lib/standard/ropes: Search method and classes added.

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

diff --git a/lib/standard/ropes.nit b/lib/standard/ropes.nit
index eef9360..30966ee 100644 (file)
--- a/lib/standard/ropes.nit
+++ b/lib/standard/ropes.nit
@@ -17,6 +17,29 @@ module ropes
 
 intrude import string
 
+# Used when searching for a particular node
+# Returns the path to the node from the root of the rope
+# Also, the node and the offset for seeked position in the rope
+private class Path
+       # Leaf found
+       var leaf: Leaf
+       # Offset in leaf
+       var offset: Int
+       # Stack of the nodes traversed, and the path used
+       var stack: List[PathElement]
+end
+
+# An element for a Path, has the concat node and whether or not
+# left or right child was visited.
+private class PathElement
+       # Visited node
+       var node: Concat
+       # Was the left child visited ?
+       var left = false
+       # Was the right child visited ?
+       var right = false
+end
+
 # A node for a Rope
 private abstract class RopeNode
        # Length of the node
@@ -87,6 +110,38 @@ abstract class Rope
        end
 
        redef fun length do return root.length
+
+       # Path to the Leaf for `position`
+       private fun node_at(position: Int): Path
+       do
+               assert position >= 0 and position < length
+               return get_node_from(root.as(not null), 0, position, new List[PathElement])
+       end
+
+       # Builds the path to Leaf at position `seek_pos`
+       private fun get_node_from(node: RopeNode, curr_pos: Int, seek_pos: Int, stack: List[PathElement]): Path
+       do
+               assert curr_pos >= 0
+               if node isa Leaf then return new Path(node, seek_pos - curr_pos, stack)
+               node = node.as(Concat)
+
+               if node.left != null then
+                       var next_pos = curr_pos + node.left.length
+                       stack.add(new PathElement(node))
+                       if next_pos > seek_pos then
+                               stack.last.left = true
+                               return get_node_from(node.left.as(not null), curr_pos, seek_pos, stack)
+                       end
+                       stack.last.right = true
+                       return get_node_from(node.right.as(not null), next_pos, seek_pos, stack)
+               else
+                       var vis = new PathElement(node)
+                       vis.right = true
+                       stack.add(vis)
+                       return get_node_from(node.right.as(not null), curr_pos, seek_pos, stack)
+               end
+       end
+
 end
 
 # Rope that cannot be modified