Coalesce identical adjacent microdescriptor vote lines.

changes/bug8158

@@ -0,0 +1,3 @@
+  o Minor bugfixes:
+    - Use less space when formatting identical microdescriptor lines in
+      directory votes. Fixes bug 8158; bugfix on 0.2.4.1-alpha.

src/or/dirvote.c

@@ -3664,31 +3664,66 @@ static const struct consensus_method_range_t {
   {-1, -1}
 };
 
+typedef struct microdesc_vote_line_t {
+  int low;
+  int high;
+  microdesc_t *md;
+  struct microdesc_vote_line_t *next;
+} microdesc_vote_line_t;
+
 vote_microdesc_hash_t *
 dirvote_format_all_microdesc_vote_lines(const routerinfo_t *ri, time_t now,
                                         smartlist_t *microdescriptors_out)
 {
   const struct consensus_method_range_t *cmr;
+  microdesc_vote_line_t *entries = NULL, *ep;
   vote_microdesc_hash_t *result = NULL;
 
+  /* Generate the microdescriptors. */
   for (cmr = microdesc_consensus_methods;
        cmr->low != -1 && cmr->high != -1;
        cmr++) {
     microdesc_t *md = dirvote_create_microdescriptor(ri, cmr->low);
     if (md) {
-      char buf[128];
-      vote_microdesc_hash_t *h;
-      dirvote_format_microdesc_vote_line(buf, sizeof(buf), md,
-                                         cmr->low, cmr->high);
-      h = tor_malloc_zero(sizeof(vote_microdesc_hash_t));
-      h->microdesc_hash_line = tor_strdup(buf);
-      h->next = result;
-      result = h;
-      md->last_listed = now;
-      smartlist_add(microdescriptors_out, md);
+      microdesc_vote_line_t *e =
+        tor_malloc_zero(sizeof(microdesc_vote_line_t));
+      e->md = md;
+      e->low = cmr->low;
+      e->high = cmr->high;
+      e->next = entries;
+      entries = e;
     }
   }
 
+  /* Compress adjacent identical ones */
+  for (ep = entries; ep; ep = ep->next) {
+    while (ep->next &&
+           fast_memeq(ep->md->digest, ep->next->md->digest, DIGEST256_LEN) &&
+           ep->low == ep->next->high + 1) {
+      microdesc_vote_line_t *next = ep->next;
+      ep->low = next->low;
+      microdesc_free(next->md);
+      ep->next = next->next;
+      tor_free(next);
+    }
+  }
+
+  /* Format them into vote_microdesc_hash_t, and add to microdescriptors_out.*/
+  while ((ep = entries)) {
+    char buf[128];
+    vote_microdesc_hash_t *h;
+    dirvote_format_microdesc_vote_line(buf, sizeof(buf), ep->md,
+                                       ep->low, ep->high);
+    h = tor_malloc_zero(sizeof(vote_microdesc_hash_t));
+    h->microdesc_hash_line = tor_strdup(buf);
+    h->next = result;
+    result = h;
+    ep->md->last_listed = now;
+    smartlist_add(microdescriptors_out, ep->md);
+    entries = ep->next;
+    tor_free(ep);
+  }
+
   return result;
 }