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/*************************************************************************
* Copyright (c) 2011 AT&T Intellectual Property
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* https://www.eclipse.org/legal/epl-v10.html
*
* Contributors: Details at https://graphviz.org
*************************************************************************/
/*
* Decompose finds the connected components of a graph.
* It searches the temporary edges and ignores non-root nodes.
* The roots of the search are the real nodes of the graph,
* but any virtual nodes discovered are also included in the
* component.
*/
#include "config.h"
#include <dotgen/dot.h>
#include <stddef.h>
#include <stdint.h>
#include <util/alloc.h>
#include <util/list.h>
static node_t *Last_node;
static size_t Cmark;
static void
begin_component(graph_t* g)
{
Last_node = GD_nlist(g) = NULL;
}
static void
add_to_component(graph_t* g, node_t * n)
{
ND_mark(n) = Cmark;
if (Last_node) {
ND_prev(n) = Last_node;
ND_next(Last_node) = n;
} else {
ND_prev(n) = NULL;
GD_nlist(g) = n;
}
Last_node = n;
ND_next(n) = NULL;
}
static void
end_component(graph_t* g)
{
size_t i = GD_comp(g).size++;
GD_comp(g).list = gv_recalloc(GD_comp(g).list, GD_comp(g).size - 1,
GD_comp(g).size, sizeof(node_t *));
GD_comp(g).list[i] = GD_nlist(g);
}
typedef LIST(node_t *) node_stack_t;
static void push(node_stack_t *sp, node_t *np) {
ND_mark(np) = Cmark + 1;
LIST_PUSH_BACK(sp, np);
}
static node_t *pop(node_stack_t *sp) {
if (LIST_IS_EMPTY(sp)) {
return NULL;
}
return LIST_POP_BACK(sp);
}
/* iterative dfs for components.
* We process the edges in reverse order of the recursive version to maintain
* the processing order of the nodes.
* Since we are using a stack, we need to indicate nodes on the stack. Nodes
* unprocessed in this call to decompose will have mark < Cmark; processed nodes
* will have mark=Cmark; so we use mark = Cmark+1 to indicate nodes on the
* stack.
*/
static void search_component(node_stack_t *stk, graph_t *g, node_t *n) {
node_t *other;
push(stk, n);
while ((n = pop(stk))) {
if (ND_mark(n) == Cmark) continue;
add_to_component(g, n);
elist vec[] = {ND_flat_in(n), ND_flat_out(n), ND_in(n), ND_out(n)};
for (size_t c = 0; c < sizeof(vec) / sizeof(vec[0]); ++c) {
if (vec[c].list && vec[c].size != 0) {
for (size_t i = vec[c].size - 1; i != SIZE_MAX; i--) {
edge_t *const e = vec[c].list[i];
if ((other = aghead(e)) == n)
other = agtail(e);
if (ND_mark(other) != Cmark && other == UF_find(other))
push(stk, other);
}
}
}
}
}
void decompose(graph_t * g, int pass)
{
graph_t *subg;
node_t *n, *v;
node_stack_t stk = {0};
if (++Cmark == 0)
Cmark = 1;
GD_comp(g).size = 0;
for (n = agfstnode(g); n; n = agnxtnode(g, n)) {
v = n;
if (pass > 0 && (subg = ND_clust(v)))
v = GD_rankleader(subg)[ND_rank(v)];
else if (v != UF_find(v))
continue;
if (ND_mark(v) != Cmark) {
begin_component(g);
search_component(&stk, g, v);
end_component(g);
}
}
LIST_FREE(&stk);
}
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