpu */
 332         reset_cpu();
 333
 334         printf("**********************************\n");
 335         printf("* Welcome to Mercenary Reloaded! *\n");
 336         printf("**********************************\n\n");
 337         printf("Press CTRL + cursor keys to select inventory or pickup/drop item.\n");
 338         printf("Press CTRL + f to toggle full screen.\n");
 339         printf("Press CTRL + s to toggle rendering speed.\n");
 340         printf("Press CTRL + v to toggle video filter.\n");
 341         printf("Press CTRL + a to toggle audio filter.\n");
 342         printf("Press CTRL + c to exit game.\n\n");
 343         printf("Use '--help' as command line option for configuration settings.\n\n");
 344
 345         /* run game */
 346         main_loop();
 347
 348 done:
 349         exit_opengl();
 350         exit_sdl();
 351
 352         if (chipreg)
 353                 free(chipreg);
 354         if (memory)
 355                 free(memory);
 356         if (sound_buffer)
 357                 free(sound_buffer);
 358         if (image)
 359                 free(image);
 360
 361         return 0;
 362 }
 363
 364 void audio_sdl(float *data, int length)
 365 {
 366         int fill, s;
 367
 368         /* read sound from sound buffer
 369          * buffer pointer read and write is atomic, so no locking required!
 370          */
 371         fill = (sound_buffer_writep - sound_buffer_readp + sound_buffer_size) % sound_buffer_size;
 372         if (fill < length) {
 373 #ifdef DEBUG_SOUND_BUFFERING
 374                 fprintf(stderr, "sound buffer underrun\n");
 375 #endif
 376                 /* correct read pointer as if the buffer would have 'length' of samples stored inside */
 377                 sound_buffer_readp = (sound_buffer_readp + fill - length + sound_buffer_size) % sound_buffer_size;
 378         }
 379         for (s = 0; s < length; s++)
 380                 *data++ = sound_buffer[(sound_buffer_readp + s) % sound_buffer_size];
 381 #ifdef DEBUG_SOUND_BUFFERING
 382         printf("fill %d = %.4f\n", length, sound_buffer[sound_buffer_readp]);
 383 #endif
 384         sound_buffer_readp =(sound_buffer_readp + length) % sound_buffer_size;
 385 }
 386
 387 static int shift = 0, ctrl = 0;
 388
 389 void keyboard_sdl(int down, SDL_Keycode sym)
 390 {
 391         switch (sym) {
 392         case SDLK_LCTRL:
 393         case SDLK_RCTRL:
 394                 ctrl = down;
 395                 break;
 396         case SDLK_v:
 397                 if (down && ctrl) {
 398                         config_video_filter ^= 1;
 399                         printf("video filter: %s\n", (config_video_filter) ? "on" : "off");
 400                 }
 401                 break;
 402         case SDLK_a:
 403                 if (down && ctrl) {
 404                         config_audio_filter ^= 1;
 405                         printf("audio filter: %s\n", (config_audio_filter) ? "on" : "off");
 406                 }
 407                 break;
 408         case SDLK_s:
 409                 if (down && ctrl) {
 410                         config_amiga_speed ^= 1;
 411                         printf("amiga speed: %s\n", (config_amiga_speed) ? "original" : "full");
 412                 }
 413                 break;
 414         case SDLK_c:
 415                 if (down)
 416                         quit = 1;
 417                 break;
 418         }
 419
 420         switch (sym) {
 421         case SDLK_LSHIFT:
 422                 set_key("LSH", down);
 423                 shift = down;
 424                 break;
 425         case SDLK_RSHIFT:
 426                 set_key("RSH", down);
 427                 shift = down;
 428                 break;
 429         case SDLK_LEFT:
 430                 if (shift && down) {
 431                         set_key("LF", down);
 432                         set_joystick(-1, -1, -1, -1, -1);
 433                         break;
 434                 }
 435                 set_key("LF", 0);
 436                 set_joystick(down, -1, -1, -1, -1);
 437                 break;
 438         case SDLK_RIGHT:
 439                 if (shift && down) {
 440                         set_key("RT", down);
 441                         set_joystick(-1, -1, -1, -1, -1);
 442                         break;
 443                 }
 444                 set_key("RT", 0);
 445                 set_joystick(-1, down, -1, -1, -1);
 446                 break;
 447         case SDLK_UP:
 448                 if (shift && down) {
 449                         set_key("UP", down);
 450                         set_joystick(-1, -1, -1, -1, -1);
 451                         break;
 452                 }
 453                 set_key("UP", 0);
 454                 set_joystick(-1, -1, down, -1, -1);
 455                 break;
 456         case SDLK_DOWN:
 457                 if (shift && down) {
 458                         set_key("DN", down);
 459                         set_joystick(-1, -1, -1, -1, -1);
 460                         break;
 461                 }
 462                 set_key("DN", 0);
 463                 set_joystick(-1, -1, -1, down, -1);
 464                 break;
 465         case SDLK_END:
 466                 set_joystick(-1, -1, -1, -1, down);
 467                 break;
 468
 469         case SDLK_a: set_key("A", down); break;
 470         case SDLK_b: set_key("B", down); break;
 471         case SDLK_c: set_key("C", down); break;
 472         case SDLK_d: set_key("D", down); break;
 473         case SDLK_e: set_key("E", down); break;
 474         case SDLK_f: set_key("F", down); break;
 475         case SDLK_g: set_key("G", down); break;
 476         case SDLK_h: set_key("H", down); break;
 477         case SDLK_i: set_key("I", down); break;
 478         case SDLK_j: set_key("J", down); break;
 479         case SDLK_k: set_key("K", down); break;
 480         case SDLK_l: set_key("L", down); break;
 481         case SDLK_m: set_key("M", down); break;
 482         case SDLK_n: set_key("N", down); break;
 483         case SDLK_o: set_key("O", down); break;
 484         case SDLK_p: set_key("P", down); break;
 485         case SDLK_q: set_key("Q", down); break;
 486         case SDLK_r: set_key("R", down); break;
 487         case SDLK_s: set_key("S", down); break;
 488         case SDLK_t: set_key("T", down); break;
 489         case SDLK_u: set_key("U", down); break;
 490         case SDLK_v: set_key("V", down); break;
 491         case SDLK_w: set_key("W", down); break;
 492         case SDLK_x: set_key("X", down); break;
 493         case SDLK_y: set_key("Y", down); break;
 494         case SDLK_z: set_key("Z", down); break;
 495
 496         case SDLK_0: set_key("0", down); break;
 497         case SDLK_1: set_key("1", down); break;
 498         case SDLK_2: set_key("2", down); break;
 499         case SDLK_3: set_key("3", down); break;
 500         case SDLK_4: set_key("4", down); break;
 501         case SDLK_5: set_key("5", down); break;
 502         case SDLK_6: set_key("6", down); break;
 503         case SDLK_7: set_key("7", down); break;
 504         case SDLK_8: set_key("8", down); break;
 505         case SDLK_9: set_key("9", down); break;
 506
 507         case SDLK_KP_0: set_key("NP0", down); break;
 508         case SDLK_KP_1: set_key("NP1", down); break;
 509         case SDLK_KP_2: set_key("NP2", down); break;
 510         case SDLK_KP_3: set_key("NP3", down); break;
 511         case SDLK_KP_4: set_key("NP4", down); break;
 512         case SDLK_KP_5: set_key("NP5", down); break;
 513         case SDLK_KP_6: set_key("NP6", down); break;
 514         case SDLK_KP_7: set_key("NP7", down); break;
 515         case SDLK_KP_8: set_key("NP8", down); break;
 516         case SDLK_KP_9: set_key("NP9", down); break;
 517         case SDLK_KP_DIVIDE: set_key("NPDIV", down); break;
 518         case SDLK_KP_MULTIPLY: set_key("NPMUL", down); break;
 519         case SDLK_KP_MINUS: set_key("NPSUB", down); break;
 520         case SDLK_KP_PLUS: set_key("NPADD", down); break;
 521         case SDLK_KP_PERIOD: set_key("NPDEL", down); break;
 522         // NPLPAREN and NPRPAREN are not emulated
 523
 524         case SDLK_F1: set_key("F1", down); break;
 525         case SDLK_F2: set_key("F2", down); break;
 526         case SDLK_F3: set_key("F3", down); break;
 527         case SDLK_F4: set_key("F4", down); break;
 528         case SDLK_F5: set_key("F5", down); break;
 529         case SDLK_F6: set_key("F6", down); break;
 530         case SDLK_F7: set_key("F7", down); break;
 531         case SDLK_F8: set_key("F8", down); break;
 532         case SDLK_F9: set_key("F9", down); break;
 533         case SDLK_F10: set_key("F10", down); break;
 534
 535         case SDLK_SPACE: set_key("SPC", down); break;
 536         case SDLK_BACKSPACE: set_key("BS", down); break;
 537         case SDLK_TAB: set_key("TAB", down); break;
 538         case SDLK_KP_ENTER: set_key("ENT", down); break;
 539         case SDLK_RETURN: set_key("RET", down); break;
 540         case SDLK_ESCAPE: set_key("ESC", down); break;
 541         case SDLK_DELETE: set_key("DEL", down); break;
 542         case SDLK_INSERT: set_key("HELP", down); break;
 543
 544         }
 545 }
 546
 547 uint16_t emulate_io_read(uint32_t address)
 548 {
 549         uint16_t value = 0xffff;
 550
 551         /* joystick and fire button */
 552         if (address == 0xbfe000 || address == 0xdff00c)
 553                 value &= emulate_joystick_read(address);
 554         /* keyboard */
 555         if (address == 0xbfec00 || address == 0xbfed00 || address == 0xbfee00)
 556                 value &= emulate_keyboard_read(address);
 557         /* diskette */
 558         if (address == 0xbfd100 || address == 0xbfe000 || address == 0xdff01a || address == 0xdff01e)
 559                 value &= emulate_disk_read(address);
 560
 561         return value;
 562 }
 563
 564 void emulate_io_write(uint32_t address, uint16_t value)
 565 {
 566         /* dmacon and sound registers */
 567         if (address == 0xdff096 || (address >= 0xdff0a0 && address <= 0xdff0df))
 568                 emulate_sound_write(address, value, SOUND_SAMPLERATE);
 569         if (address == 0xbfd100 || (address >= 0xdff020 && address <= 0xdff024))
 570                 emulate_disk_write(address, value);
 571 }
 572
 573 /* two tracks with 0x1820 words of length */
 574 static uint8_t game_save[2][0x1820 << 1];
 575 static int last_track = 0;
 576
 577 /* game reads track with saved game */
 578 void disk_read(int track, int __attribute__((unused)) side, uint32_t data, uint16_t length)
 579 {
 580         if (length > sizeof(game_save[0])) {
 581                 fprintf(stderr, "loading game state failed, because length exceeds game save data size, please fix!\n");
 582                 return;
 583         }
 584
 585         /* if even track is selected, load game */
 586         if (!(track & 1)) {
 587                 char filename[256];
 588                 int gamesave_num = (track - 2) >> 1;
 589                 int got;
 590                 FILE *fp;
 591
 592                 memset(game_save, 0, sizeof(game_save)); /* clear so make the game fail, if we fail */
 593                 sprintf(filename, "%s/%s/%d.gamesave", home_dir, config_gamesave_dir, gamesave_num);
 594                 fp = fopen(filename, "r");
 595                 if (!fp) {
 596 fail:
 597                         fprintf(stderr, "failed to load game from '%s'\n", filename);
 598                         goto copy;
 599                 }
 600                 got = fread(game_save, sizeof(game_save[0]), 2, fp);
 601                 fclose(fp);
 602                 if (got != 2)
 603                         goto fail;
 604         }
 605
 606 copy:
 607         /* copy track */
 608         memcpy(memory + data, game_save[track & 1], length /* sizeof(game_save[0])*/);
 609 }
 610
 611 /* game writes track with saved game */
 612 void disk_write(int track, int __attribute__((unused)) side, uint32_t data, uint16_t length)
 613 {
 614         /* skip sync info that is provided by game and only relevant for a real disk track */
 615         data += 0x200;
 616         length -= 0x200;
 617
 618         if (length != sizeof(game_save[0])) {
 619                 fprintf(stderr, "saving game state failed, because length of data does not match, please fix!\n");
 620                 return;
 621         }
 622
 623         /* don't save if last track is the same, because disk is written on both sides with the same data */
 624         if (track == last_track) {
 625                 if (memcmp(memory + data, game_save[track & 1], length)) {
 626                         fprintf(stderr, "saving game data on other side of the disk is different, please fix!\n");
 627                 }
 628                 return;
 629         }
 630         last_track = track;
 631
 632         /* save game data */
 633         memcpy(game_save[track & 1], memory + data, length);
 634
 635         /* if done with saving */
 636         if ((track & 1)) {
 637                 char filename[256];
 638                 int gamesave_num = (track - 2) >> 1;
 639                 int wrote;
 640                 FILE *fp;
 641
 642                 sprintf(filename, "%s/%s", home_dir, config_gamesave_dir);
 643                 mkdir(filename, 0777);
 644                 sprintf(filename + strlen(filename), "/%d.gamesave", gamesave_num);
 645                 fp = fopen(filename, "w");
 646                 if (!fp) {
 647 fail:
 648                         fprintf(stderr, "failed to save game to '%s'\n", filename);
 649                         return;
 650                 }
 651                 printf("Game state saved to '%s'\n", filename);
 652                 wrote = fwrite(game_save, sizeof(game_save[0]), 2, fp);
 653                 fclose(fp);
 654                 if (wrote != 2)
 655                         goto fail;
 656         }
 657 }