lib/standard/ropes: Adapted substring method for Ropes.

Signed-off-by: Lucas Bajolet <r4pass@hotmail.com>

diff --git a/lib/standard/ropes.nit b/lib/standard/ropes.nit
index f992f66..940939d 100644 (file)
--- a/lib/standard/ropes.nit
+++ b/lib/standard/ropes.nit
@@ -224,5 +224,63 @@ class RopeString
                return cct
        end
 
+       # O(log(n))
+       #
+       #     var rope = new RopeString.from("abcd")
+       #     assert rope.substring(1, 2)         ==  "bc"
+       #     assert rope.substring(-1, 2)         ==  "a"
+       #     assert rope.substring(1, 0)         ==  ""
+       #     assert rope.substring(2, 5)         ==  "cd"
+       #
+       redef fun substring(pos, len)
+       do
+               if pos < 0 then
+                       len += pos
+                       pos = 0
+               end
+
+               if pos + len > length then len = length - pos
+
+               if len <= 0 then return new RopeString.from("")
+
+               var path = node_at(pos)
+
+               var lf = path.leaf
+               var offset = path.offset
+
+               if path.leaf.str.length - offset > len then lf = new Leaf(lf.str.substring(offset,len)) else lf = new Leaf(lf.str.substring_from(offset))
+
+               var nod: RopeNode = lf
+
+               for i in path.stack.reverse_iterator do
+                       if i.right then continue
+                       var tmp = new Concat
+                       tmp.left = nod
+                       var r = i.node.right
+                       if r != null then tmp.right = r
+                       nod = tmp
+               end
+
+               var ret = new RopeString
+               ret.root = nod
+
+               path = ret.node_at(len-1)
+
+               offset = path.offset
+               nod = new Leaf(path.leaf.str.substring(0, offset+1))
+
+               for i in path.stack.reverse_iterator do
+                       if i.left then continue
+                       var tmp = new Concat
+                       tmp.right = nod
+                       var l = i.node.left
+                       if l != null then tmp.left = l
+                       nod = tmp
+               end
+
+               ret.root = nod
+
+               return ret
+       end
 end