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 = 1;
  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 static int double_size = 1; /* render in double size, so each pixle is 2*2 pixles wide */
  76
  77 static const char *home_dir;
  78
  79 static int quit = 0;
  80
  81 int parse_args(int argc, char *argv[])
  82 {
  83         int i = 1;
  84
  85         while (argc > i) {
  86                 if (!strcmp(argv[i], "-h") || !strcmp(argv[i], "--help")) {
  87                         printf("Usage: %s\n", argv[0]);
  88                         printf(" -s --amiga-speed original | full\n");
  89                         printf("        Set speed of rendering to original Amiga or full speed.\n");
  90                         printf(" -v --video-filter on | off\n");
  91                         printf("        Set video filter.\n");
  92                         printf(" -a --audio-filter on | off\n");
  93                         printf("        Set audio filter.\n");
  94                         return -1;
  95                 } else
  96                 if (!strcmp(argv[i], "-s") || !strcmp(argv[i], "--amiga-speed")) {
  97                         i++;
  98                         if (argc == i) {
  99 missing_parameter:
 100                                 printf("Missing parameter, use '--help'!\n");
 101                                 return -1;
 102                         }
 103                         if (!strcmp(argv[i], "original"))
 104                                 config_amiga_speed = 1;
 105                         else
 106                         if (!strcmp(argv[i], "full"))
 107                                 config_amiga_speed = 0;
 108                         else {
 109 illegal_parameter:
 110                                 printf("Illegal parameter, use '--help'!\n");
 111                                 return -1;
 112                         }
 113                 } else
 114                 if (!strcmp(argv[i], "-v") || !strcmp(argv[i], "--video-filter")) {
 115                         i++;
 116                         if (argc == i)
 117                                 goto missing_parameter;
 118                         if (!strcmp(argv[i], "on"))
 119                                 config_video_filter = 1;
 120                         else
 121                         if (!strcmp(argv[i], "off"))
 122                                 config_video_filter = 0;
 123                         else
 124                                 goto illegal_parameter;
 125                 } else
 126                 if (!strcmp(argv[i], "-a") || !strcmp(argv[i], "--audio-filter")) {
 127                         i++;
 128                         if (argc == i)
 129                                 goto missing_parameter;
 130                         if (!strcmp(argv[i], "on"))
 131                                 config_audio_filter = 1;
 132                         else
 133                         if (!strcmp(argv[i], "off"))
 134                                 config_audio_filter = 0;
 135                         else
 136                                 goto illegal_parameter;
 137                 } else {
 138                         printf("Illegal option '%s', use '--help'!\n", argv[i]);
 139                         return -1;
 140                 }
 141                 i++;
 142         }
 143
 144         return 0;
 145 }
 146
 147 static void special_event(int event)
 148 {
 149 }
 150
 151 static void main_loop(void)
 152 {
 153         int had_first_irq = 0;
 154         static uint32_t current_time, last_time = 0, diff;
 155         int i, rc;
 156         int space, length;
 157         int cycle_count, event;
 158         double render_delay = 0.0;
 159         uint32_t palette_address;
 160         uint16_t palette[16];
 161
 162         last_time = SDL_GetTicks();
 163
 164         /* render result on window */
 165         while (!quit) {
 166                 /* STEP 1: let the CPU render/process the game */
 167                 /* don't render if we still delay */
 168                 if (!render_delay) {
 169                         /* execute until the rendered image is ready (wait for VBL) */
 170                         cycle_count = 0;
 171                         do {
 172                                 cycle_count += execute_cpu(0, mercenary_stop_at, &event);
 173                                 /* handle special events */
 174                                 if (event != STOP_AT_WAIT_VBL)
 175                                         special_event(event);
 176                         } while (event != STOP_AT_WAIT_VBL);
 177                         /* copy palette */
 178                         palette_address = mercenary_palette();
 179                         for (i = 0; i < 16; i++)
 180                                 palette[i] = m68k_read_memory_16(palette_address + i*2);
 181                         /* for amiga speed: set delay by the number of cycles */
 182                         if (config_amiga_speed)
 183                                 render_delay = (double)cycle_count / CPU_SPEED;
 184                 }
 185
 186                 /* STEP 2: render image in memory via OpenGL */
 187                 if (had_first_irq) {
 188                         /* render game view without benson
 189                          * because benson is not updated before VBL IRQ, we don't want old image from double buffer
 190                          */
 191                         emul_video(image, memory, palette, IMAGE_WIDTH, IMAGE_HEIGHT, IMAGE_DIWSTART, chipreg, 0, BENSON_AT_LINE, double_size);
 192                 }
 193                 rc = event_sdl();
 194                 if (rc)
 195                         break;
 196                 render_opengl(image, config_video_filter);
 197                 swap_sdl();
 198
 199                 /* STEP 3: execute interrupt at rate of 50Hz, render sound */
 200                 current_time = SDL_GetTicks();
 201                 diff = current_time - last_time;
 202                 /* in case of timer glitch, execute IRQ only by maximum number of SOUND_CHUNKS */
 203                 if (diff > 1000 * SOUND_CHUNKS / IRQ_RATE) {
 204                         diff = 1000 * SOUND_CHUNKS / IRQ_RATE;
 205                         last_time = current_time - 1000 * SOUND_CHUNKS / IRQ_RATE;
 206                 }
 207                 while (diff > 1000 / IRQ_RATE) {
 208                         execute_cpu(3, NULL, NULL);
 209                         execute_cpu(4, NULL, NULL);
 210                         had_first_irq = 1;
 211                         /* render benson without game view
 212                          * because we only got benson refreshed during VBL IRQ
 213                          */
 214                         emul_video(image, memory, palette, IMAGE_WIDTH, IMAGE_HEIGHT, IMAGE_DIWSTART, chipreg, BENSON_AT_LINE, IMAGE_HEIGHT, double_size);
 215                         /* render sound to sound buffer
 216                          * buffer pointer read and write is atomic, so no locking required!
 217                          */
 218                         space = (sound_buffer_readp - sound_buffer_writep - 1 + sound_buffer_size) % sound_buffer_size;
 219                         if (space < SOUND_SAMPLERATE / IRQ_RATE) {
 220 #ifdef DEBUG_SOUND_BUFFERING
 221                                 fprintf(stderr, "sound buffer overflow\n");
 222 #endif
 223                                 length = space;
 224                         } else
 225                                 length = SOUND_SAMPLERATE / IRQ_RATE;
 226 #ifdef DEBUG_SOUND_BUFFERING
 227                         printf("can write %d, write %d\n", space, length);
 228                         static int cnt = 0;
 229                         int s;
 230                         for (s = 0; s < length; s++) {
 231                                 sound_buffer[(sound_buffer_writep + s) % sound_buffer_size]
 232                                         = sin(2 * M_PI * 999 * cnt / SOUND_SAMPLERATE)
 233                                         * sin(2 * M_PI * 21 * cnt / SOUND_SAMPLERATE)
 234                                         * sin(2 * M_PI * 0.5 * cnt / SOUND_SAMPLERATE);
 235                                  cnt++;
 236                         }
 237 #else
 238                         render_sound(memory, sound_buffer, sound_buffer_size, sound_buffer_writep, length, config_audio_filter);
 239 #endif
 240                         sound_buffer_writep = (sound_buffer_writep + length) % sound_buffer_size;
 241                         diff -= 1000 / IRQ_RATE;
 242                         last_time += 1000 / IRQ_RATE;
 243
 244                         /* count down render delay */
 245                         if (render_delay) {
 246                                 render_delay -= 1.0 / (double)IRQ_RATE;
 247                                 if (render_delay < 0.0)
 248                                         render_delay = 0.0;
 249                         }
 250                 }
 251         }
 252 }
 253
 254 int main(int argc, char *argv[])
 255 {
 256         int rc;
 257         int sdl_sound_chunk;
 258
 259         home_dir = getenv("HOME");
 260         if (!home_dir)
 261                 home_dir = "";
 262
 263         rc = parse_args(argc, argv);
 264         if (rc)
 265                 return 0;
 266
 267         /* allocate image */
 268         image = calloc(IMAGE_WIDTH * IMAGE_HEIGHT * ((double_size) ? 4 : 1), 3);
 269         if (!image) {
 270                 fprintf(stderr, "Failed to allocate image buffer\n");
 271                 goto done;
 272         }
 273
 274         if ((SOUND_SAMPLERATE % IRQ_RATE)) {
 275                 fprintf(stderr, "Sample rate must be a multiple of IRQ rate, please fix!\n");
 276                 goto done;
 277         }
 278         if ((1000 % IRQ_RATE)) {
 279                 fprintf(stderr, "1000 (Ticks per second) rate must be a multiple of IRQ rate, please fix!\n");
 280                 goto done;
 281         }
 282
 283         /* calculate SDL chunk size for audio
 284          * it must be a power of two, but not more than the chunk size for each IRQ!
 285          */
 286         for (sdl_sound_chunk = 2; sdl_sound_chunk <= (SOUND_SAMPLERATE / IRQ_RATE); sdl_sound_chunk <<= 1)
 287                 ;
 288         sdl_sound_chunk >>= 1;
 289 //      printf("samples per IRQ = %d, samples per SDL audio = %d\n", SOUND_SAMPLERATE / IRQ_RATE, sdl_sound_chunk); exit(0);
 290
 291         /* allocate sound buffers */
 292         sound_buffer_size = SOUND_SAMPLERATE / IRQ_RATE * SOUND_CHUNKS;
 293         sound_buffer = calloc(sound_buffer_size, sizeof(*sound_buffer));
 294         if (!sound_buffer) {
 295                 fprintf(stderr, "Failed to allocate image buffer\n");
 296                 goto done;
 297         }
 298
 299         /* allocate memory */
 300         memory = calloc(MEMORY_SIZE, 1);
 301         if (!memory) {
 302                 fprintf(stderr, "Failed to allocate cpu's memory\n");
 303                 goto done;
 304         }
 305         chipreg = calloc(IOSIZE, 1);
 306         if (!chipreg) {
 307                 fprintf(stderr, "Failed to allocate chip register\n");
 308                 goto done;
 309         }
 310
 311         /* init cpu code */
 312         execute_init(MEMORY_SIZE, memory, chipreg);
 313
 314         /* load binary */
 315         mercenary_load();
 316
 317         /* patch some stuff */
 318         mercenary_patch();
 319
 320         /* init SDL and OpenGL */
 321         rc = init_sdl(argv[0], SCREEN_WIDTH, SCREEN_HEIGHT, SOUND_SAMPLERATE, sdl_sound_chunk);
 322         if (rc < 0)
 323                 goto done;
 324         rc = init_opengl((double_size) ? IMAGE_WIDTH * 2 : IMAGE_WIDTH, (double_size) ? IMAGE_HEIGHT * 2 : IMAGE_HEIGHT);
 325         if (rc < 0)
 326                 goto done;
 327         resize_opengl(SCREEN_WIDTH, SCREEN_HEIGHT);
 328
 329         /* init audio filter */
 330         sound_init_filter(SOUND_SAMPLERATE);
 331
 332         /* start cpu */
 333         reset_cpu();
 334
 335         printf("**********************************\n");
 336         printf("* Welcome to Mercenary Reloaded! *\n");
 337         printf("**********************************\n\n");
 338         printf("Press CTRL + cursor keys to select inventory or pickup/drop item.\n");
 339         printf("Press CTRL + f to toggle full screen.\n");
 340         printf("Press CTRL + s to toggle rendering speed.\n");
 341         printf("Press CTRL + v to toggle video filter.\n");
 342         printf("Press CTRL + a to toggle audio filter.\n");
 343         printf("Press CTRL + c to exit game.\n\n");
 344         printf("Use '--help' as command line option for configuration settings.\n\n");
 345
 346         /* run game */
 347         main_loop();
 348
 349 done:
 350         exit_opengl();
 351         exit_sdl();
 352
 353         if (chipreg)
 354                 free(chipreg);
 355         if (memory)
 356                 free(memory);
 357         if (sound_buffer)
 358                 free(sound_buffer);
 359         if (image)
 360                 free(image);
 361
 362         return 0;
 363 }
 364
 365 void audio_sdl(float *data, int length)
 366 {
 367         int fill, s;
 368
 369         /* read sound from sound buffer
 370          * buffer pointer read and write is atomic, so no locking required!
 371          */
 372         fill = (sound_buffer_writep - sound_buffer_readp + sound_buffer_size) % sound_buffer_size;
 373         if (fill < length) {
 374 #ifdef DEBUG_SOUND_BUFFERING
 375                 fprintf(stderr, "sound buffer underrun\n");
 376 #endif
 377                 /* correct read pointer as if the buffer would have 'length' of samples stored inside */
 378                 sound_buffer_readp = (sound_buffer_readp + fill - length + sound_buffer_size) % sound_buffer_size;
 379         }
 380         for (s = 0; s < length; s++)
 381                 *data++ = sound_buffer[(sound_buffer_readp + s) % sound_buffer_size];
 382 #ifdef DEBUG_SOUND_BUFFERING
 383         printf("fill %d = %.4f\n", length, sound_buffer[sound_buffer_readp]);
 384 #endif
 385         sound_buffer_readp =(sound_buffer_readp + length) % sound_buffer_size;
 386 }
 387
 388 static int shift = 0, ctrl = 0;
 389
 390 void keyboard_sdl(int down, SDL_Keycode sym)
 391 {
 392         switch (sym) {
 393         case SDLK_LCTRL:
 394         case SDLK_RCTRL:
 395                 ctrl = down;
 396                 break;
 397         case SDLK_v:
 398                 if (down && ctrl) {
 399                         config_video_filter ^= 1;
 400                         printf("video filter: %s\n", (config_video_filter) ? "on" : "off");
 401                 }
 402                 break;
 403         case SDLK_a:
 404                 if (down && ctrl) {
 405                         config_audio_filter ^= 1;
 406                         printf("audio filter: %s\n", (config_audio_filter) ? "on" : "off");
 407                 }
 408                 break;
 409         case SDLK_s:
 410                 if (down && ctrl) {
 411                         config_amiga_speed ^= 1;
 412                         printf("amiga speed: %s\n", (config_amiga_speed) ? "original" : "full");
 413                 }
 414                 break;
 415         case SDLK_c:
 416                 if (down)
 417                         quit = 1;
 418                 break;
 419         }
 420
 421         switch (sym) {
 422         case SDLK_LSHIFT:
 423                 set_key("LSH", down);
 424                 shift = down;
 425                 break;
 426         case SDLK_RSHIFT:
 427                 set_key("RSH", down);
 428                 shift = down;
 429                 break;
 430         case SDLK_LEFT:
 431                 if (shift && down) {
 432                         set_key("LF", down);
 433                         set_joystick(-1, -1, -1, -1, -1);
 434                         break;
 435                 }
 436                 set_key("LF", 0);
 437                 set_joystick(down, -1, -1, -1, -1);
 438                 break;
 439         case SDLK_RIGHT:
 440                 if (shift && down) {
 441                         set_key("RT", down);
 442                         set_joystick(-1, -1, -1, -1, -1);
 443                         break;
 444                 }
 445                 set_key("RT", 0);
 446                 set_joystick(-1, down, -1, -1, -1);
 447                 break;
 448         case SDLK_UP:
 449                 if (shift && down) {
 450                         set_key("UP", down);
 451                         set_joystick(-1, -1, -1, -1, -1);
 452                         break;
 453                 }
 454                 set_key("UP", 0);
 455                 set_joystick(-1, -1, down, -1, -1);
 456                 break;
 457         case SDLK_DOWN:
 458                 if (shift && down) {
 459                         set_key("DN", down);
 460                         set_joystick(-1, -1, -1, -1, -1);
 461                         break;
 462                 }
 463                 set_key("DN", 0);
 464                 set_joystick(-1, -1, -1, down, -1);
 465                 break;
 466         case SDLK_END:
 467                 set_joystick(-1, -1, -1, -1, down);
 468                 break;
 469
 470         case SDLK_a: set_key("A", down); break;
 471         case SDLK_b: set_key("B", down); break;
 472         case SDLK_c: set_key("C", down); break;
 473         case SDLK_d: set_key("D", down); break;
 474         case SDLK_e: set_key("E", down); break;
 475         case SDLK_f: set_key("F", down); break;
 476         case SDLK_g: set_key("G", down); break;
 477         case SDLK_h: set_key("H", down); break;
 478         case SDLK_i: set_key("I", down); break;
 479         case SDLK_j: set_key("J", down); break;
 480         case SDLK_k: set_key("K", down); break;
 481         case SDLK_l: set_key("L", down); break;
 482         case SDLK_m: set_key("M", down); break;
 483         case SDLK_n: set_key("N", down); break;
 484         case SDLK_o: set_key("O", down); break;
 485         case SDLK_p: set_key("P", down); break;
 486         case SDLK_q: set_key("Q", down); break;
 487         case SDLK_r: set_key("R", down); break;
 488         case SDLK_s: set_key("S", down); break;
 489         case SDLK_t: set_key("T", down); break;
 490         case SDLK_u: set_key("U", down); break;
 491         case SDLK_v: set_key("V", down); break;
 492         case SDLK_w: set_key("W", down); break;
 493         case SDLK_x: set_key("X", down); break;
 494         case SDLK_y: set_key("Y", down); break;
 495         case SDLK_z: set_key("Z", down); break;
 496
 497         case SDLK_0: set_key("0", down); break;
 498         case SDLK_1: set_key("1", down); break;
 499         case SDLK_2: set_key("2", down); break;
 500         case SDLK_3: set_key("3", down); break;
 501         case SDLK_4: set_key("4", down); break;
 502         case SDLK_5: set_key("5", down); break;
 503         case SDLK_6: set_key("6", down); break;
 504         case SDLK_7: set_key("7", down); break;
 505         case SDLK_8: set_key("8", down); break;
 506         case SDLK_9: set_key("9", down); break;
 507
 508         case SDLK_KP_0: set_key("NP0", down); break;
 509         case SDLK_KP_1: set_key("NP1", down); break;
 510         case SDLK_KP_2: set_key("NP2", down); break;
 511         case SDLK_KP_3: set_key("NP3", down); break;
 512         case SDLK_KP_4: set_key("NP4", down); break;
 513         case SDLK_KP_5: set_key("NP5", down); break;
 514         case SDLK_KP_6: set_key("NP6", down); break;
 515         case SDLK_KP_7: set_key("NP7", down); break;
 516         case SDLK_KP_8: set_key("NP8", down); break;
 517         case SDLK_KP_9: set_key("NP9", down); break;
 518         case SDLK_KP_DIVIDE: set_key("NPDIV", down); break;
 519         case SDLK_KP_MULTIPLY: set_key("NPMUL", down); break;
 520         case SDLK_KP_MINUS: set_key("NPSUB", down); break;
 521         case SDLK_KP_PLUS: set_key("NPADD", down); break;
 522         case SDLK_KP_PERIOD: set_key("NPDEL", down); break;
 523         // NPLPAREN and NPRPAREN are not emulated
 524
 525         case SDLK_F1: set_key("F1", down); break;
 526         case SDLK_F2: set_key("F2", down); break;
 527         case SDLK_F3: set_key("F3", down); break;
 528         case SDLK_F4: set_key("F4", down); break;
 529         case SDLK_F5: set_key("F5", down); break;
 530         case SDLK_F6: set_key("F6", down); break;
 531         case SDLK_F7: set_key("F7", down); break;
 532         case SDLK_F8: set_key("F8", down); break;
 533         case SDLK_F9: set_key("F9", down); break;
 534         case SDLK_F10: set_key("F10", down); break;
 535
 536         case SDLK_SPACE: set_key("SPC", down); break;
 537         case SDLK_BACKSPACE: set_key("BS", down); break;
 538         case SDLK_TAB: set_key("TAB", down); break;
 539         case SDLK_KP_ENTER: set_key("ENT", down); break;
 540         case SDLK_RETURN: set_key("RET", down); break;
 541         case SDLK_ESCAPE: set_key("ESC", down); break;
 542         case SDLK_DELETE: set_key("DEL", down); break;
 543         case SDLK_INSERT: set_key("HELP", down); break;
 544
 545         }
 546 }
 547
 548 uint16_t emulate_io_read(uint32_t address)
 549 {
 550         uint16_t value = 0xffff;
 551
 552         /* joystick and fire button */
 553         if (address == 0xbfe000 || address == 0xdff00c)
 554                 value &= emulate_joystick_read(address);
 555         /* keyboard */
 556         if (address == 0xbfec00 || address == 0xbfed00 || address == 0xbfee00)
 557                 value &= emulate_keyboard_read(address);
 558         /* diskette */
 559         if (address == 0xbfd100 || address == 0xbfe000 || address == 0xdff01a || address == 0xdff01e)
 560                 value &= emulate_disk_read(address);
 561
 562         return value;
 563 }
 564
 565 void emulate_io_write(uint32_t address, uint16_t value)
 566 {
 567         /* dmacon and sound registers */
 568         if (address == 0xdff096 || (address >= 0xdff0a0 && address <= 0xdff0df))
 569                 emulate_sound_write(address, value, SOUND_SAMPLERATE);
 570         if (address == 0xbfd100 || (address >= 0xdff020 && address <= 0xdff024))
 571                 emulate_disk_write(address, value);
 572 }
 573
 574 /* two tracks with 0x1820 words of length */
 575 static uint8_t game_save[2][0x1820 << 1];
 576 static int last_track = 0;
 577
 578 /* game reads track with saved game */
 579 void disk_read(int track, int __attribute__((unused)) side, uint32_t data, uint16_t length)
 580 {
 581         if (length > sizeof(game_save[0])) {
 582                 fprintf(stderr, "loading game state failed, because length exceeds game save data size, please fix!\n");
 583                 return;
 584         }
 585
 586         /* if even track is selected, load game */
 587         if (!(track & 1)) {
 588                 char filename[256];
 589                 int gamesave_num = (track - 2) >> 1;
 590                 int got;
 591                 FILE *fp;
 592
 593                 memset(game_save, 0, sizeof(game_save)); /* clear so make the game fail, if we fail */
 594                 sprintf(filename, "%s/%s/%d.gamesave", home_dir, config_gamesave_dir, gamesave_num);
 595                 fp = fopen(filename, "r");
 596                 if (!fp) {
 597 fail:
 598                         fprintf(stderr, "failed to load game from '%s'\n", filename);
 599                         goto copy;
 600                 }
 601                 got = fread(game_save, sizeof(game_save[0]), 2, fp);
 602                 fclose(fp);
 603                 if (got != 2)
 604                         goto fail;
 605         }
 606
 607 copy:
 608         /* copy track */
 609         memcpy(memory + data, game_save[track & 1], length /* sizeof(game_save[0])*/);
 610 }
 611
 612 /* game writes track with saved game */
 613 void disk_write(int track, int __attribute__((unused)) side, uint32_t data, uint16_t length)
 614 {
 615         /* skip sync info that is provided by game and only relevant for a real disk track */
 616         data += 0x200;
 617         length -= 0x200;
 618
 619         if (length != sizeof(game_save[0])) {
 620                 fprintf(stderr, "saving game state failed, because length of data does not match, please fix!\n");
 621                 return;
 622         }
 623
 624         /* don't save if last track is the same, because disk is written on both sides with the same data */
 625         if (track == last_track) {
 626                 if (memcmp(memory + data, game_save[track & 1], length)) {
 627                         fprintf(stderr, "saving game data on other side of the disk is different, please fix!\n");
 628                 }
 629                 return;
 630         }
 631         last_track = track;
 632
 633         /* save game data */
 634         memcpy(game_save[track & 1], memory + data, length);
 635
 636         /* if done with saving */
 637         if ((track & 1)) {
 638                 char filename[256];
 639                 int gamesave_num = (track - 2) >> 1;
 640                 int wrote;
 641                 FILE *fp;
 642
 643                 sprintf(filename, "%s/%s", home_dir, config_gamesave_dir);
 644                 mkdir(filename, 0777);
 645                 sprintf(filename + strlen(filename), "/%d.gamesave", gamesave_num);
 646                 fp = fopen(filename, "w");
 647                 if (!fp) {
 648 fail:
 649                         fprintf(stderr, "failed to save game to '%s'\n", filename);
 650                         return;
 651                 }
 652                 printf("Game state saved to '%s'\n", filename);
 653                 wrote = fwrite(game_save, sizeof(game_save[0]), 2, fp);
 654                 fclose(fp);
 655                 if (wrote != 2)
 656                         goto fail;
 657         }
 658 }