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