ref: 3663603627809a11908dc1dfadd158cfde8e0672
dir: /net.c/
/*
* net.c: Net game.
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include "puzzles.h"
#include "tree234.h"
/* Direction bitfields */
#define R 0x01
#define U 0x02
#define L 0x04
#define D 0x08
#define LOCKED 0x10
/* Rotations: Anticlockwise, Clockwise, Flip, general rotate */
#define A(x) ( (((x) & 0x07) << 1) | (((x) & 0x08) >> 3) )
#define C(x) ( (((x) & 0x0E) >> 1) | (((x) & 0x01) << 3) )
#define F(x) ( (((x) & 0x0C) >> 2) | (((x) & 0x03) << 2) )
#define ROT(x, n) ( ((n)&3) == 0 ? (x) : \
((n)&3) == 1 ? A(x) : \
((n)&3) == 2 ? F(x) : C(x) )
/* X and Y displacements */
#define X(x) ( (x) == R ? +1 : (x) == L ? -1 : 0 )
#define Y(x) ( (x) == D ? +1 : (x) == U ? -1 : 0 )
/* Bit count */
#define COUNT(x) ( (((x) & 0x08) >> 3) + (((x) & 0x04) >> 2) + \
(((x) & 0x02) >> 1) + ((x) & 0x01) )
#define TILE_SIZE 32
#define TILE_BORDER 1
#define WINDOW_OFFSET 16
struct game_params {
int width;
int height;
int wrapping;
float barrier_probability;
};
struct game_state {
int width, height, wrapping, completed;
unsigned char *tiles;
unsigned char *barriers;
};
#define OFFSET(x2,y2,x1,y1,dir,state) \
( (x2) = ((x1) + (state)->width + X((dir))) % (state)->width, \
(y2) = ((y1) + (state)->height + Y((dir))) % (state)->height)
#define index(state, a, x, y) ( a[(y) * (state)->width + (x)] )
#define tile(state, x, y) index(state, (state)->tiles, x, y)
#define barrier(state, x, y) index(state, (state)->barriers, x, y)
struct xyd {
int x, y, direction;
};
static int xyd_cmp(void *av, void *bv) {
struct xyd *a = (struct xyd *)av;
struct xyd *b = (struct xyd *)bv;
if (a->x < b->x)
return -1;
if (a->x > b->x)
return +1;
if (a->y < b->y)
return -1;
if (a->y > b->y)
return +1;
if (a->direction < b->direction)
return -1;
if (a->direction > b->direction)
return +1;
return 0;
};
static struct xyd *new_xyd(int x, int y, int direction)
{
struct xyd *xyd = snew(struct xyd);
xyd->x = x;
xyd->y = y;
xyd->direction = direction;
return xyd;
}
/* ----------------------------------------------------------------------
* Randomly select a new game seed.
*/
char *new_game_seed(game_params *params)
{
/*
* The full description of a Net game is far too large to
* encode directly in the seed, so by default we'll have to go
* for the simple approach of providing a random-number seed.
*
* (This does not restrict me from _later on_ inventing a seed
* string syntax which can never be generated by this code -
* for example, strings beginning with a letter - allowing me
* to type in a precise game, and have new_game detect it and
* understand it and do something completely different.)
*/
char buf[40];
sprintf(buf, "%d", rand());
return dupstr(buf);
}
/* ----------------------------------------------------------------------
* Construct an initial game state, given a seed and parameters.
*/
game_state *new_game(game_params *params, char *seed)
{
random_state *rs;
game_state *state;
tree234 *possibilities, *barriers;
int w, h, x, y, nbarriers;
assert(params->width > 2);
assert(params->height > 2);
/*
* Create a blank game state.
*/
state = snew(game_state);
w = state->width = params->width;
h = state->height = params->height;
state->wrapping = params->wrapping;
state->completed = FALSE;
state->tiles = snewn(state->width * state->height, unsigned char);
memset(state->tiles, 0, state->width * state->height);
state->barriers = snewn(state->width * state->height, unsigned char);
memset(state->barriers, 0, state->width * state->height);
/*
* Set up border barriers if this is a non-wrapping game.
*/
if (!state->wrapping) {
for (x = 0; x < state->width; x++) {
barrier(state, x, 0) |= U;
barrier(state, x, state->height-1) |= D;
}
for (y = 0; y < state->height; y++) {
barrier(state, y, 0) |= L;
barrier(state, y, state->width-1) |= R;
}
}
/*
* Seed the internal random number generator.
*/
rs = random_init(seed, strlen(seed));
/*
* Construct the unshuffled grid.
*
* To do this, we simply start at the centre point, repeatedly
* choose a random possibility out of the available ways to
* extend a used square into an unused one, and do it. After
* extending the third line out of a square, we remove the
* fourth from the possibilities list to avoid any full-cross
* squares (which would make the game too easy because they
* only have one orientation).
*
* The slightly worrying thing is the avoidance of full-cross
* squares. Can this cause our unsophisticated construction
* algorithm to paint itself into a corner, by getting into a
* situation where there are some unreached squares and the
* only way to reach any of them is to extend a T-piece into a
* full cross?
*
* Answer: no it can't, and here's a proof.
*
* Any contiguous group of such unreachable squares must be
* surrounded on _all_ sides by T-pieces pointing away from the
* group. (If not, then there is a square which can be extended
* into one of the `unreachable' ones, and so it wasn't
* unreachable after all.) In particular, this implies that
* each contiguous group of unreachable squares must be
* rectangular in shape (any deviation from that yields a
* non-T-piece next to an `unreachable' square).
*
* So we have a rectangle of unreachable squares, with T-pieces
* forming a solid border around the rectangle. The corners of
* that border must be connected (since every tile connects all
* the lines arriving in it), and therefore the border must
* form a closed loop around the rectangle.
*
* But this can't have happened in the first place, since we
* _know_ we've avoided creating closed loops! Hence, no such
* situation can ever arise, and the naive grid construction
* algorithm will guaranteeably result in a complete grid
* containing no unreached squares, no full crosses _and_ no
* closed loops. []
*/
possibilities = newtree234(xyd_cmp);
add234(possibilities, new_xyd(w/2, h/2, R));
add234(possibilities, new_xyd(w/2, h/2, U));
add234(possibilities, new_xyd(w/2, h/2, L));
add234(possibilities, new_xyd(w/2, h/2, D));
while (count234(possibilities) > 0) {
int i;
struct xyd *xyd;
int x1, y1, d1, x2, y2, d2, d;
/*
* Extract a randomly chosen possibility from the list.
*/
i = random_upto(rs, count234(possibilities));
xyd = delpos234(possibilities, i);
x1 = xyd->x;
y1 = xyd->y;
d1 = xyd->direction;
sfree(xyd);
OFFSET(x2, y2, x1, y1, d1, state);
d2 = F(d1);
#ifdef DEBUG
printf("picked (%d,%d,%c) <-> (%d,%d,%c)\n",
x1, y1, "0RU3L567D9abcdef"[d1], x2, y2, "0RU3L567D9abcdef"[d2]);
#endif
/*
* Make the connection. (We should be moving to an as yet
* unused tile.)
*/
tile(state, x1, y1) |= d1;
assert(tile(state, x2, y2) == 0);
tile(state, x2, y2) |= d2;
/*
* If we have created a T-piece, remove its last
* possibility.
*/
if (COUNT(tile(state, x1, y1)) == 3) {
struct xyd xyd1, *xydp;
xyd1.x = x1;
xyd1.y = y1;
xyd1.direction = 0x0F ^ tile(state, x1, y1);
xydp = find234(possibilities, &xyd1, NULL);
if (xydp) {
#ifdef DEBUG
printf("T-piece; removing (%d,%d,%c)\n",
xydp->x, xydp->y, "0RU3L567D9abcdef"[xydp->direction]);
#endif
del234(possibilities, xydp);
sfree(xydp);
}
}
/*
* Remove all other possibilities that were pointing at the
* tile we've just moved into.
*/
for (d = 1; d < 0x10; d <<= 1) {
int x3, y3, d3;
struct xyd xyd1, *xydp;
OFFSET(x3, y3, x2, y2, d, state);
d3 = F(d);
xyd1.x = x3;
xyd1.y = y3;
xyd1.direction = d3;
xydp = find234(possibilities, &xyd1, NULL);
if (xydp) {
#ifdef DEBUG
printf("Loop avoidance; removing (%d,%d,%c)\n",
xydp->x, xydp->y, "0RU3L567D9abcdef"[xydp->direction]);
#endif
del234(possibilities, xydp);
sfree(xydp);
}
}
/*
* Add new possibilities to the list for moving _out_ of
* the tile we have just moved into.
*/
for (d = 1; d < 0x10; d <<= 1) {
int x3, y3;
if (d == d2)
continue; /* we've got this one already */
if (!state->wrapping) {
if (d == U && y2 == 0)
continue;
if (d == D && y2 == state->height-1)
continue;
if (d == L && x2 == 0)
continue;
if (d == R && x2 == state->width-1)
continue;
}
OFFSET(x3, y3, x2, y2, d, state);
if (tile(state, x3, y3))
continue; /* this would create a loop */
#ifdef DEBUG
printf("New frontier; adding (%d,%d,%c)\n",
x2, y2, "0RU3L567D9abcdef"[d]);
#endif
add234(possibilities, new_xyd(x2, y2, d));
}
}
/* Having done that, we should have no possibilities remaining. */
assert(count234(possibilities) == 0);
freetree234(possibilities);
/*
* Now compute a list of the possible barrier locations.
*/
barriers = newtree234(xyd_cmp);
for (y = 0; y < state->height - (!state->wrapping); y++) {
for (x = 0; x < state->width - (!state->wrapping); x++) {
if (!(tile(state, x, y) & R))
add234(barriers, new_xyd(x, y, R));
if (!(tile(state, x, y) & D))
add234(barriers, new_xyd(x, y, D));
}
}
/*
* Now shuffle the grid.
*/
for (y = 0; y < state->height - (!state->wrapping); y++) {
for (x = 0; x < state->width - (!state->wrapping); x++) {
int orig = tile(state, x, y);
int rot = random_upto(rs, 4);
tile(state, x, y) = ROT(orig, rot);
}
}
/*
* And now choose barrier locations. (We carefully do this
* _after_ shuffling, so that changing the barrier rate in the
* params while keeping the game seed the same will give the
* same shuffled grid and _only_ change the barrier locations.
* Also the way we choose barrier locations, by repeatedly
* choosing one possibility from the list until we have enough,
* is designed to ensure that raising the barrier rate while
* keeping the seed the same will provide a superset of the
* previous barrier set - i.e. if you ask for 10 barriers, and
* then decide that's still too hard and ask for 20, you'll get
* the original 10 plus 10 more, rather than getting 20 new
* ones and the chance of remembering your first 10.)
*/
nbarriers = params->barrier_probability * count234(barriers);
assert(nbarriers >= 0 && nbarriers <= count234(barriers));
while (nbarriers > 0) {
int i;
struct xyd *xyd;
int x1, y1, d1, x2, y2, d2;
/*
* Extract a randomly chosen barrier from the list.
*/
i = random_upto(rs, count234(barriers));
xyd = delpos234(barriers, i);
assert(xyd != NULL);
x1 = xyd->x;
y1 = xyd->y;
d1 = xyd->direction;
sfree(xyd);
OFFSET(x2, y2, x1, y1, d1, state);
d2 = F(d1);
barrier(state, x1, y1) |= d1;
barrier(state, x2, y2) |= d2;
nbarriers--;
}
/*
* Clean up the rest of the barrier list.
*/
{
struct xyd *xyd;
while ( (xyd = delpos234(barriers, 0)) != NULL)
sfree(xyd);
freetree234(barriers);
}
random_free(rs);
return state;
}
game_state *dup_game(game_state *state)
{
game_state *ret;
ret = snew(game_state);
ret->width = state->width;
ret->height = state->height;
ret->wrapping = state->wrapping;
ret->completed = state->completed;
ret->tiles = snewn(state->width * state->height, unsigned char);
memcpy(ret->tiles, state->tiles, state->width * state->height);
ret->barriers = snewn(state->width * state->height, unsigned char);
memcpy(ret->barriers, state->barriers, state->width * state->height);
return ret;
}
void free_game(game_state *state)
{
sfree(state->tiles);
sfree(state->barriers);
sfree(state);
}
/* ----------------------------------------------------------------------
* Utility routine.
*/
/*
* Compute which squares are reachable from the centre square, as a
* quick visual aid to determining how close the game is to
* completion. This is also a simple way to tell if the game _is_
* completed - just call this function and see whether every square
* is marked active.
*/
static unsigned char *compute_active(game_state *state)
{
unsigned char *active;
tree234 *todo;
struct xyd *xyd;
active = snewn(state->width * state->height, unsigned char);
memset(active, 0, state->width * state->height);
/*
* We only store (x,y) pairs in todo, but it's easier to reuse
* xyd_cmp and just store direction 0 every time.
*/
todo = newtree234(xyd_cmp);
add234(todo, new_xyd(state->width / 2, state->height / 2, 0));
while ( (xyd = delpos234(todo, 0)) != NULL) {
int x1, y1, d1, x2, y2, d2;
x1 = xyd->x;
y1 = xyd->y;
sfree(xyd);
for (d1 = 1; d1 < 0x10; d1 <<= 1) {
OFFSET(x2, y2, x1, y1, d1, state);
d2 = F(d1);
/*
* If the next tile in this direction is connected to
* us, and there isn't a barrier in the way, and it
* isn't already marked active, then mark it active and
* add it to the to-examine list.
*/
if ((tile(state, x1, y1) & d1) &&
(tile(state, x2, y2) & d2) &&
!(barrier(state, x1, y1) & d1) &&
!index(state, active, x2, y2)) {
index(state, active, x2, y2) = 1;
add234(todo, new_xyd(x2, y2, 0));
}
}
}
/* Now we expect the todo list to have shrunk to zero size. */
assert(count234(todo) == 0);
freetree234(todo);
return active;
}
/* ----------------------------------------------------------------------
* Process a move.
*/
game_state *make_move(game_state *state, int x, int y, int button)
{
game_state *ret;
int tx, ty, orig;
/*
* All moves in Net are made with the mouse.
*/
if (button != LEFT_BUTTON &&
button != MIDDLE_BUTTON &&
button != RIGHT_BUTTON)
return NULL;
/*
* The button must have been clicked on a valid tile.
*/
x -= WINDOW_OFFSET;
y -= WINDOW_OFFSET;
if (x < 0 || y < 0)
return NULL;
tx = x / TILE_SIZE;
ty = y / TILE_SIZE;
if (tx >= state->width || ty >= state->height)
return NULL;
if (tx % TILE_SIZE >= TILE_SIZE - TILE_BORDER ||
ty % TILE_SIZE >= TILE_SIZE - TILE_BORDER)
return NULL;
/*
* The middle button locks or unlocks a tile. (A locked tile
* cannot be turned, and is visually marked as being locked.
* This is a convenience for the player, so that once they are
* sure which way round a tile goes, they can lock it and thus
* avoid forgetting later on that they'd already done that one;
* and the locking also prevents them turning the tile by
* accident. If they change their mind, another middle click
* unlocks it.)
*/
if (button == MIDDLE_BUTTON) {
ret = dup_game(state);
tile(ret, tx, ty) ^= LOCKED;
return ret;
}
/*
* The left and right buttons have no effect if clicked on a
* locked tile.
*/
if (tile(state, tx, ty) & LOCKED)
return NULL;
/*
* Otherwise, turn the tile one way or the other. Left button
* turns anticlockwise; right button turns clockwise.
*/
ret = dup_game(state);
orig = tile(ret, tx, ty);
if (button == LEFT_BUTTON)
tile(ret, tx, ty) = A(orig);
else
tile(ret, tx, ty) = C(orig);
/*
* Check whether the game has been completed.
*/
{
unsigned char *active = compute_active(ret);
int x1, y1;
int complete = TRUE;
for (x1 = 0; x1 < ret->width; x1++)
for (y1 = 0; y1 < ret->height; y1++)
if (!index(ret, active, x1, y1)) {
complete = FALSE;
goto break_label; /* break out of two loops at once */
}
break_label:
sfree(active);
if (complete)
ret->completed = TRUE;
}
return ret;
}
/* ----------------------------------------------------------------------
* Routines for drawing the game position on the screen.
*/
/* ----------------------------------------------------------------------
* Test code.
*/
#ifdef TESTMODE
int main(void)
{
game_params params = { 13, 11, TRUE, 0.1 };
char *seed;
game_state *state;
unsigned char *active;
seed = "123";
state = new_game(¶ms, seed);
active = compute_active(state);
{
int x, y;
printf("\033)0\016");
for (y = 0; y < state->height; y++) {
for (x = 0; x < state->width; x++) {
if (index(state, active, x, y))
printf("\033[1;32m");
else
printf("\033[0;31m");
putchar("~``m`qjv`lxtkwua"[tile(state, x, y)]);
}
printf("\033[m\n");
}
printf("\017");
}
free_game(state);
return 0;
}
#endif