pylucene 3.5.0-3

[pylucene.git] / lucene-java-3.5.0 / lucene / contrib / spatial / src / java / org / apache / lucene / spatial / geohash / GeoHashUtils.java

diff --git a/lucene-java-3.5.0/lucene/contrib/spatial/src/java/org/apache/lucene/spatial/geohash/GeoHashUtils.java b/lucene-java-3.5.0/lucene/contrib/spatial/src/java/org/apache/lucene/spatial/geohash/GeoHashUtils.java
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+++ b/lucene-java-3.5.0/lucene/contrib/spatial/src/java/org/apache/lucene/spatial/geohash/GeoHashUtils.java
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+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.lucene.spatial.geohash;
+
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * Utilities for encoding and decoding geohashes. Based on
+ * <a href="http://en.wikipedia.org/wiki/Geohash">http://en.wikipedia.org/wiki/Geohash</a>.
+ */
+public class GeoHashUtils {
+
+  private static final char[] BASE_32 = {'0', '1', '2', '3', '4', '5', '6',
+      '7', '8', '9', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'j', 'k', 'm', 'n',
+      'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};
+
+  private final static Map<Character,Integer> DECODE_MAP = new HashMap<Character,Integer>();
+
+  private static final int PRECISION = 12;
+  private static final int[] BITS = {16, 8, 4, 2, 1};
+
+  static {
+    for (int i = 0; i < BASE_32.length; i++) {
+      DECODE_MAP.put(Character.valueOf(BASE_32[i]), Integer.valueOf(i));
+    }
+  }
+
+  private GeoHashUtils() {  
+  }
+
+  /**
+   * Encodes the given latitude and longitude into a geohash
+   *
+   * @param latitude Latitude to encode
+   * @param longitude Longitude to encode
+   * @return Geohash encoding of the longitude and latitude
+   */
+  public static String encode(double latitude, double longitude) {
+    double[] latInterval = {-90.0, 90.0};
+    double[] lngInterval = {-180.0, 180.0};
+
+    final StringBuilder geohash = new StringBuilder();
+    boolean isEven = true;
+
+    int bit = 0;
+    int ch = 0;
+
+    while (geohash.length() < PRECISION) {
+      double mid = 0.0;
+      if (isEven) {
+        mid = (lngInterval[0] + lngInterval[1]) / 2D;
+        if (longitude > mid) {
+          ch |= BITS[bit];
+          lngInterval[0] = mid;
+        } else {
+          lngInterval[1] = mid;
+        }
+      } else {
+        mid = (latInterval[0] + latInterval[1]) / 2D;
+        if (latitude > mid) {
+          ch |= BITS[bit];
+          latInterval[0] = mid;
+        } else {
+          latInterval[1] = mid;
+        }
+      }
+
+      isEven = !isEven;
+
+      if (bit < 4) {
+        bit++;
+      } else {
+        geohash.append(BASE_32[ch]);
+        bit = 0;
+        ch = 0;
+      }
+    }
+
+    return geohash.toString();
+  }
+
+  /**
+   * Decodes the given geohash into a latitude and longitude
+   *
+   * @param geohash Geohash to deocde
+   * @return Array with the latitude at index 0, and longitude at index 1
+   */
+  public static double[] decode(String geohash) {
+    final double[] latInterval = {-90.0, 90.0};
+    final double[] lngInterval = {-180.0, 180.0};
+
+    boolean isEven = true;
+
+    double latitude;
+    double longitude;
+    for (int i = 0; i < geohash.length(); i++) {
+      final int cd = DECODE_MAP.get(Character.valueOf(
+          geohash.charAt(i))).intValue();
+
+      for (int mask : BITS) {
+        if (isEven) {
+          if ((cd & mask) != 0) {
+            lngInterval[0] = (lngInterval[0] + lngInterval[1]) / 2D;
+          } else {
+            lngInterval[1] = (lngInterval[0] + lngInterval[1]) / 2D;
+          }
+        } else {
+          if ((cd & mask) != 0) {
+            latInterval[0] = (latInterval[0] + latInterval[1]) / 2D;
+          } else {
+            latInterval[1] = (latInterval[0] + latInterval[1]) / 2D;
+          }
+        }
+        isEven = !isEven;
+      }
+
+    }
+    latitude = (latInterval[0] + latInterval[1]) / 2D;
+    longitude = (lngInterval[0] + lngInterval[1]) / 2D;
+
+    return new double[] {latitude, longitude};
+       }
+}
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