--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/flys-artifacts/src/main/java/de/intevation/flys/artifacts/model/QRangeTree.java	Fri Sep 28 12:14:35 2012 +0200
@@ -0,0 +1,271 @@
+package de.intevation.flys.artifacts.model;
+
+import java.io.Serializable;
+
+import java.util.List;
+import java.util.ArrayList;
+
+import org.apache.log4j.Logger;
+
+public class QRangeTree
+implements   Serializable
+{
+    private static Logger log = Logger.getLogger(QRangeTree.class);
+
+    public static final double EPSILON = 1e-4;
+
+    public static class Node
+    implements          Serializable
+    {
+        Node left;
+        Node right;
+        Node prev;
+        Node next;
+
+        double a;
+        double b;
+        double q;
+
+        public Node() {
+        }
+
+        public Node(double a, double b, double q) {
+            this.a = a;
+            this.b = b;
+            this.q = q;
+        }
+
+        protected final double interpolatePrev(double pos) {
+            /*
+            f(prev.b) = prev.q
+            f(a)      = q
+
+            prev.q = m*prev.b + n
+            q      = m*a      + n <=> n = q - m*a
+
+            q - prev.q = m*(a - prev.b)
+
+            m = (q - prev.q)/(a - prev.b) # a != prev.b
+            */
+
+            if (a == prev.b) {
+                return 0.5*(q + prev.q);
+            }
+            double m = (q - prev.q)/(a - prev.b);
+            double n = q - m*a;
+            return m*pos + n;
+        }
+
+        protected final double interpolateNext(double pos) {
+            /*
+            f(next.a) = next.q
+            f(b)      = q
+
+            next.q = m*next.a + n
+            q      = m*b      + n <=> n = q - m*b
+
+            q - next.q = m*(b - next.a)
+            m = (q - next.q)/(b - next.a) # b != next.a
+            */
+
+            if (b == next.a) {
+                return 0.5*(q + next.q);
+            }
+            double m = (q - next.q)/(b - next.a);
+            double n = q - m*b;
+            return m*pos + n;
+        }
+
+        public double findQ(double pos) {
+
+            Node current = this;
+            for (;;) {
+                if (pos < current.a) {
+                    if (current.left != null) {
+                        current = current.left;
+                        continue;
+                    }
+                    return current.prev != null
+                        ? current.interpolatePrev(pos)
+                        : Double.NaN;
+                }
+                if (pos > current.b) {
+                    if (current.right != null) {
+                        current = current.right;
+                        continue;
+                    }
+                    return current.next != null
+                        ? current.interpolateNext(pos)
+                        : Double.NaN;
+                }
+                return current.q;
+            }
+        }
+    } // class Node
+
+    protected Node root;
+
+    public QRangeTree() {
+    }
+
+    public static final class AccessQAB {
+        private int startIndex;
+
+        public AccessQAB(int startIndex) {
+            this.startIndex = startIndex;
+        }
+
+        public Double getQ(Object [] row) {
+            return (Double)row[startIndex];
+        }
+
+        public Double getA(Object [] row) {
+            return (Double)row[startIndex+1];
+        }
+
+        public Double getB(Object [] row) {
+            return (Double)row[startIndex+2];
+        }
+    }
+
+    public static final AccessQAB WITH_COLUMN    = new AccessQAB(1);
+    public static final AccessQAB WITHOUT_COLUMN = new AccessQAB(0);
+
+    /** wstQRanges need to be sorted by range.a */
+    public QRangeTree(List<Object []> qRanges, int start, int stop) {
+        this(qRanges, WITH_COLUMN, start, stop);
+    }
+
+    public QRangeTree(
+        List<Object []> qRanges,
+        AccessQAB       accessQAB,
+        int             start,
+        int             stop
+    ) {
+        if (stop <= start) {
+            return;
+        }
+
+        int N = stop-start;
+
+        List<Node> nodes = new ArrayList<Node>(N);
+
+        Node last = null;
+
+        for (int i = 0; i < N; ++i) {
+            Object [] qRange = qRanges.get(start + i);
+            Double q = accessQAB.getQ(qRange);
+            Double a = accessQAB.getA(qRange);
+            Double b = accessQAB.getB(qRange);
+
+            double av = a != null ? a.doubleValue() : -Double.MAX_VALUE;
+            double bv = b != null ? b.doubleValue() :  Double.MAX_VALUE;
+            double qv = q.doubleValue();
+
+            // If nodes are directly neighbored and Qs are the same
+            // join them.
+            if (last != null
+            && Math.abs(last.b - av) < EPSILON
+            && Math.abs(last.q - qv) < EPSILON) {
+                last.b = bv;
+            }
+            else {
+                nodes.add(last = new Node(av, bv, qv));
+            }
+        }
+
+        if (log.isDebugEnabled()) {
+            log.debug("Before/after nodes join: " +
+                N + "/" + nodes.size());
+        }
+
+        root = wireTree(nodes);
+    }
+
+    protected static Node wireTree(List<Node> nodes) {
+        int N = nodes.size();
+        for (int i = 0; i < N; ++i) {
+            Node node = nodes.get(i);
+            if (i > 0  ) node.prev = nodes.get(i-1);
+            if (i < N-1) node.next = nodes.get(i+1);
+        }
+
+        return buildTree(nodes, 0, N-1);
+    }
+
+    protected static Node buildTree(List<Node> nodes, int lo, int hi) {
+
+        if (lo > hi) {
+            return null;
+        }
+
+        int mid = (lo + hi) >> 1;
+        Node parent = nodes.get(mid);
+
+        parent.left  = buildTree(nodes, lo, mid-1);
+        parent.right = buildTree(nodes, mid+1, hi);
+
+        return parent;
+    }
+
+    public double findQ(double pos) {
+        return root != null ? root.findQ(pos) : Double.NaN;
+    }
+
+    @Override
+    public String toString() {
+        StringBuilder sb = new StringBuilder();
+        inorder(root, sb);
+        return sb.toString();
+    }
+
+    protected static void inorder(Node node, StringBuilder sb) {
+        if (node != null) {
+            inorder(node.left, sb);
+            sb.append('[')
+              .append(node.a)
+              .append(", ")
+              .append(node.b)
+              .append(": ")
+              .append(node.q)
+              .append(']');
+            inorder(node.right, sb);
+        }
+    }
+
+    private static final String name(Object o) {
+        return String.valueOf(System.identityHashCode(o) & 0xffffffffL);
+    }
+
+    public String toGraph() {
+        StringBuilder sb = new StringBuilder();
+        sb.append("subgraph c");
+        sb.append(name(this));
+        sb.append(" {\n");
+        if (root != null) {
+            java.util.Deque<Node> stack = new java.util.ArrayDeque<Node>();
+            stack.push(root);
+            while (!stack.isEmpty()) {
+                Node current = stack.pop();
+                String name = "n" + name(current);
+                sb.append(name);
+                sb.append(" [label=\"");
+                sb.append(current.a).append(", ").append(current.b);
+                sb.append(": ").append(current.q).append("\"]\n");
+                if (current.left != null) {
+                    String leftName = name(current.left);
+                    sb.append(name).append(" -- n").append(leftName).append("\n");
+                    stack.push(current.left);
+                }
+                if (current.right != null) {
+                    String rightName = name(current.right);
+                    sb.append(name).append(" -- n").append(rightName).append("\n");
+                    stack.push(current.right);
+                }
+            }
+        }
+        sb.append("}\n");
+        return sb.toString();
+    }
+}
+// vim:set ts=4 sw=4 si et sta sts=4 fenc=utf8 :