(update_interval): New function.

1 files changed, 39 insertions, 0 deletions

diff --git a/src/intervals.c b/src/intervals.c
index cff718d1f8e..744128b84dc 100644
--- a/src/intervals.c
+++ b/src/intervals.c
@@ -670,6 +670,45 @@ previous_interval (interval)
 
   return NULL_INTERVAL;
 }
+
+/* Find the interval containing POS given some non-NULL INTERVAL
+   in the same tree. */
+INTERVAL
+update_interval (i, pos)
+     register INTERVAL i;
+     int pos;
+{
+  if (NULL_INTERVAL_P (i))
+    return NULL_INTERVAL;
+
+  while (1) 
+    {
+      if (pos < i->position) 
+        {
+          /* Move left. */
+          if (pos >= i->position - TOTAL_LENGTH (i->left))
+            i = i->left;                /* Move to the left child */
+          else if (NULL_PARENT (i)) 
+            error ("Point before start of properties");
+          else  i = i->parent;
+          continue;
+        }
+      else if (pos >= INTERVAL_LAST_POS (i))
+        {
+          /* Move right. */
+          if (pos < INTERVAL_LAST_POS (i) + TOTAL_LENGTH (i->right))
+            i = i->right;               /* Move to the right child */
+          else if (NULL_PARENT (i)) 
+            error ("Point after end of properties");
+          else 
+            i = i->parent;
+          continue;
+        }
+      else 
+        return i;
+    }
+}
+
 
 #if 0
 /* Traverse a path down the interval tree TREE to the interval