Allow dijkstra to record shortest path info, not just distances.

diff --git a/cmd/tools/dijkstra.c b/cmd/tools/dijkstra.c
index e2e1853c71caae348558c67e07a346f62497dcc0..fc4e1b7405cb044331864fb912ce4acc1a3f4219 100644 (file)
--- a/cmd/tools/dijkstra.c
+++ b/cmd/tools/dijkstra.c
@@ -44,11 +44,13 @@ static char **Nodes;
 static int setall = 0;         /* if false, don't set dist attribute for
                                 * nodes in different components.
                                 */
+static int doPath = 0;         /* if 1, record shortest paths */
 static Agsym_t *len_sym;
 
 typedef struct nodedata_s {
     Agrec_t hdr;
     double dist;               /* always positive for scanned nodes */
+    Agnode_t* prev;
 } nodedata_t;
 
 typedef struct edgedata_s {
@@ -86,6 +88,8 @@ static void setdist(Agnode_t * n, double dist)
 #else
 #define getdist(n) (((nodedata_t*)((n)->base.data))->dist)
 #define setdist(n,d) (((nodedata_t*)((n)->base.data))->dist = (d))
+#define getprev(n) (((nodedata_t*)((n)->base.data))->prev)
+#define setprev(n,p) (((nodedata_t*)((n)->base.data))->prev = (p))
 #endif
 
 static int cmpf(Dt_t * d, void *key1, void *key2, Dtdisc_t * disc)
@@ -130,10 +134,12 @@ static void update(Dict_t * Q, Agnode_t * dest, Agnode_t * src, double len)
 
     if (oldlen == 0) {         /* first time to see dest */
        setdist(dest, newlen);
+       if (doPath) setprev(dest, src);
        dtinsert(Q, dest);
     } else if (newlen < oldlen) {
        dtdelete(Q, dest);
        setdist(dest, newlen);
+       if (doPath) setprev(dest, src);
        dtinsert(Q, dest);
     }
 }
@@ -148,13 +154,17 @@ static void pre(Agraph_t * g)
 static void post(Agraph_t * g)
 {
     Agnode_t *v;
+    Agnode_t *prev;
     char buf[256];
     char dflt[256];
     Agsym_t *sym;
+    Agsym_t *psym;
     double dist, oldmax;
     double maxdist = 0.0;      /* maximum "finite" distance */
 
     sym = agattr(g, AGNODE, "dist", "");
+    if (doPath)
+       psym = agattr(g, AGNODE, "prev", "");
 
     if (setall)
        sprintf(dflt, "%.3lf", HUGE);
@@ -169,6 +179,8 @@ static void post(Agraph_t * g)
            dist--;
            sprintf(buf, "%.3lf", dist);
            agxset(v, sym, buf);
+           if (doPath && (prev = getprev(v)))
+               agxset(v, psym, agnameof(prev));
            if (maxdist < dist)
                maxdist = dist;
        } else if (setall)
@@ -219,6 +231,7 @@ void dijkstra(Dict_t * Q, Agraph_t * G, Agnode_t * n)
 static char *useString =
     "Usage: dijkstra [-a?] <node> [<file> <node> <file>]\n\
   -a - for nodes in a different component, set dist very large\n\
+  -p - attach shortest path info\n\
   -? - print usage\n\
 If no files are specified, stdin is used\n";
 
@@ -233,11 +246,14 @@ static void init(int argc, char *argv[])
     int i, j, c;
 
     CmdName = argv[0];
-    while ((c = getopt(argc, argv, ":a?")) != -1) {
+    while ((c = getopt(argc, argv, ":ap?")) != -1) {
        switch (c) {
        case 'a':
            setall = 1;
            break;
+       case 'p':
+           doPath = 1;
+           break;
        case '?':
            if (optopt == '?')
                usage(0);