viiper.c

   1 /*******************************************************************************
   2  viiper 0.1
   3  By Tobias Girstmair, 2018
   4
   5  ./viiper 40x25
   6  (see ./viiper -h for full list of options)
   7
   8  KEYBINDINGS:  - hjkl to move
   9                - p to pause and resume
  10                - r to restart
  11                - q to quit
  12                - (see `./minesviiper -h' for all keybindings)
  13
  14  GNU GPL v3, see LICENSE or https://www.gnu.org/licenses/gpl-3.0.txt
  15 *******************************************************************************/
  16
  17
  18 #define _POSIX_C_SOURCE 2 /*for getopt and sigaction in c99, sigsetjmp*/
  19 #include <setjmp.h>
  20 #include <signal.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <sys/ioctl.h>
  25 #include <sys/time.h>
  26 #include <termios.h>
  27 #include <time.h>
  28 #include <unistd.h>
  29
  30 #include "viiper.h"
  31 #include "schemes.h"
  32
  33 #define MIN(a,b) (a>b?b:a)
  34 #define MAX(a,b) (a>b?a:b)
  35 #define CLAMP(a,m,M) (a<m?m:(a>M?M:a))
  36 #define printm(n, s) for (int _loop = 0; _loop < n; _loop++) fputs (s, stdout)
  37 #define print(str) fputs (str?str:"", stdout)
  38 #define CTRL_ 0x1F &
  39
  40 #define BORDER(v,h) (g.b.t&1<<BONUS_WRAP?op.sch->permeable:op.sch->border) \
  41         [BORDER_ ## v][BORDER_ ## h]
  42 #define OPPOSITE(dir) ( \
  43         dir == EAST  ? WEST  :   \
  44         dir == WEST  ? EAST  :   \
  45         dir == NORTH ? SOUTH :   \
  46         dir == SOUTH ? NORTH : -1)
  47
  48 #define COL_OFFSET 1
  49 #define LINE_OFFSET 1
  50 #define LINES_AFTER 1
  51 #define CW op.sch->cell_width
  52 #define DW op.sch->display_width
  53
  54 #define SPEEDUP_AFTER 100 /* increment speed every n points */
  55 #define BONUS_INTERVAL 90 /* how often a bonus item is spawned */
  56 #define BONUS_DURATION 15 /* how long one can catch the bonus */
  57 #define BONUS_WARN      5 /* how long before the removal to warn */
  58 #define BONUS_STOP_NUM 10 /* how many steps the time freezes */
  59
  60 struct game {
  61         int w; /* field width */
  62         int h; /* field height */
  63         int d; /* direction the snake is looking */
  64         int p; /* score */
  65         float v; /* velocity in moves per second */
  66         time_t t; /* time of game start */
  67         struct snake* s; /* snek */
  68         struct item* i; /* items (food, boni) */
  69         struct bonus {
  70                 int t; /* bonus type (bitmask based on enum bonus_value) */
  71                 int s; /* steps left of time freeze bonus */
  72                 time_t n; /* time of next bonus item spawn */
  73                 time_t w; /* time of wall-wrap end */
  74         } b; /* bonus-related values */
  75         struct directions {
  76                 int h; /* write head */
  77                 int n; /* number of elements */
  78                 int c[16];
  79         } k; /* ring buffer for direction events */
  80 } g;
  81
  82 struct opt {
  83         int l; /* initial snake length */
  84         int s; /* initial snake speed */
  85         struct scheme* sch;
  86 } op;
  87
  88 sigjmp_buf game_over;
  89
  90 int main (int argc, char** argv) {
  91         /* defaults: */
  92         g.w = 30;
  93         g.h = 20;
  94         op.l = 10;
  95         op.s = 8;
  96         op.sch = &unic0de;
  97
  98         int optget;
  99         opterr = 0; /* don't print message on unrecognized option */
 100         while ((optget = getopt (argc, argv, "+s:l:h")) != -1) {
 101                 switch (optget) {
 102                 case 's':
 103                         op.s = atof(optarg);
 104                         if (op.s < 1) {
 105                                 fprintf (stderr, "speed must be >= 1\n");
 106                                 return 1;
 107                         }
 108                         break;
 109                 case 'l':
 110                         op.l = atoi(optarg);
 111                         if (op.s < 2 || op.s > g.w*g.h-1) {
 112                                 fprintf (stderr, "length must be >= 2 and < W*H\n");
 113                                 return 1;
 114                         }
 115                         break;
 116                 case 'h':
 117                 default:
 118                         fprintf (stderr, SHORTHELP LONGHELP, argv[0]);
 119                         return !(optget=='h');
 120                 }
 121         } if (optind < argc) { /* parse Fieldspec */
 122                 int n = sscanf (argv[optind], "%dx%d", &g.w, &g.h);
 123
 124                 if (n < 2) {
 125                         fprintf(stderr,"FIELDSIZE is WxH (width 'x' height)\n");
 126                         return 1;
 127                 }
 128         }
 129
 130         clamp_fieldsize();
 131
 132         srand(time(0));
 133         signal_setup();
 134         screen_setup(1);
 135         atexit (*quit);
 136
 137         char* end_screen_msg = "";
 138 restart:
 139         switch (sigsetjmp(game_over, 1)) {
 140         case GAME_INIT:
 141         case GAME_START:
 142                 viiper();
 143                 break; /* function doesn't return, but `-Wextra' complains */
 144         case GAME_OVER:
 145                 end_screen_msg = " GAME  OVER ";
 146                 goto end_screen;
 147         case GAME_WON:
 148                 end_screen_msg = "CONGRATULATIONS!";
 149                 goto end_screen;
 150 end_screen:
 151                 timer_setup(0);
 152                 show_playfield();
 153                 for (;;) switch (end_screen(end_screen_msg)) {
 154                 case 'r': goto restart;
 155                 case 'q': goto quit;
 156                 case CTRL_'L':
 157                         screen_setup(1);
 158                         show_playfield();
 159                         break;
 160                 default: continue;
 161                 }
 162         case GAME_EXIT:
 163                 goto quit;
 164         }
 165
 166 quit:
 167         return 0;
 168 }
 169
 170 int viiper(void) {
 171         init_snake();
 172         show_playfield ();
 173         g.d = EAST;
 174         g.v = op.s;
 175
 176         timer_setup(1);
 177         g.t = time(NULL);
 178         g.p = 0;
 179         g.k.n = 0;
 180         g.b.n = time(NULL) + BONUS_INTERVAL;
 181         g.b.s = 0;
 182         g.b.t = 0;
 183
 184         spawn_item(FOOD, rand() % NUM_FOODS, NULL);
 185
 186         for(;;) {
 187                 switch (getctrlseq()) {
 188                 case 'h': case CTRSEQ_CURSOR_LEFT: append_movement(WEST); break;
 189                 case 'j': case CTRSEQ_CURSOR_DOWN: append_movement(SOUTH);break;
 190                 case 'k': case CTRSEQ_CURSOR_UP:   append_movement(NORTH);break;
 191                 case 'l': case CTRSEQ_CURSOR_RIGHT:append_movement(EAST); break;
 192                 case 'p': pause_game(); break;
 193                 case 'r': siglongjmp(game_over, GAME_START);
 194                 case 'q': siglongjmp(game_over, GAME_EXIT);
 195                 case CTRL_'L':
 196                         screen_setup(1);
 197                         show_playfield();
 198                         break;
 199                 case 0x02: /* STX; gets sent when returning from SIGALRM */
 200                         continue;
 201                 }
 202
 203                 if (g.b.s) { /* highjack keyboard function for time freeze */
 204                         snake_advance();
 205                         if (!--g.b.s) timer_setup(1);/*turn back on afterwards*/
 206                 }
 207         }
 208
 209 }
 210
 211 #define pop_dir() (g.k.n? g.k.c[(16+g.k.h-g.k.n--)%16] : NONE)
 212 void snake_advance (void) {
 213         int respawn = 0;
 214         struct item* i; /*temporary item (defined here to respawn at the end) */
 215         int new_dir = pop_dir();
 216         /* switch direction if new one is in the buffer and it won't kill us: */
 217         if (new_dir && g.d != OPPOSITE(new_dir)) g.d = new_dir;
 218
 219         int new_row = g.s->r +(g.d==SOUTH) -(g.d==NORTH);
 220         int new_col = g.s->c +(g.d==EAST)  -(g.d==WEST);
 221
 222         /* detect food hit and spawn a new food */
 223         for (i = g.i; i; i = i->next) {
 224                 if (i->r == new_row && i->c == new_col) {
 225                         consume_item (i);
 226
 227                         switch (i->t) {
 228                         case FOOD: respawn = 1; break;
 229                         case BONUS: remove_bonus(i); break;
 230                         }
 231                         break;
 232                 }
 233         }
 234
 235         if (g.b.t & 1<<BONUS_WRAP) {
 236           if (new_row >= g.h) new_row = 0;
 237           if (new_col >= g.w) new_col = 0;
 238           if (new_row < 0) new_row = g.h-1;
 239           if (new_col < 0) new_col = g.w-1;
 240         } else {
 241           if (new_row >= g.h || new_col >= g.w || new_row < 0 || new_col < 0)
 242                 siglongjmp(game_over, GAME_OVER);
 243         }
 244
 245         struct snake* new_head;
 246         struct snake* new_tail; /* former second-to-last element */
 247         for (new_tail = g.s; new_tail->next->next; new_tail = new_tail->next)
 248                 /*use the opportunity of looping to check if we eat ourselves:*/
 249                 if(new_tail->next->r == new_row && new_tail->next->c == new_col)
 250                         siglongjmp(game_over, GAME_OVER);
 251         int old_tail[2] = {new_tail->next->r, new_tail->next->c};/*gets erased*/
 252         new_head = new_tail->next; /* reuse element instead of malloc() */
 253         new_tail->next = NULL;
 254
 255         new_head->r = new_row;
 256         new_head->c = new_col;
 257         new_head->next = g.s;
 258
 259         g.s = new_head;
 260
 261         /* bonus mode(s) still active? */
 262         if (g.b.t&1<<BONUS_WRAP && g.b.w < time(NULL)) {
 263                 g.b.t &= ~(1<<BONUS_WRAP);
 264                 show_playfield();
 265         }
 266
 267         if (respawn) spawn_item(FOOD, rand() % NUM_FOODS, i);
 268         draw_sprites (old_tail[0], old_tail[1]);
 269 }
 270
 271 void spawn_item (int type, int value, struct item* p_item) {
 272         int row, col;
 273         char occupied[g.w][g.h]; int snake_len = 0;
 274         memset(*occupied, 0, g.w*g.h);
 275 try_again:
 276         row = rand() % g.h;
 277         col = rand() % g.w;
 278         if (snake_len >= g.w*g.h-1) siglongjmp(game_over, GAME_WON);
 279         /* loop through snake to check if we aren't on it */
 280         if (occupied[row][col]) goto try_again; /* shortcut */
 281         for (struct snake* s = g.s; s; s = s->next)
 282                 if (s->r == row && s->c == col) {
 283                         occupied[s->r][s->c] = 1; snake_len++;
 284                         goto try_again;
 285                 }
 286
 287         /* if we got a item buffer reuse it, otherwise create a new one: */
 288         struct item* new_item;
 289         if (p_item) new_item = p_item;
 290         else new_item = malloc (sizeof(struct item));
 291
 292         new_item->r = row;
 293         new_item->c = col;
 294         new_item->t = type;
 295         new_item->v = value;
 296         new_item->s = time(0);
 297         if (g.i) g.i->prev = new_item;
 298         new_item->next = g.i;
 299         new_item->prev = NULL;
 300
 301         g.i = new_item;
 302 }
 303
 304 void consume_item (struct item* i) {
 305         int old_score = g.p;
 306
 307         switch (i->t) {
 308         case FOOD:
 309                 switch (i->v) {
 310                 case FOOD_PEAR:
 311                 case FOOD_WMELON:
 312                 case FOOD_BANANA:
 313                 case FOOD_KIWI:
 314                         g.p +=  5;
 315                         break;
 316                 case FOOD_APPLER:
 317                 case FOOD_CHERRY:
 318                         g.p += 10;
 319                         break;
 320                 case FOOD_AVOCADO:
 321                         g.p += 20;
 322                         break;
 323                 }
 324                 snake_append(&g.s, -1, -1);
 325                 break; /* will be reused as the head before it is drawn */
 326         case BONUS:
 327                 switch (i->v) {
 328                 case BONUS_SNIP:
 329                         for (int i = 5; i && g.s->next->next; i--) {
 330                                 struct snake* p = g.s;
 331                                 while (p->next->next) p = p->next;
 332                                 free (p->next);
 333                                 p->next = NULL;
 334                         }
 335                         show_playfield();
 336                         break;
 337                 case BONUS_GROW:
 338                         for (int i = 5; i; i--) snake_append(&g.s, -1, -1);
 339                         break;
 340                 case BONUS_SLOW:
 341                         if (g.v > 1) g.v--;
 342                         timer_setup(1);
 343                         break;
 344                 case BONUS_FAST:
 345                         g.v++;
 346                         timer_setup(1);
 347                         break;
 348                 case BONUS_WRAP:
 349                         g.b.w = time(NULL)+30;
 350                         g.b.t |= 1<<BONUS_WRAP;
 351                         show_playfield();
 352                         break;
 353                 case BONUS_STOP:
 354                         g.b.s = BONUS_STOP_NUM; /* stop the time for 5 steps */
 355                         timer_setup(0);
 356                         break;
 357                 }
 358                 g.b.n = time(NULL) + BONUS_INTERVAL; /*next bonus in x seconds*/
 359                 break;
 360         }
 361
 362         if (i->next) i->next->prev = i->prev;
 363         if (i->prev) i->prev->next = i->next;
 364         else g.i = i->next;
 365
 366         /* snake speedup every 100 points: */
 367         if (g.p/SPEEDUP_AFTER - old_score/SPEEDUP_AFTER) g.v++, timer_setup(1);
 368 }
 369
 370 void spawn_bonus(void) {
 371         for (struct item* i = g.i; i; i = i->next)
 372                 if (i->t == BONUS) { /* bonus already there */
 373                         if (((i->s+BONUS_DURATION)-time(NULL)) < 0) {
 374                                 remove_bonus(i); /* remove if over lifetime */
 375                         }
 376                         return;
 377                 }
 378         if (g.b.n < time(NULL)) { /* time to spawn item: */
 379                 spawn_item(BONUS, rand() % NUM_BONI, NULL);
 380                 g.b.n = time(NULL) + BONUS_INTERVAL + BONUS_DURATION;
 381         }
 382 }
 383
 384 void show_playfield (void) {
 385         move_ph (0,0);
 386
 387         /* top border */
 388         print(BORDER(T,L));
 389         printm (g.w, BORDER(T,C));
 390         printf ("%s\n", BORDER(T,R));
 391
 392         /* main area */
 393         for (int row = 0; row < g.h; row++)
 394                 printf ("%s%*s%s\n", BORDER(C,L), CW*g.w, "", BORDER(C,R));
 395
 396         /* bottom border */
 397         print(BORDER(B,L));
 398         printm (g.w, BORDER(B,C));
 399         print (BORDER(B,R));
 400
 401         draw_sprites (-1,-1);
 402 }
 403
 404 void draw_sprites (int erase_r, int erase_c) {
 405         /* erase old tail, if any */
 406         if (erase_r >= 0 && erase_c >= 0) {
 407                 move_ph (erase_r+LINE_OFFSET, erase_c*CW+COL_OFFSET);
 408                 printm (CW, " ");
 409         }
 410
 411         /* print snake */
 412         struct snake* last = NULL;
 413         int color = 2;
 414         for (struct snake* s = g.s; s; s = s->next) {
 415                 if (s->r < 0 || s->c < 0) continue; /*can't draw outside term.*/
 416                 move_ph (s->r+LINE_OFFSET, s->c*CW+COL_OFFSET);
 417
 418                 int predecessor = (last==NULL)?NONE:
 419                         (last->r < s->r) ? NORTH:
 420                         (last->r > s->r) ? SOUTH:
 421                         (last->c > s->c) ? EAST:
 422                         (last->c < s->c) ? WEST:NONE;
 423                 int successor = (s->next == NULL)?NONE:
 424                         (s->next->r < s->r) ? NORTH:
 425                         (s->next->r > s->r) ? SOUTH:
 426                         (s->next->c > s->c) ? EAST:
 427                         (s->next->c < s->c) ? WEST:NONE;
 428
 429                 printf ("\033[%sm", op.sch->color[color]);
 430                 print (op.sch->snake[predecessor][successor]);
 431                 printf ("\033[0m");
 432                 last = s;
 433                 color = !color;
 434         }
 435
 436         /* print item queue */
 437         for (struct item* i = g.i; i; i = i->next) {
 438                 move_ph (i->r+LINE_OFFSET, i->c*CW+COL_OFFSET);
 439                 if      (i->t == FOOD)  print(op.sch->food[i->v]);
 440                 else if (i->t == BONUS) {
 441                         if (i->s + BONUS_DURATION-BONUS_WARN < time(NULL))
 442                                 printf("\033[5m%s\033[25m", op.sch->boni[i->v]);
 443                         else print(op.sch->boni[i->v]);
 444                 }
 445         }
 446
 447         /* print score */
 448         int score_width = g.p > 9999?6:4;
 449         move_ph (0, (g.w*CW-score_width)/2-COL_OFFSET);
 450         printf ("%s %0*d %s", BORDER(S,L), score_width, g.p, BORDER(S,R));
 451 }
 452
 453 void pause_game (void) {
 454         time_t pause_start = time(NULL);
 455         time_t pause_diff;
 456         timer_setup(0);
 457
 458         move_ph (g.h/2+LINE_OFFSET, g.w*CW/2);
 459         printf ("\033[5;7m PAUSE \033[0m"); /* blinking reverse text */
 460         if (getchar() == 'q')
 461                 siglongjmp(game_over, GAME_EXIT);
 462
 463         /* update all timers, so bonus items don't get out of sync: */
 464         pause_diff = time(NULL) - pause_start;
 465         g.b.n += pause_diff;
 466         for (struct item* i = g.i; i; i = i->next)
 467                 i->s += pause_diff;
 468
 469         show_playfield();
 470         timer_setup(1);
 471 }
 472
 473 #define MOVE_POPUP(WIDTH, LINE) \
 474         move_ph(g.h/2+LINE_OFFSET-1+LINE,(g.w*DW-WIDTH)/2)
 475 int end_screen(char* message) {
 476         int msg_w = strlen(message);
 477         MOVE_POPUP(msg_w, -1);
 478         print(BORDER(T,L));
 479         printm ((msg_w+2)/DW, BORDER(T,C));
 480         print (BORDER(T,R));
 481
 482         MOVE_POPUP(msg_w, 0);
 483         printf("%s %s %s", BORDER(C,L), message, BORDER(C,R));
 484         MOVE_POPUP(msg_w, 1);
 485         printf("%s `r' restart%*s%s", BORDER(C,L), msg_w-10, "", BORDER(C,R));
 486         MOVE_POPUP(msg_w, 2);
 487         printf("%s `q' quit%*s%s", BORDER(C,L), msg_w-7, "", BORDER(C,R));
 488
 489         MOVE_POPUP(msg_w, 3);
 490         print(BORDER(B,L));
 491         printm ((msg_w+2)/DW, BORDER(B,C));
 492         print (BORDER(B,R));
 493         fflush(stdout);
 494
 495         return getctrlseq();
 496 }
 497
 498 void snake_append (struct snake** s, int row, int col) {
 499         struct snake* new = malloc (sizeof(struct snake));
 500         new->r = row;
 501         new->c = col;
 502         new->next = NULL;
 503
 504         if (*s) {
 505                 struct snake* p = *s;
 506                 while (p->next) p = p->next;
 507                 p->next = new;
 508         } else {
 509                 *s = new;
 510         }
 511 }
 512
 513 void remove_bonus (struct item*  i) {
 514         if (i->next) i->next->prev = i->prev;
 515         if (i->prev) i->prev->next = i->next;
 516         else g.i = i->next;
 517
 518         draw_sprites (i->r, i->c); /* overwrite sprite */
 519
 520         free(i);
 521 }
 522
 523 #define free_ll(head) do{ \
 524         while (head) { \
 525                 void* tmp = head; \
 526                 head = head->next; \
 527                 free(tmp); \
 528         } \
 529         head = NULL; \
 530 }while(0)
 531
 532 void init_snake() {
 533         free_ll(g.s);
 534         free_ll(g.i);
 535
 536         int direction = WEST;
 537         int r = g.h/2;
 538         int c = g.w/2;
 539         int min_r = 0;
 540         int max_r = g.h-1;
 541         int min_c = 0;
 542         int max_c = g.w-1;
 543         for (int i = 0; i < op.l; i++) {
 544                 switch (direction) {
 545                 case NORTH: r--; if(r <= min_r){direction=EAST; min_r++;}break;
 546                 case EAST:  c++; if(c >= max_c){direction=SOUTH;max_c--;}break;
 547                 case SOUTH: r++; if(r >= max_r){direction=WEST; max_r--;}break;
 548                 case WEST:  c--; if(c <= min_c){direction=NORTH;min_c++;}break;
 549                 }
 550
 551                 snake_append(&g.s, r, c);
 552         }
 553 }
 554
 555 void quit (void) {
 556         screen_setup(0);
 557         free_ll(g.s);
 558         free_ll(g.i);
 559 }
 560
 561 enum esc_states {
 562         START,
 563         ESC_SENT,
 564         CSI_SENT,
 565         MOUSE_EVENT,
 566 };
 567 int getctrlseq (void) {
 568         int c;
 569         int state = START;
 570         while ((c = getchar()) != EOF) {
 571                 switch (state) {
 572                 case START:
 573                         switch (c) {
 574                         case '\033': state=ESC_SENT; break;
 575                         default: return c;
 576                         }
 577                         break;
 578                 case ESC_SENT:
 579                         switch (c) {
 580                         case '[': state=CSI_SENT; break;
 581                         default: return CTRSEQ_INVALID;
 582                         }
 583                         break;
 584                 case CSI_SENT:
 585                         switch (c) {
 586                         case 'A': return CTRSEQ_CURSOR_UP;
 587                         case 'B': return CTRSEQ_CURSOR_DOWN;
 588                         case 'C': return CTRSEQ_CURSOR_RIGHT;
 589                         case 'D': return CTRSEQ_CURSOR_LEFT;
 590                         default: return CTRSEQ_INVALID;
 591                         }
 592                         break;
 593                 default:
 594                         return CTRSEQ_INVALID;
 595                 }
 596         }
 597         return 2;
 598 }
 599
 600 void append_movement (int dir) {
 601         if (g.k.n > 15) return; /* no space in buffer */
 602         if (g.k.n && g.k.c[(16+g.k.h-1)%16] == dir)
 603                 return; /* don't add the same direction twice */
 604
 605         g.k.c[g.k.h] = dir;
 606         g.k.n++;
 607         g.k.h = (g.k.h+1) % 16;
 608 }
 609
 610 void move_ph (int line, int col) {
 611         /* move printhead to zero-indexed position */
 612         printf ("\033[%d;%dH", line+1, col+1);
 613 }
 614
 615 void clamp_fieldsize (void) {
 616         /* clamp field size to terminal size and mouse maximum: */
 617         struct winsize w;
 618         ioctl(STDOUT_FILENO, TIOCGWINSZ, &w);
 619
 620         if (g.w < 10) g.w = 10;
 621         if (g.h < 10) g.h = 10;
 622
 623         if (COL_OFFSET + g.w*CW + COL_OFFSET > w.ws_col)
 624                 g.w = (w.ws_col - 2*COL_OFFSET) / DW;
 625         if (LINE_OFFSET + g.h + LINES_AFTER > w.ws_row)
 626                 g.h = w.ws_row - (LINE_OFFSET+LINES_AFTER);
 627 }
 628
 629 void timer_setup (int enable) {
 630         static struct itimerval tbuf;
 631         tbuf.it_interval.tv_sec  = 0;
 632         tbuf.it_interval.tv_usec = (1000000/g.v)-1; /*WARN: 1 <= g.v <= 999999*/
 633
 634         if (enable) {
 635                 tbuf.it_value.tv_sec  = tbuf.it_interval.tv_sec;
 636                 tbuf.it_value.tv_usec = tbuf.it_interval.tv_usec;
 637         } else {
 638                 tbuf.it_value.tv_sec  = 0;
 639                 tbuf.it_value.tv_usec = 0;
 640         }
 641
 642         if ( setitimer(ITIMER_REAL, &tbuf, NULL) == -1 ) {
 643                 perror("setitimer");
 644                 exit(1);
 645         }
 646
 647 }
 648
 649 void signal_setup (void) {
 650         struct sigaction saction;
 651
 652         saction.sa_handler = signal_handler;
 653         sigemptyset(&saction.sa_mask);
 654         saction.sa_flags = 0;
 655         if (sigaction(SIGALRM, &saction, NULL) < 0 ) {
 656                 perror("SIGALRM");
 657                 exit(1);
 658         }
 659
 660         if (sigaction(SIGINT, &saction, NULL) < 0 ) {
 661                 perror ("SIGINT");
 662                 exit (1);
 663         }
 664
 665         if (sigaction(SIGTSTP, &saction, NULL) < 0 ) {
 666                 perror ("SIGTSTP");
 667                 exit (1);
 668         }
 669
 670         if (sigaction(SIGCONT, &saction, NULL) < 0 ) {
 671                 perror ("SIGCONT");
 672                 exit (1);
 673         }
 674 }
 675
 676 void signal_handler (int signum) {
 677         switch (signum) {
 678         case SIGALRM:
 679                 snake_advance();
 680                 spawn_bonus();
 681                 break;
 682         case SIGINT:
 683                 exit(128+SIGINT);
 684         case SIGTSTP:
 685                 screen_setup(0);
 686                 signal(SIGTSTP, SIG_DFL); /* NOTE: assumes SysV semantics! */
 687                 raise(SIGTSTP);
 688                 break;
 689         case SIGCONT:
 690                 screen_setup(1);
 691                 show_playfield();
 692         }
 693 }
 694
 695 void screen_setup (int enable) {
 696         if (enable) {
 697                 raw_mode(1);
 698                 printf ("\033[s\033[?47h"); /* save cursor, alternate screen */
 699                 printf ("\033[H\033[J"); /* reset cursor, clear screen */
 700                 printf ("\033[?25l"); /* hide cursor */
 701         } else {
 702                 printf ("\033[?25h"); /* show cursor */
 703                 printf ("\033[?47l\033[u"); /* primary screen, restore cursor */
 704                 raw_mode(0);
 705         }
 706 }
 707
 708 /* http://users.csc.calpoly.edu/~phatalsk/357/lectures/code/sigalrm.c */
 709 void raw_mode(int enable) {
 710         static struct termios saved_term_mode;
 711         struct termios raw_term_mode;
 712
 713         if (enable) {
 714                 if (saved_term_mode.c_lflag == 0)/*don't overwrite stored mode*/
 715                         tcgetattr(STDIN_FILENO, &saved_term_mode);
 716                 raw_term_mode = saved_term_mode;
 717                 raw_term_mode.c_lflag &= ~(ICANON | ECHO);
 718                 raw_term_mode.c_cc[VMIN] = 1 ;
 719                 raw_term_mode.c_cc[VTIME] = 0;
 720                 tcsetattr(STDIN_FILENO, TCSAFLUSH, &raw_term_mode);
 721         } else {
 722                 tcsetattr(STDIN_FILENO, TCSAFLUSH, &saved_term_mode);
 723         }
 724 }