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nothings-stb/stb_connected_components.h

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// stb_connected_components - v0.91 - public domain connected components on grids
// http://github.com/nothings/stb
//
// Finds connected components on 2D grids for testing reachability between
// two points, with fast updates when changing reachability (e.g. on one machine
// it was typically 0.2ms w/ 1024x1024 grid). Each grid square must be "open" or
// "closed" (traversable or untraversable), and grid squares are only connected
// to their orthogonal neighbors, not diagonally.
//
// In one source file, create the implementation by doing something like this:
//
// #define STBCC_GRID_COUNT_X_LOG2 10
// #define STBCC_GRID_COUNT_Y_LOG2 10
// #define STB_CONNECTED_COMPONENTS_IMPLEMENTATION
// #include "stb_connected_components.h"
//
// The above creates an implementation that can run on maps up to 1024x1024.
// Map sizes must be a multiple of 32 on each axis.
//
// LICENSE
//
// This software is dual-licensed to the public domain and under the following
// license: you are granted a perpetual, irrevocable license to copy, modify,
// publish, and distribute this file as you see fit.
//
//
// CHANGELOG
//
// 0.92 (2016-04-16) Compute sqrt(N) cluster size by default
// 0.91 (2016-04-15) Initial release
//
// TODO:
// - better API documentation
// - more comments
// - try re-integrating naive algorithm & compare performance
// - more optimized batching (current approach still recomputes local clumps many times)
// - function for setting a grid of squares at once (just use batching)
// - shrink data by storing only, say, 2X max exits
// (instead of max exits per clump), and repack cluster
// if it runs out (possibly by just rebuilding from scratch,
// could even use dirty-cluster data structure)
// should reduce 1Kx1K from ~66MB to ~8MB
//
// ALGORITHM
//
// The NxN grid map is split into sqrt(N) x sqrt(N) blocks called
// "clusters". Each cluster independently computes a set of connected
// components within that cluster (ignoring all connectivity out of
// that cluster) using a union-find disjoint set forest. This produces a bunch
// of locally connected components called "clumps". Each clump is (a) connected
// within its cluster, (b) does not directly connect to any other clumps in the
// cluster (though it may connect to them by paths that lead outside the cluster,
// but those are ignored at this step), and (c) maintains an adjacency list of
// all clumps in adjacent clusters that it _is_ connected to. Then a second
// union-find disjoint set forest is used to compute connected clumps
// globally, across the whole map. Reachability is then computed by
// finding which clump each input point belongs to, and checking whether
// those clumps are in the same "global" connected component.
//
// The above data structure can be updated efficiently; on a change
// of a single grid square on the map, only one cluster changes its
// purely-local state, so only one cluster needs its clumps fully
// recomputed. Clumps in adjacent clusters need their adjacency lists
// updated: first to remove all references to the old clumps in the
// rebuilt cluster, then to add new references to the new clumps. Both
// of these operations can use the existing "find which clump each input
// point belongs to" query to compute that adjacency information rapidly.
// In one 1024x1024 test on a specific machine, a one-tile update was
// about 250 times faster than a full disjoint-set-forest on the full map.
#ifndef INCLUDE_STB_CONNECTED_COMPONENTS_H
#define INCLUDE_STB_CONNECTED_COMPONENTS_H
#include <stdlib.h>
#include <assert.h>
typedef struct st_stbcc_grid stbcc_grid;
#ifdef __cplusplus
extern "C" {
#endif
//////////////////////////////////////////////////////////////////////////////////////////
//
// initialization
//
// you allocate the grid data structure to this size (note that it will be very big!!!)
extern size_t stbcc_grid_sizeof(void);
// initialize the grid, value of map[] is 0 = traversable, non-0 is solid
extern void stbcc_init_grid(stbcc_grid *g, unsigned char *map, int w, int h);
//////////////////////////////////////////////////////////////////////////////////////////
//
// main functionality
//
// update a grid square state, 0 = traversable, non-0 is solid
// i can add a batch-update if it's needed
extern void stbcc_update_grid(stbcc_grid *g, int x, int y, int solid);
// query if two grid squares are reachable from each other
extern int stbcc_query_grid_node_connection(stbcc_grid *g, int x1, int y1, int x2, int y2);
//////////////////////////////////////////////////////////////////////////////////////////
//
// bonus functions
//
// wrap multiple stbcc_update_grid calls in these function to compute
// multiple updates more efficiently; cannot make queries inside batch
extern void stbcc_update_batch_begin(stbcc_grid *g);
extern void stbcc_update_batch_end(stbcc_grid *g);
// query the grid data structure for whether a given square is open or not
extern int stbcc_query_grid_open(stbcc_grid *g, int x, int y);
// get a unique id for the connected component this is in; it's not necessarily
// small, you'll need a hash table or something to remap it (or just use
extern unsigned int stbcc_get_unique_id(stbcc_grid *g, int x, int y);
#define STBCC_NULL_UNIQUE_ID 0xffffffff // returned for closed map squares
#ifdef __cplusplus
}
#endif
#endif // INCLUDE_STB_CONNECTED_COMPONENTS_H
#ifdef STB_CONNECTED_COMPONENTS_IMPLEMENTATION
#if !defined(STBCC_GRID_COUNT_X_LOG2) || !defined(STBCC_GRID_COUNT_Y_LOG2)
#error "You must define STBCC_GRID_COUNT_X_LOG2 and STBCC_GRID_COUNT_Y_LOG2 to define the max grid supported."
#endif
#define STBCC__GRID_COUNT_X (1 << STBCC_GRID_COUNT_X_LOG2)
#define STBCC__GRID_COUNT_Y (1 << STBCC_GRID_COUNT_Y_LOG2)
#define STBCC__MAP_STRIDE (1 << (STBCC_GRID_COUNT_X_LOG2-3))
#ifndef STBCC_CLUSTER_SIZE_X_LOG2
#define STBCC_CLUSTER_SIZE_X_LOG2 (STBCC_GRID_COUNT_X_LOG2/2) // log2(sqrt(2^N)) = 1/2 * log2(2^N)) = 1/2 * N
#if STBCC_CLUSTER_SIZE_X_LOG2 > 6
#undef STBCC_CLUSTER_SIZE_X_LOG2
#define STBCC_CLUSTER_SIZE_X_LOG2 6
#endif
#endif
#ifndef STBCC_CLUSTER_SIZE_Y_LOG2
#define STBCC_CLUSTER_SIZE_Y_LOG2 (STBCC_GRID_COUNT_Y_LOG2/2)
#if STBCC_CLUSTER_SIZE_Y_LOG2 > 6
#undef STBCC_CLUSTER_SIZE_Y_LOG2
#define STBCC_CLUSTER_SIZE_Y_LOG2 6
#endif
#endif
#define STBCC__CLUSTER_SIZE_X (1 << STBCC_CLUSTER_SIZE_X_LOG2)
#define STBCC__CLUSTER_SIZE_Y (1 << STBCC_CLUSTER_SIZE_Y_LOG2)
#define STBCC__CLUSTER_COUNT_X_LOG2 (STBCC_GRID_COUNT_X_LOG2 - STBCC_CLUSTER_SIZE_X_LOG2)
#define STBCC__CLUSTER_COUNT_Y_LOG2 (STBCC_GRID_COUNT_Y_LOG2 - STBCC_CLUSTER_SIZE_Y_LOG2)
#define STBCC__CLUSTER_COUNT_X (1 << STBCC__CLUSTER_COUNT_X_LOG2)
#define STBCC__CLUSTER_COUNT_Y (1 << STBCC__CLUSTER_COUNT_Y_LOG2)
#if STBCC__CLUSTER_SIZE_X >= STBCC__GRID_COUNT_X || STBCC__CLUSTER_SIZE_Y >= STBCC__GRID_COUNT_Y
#error "STBCC_CLUSTER_SIZE_X/Y_LOG2 must be smaller than STBCC_GRID_COUNT_X/Y_LOG2"
#endif
// worst case # of clumps per cluster
#define STBCC__MAX_CLUMPS_PER_CLUSTER_LOG2 (STBCC_CLUSTER_SIZE_X_LOG2 + STBCC_CLUSTER_SIZE_Y_LOG2-1)
#define STBCC__MAX_CLUMPS_PER_CLUSTER (1 << STBCC__MAX_CLUMPS_PER_CLUSTER_LOG2)
#define STBCC__MAX_CLUMPS (STBCC__MAX_CLUMPS_PER_CLUSTER * STBCC__CLUSTER_COUNT_X * STBCC__CLUSTER_COUNT_Y)
#define STBCC__NULL_CLUMPID STBCC__MAX_CLUMPS_PER_CLUSTER
#define STBCC__CLUSTER_X_FOR_COORD_X(x) ((x) >> STBCC_CLUSTER_SIZE_X_LOG2)
#define STBCC__CLUSTER_Y_FOR_COORD_Y(y) ((y) >> STBCC_CLUSTER_SIZE_Y_LOG2)
#define STBCC__MAP_BYTE_MASK(x,y) (1 << ((x) & 7))
#define STBCC__MAP_BYTE(g,x,y) ((g)->map[y][(x) >> 3])
#define STBCC__MAP_OPEN(g,x,y) (STBCC__MAP_BYTE(g,x,y) & STBCC__MAP_BYTE_MASK(x,y))
typedef unsigned short stbcc__clumpid;
typedef unsigned char stbcc__verify_max_clumps[STBCC__MAX_CLUMPS_PER_CLUSTER < (1 << (8*sizeof(stbcc__clumpid))) ? 1 : -1];
#define STBCC__MAX_EXITS_PER_CLUMP (STBCC__CLUSTER_SIZE_X + STBCC__CLUSTER_SIZE_Y) // 64
// 2^19 * 2^6 => 2^25 exits => 2^26 => 64MB for 1024x1024
typedef unsigned char stbcc__verify_max_exits[STBCC__MAX_EXITS_PER_CLUMP <= 256];
typedef struct
{
unsigned short clump_index:12;
signed short cluster_dx:2;
signed short cluster_dy:2;
} stbcc__relative_clumpid;
typedef union
{
struct {
unsigned int clump_index:12;
unsigned int cluster_x:10;
unsigned int cluster_y:10;
} f;
unsigned int c;
} stbcc__global_clumpid;
// rebuilt cluster 3,4
// what changes in cluster 2,4
typedef struct
{
stbcc__global_clumpid global_label;
unsigned short num_adjacent;
stbcc__relative_clumpid adjacent_clumps[STBCC__MAX_EXITS_PER_CLUMP];
} stbcc__clump;
typedef struct
{
unsigned int num_clumps;
stbcc__clump clump[STBCC__MAX_CLUMPS_PER_CLUSTER];
} stbcc__cluster;
struct st_stbcc_grid
{
int w,h,cw,ch;
int in_batched_update;
//unsigned char cluster_dirty[STBCC__CLUSTER_COUNT_Y][STBCC__CLUSTER_COUNT_X]; // could bitpack, but: 1K x 1K => 1KB
unsigned char map[STBCC__GRID_COUNT_Y][STBCC__MAP_STRIDE]; // 1K x 1K => 1K x 128 => 128KB
stbcc__clumpid clump_for_node[STBCC__GRID_COUNT_Y][STBCC__GRID_COUNT_X]; // 1K x 1K x 2 = 2MB
stbcc__cluster cluster[STBCC__CLUSTER_COUNT_Y][STBCC__CLUSTER_COUNT_X]; // 1K x 1K x 0.5 x 64 x 2 = 64MB
};
int stbcc_query_grid_node_connection(stbcc_grid *g, int x1, int y1, int x2, int y2)
{
stbcc__global_clumpid label1, label2;
stbcc__clumpid c1 = g->clump_for_node[y1][x1];
stbcc__clumpid c2 = g->clump_for_node[y2][x2];
int cx1 = STBCC__CLUSTER_X_FOR_COORD_X(x1);
int cy1 = STBCC__CLUSTER_Y_FOR_COORD_Y(y1);
int cx2 = STBCC__CLUSTER_X_FOR_COORD_X(x2);
int cy2 = STBCC__CLUSTER_Y_FOR_COORD_Y(y2);
assert(!g->in_batched_update);
if (c1 == STBCC__NULL_CLUMPID || c2 == STBCC__NULL_CLUMPID)
return 0;
label1 = g->cluster[cy1][cx1].clump[c1].global_label;
label2 = g->cluster[cy2][cx2].clump[c2].global_label;
if (label1.c == label2.c)
return 1;
return 0;
}
int stbcc_query_grid_open(stbcc_grid *g, int x, int y)
{
return STBCC__MAP_OPEN(g, x, y) != 0;
}
unsigned int stbcc_get_unique_id(stbcc_grid *g, int x, int y)
{
stbcc__clumpid c = g->clump_for_node[y][x];
int cx = STBCC__CLUSTER_X_FOR_COORD_X(x);
int cy = STBCC__CLUSTER_Y_FOR_COORD_Y(y);
assert(!g->in_batched_update);
if (c == STBCC__NULL_CLUMPID) return STBCC_NULL_UNIQUE_ID;
return g->cluster[cy][cx].clump[c].global_label.c;
}
typedef struct
{
unsigned char x,y;
} stbcc__tinypoint;
typedef struct
{
stbcc__tinypoint parent[STBCC__CLUSTER_SIZE_Y][STBCC__CLUSTER_SIZE_X]; // 32x32 => 2KB
stbcc__clumpid label[STBCC__CLUSTER_SIZE_Y][STBCC__CLUSTER_SIZE_X];
} stbcc__cluster_build_info;
static void stbcc__build_clumps_for_cluster(stbcc_grid *g, int cx, int cy);
static void stbcc__remove_connections_to_adjacent_cluster(stbcc_grid *g, int cx, int cy, int dx, int dy);
static void stbcc__add_connections_to_adjacent_cluster(stbcc_grid *g, int cx, int cy, int dx, int dy);
static stbcc__global_clumpid stbcc__clump_find(stbcc_grid *g, stbcc__global_clumpid n)
{
stbcc__global_clumpid q;
stbcc__clump *c = &g->cluster[n.f.cluster_y][n.f.cluster_x].clump[n.f.clump_index];
if (c->global_label.c == n.c)
return n;
q = stbcc__clump_find(g, c->global_label);
c->global_label = q;
return q;
}
typedef struct
{
unsigned int cluster_x;
unsigned int cluster_y;
unsigned int clump_index;
} stbcc__unpacked_clumpid;
// @OPTIMIZE: pass in these parameters unpacked, not packed
static void stbcc__clump_union(stbcc_grid *g, stbcc__unpacked_clumpid m, int x, int y, int idx)
{
stbcc__clump *mc = &g->cluster[m.cluster_y][m.cluster_x].clump[m.clump_index];
stbcc__clump *nc = &g->cluster[y][x].clump[idx];
stbcc__global_clumpid mp = stbcc__clump_find(g, mc->global_label);
stbcc__global_clumpid np = stbcc__clump_find(g, nc->global_label);
if (mp.c == np.c)
return;
g->cluster[mp.f.cluster_y][mp.f.cluster_x].clump[mp.f.clump_index].global_label = np;
}
static void stbcc__build_connected_components_for_clumps(stbcc_grid *g)
{
int i,j,k,h;
for (j=0; j < STBCC__CLUSTER_COUNT_Y; ++j) {
for (i=0; i < STBCC__CLUSTER_COUNT_X; ++i) {
stbcc__cluster *cluster = &g->cluster[j][i];
for (k=0; k < (int) cluster->num_clumps; ++k) {
stbcc__global_clumpid m;
m.f.clump_index = k;
m.f.cluster_x = i;
m.f.cluster_y = j;
assert((int) m.f.clump_index == k && (int) m.f.cluster_x == i && (int) m.f.cluster_y == j);
cluster->clump[k].global_label = m;
}
}
}
for (j=0; j < STBCC__CLUSTER_COUNT_Y; ++j) {
for (i=0; i < STBCC__CLUSTER_COUNT_X; ++i) {
stbcc__cluster *cluster = &g->cluster[j][i];
for (k=0; k < (int) cluster->num_clumps; ++k) {
stbcc__clump *clump = &cluster->clump[k];
stbcc__unpacked_clumpid m;
m.clump_index = k;
m.cluster_x = i;
m.cluster_y = j;
for (h=0; h < clump->num_adjacent; ++h) {
unsigned int clump_index = clump->adjacent_clumps[h].clump_index;
unsigned int x = clump->adjacent_clumps[h].cluster_dx + i;
unsigned int y = clump->adjacent_clumps[h].cluster_dy + j;
stbcc__clump_union(g, m, x, y, clump_index);
}
}
}
}
for (j=0; j < STBCC__CLUSTER_COUNT_Y; ++j) {
for (i=0; i < STBCC__CLUSTER_COUNT_X; ++i) {
stbcc__cluster *cluster = &g->cluster[j][i];
for (k=0; k < (int) cluster->num_clumps; ++k) {
stbcc__global_clumpid m;
m.f.clump_index = k;
m.f.cluster_x = i;
m.f.cluster_y = j;
stbcc__clump_find(g, m);
}
}
}
}
void stbcc_update_grid(stbcc_grid *g, int x, int y, int solid)
{
int cx,cy;
if (!solid) {
if (STBCC__MAP_OPEN(g,x,y))
return;
} else {
if (!STBCC__MAP_OPEN(g,x,y))
return;
}
cx = STBCC__CLUSTER_X_FOR_COORD_X(x);
cy = STBCC__CLUSTER_Y_FOR_COORD_Y(y);
stbcc__remove_connections_to_adjacent_cluster(g, cx-1, cy, 1, 0);
stbcc__remove_connections_to_adjacent_cluster(g, cx+1, cy, -1, 0);
stbcc__remove_connections_to_adjacent_cluster(g, cx, cy-1, 0, 1);
stbcc__remove_connections_to_adjacent_cluster(g, cx, cy+1, 0,-1);
if (!solid)
STBCC__MAP_BYTE(g,x,y) |= STBCC__MAP_BYTE_MASK(x,y);
else
STBCC__MAP_BYTE(g,x,y) &= ~STBCC__MAP_BYTE_MASK(x,y);
stbcc__build_clumps_for_cluster(g, cx, cy);
stbcc__add_connections_to_adjacent_cluster(g, cx, cy, -1, 0);
stbcc__add_connections_to_adjacent_cluster(g, cx, cy, 1, 0);
stbcc__add_connections_to_adjacent_cluster(g, cx, cy, 0,-1);
stbcc__add_connections_to_adjacent_cluster(g, cx, cy, 0, 1);
stbcc__add_connections_to_adjacent_cluster(g, cx-1, cy, 1, 0);
stbcc__add_connections_to_adjacent_cluster(g, cx+1, cy, -1, 0);
stbcc__add_connections_to_adjacent_cluster(g, cx, cy-1, 0, 1);
stbcc__add_connections_to_adjacent_cluster(g, cx, cy+1, 0,-1);
if (!g->in_batched_update)
stbcc__build_connected_components_for_clumps(g);
#if 0
else
g->cluster_dirty[cy][cx] = 1;
#endif
}
void stbcc_update_batch_begin(stbcc_grid *g)
{
assert(!g->in_batched_update);
g->in_batched_update = 1;
}
void stbcc_update_batch_end(stbcc_grid *g)
{
assert(g->in_batched_update);
g->in_batched_update = 0;
stbcc__build_connected_components_for_clumps(g); // @OPTIMIZE: only do this if update was non-empty
}
size_t stbcc_grid_sizeof(void)
{
return sizeof(stbcc_grid);
}
void stbcc_init_grid(stbcc_grid *g, unsigned char *map, int w, int h)
{
int i,j,k;
assert(w % STBCC__CLUSTER_SIZE_X == 0);
assert(h % STBCC__CLUSTER_SIZE_Y == 0);
assert(w % 8 == 0);
g->w = w;
g->h = h;
g->cw = w >> STBCC_CLUSTER_SIZE_X_LOG2;
g->ch = h >> STBCC_CLUSTER_SIZE_Y_LOG2;
g->in_batched_update = 0;
#if 0
for (j=0; j < STBCC__CLUSTER_COUNT_Y; ++j)
for (i=0; i < STBCC__CLUSTER_COUNT_X; ++i)
g->cluster_dirty[j][i] = 0;
#endif
for (j=0; j < h; ++j) {
for (i=0; i < w; i += 8) {
unsigned char c = 0;
for (k=0; k < 8; ++k)
if (map[j*w + (i+k)] == 0)
c |= (1 << k);
g->map[j][i>>3] = c;
}
}
for (j=0; j < g->ch; ++j)
for (i=0; i < g->cw; ++i)
stbcc__build_clumps_for_cluster(g, i, j);
for (j=0; j < g->ch; ++j) {
for (i=0; i < g->cw; ++i) {
stbcc__add_connections_to_adjacent_cluster(g, i, j, -1, 0);
stbcc__add_connections_to_adjacent_cluster(g, i, j, 1, 0);
stbcc__add_connections_to_adjacent_cluster(g, i, j, 0,-1);
stbcc__add_connections_to_adjacent_cluster(g, i, j, 0, 1);
}
}
stbcc__build_connected_components_for_clumps(g);
for (j=0; j < g->h; ++j)
for (i=0; i < g->w; ++i)
assert(g->clump_for_node[j][i] <= STBCC__NULL_CLUMPID);
}
static void stbcc__add_clump_connection(stbcc_grid *g, int x1, int y1, int x2, int y2)
{
stbcc__clump *clump;
int cx1 = STBCC__CLUSTER_X_FOR_COORD_X(x1);
int cy1 = STBCC__CLUSTER_Y_FOR_COORD_Y(y1);
int cx2 = STBCC__CLUSTER_X_FOR_COORD_X(x2);
int cy2 = STBCC__CLUSTER_Y_FOR_COORD_Y(y2);
stbcc__clumpid c1 = g->clump_for_node[y1][x1];
stbcc__clumpid c2 = g->clump_for_node[y2][x2];
stbcc__relative_clumpid rc;
assert(cx1 != cx2 || cy1 != cy2);
assert(abs(cx1-cx2) + abs(cy1-cy2) == 1);
// add connection to c2 in c1
rc.clump_index = c2;
rc.cluster_dx = x2-x1;
rc.cluster_dy = y2-y1;
clump = &g->cluster[cy1][cx1].clump[c1];
assert(clump->num_adjacent < STBCC__MAX_EXITS_PER_CLUMP);
clump->adjacent_clumps[clump->num_adjacent++] = rc;
}
static void stbcc__remove_clump_connection(stbcc_grid *g, int x1, int y1, int x2, int y2)
{
stbcc__clump *clump;
int i;
int cx1 = STBCC__CLUSTER_X_FOR_COORD_X(x1);
int cy1 = STBCC__CLUSTER_Y_FOR_COORD_Y(y1);
int cx2 = STBCC__CLUSTER_X_FOR_COORD_X(x2);
int cy2 = STBCC__CLUSTER_Y_FOR_COORD_Y(y2);
stbcc__clumpid c1 = g->clump_for_node[y1][x1];
stbcc__clumpid c2 = g->clump_for_node[y2][x2];
stbcc__relative_clumpid rc;
assert(cx1 != cx2 || cy1 != cy2);
assert(abs(cx1-cx2) + abs(cy1-cy2) == 1);
// add connection to c2 in c1
rc.clump_index = c2;
rc.cluster_dx = x2-x1;
rc.cluster_dy = y2-y1;
clump = &g->cluster[cy1][cx1].clump[c1];
for (i=0; i < clump->num_adjacent; ++i)
if (rc.clump_index == clump->adjacent_clumps[i].clump_index &&
rc.cluster_dx == clump->adjacent_clumps[i].cluster_dx &&
rc.cluster_dy == clump->adjacent_clumps[i].cluster_dy)
break;
if (i < clump->num_adjacent)
clump->adjacent_clumps[i] = clump->adjacent_clumps[--clump->num_adjacent];
else
assert(0);
}
static void stbcc__add_connections_to_adjacent_cluster(stbcc_grid *g, int cx, int cy, int dx, int dy)
{
unsigned char connected[STBCC__MAX_CLUMPS_PER_CLUSTER/8] = { 0 };
int x = cx * STBCC__CLUSTER_SIZE_X;
int y = cy * STBCC__CLUSTER_SIZE_Y;
int step_x, step_y=0, i, j, k, n;
if (cx < 0 || cx >= g->cw || cy < 0 || cy >= g->ch)
return;
if (cx+dx < 0 || cx+dx >= g->cw || cy+dy < 0 || cy+dy >= g->ch)
return;
assert(abs(dx) + abs(dy) == 1);
if (dx == 1) {
i = STBCC__CLUSTER_SIZE_X-1;
j = 0;
step_x = 0;
step_y = 1;
n = STBCC__CLUSTER_SIZE_Y;
} else if (dx == -1) {
i = 0;
j = 0;
step_x = 0;
step_y = 1;
n = STBCC__CLUSTER_SIZE_Y;
} else if (dy == -1) {
i = 0;
j = 0;
step_x = 1;
step_y = 0;
n = STBCC__CLUSTER_SIZE_X;
} else if (dy == 1) {
i = 0;
j = STBCC__CLUSTER_SIZE_Y-1;
step_x = 1;
step_y = 0;
n = STBCC__CLUSTER_SIZE_X;
} else {
assert(0);
}
for (k=0; k < n; ++k) {
if (STBCC__MAP_OPEN(g, x+i, y+j) && STBCC__MAP_OPEN(g, x+i+dx, y+j+dy)) {
stbcc__clumpid c = g->clump_for_node[y+j+dy][x+i+dx];
if (0 == (connected[c>>3] & (1 << (c & 7)))) {
connected[c>>3] |= 1 << (c & 7);
stbcc__add_clump_connection(g, x+i, y+j, x+i+dx, y+j+dy);
}
}
i += step_x;
j += step_y;
}
}
static void stbcc__remove_connections_to_adjacent_cluster(stbcc_grid *g, int cx, int cy, int dx, int dy)
{
unsigned char disconnected[STBCC__MAX_CLUMPS_PER_CLUSTER/8] = { 0 };
int x = cx * STBCC__CLUSTER_SIZE_X;
int y = cy * STBCC__CLUSTER_SIZE_Y;
int step_x, step_y=0, i, j, k, n;
if (cx < 0 || cx >= g->cw || cy < 0 || cy >= g->ch)
return;
if (cx+dx < 0 || cx+dx >= g->cw || cy+dy < 0 || cy+dy >= g->ch)
return;
assert(abs(dx) + abs(dy) == 1);
if (dx == 1) {
i = STBCC__CLUSTER_SIZE_X-1;
j = 0;
step_x = 0;
step_y = 1;
n = STBCC__CLUSTER_SIZE_Y;
} else if (dx == -1) {
i = 0;
j = 0;
step_x = 0;
step_y = 1;
n = STBCC__CLUSTER_SIZE_Y;
} else if (dy == -1) {
i = 0;
j = 0;
step_x = 1;
step_y = 0;
n = STBCC__CLUSTER_SIZE_X;
} else if (dy == 1) {
i = 0;
j = STBCC__CLUSTER_SIZE_Y-1;
step_x = 1;
step_y = 0;
n = STBCC__CLUSTER_SIZE_X;
} else {
assert(0);
}
for (k=0; k < n; ++k) {
if (STBCC__MAP_OPEN(g, x+i, y+j) && STBCC__MAP_OPEN(g, x+i+dx, y+j+dy)) {
stbcc__clumpid c = g->clump_for_node[y+j+dy][x+i+dx];
if (0 == (disconnected[c>>3] & (1 << (c & 7)))) {
disconnected[c>>3] |= 1 << (c & 7);
stbcc__remove_clump_connection(g, x+i, y+j, x+i+dx, y+j+dy);
}
}
i += step_x;
j += step_y;
}
}
static stbcc__tinypoint stbcc__incluster_find(stbcc__cluster_build_info *cbi, int x, int y)
{
stbcc__tinypoint p,q;
p = cbi->parent[y][x];
if (p.x == x && p.y == y)
return p;
q = stbcc__incluster_find(cbi, p.x, p.y);
cbi->parent[y][x] = q;
return q;
}
static void stbcc__incluster_union(stbcc__cluster_build_info *cbi, int x1, int y1, int x2, int y2)
{
stbcc__tinypoint p = stbcc__incluster_find(cbi, x1,y1);
stbcc__tinypoint q = stbcc__incluster_find(cbi, x2,y2);
if (p.x == q.x && p.y == q.y)
return;
cbi->parent[p.y][p.x] = q;
}
static void stbcc__build_clumps_for_cluster(stbcc_grid *g, int cx, int cy)
{
stbcc__cluster *c;
stbcc__cluster_build_info cbi;
int label=0;
int i,j;
int x = cx * STBCC__CLUSTER_SIZE_X;
int y = cy * STBCC__CLUSTER_SIZE_Y;
// set initial disjoint set forest state
for (j=0; j < STBCC__CLUSTER_SIZE_Y; ++j) {
for (i=0; i < STBCC__CLUSTER_SIZE_X; ++i) {
cbi.parent[j][i].x = i;
cbi.parent[j][i].y = j;
}
}
// join all sets that are connected
for (j=0; j < STBCC__CLUSTER_SIZE_Y; ++j) {
// check down only if not on bottom row
if (j < STBCC__CLUSTER_SIZE_Y-1)
for (i=0; i < STBCC__CLUSTER_SIZE_X; ++i)
if (STBCC__MAP_OPEN(g,x+i,y+j) && STBCC__MAP_OPEN(g,x+i ,y+j+1))
stbcc__incluster_union(&cbi, i,j, i,j+1);
// check right for everything but rightmost column
for (i=0; i < STBCC__CLUSTER_SIZE_X-1; ++i)
if (STBCC__MAP_OPEN(g,x+i,y+j) && STBCC__MAP_OPEN(g,x+i+1,y+j ))
stbcc__incluster_union(&cbi, i,j, i+1,j);
}
// label all non-empty leaders
for (j=0; j < STBCC__CLUSTER_SIZE_Y; ++j) {
for (i=0; i < STBCC__CLUSTER_SIZE_X; ++i) {
stbcc__tinypoint p = cbi.parent[j][i];
if (p.x == i && p.y == j)
if (STBCC__MAP_OPEN(g,x+i,y+j))
cbi.label[j][i] = label++;
else
cbi.label[j][i] = STBCC__NULL_CLUMPID;
}
}
// label all other nodes
for (j=0; j < STBCC__CLUSTER_SIZE_Y; ++j) {
for (i=0; i < STBCC__CLUSTER_SIZE_X; ++i) {
stbcc__tinypoint p = stbcc__incluster_find(&cbi, i,j);
if (p.x != i || p.y != j) {
if (STBCC__MAP_OPEN(g,x+i,y+j))
cbi.label[j][i] = cbi.label[p.y][p.x];
}
}
}
c = &g->cluster[cy][cx];
c->num_clumps = label;
for (i=0; i < label; ++i)
c->clump[i].num_adjacent = 0;
for (j=0; j < STBCC__CLUSTER_SIZE_Y; ++j)
for (i=0; i < STBCC__CLUSTER_SIZE_X; ++i) {
g->clump_for_node[y+j][x+i] = cbi.label[j][i]; // @OPTIMIZE: remove cbi.label entirely
assert(g->clump_for_node[y+j][x+i] <= STBCC__NULL_CLUMPID);
}
}
#endif // STB_CONNECTED_COMPONENTS_IMPLEMENTATION
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