357 lines
7.9 KiB
C
357 lines
7.9 KiB
C
/* topo - topological sort Author: Kent Williams */
|
|
|
|
/*
|
|
** topo - perform a topological sort of the output of lorder.
|
|
**
|
|
** Usage : topo [infile] [outfile]
|
|
**
|
|
** Author: Kent Williams (williams@umaxc.weeg.uiowa.edu)
|
|
*/
|
|
|
|
#include <ctype.h>
|
|
#include <stdlib.h>
|
|
#include <string.h>
|
|
#include <stdio.h>
|
|
|
|
typedef struct __v {
|
|
struct __v *next; /* link list node */
|
|
int indegree, /* number of edges into this vertex */
|
|
visited, /* depth-first search visited flag */
|
|
on_the_path, /* used to find cycles */
|
|
has_a_cycle; /* true if a cycle at this vertex */
|
|
struct __e *out; /* outgoing edges from this vertex */
|
|
char key[1]; /* name of this vertex */
|
|
} vertex;
|
|
|
|
typedef struct __e {
|
|
struct __e *next; /* link list node */
|
|
vertex *v; /* vertex to which this edge goes */
|
|
} edge;
|
|
|
|
int main(int argc, char **argv);
|
|
void *xmalloc(size_t siz);
|
|
edge *new_edge(vertex *v);
|
|
char *copyupto(char *name, char *buf, int stop);
|
|
int child_of(vertex *parent, vertex *child);
|
|
vertex *add_v(char *s);
|
|
void readin(void);
|
|
void pushname(char *s);
|
|
char *popname(void);
|
|
void topo(void);
|
|
void print_cycle(vertex *parent, vertex *child);
|
|
void dfs(vertex *v);
|
|
void check_cycles(void);
|
|
|
|
/*
|
|
** xmalloc -- standard do or die malloc front end.
|
|
*/
|
|
void *
|
|
xmalloc(siz)
|
|
size_t siz;
|
|
{
|
|
void *rval = (void *)malloc(siz);
|
|
if(rval == NULL) {
|
|
fputs("Out of memory.\n",stderr);
|
|
exit(1);
|
|
}
|
|
return rval;
|
|
}
|
|
|
|
/*
|
|
** edge allocater.
|
|
*/
|
|
edge *
|
|
new_edge(v)
|
|
vertex *v;
|
|
{
|
|
edge *rval;
|
|
rval = (edge *)xmalloc(sizeof(edge));
|
|
rval->v = v; return rval;
|
|
}
|
|
|
|
/*
|
|
** copyupto - copy until you see the stop character.
|
|
*/
|
|
char *
|
|
copyupto(name,buf,stop)
|
|
char *name,*buf,stop;
|
|
{
|
|
while(*buf != '\0' && *buf != stop)
|
|
*name++ = *buf++;
|
|
*name = '\0';
|
|
while(*buf != '\0' && isspace(*buf))
|
|
buf++;
|
|
return buf;
|
|
}
|
|
|
|
/*
|
|
** find out if the vertex child is a child of the vertex parent.
|
|
*/
|
|
int
|
|
child_of(parent,child)
|
|
vertex *parent,*child;
|
|
{
|
|
edge *e;
|
|
for(e = parent->out; e != NULL && e->v != child; e = e->next)
|
|
;
|
|
return e == NULL ? 0 : 1;
|
|
}
|
|
|
|
/*
|
|
** the vertex set.
|
|
**
|
|
** add_v adds a vertex to the set if it's not already there.
|
|
*/
|
|
vertex *vset = NULL;
|
|
|
|
vertex *
|
|
add_v(s)
|
|
char *s;
|
|
{
|
|
vertex *v,*last;
|
|
/*
|
|
** go looking for this key in the vertex set.
|
|
*/
|
|
for(last = v = vset; v != NULL && strcmp(v->key,s) != 0;
|
|
last = v, v = v->next)
|
|
;
|
|
if(v != NULL) {
|
|
/*
|
|
** use the move-to-front heuristic to keep this from being
|
|
** an O(N^2) algorithm.
|
|
*/
|
|
if(last != vset) {
|
|
last->next = v->next;
|
|
v->next = vset;
|
|
vset = v;
|
|
}
|
|
return v;
|
|
}
|
|
|
|
v = (vertex *)xmalloc(sizeof(vertex) + strlen(s));
|
|
|
|
v->out = NULL;
|
|
strcpy(v->key,s);
|
|
v->indegree =
|
|
v->on_the_path =
|
|
v->has_a_cycle =
|
|
v->visited = 0;
|
|
v->next = vset;
|
|
vset = v;
|
|
return v;
|
|
}
|
|
|
|
/*
|
|
** readin -- read in the dependency pairs.
|
|
*/
|
|
void
|
|
readin()
|
|
{
|
|
static char buf[128];
|
|
static char name[64];
|
|
char *bp;
|
|
vertex *child,*parent;
|
|
edge *e;
|
|
while(fgets(buf,sizeof(buf),stdin) != NULL) {
|
|
bp = buf + strlen(buf);
|
|
if (bp > buf && bp[-1] == '\n') *--bp = 0;
|
|
bp = copyupto(name,buf,' ');
|
|
child = add_v(name);
|
|
parent = add_v(bp);
|
|
if(child != parent && !child_of(parent,child)) {
|
|
e = new_edge(child);
|
|
e->next = parent->out;
|
|
parent->out = e;
|
|
child->indegree++;
|
|
}
|
|
}
|
|
}
|
|
|
|
/*
|
|
** the topological sort produces names of modules in reverse of
|
|
** the order we want them in, so use a stack to hold the names
|
|
** until we get them all, then pop them off to print them.
|
|
*/
|
|
struct name { struct name *next; char *s; }
|
|
*namelist = NULL;
|
|
|
|
void
|
|
pushname(s)
|
|
char *s;
|
|
{
|
|
struct name *x = (struct name *)xmalloc(sizeof(struct name));
|
|
x->s = s;
|
|
x->next = namelist;
|
|
namelist = x;
|
|
}
|
|
|
|
char *
|
|
popname() {
|
|
char *rval;
|
|
struct name *tmp;
|
|
if(namelist == NULL)
|
|
return NULL;
|
|
tmp = namelist;
|
|
rval = namelist->s;
|
|
namelist = namelist->next;
|
|
free(tmp);
|
|
return rval;
|
|
}
|
|
|
|
/*
|
|
** topo - do a topological sort of the dependency graph.
|
|
*/
|
|
void topo() {
|
|
vertex *x = vset,*n;
|
|
edge *e;
|
|
vertex *outq = NULL,*tmp;
|
|
#define insq(x) ((x->next = outq),(outq = x))
|
|
#define deq() ((tmp = outq),(outq = outq->next),tmp)
|
|
|
|
/*
|
|
** find all vertices that don't depend on any other vertices
|
|
** Since it breaks the "next" links to insert x into the queue,
|
|
** x->next is saved before insq, to resume the list traversal.
|
|
*/
|
|
while (x != NULL) {
|
|
n = x->next;
|
|
if(x->indegree == 0) {
|
|
insq(x);
|
|
pushname(x->key);
|
|
}
|
|
x = n;
|
|
}
|
|
|
|
/*
|
|
** for each vertex V with indegree of zero,
|
|
** for each edge E from vertex V
|
|
** subtract one from the indegree of the vertex V'
|
|
** pointed to by E. If V' now has an indegree of zero,
|
|
** add it to the set of vertices with indegree zero, and
|
|
** push its name on the output stack.
|
|
*/
|
|
while(outq != NULL) {
|
|
x = deq();
|
|
e = x->out;
|
|
while(e != NULL) {
|
|
if(--(e->v->indegree) == 0) {
|
|
insq(e->v);
|
|
pushname(e->v->key);
|
|
}
|
|
e = e->next;
|
|
}
|
|
}
|
|
|
|
/*
|
|
** print the vertex names in opposite of the order they were
|
|
** encountered.
|
|
*/
|
|
while(namelist != NULL)
|
|
puts(popname());
|
|
}
|
|
|
|
/*
|
|
** print_cycle --
|
|
** A cycle has been detected between parent and child.
|
|
** Start with the child, and look at each of its edges for
|
|
** the parent.
|
|
**
|
|
** We know a vertex is on the path from the child to the parent
|
|
** because the depth-first search sets on_the_path true for each
|
|
** vertex it visits.
|
|
*/
|
|
void
|
|
print_cycle(parent,child)
|
|
vertex *parent, *child;
|
|
{
|
|
char *s;
|
|
vertex *x;
|
|
edge *e;
|
|
for(x = child; x != parent; ) {
|
|
pushname(x->key);
|
|
for(e = x->out; e != NULL; e = e->next) {
|
|
/*
|
|
** stop looking for the path at the first node found
|
|
** that's on the path. Watch out for cycles already
|
|
** detected, because if you follow an edge into a cycle,
|
|
** you're stuck in an infinite loop!
|
|
*/
|
|
if(e->v->on_the_path && !e->v->has_a_cycle) {
|
|
x = e->v;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
/*
|
|
** print the name of the parent, and then names of each of the
|
|
** vertices on the path from the child to the parent.
|
|
*/
|
|
fprintf(stderr,"%s\n",x->key);
|
|
while((s = popname()) != NULL)
|
|
fprintf(stderr,"%s\n",s);
|
|
}
|
|
|
|
/*
|
|
** depth first search for cycles in the dependency graph.
|
|
** See "Introduction to Algorithms" by Udi Manber Addison-Wesley 1989
|
|
*/
|
|
void
|
|
dfs(v)
|
|
vertex *v;
|
|
{
|
|
edge *e;
|
|
|
|
if(v->visited) /* If you've been here before, don't go again! */
|
|
return;
|
|
v->visited++;
|
|
v->on_the_path++; /* this node is on the path from the root. */
|
|
|
|
/*
|
|
** depth-first search all outgoing edges.
|
|
*/
|
|
for(e = v->out; e != NULL; e = e->next) {
|
|
if(!e->v->visited)
|
|
dfs(e->v);
|
|
if(e->v->on_the_path) {
|
|
fprintf(stderr,"cycle found between %s and %s\n",
|
|
v->key,e->v->key);
|
|
print_cycle(v,e->v);
|
|
v->has_a_cycle++;
|
|
}
|
|
}
|
|
v->on_the_path = 0;
|
|
}
|
|
|
|
/*
|
|
** check cycles starts the recursive depth-first search from
|
|
** each vertex in vset.
|
|
*/
|
|
void
|
|
check_cycles()
|
|
{
|
|
vertex *v;
|
|
for(v = vset; v != NULL; v = v->next)
|
|
dfs(v);
|
|
}
|
|
|
|
/*
|
|
** main program.
|
|
*/
|
|
int main(argc,argv)
|
|
int argc;
|
|
char **argv;
|
|
{
|
|
if(argc > 1 && freopen(argv[1],"r",stdin) == NULL) {
|
|
perror(argv[1]);
|
|
exit(0);
|
|
}
|
|
if(argc > 2 && freopen(argv[2],"w",stdout) == NULL) {
|
|
perror(argv[2]);
|
|
exit(0);
|
|
}
|
|
readin();
|
|
check_cycles();
|
|
topo();
|
|
return(0);
|
|
}
|