Replaces the algorithm for building balanced trees.

Changes the time complexity of the algorithm from O(n^2) to O(n*log(n)).
This speeds up loading of huge DEC-IX config from 128 s to 15 s. It also
makes the code significantly simpler.

4 files changed, 65 insertions, 71 deletions

diff --git a/filter/filter.c b/filter/filter.c
index b88039fb..ec155ee6 100644
--- a/filter/filter.c
+++ b/filter/filter.c
@@ -164,6 +164,11 @@ val_compare(struct f_val v1, struct f_val v2)
   }
 }
 
+int 
+tree_compare(const void *p1, const void *p2)
+{
+  return val_compare((* (struct f_tree **) p1)->from, (* (struct f_tree **) p2)->from);
+}
 
 void
 f_prefix_get_bounds(struct f_prefix *px, int *l, int *h)
diff --git a/filter/filter.h b/filter/filter.h
index e526a79b..11e0623a 100644
--- a/filter/filter.h
+++ b/filter/filter.h
@@ -91,6 +91,7 @@ void f_prefix_get_bounds(struct f_prefix *px, int *l, int *h);
 
 void f_prefix_get_bounds(struct f_prefix *px, int *l, int *h);
 int val_compare(struct f_val v1, struct f_val v2);
+int tree_compare(const void *p1, const void *p2);
 void val_print(struct f_val v);
 
 #define F_NOP 0
diff --git a/filter/test.conf b/filter/test.conf
index fb35afbe..395699b0 100644
--- a/filter/test.conf
+++ b/filter/test.conf
@@ -131,6 +131,9 @@ prefix px;
 ip p;
 pair pp;
 int set is;
+int set is1;
+int set is2;
+int set is3;
 prefix set pxs;
 string s;
 {
@@ -156,6 +159,18 @@ string s;
 	print "  must be true: ", defined(1), ",", defined(1.2.3.4), ",", 1 != 2, ",", 1 <= 2;
 	print "  data types: must be false: ", 1 ~ [ 2, 3, 4 ], ",", 5 ~ is, ",", 1.2.3.4 ~ [ 1.2.3.3, 1.2.3.5 ], ",", (1,2) > (2,2), ",", (1,1) > (1,1), ",", 1.0.0.0/9 ~ [ 1.0.0.0/8- ], ",", 1.2.0.0/17 ~ [ 1.0.0.0/8{ 15 , 16 } ], ",", true && false;
 
+	is1 = [2, 3, 5, 8, 11, 15, 17, 19];
+	is2 = [19, 17, 15, 11, 8, 5, 3, 2];
+	is3 = [5, 17, 2, 11, 8, 15, 3, 19];
+
+	print "  must be true:  ", 2 ~ is1, "  ", 2 ~ is2, "  ", 2 ~ is3;
+	print "  must be false: ", 4 ~ is1, " ", 4 ~ is2, " ", 4 ~ is3;
+	print "  must be false: ", 10 ~ is1, " ", 10 ~ is2, " ", 10 ~ is3;
+	print "  must be true:  ", 15 ~ is1, "  ", 15 ~ is2, "  ", 15 ~ is3;
+	print "  must be false: ", 18 ~ is1, " ", 18 ~ is2, " ", 18 ~ is3;
+	print "  must be true:  ", 19 ~ is1, "  ", 19 ~ is2, "  ", 19 ~ is3;
+	print "  must be false: ", 20 ~ is1, " ", 20 ~ is2, " ", 20 ~ is3;
+
 	px = 1.2.0.0/18;
 	print "Testing prefixes: 1.2.0.0/18 = ", px;
 	print "  must be true:  ",	192.168.0.0/16 ~ 192.168.0.0/16, " ", 192.168.0.0/17 ~ 192.168.0.0/16, " ", 192.168.254.0/24 ~ 192.168.0.0/16;
diff --git a/filter/tree.c b/filter/tree.c
index a67ddd09..f6ab75b4 100644
--- a/filter/tree.c
+++ b/filter/tree.c
@@ -6,61 +6,11 @@
  *	Can be freely distributed and used under the terms of the GNU GPL.
  */
 
+#include "lib/alloca.h"
 #include "nest/bird.h"
 #include "conf/conf.h"
 #include "filter/filter.h"
 
-/*
- * find_nth - finds n-th element in linked list. Don't be confused by types, it is really a linked list.
- */
-static struct f_tree *
-find_nth(struct f_tree *from, int nth)
-{
-  struct f_tree *pivot;
-  int lcount = 0, rcount = 0;
-  struct f_tree *left, *right, *next;
-
-  pivot = from;
-
-  left = right = NULL;
-  next = from->right;
-  while (from = next) {
-    next = from->right;
-    if (val_compare(pivot->from, from->from)==1) {
-      from->right = left;
-      left = from;
-      lcount++;
-    } else {
-      from->right = right;
-      right = from;
-      rcount++;
-    }
-  }
-  if (lcount == nth) 
-    return pivot;
-  if (lcount < nth)
-    return find_nth(right, nth-lcount-1);
-  return find_nth(left, nth);
-}
-
-/*
- * find_median - Gets list linked by @left, finds its median, trashes pointers in @right.
- */
-static struct f_tree *
-find_median(struct f_tree *from)
-{
-  struct f_tree *t = from;
-  int cnt = 0;
-
-  if (!from)
-    return NULL;
-  do {
-    t->right = t->left;
-    cnt++;
-  } while (t = t->left);
-  return find_nth(from, cnt/2);
-}
-
 /**
  * find_tree
  * @t: tree to search in
@@ -87,6 +37,23 @@ find_tree(struct f_tree *t, struct f_val val)
     return find_tree(t->left, val);
 }
 
+static struct f_tree *
+build_tree_rec(struct f_tree **buf, int l, int h)
+{
+  struct f_tree *n;
+  int pos;
+
+  if (l >= h)
+    return NULL;
+
+  pos = (l+h)/2;
+  n = buf[pos];
+  n->left = build_tree_rec(buf, l, pos);
+  n->right = build_tree_rec(buf, pos+1, h);
+  return n;
+}
+
+
 /**
  * build_tree
  * @from: degenerated tree (linked by @tree->left) to be transformed into form suitable for find_tree()
@@ -96,29 +63,35 @@ find_tree(struct f_tree *t, struct f_val val)
 struct f_tree *
 build_tree(struct f_tree *from)
 {
-  struct f_tree *median, *t = from, *next, *left = NULL, *right = NULL;
+  struct f_tree *tmp, *root;
+  struct f_tree **buf;
+  int len, i;
 
-  median = find_median(from);
-  if (!median)
+  if (from == NULL)
     return NULL;
 
-  do {
-    next = t->left;
-    if (t == median)
-      continue;
-
-    if (val_compare(median->from, t->from)==1) {
-      t->left = left;
-      left = t;
-    } else {
-      t->left = right;
-      right = t;
-    }
-  } while(t = next);
-
-  median->left = build_tree(left);
-  median->right = build_tree(right);
-  return median;
+  len = 0;
+  for (tmp = from; tmp != NULL; tmp = tmp->left)
+    len++;
+
+  if (len <= 1024)
+    buf = alloca(len * sizeof(struct f_tree *));
+  else
+    buf = malloc(len * sizeof(struct f_tree *));
+
+  /* Convert a degenerated tree into an sorted array */
+  i = 0;
+  for (tmp = from; tmp != NULL; tmp = tmp->left)
+    buf[i++] = tmp;
+
+  qsort(buf, len, sizeof(struct f_tree *), tree_compare);
+
+  root = build_tree_rec(buf, 0, len);
+
+  if (len > 1024)
+    free(buf);
+
+  return root;
 }
 
 struct f_tree *