1 files changed, 455 insertions, 0 deletions
diff --git a/plugin/file/tree/tree.go b/plugin/file/tree/tree.go
new file mode 100644
index 000000000..ed33c09a4
--- /dev/null
+++ b/plugin/file/tree/tree.go
@@ -0,0 +1,455 @@
+// Copyright ©2012 The bíogo Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found at the end of this file.
+
+// Package tree implements Left-Leaning Red Black trees as described by Robert Sedgewick.
+//
+// More details relating to the implementation are available at the following locations:
+//
+// http://www.cs.princeton.edu/~rs/talks/LLRB/LLRB.pdf
+// http://www.cs.princeton.edu/~rs/talks/LLRB/Java/RedBlackBST.java
+// http://www.teachsolaisgames.com/articles/balanced_left_leaning.html
+//
+// Heavily modified by Miek Gieben for use in DNS zones.
+package tree
+
+import "github.com/miekg/dns"
+
+const (
+	td234 = iota
+	bu23
+)
+
+// Operation mode of the LLRB tree.
+const mode = bu23
+
+func init() {
+	if mode != td234 && mode != bu23 {
+		panic("tree: unknown mode")
+	}
+}
+
+// A Color represents the color of a Node.
+type Color bool
+
+const (
+	// Red as false give us the defined behaviour that new nodes are red. Although this
+	// is incorrect for the root node, that is resolved on the first insertion.
+	red   Color = false
+	black Color = true
+)
+
+// A Node represents a node in the LLRB tree.
+type Node struct {
+	Elem        *Elem
+	Left, Right *Node
+	Color       Color
+}
+
+// A Tree manages the root node of an LLRB tree. Public methods are exposed through this type.
+type Tree struct {
+	Root  *Node // Root node of the tree.
+	Count int   // Number of elements stored.
+}
+
+// Helper methods
+
+// color returns the effect color of a Node. A nil node returns black.
+func (n *Node) color() Color {
+	if n == nil {
+		return black
+	}
+	return n.Color
+}
+
+// (a,c)b -rotL-> ((a,)b,)c
+func (n *Node) rotateLeft() (root *Node) {
+	// Assumes: n has two children.
+	root = n.Right
+	n.Right = root.Left
+	root.Left = n
+	root.Color = n.Color
+	n.Color = red
+	return
+}
+
+// (a,c)b -rotR-> (,(,c)b)a
+func (n *Node) rotateRight() (root *Node) {
+	// Assumes: n has two children.
+	root = n.Left
+	n.Left = root.Right
+	root.Right = n
+	root.Color = n.Color
+	n.Color = red
+	return
+}
+
+// (aR,cR)bB -flipC-> (aB,cB)bR | (aB,cB)bR -flipC-> (aR,cR)bB
+func (n *Node) flipColors() {
+	// Assumes: n has two children.
+	n.Color = !n.Color
+	n.Left.Color = !n.Left.Color
+	n.Right.Color = !n.Right.Color
+}
+
+// fixUp ensures that black link balance is correct, that red nodes lean left,
+// and that 4 nodes are split in the case of BU23 and properly balanced in TD234.
+func (n *Node) fixUp() *Node {
+	if n.Right.color() == red {
+		if mode == td234 && n.Right.Left.color() == red {
+			n.Right = n.Right.rotateRight()
+		}
+		n = n.rotateLeft()
+	}
+	if n.Left.color() == red && n.Left.Left.color() == red {
+		n = n.rotateRight()
+	}
+	if mode == bu23 && n.Left.color() == red && n.Right.color() == red {
+		n.flipColors()
+	}
+	return n
+}
+
+func (n *Node) moveRedLeft() *Node {
+	n.flipColors()
+	if n.Right.Left.color() == red {
+		n.Right = n.Right.rotateRight()
+		n = n.rotateLeft()
+		n.flipColors()
+		if mode == td234 && n.Right.Right.color() == red {
+			n.Right = n.Right.rotateLeft()
+		}
+	}
+	return n
+}
+
+func (n *Node) moveRedRight() *Node {
+	n.flipColors()
+	if n.Left.Left.color() == red {
+		n = n.rotateRight()
+		n.flipColors()
+	}
+	return n
+}
+
+// Len returns the number of elements stored in the Tree.
+func (t *Tree) Len() int {
+	return t.Count
+}
+
+// Search returns the first match of qname in the Tree.
+func (t *Tree) Search(qname string) (*Elem, bool) {
+	if t.Root == nil {
+		return nil, false
+	}
+	n, res := t.Root.search(qname)
+	if n == nil {
+		return nil, res
+	}
+	return n.Elem, res
+}
+
+// search searches the tree for qname and type.
+func (n *Node) search(qname string) (*Node, bool) {
+	for n != nil {
+		switch c := Less(n.Elem, qname); {
+		case c == 0:
+			return n, true
+		case c < 0:
+			n = n.Left
+		default:
+			n = n.Right
+		}
+	}
+
+	return n, false
+}
+
+// Insert inserts rr into the Tree at the first match found
+// with e or when a nil node is reached.
+func (t *Tree) Insert(rr dns.RR) {
+	var d int
+	t.Root, d = t.Root.insert(rr)
+	t.Count += d
+	t.Root.Color = black
+}
+
+// insert inserts rr in to the tree.
+func (n *Node) insert(rr dns.RR) (root *Node, d int) {
+	if n == nil {
+		return &Node{Elem: newElem(rr)}, 1
+	} else if n.Elem == nil {
+		n.Elem = newElem(rr)
+		return n, 1
+	}
+
+	if mode == td234 {
+		if n.Left.color() == red && n.Right.color() == red {
+			n.flipColors()
+		}
+	}
+
+	switch c := Less(n.Elem, rr.Header().Name); {
+	case c == 0:
+		n.Elem.Insert(rr)
+	case c < 0:
+		n.Left, d = n.Left.insert(rr)
+	default:
+		n.Right, d = n.Right.insert(rr)
+	}
+
+	if n.Right.color() == red && n.Left.color() == black {
+		n = n.rotateLeft()
+	}
+	if n.Left.color() == red && n.Left.Left.color() == red {
+		n = n.rotateRight()
+	}
+
+	if mode == bu23 {
+		if n.Left.color() == red && n.Right.color() == red {
+			n.flipColors()
+		}
+	}
+
+	root = n
+
+	return
+}
+
+// DeleteMin deletes the node with the minimum value in the tree.
+func (t *Tree) DeleteMin() {
+	if t.Root == nil {
+		return
+	}
+	var d int
+	t.Root, d = t.Root.deleteMin()
+	t.Count += d
+	if t.Root == nil {
+		return
+	}
+	t.Root.Color = black
+}
+
+func (n *Node) deleteMin() (root *Node, d int) {
+	if n.Left == nil {
+		return nil, -1
+	}
+	if n.Left.color() == black && n.Left.Left.color() == black {
+		n = n.moveRedLeft()
+	}
+	n.Left, d = n.Left.deleteMin()
+
+	root = n.fixUp()
+
+	return
+}
+
+// DeleteMax deletes the node with the maximum value in the tree.
+func (t *Tree) DeleteMax() {
+	if t.Root == nil {
+		return
+	}
+	var d int
+	t.Root, d = t.Root.deleteMax()
+	t.Count += d
+	if t.Root == nil {
+		return
+	}
+	t.Root.Color = black
+}
+
+func (n *Node) deleteMax() (root *Node, d int) {
+	if n.Left != nil && n.Left.color() == red {
+		n = n.rotateRight()
+	}
+	if n.Right == nil {
+		return nil, -1
+	}
+	if n.Right.color() == black && n.Right.Left.color() == black {
+		n = n.moveRedRight()
+	}
+	n.Right, d = n.Right.deleteMax()
+
+	root = n.fixUp()
+
+	return
+}
+
+// Delete removes rr from the tree, is the node turns empty, that node is deleted with DeleteNode.
+func (t *Tree) Delete(rr dns.RR) {
+	if t.Root == nil {
+		return
+	}
+
+	el, _ := t.Search(rr.Header().Name)
+	if el == nil {
+		t.deleteNode(rr)
+		return
+	}
+	// Delete from this element.
+	empty := el.Delete(rr)
+	if empty {
+		t.deleteNode(rr)
+		return
+	}
+}
+
+// DeleteNode deletes the node that matches rr according to Less().
+func (t *Tree) deleteNode(rr dns.RR) {
+	if t.Root == nil {
+		return
+	}
+	var d int
+	t.Root, d = t.Root.delete(rr)
+	t.Count += d
+	if t.Root == nil {
+		return
+	}
+	t.Root.Color = black
+}
+
+func (n *Node) delete(rr dns.RR) (root *Node, d int) {
+	if Less(n.Elem, rr.Header().Name) < 0 {
+		if n.Left != nil {
+			if n.Left.color() == black && n.Left.Left.color() == black {
+				n = n.moveRedLeft()
+			}
+			n.Left, d = n.Left.delete(rr)
+		}
+	} else {
+		if n.Left.color() == red {
+			n = n.rotateRight()
+		}
+		if n.Right == nil && Less(n.Elem, rr.Header().Name) == 0 {
+			return nil, -1
+		}
+		if n.Right != nil {
+			if n.Right.color() == black && n.Right.Left.color() == black {
+				n = n.moveRedRight()
+			}
+			if Less(n.Elem, rr.Header().Name) == 0 {
+				n.Elem = n.Right.min().Elem
+				n.Right, d = n.Right.deleteMin()
+			} else {
+				n.Right, d = n.Right.delete(rr)
+			}
+		}
+	}
+
+	root = n.fixUp()
+	return
+}
+
+// Min returns the minimum value stored in the tree.
+func (t *Tree) Min() *Elem {
+	if t.Root == nil {
+		return nil
+	}
+	return t.Root.min().Elem
+}
+
+func (n *Node) min() *Node {
+	for ; n.Left != nil; n = n.Left {
+	}
+	return n
+}
+
+// Max returns the maximum value stored in the tree.
+func (t *Tree) Max() *Elem {
+	if t.Root == nil {
+		return nil
+	}
+	return t.Root.max().Elem
+}
+
+func (n *Node) max() *Node {
+	for ; n.Right != nil; n = n.Right {
+	}
+	return n
+}
+
+// Prev returns the greatest value equal to or less than the qname according to Less().
+func (t *Tree) Prev(qname string) (*Elem, bool) {
+	if t.Root == nil {
+		return nil, false
+	}
+
+	n := t.Root.floor(qname)
+	if n == nil {
+		return nil, false
+	}
+	return n.Elem, true
+}
+
+func (n *Node) floor(qname string) *Node {
+	if n == nil {
+		return nil
+	}
+	switch c := Less(n.Elem, qname); {
+	case c == 0:
+		return n
+	case c <= 0:
+		return n.Left.floor(qname)
+	default:
+		if r := n.Right.floor(qname); r != nil {
+			return r
+		}
+	}
+	return n
+}
+
+// Next returns the smallest value equal to or greater than the qname according to Less().
+func (t *Tree) Next(qname string) (*Elem, bool) {
+	if t.Root == nil {
+		return nil, false
+	}
+	n := t.Root.ceil(qname)
+	if n == nil {
+		return nil, false
+	}
+	return n.Elem, true
+}
+
+func (n *Node) ceil(qname string) *Node {
+	if n == nil {
+		return nil
+	}
+	switch c := Less(n.Elem, qname); {
+	case c == 0:
+		return n
+	case c > 0:
+		return n.Right.ceil(qname)
+	default:
+		if l := n.Left.ceil(qname); l != nil {
+			return l
+		}
+	}
+	return n
+}
+
+/*
+Copyright ©2012 The bíogo Authors. All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+* Redistributions of source code must retain the above copyright
+  notice, this list of conditions and the following disclaimer.
+* Redistributions in binary form must reproduce the above copyright
+  notice, this list of conditions and the following disclaimer in the
+  documentation and/or other materials provided with the distribution.
+* Neither the name of the bíogo project nor the names of its authors and
+  contributors may be used to endorse or promote products derived from this
+  software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+*/