Updated Geohash features

src/de/tudarmstadt/maki/simonstrator/api/util/Geohash.java

@@ -45,14 +45,14 @@ public class Geohash {
 		        double currentCellY = pLocation.getLatitude() - offsetY;
 		        
 		        boolean nextBit;
-		        if (i % 2 == 0) {
+				if ((i + j) % 2 == 0) {
 		            nextBit = getNextBit(currentCellX, cellSize.getSizeX());
 		        } else {
 		            nextBit = getNextBit(currentCellY, cellSize.getSizeY());
 		        }
 		        
 		        if (nextBit) {
-		            if (i % 2 == 0) {
+					if ((i + j) % 2 == 0) {
 		                offsetX += cellSize.getSizeX() / 2.0;
 		            } else {
 		                offsetY += cellSize.getSizeY() / 2.0;
@@ -70,29 +70,143 @@ public class Geohash {
             }
 		    
         }
+
 		return encode(bytes);
 	}
 	
+	public static String[] getAdjacentGeohashes(String pGeohash) {
+		String[] geohashes = new String[] { getAdjacentGeohash(pGeohash, 1, 0), getAdjacentGeohash(pGeohash, -1, 0),
+				getAdjacentGeohash(pGeohash, 0, 1), getAdjacentGeohash(pGeohash, 0, -1) };
+
+		return geohashes;
+	}
+
+	/**
+	 * @param pGeohash
+	 * @param pX
+	 * @param pY
+	 * @return
+	 */
+	public static String getAdjacentGeohash(String pGeohash, int pX, int pY) {
+		byte[] decode = decode(pGeohash);
+
+		if (pX != 0) {
+			boolean reduce = pX < 0;
+			outer: for (int i = decode.length - 1; i >= 0; i--) {
+				for (int j = 0; j < 5; j++) {
+					if ((i + j) % 2 == 0) {
+						boolean bitSet = isBitSet(decode[i], j);
+						if (reduce) {
+							decode[i] = toogleBit(decode[i], j);
+							if (bitSet) {
+								break outer;
+							}
+						} else {
+							decode[i] = toogleBit(decode[i], j);
+							if (!bitSet) {
+								break outer;
+							}
+						}
+					}
+				}
+			}
+		}
+
+		if (pY != 0) {
+			boolean reduce = pY < 0;
+			outer: for (int i = decode.length - 1; i >= 0; i--) {
+				for (int j = 0; j < 5; j++) {
+					if ((i + j) % 2 == 1) {
+						boolean bitSet = isBitSet(decode[i], j);
+						if (reduce) {
+							decode[i] = toogleBit(decode[i], j);
+							if (bitSet) {
+								break outer;
+							}
+						} else {
+							decode[i] = toogleBit(decode[i], j);
+							if (!bitSet) {
+								break outer;
+							}
+						}
+					}
+				}
+			}
+		}
+
+		return encode(decode);
+	}
+
+	private static boolean isBitSet(byte b, int offset) {
+		return getBit(b, offset) == 1;
+	}
+
+	private static byte getBit(byte b, int offset) {
+		return (byte) ((b % Math.pow(2, offset + 1)) / Math.pow(2, offset));
+	}
+
+	private static byte setBit(byte b, int offset, int value) {
+		return (byte) (b + Math.pow(2, offset) * (value - getBit(b, offset)));
+	}
+
+	private static byte toogleBit(byte b, int offset) {
+		if (isBitSet(b, offset)) {
+			return setBit(b, offset, 0);
+		} else {
+			return setBit(b, offset, 1);
+		}
+	}
+
 	private static String encode(byte[] pBytes) {
 		StringBuffer buffer = new StringBuffer();
 		for (int i = 0; i < pBytes.length; i++) {
-			if (pBytes[i] <= 9) {
-				buffer.append(pBytes[i]);
-			} else if (pBytes[i] <= 16) {
-				buffer.append((char) (pBytes[i] + 'b' - 10));
-			} else if (pBytes[i] <= 18) {
-				buffer.append((char) (pBytes[i] + 'j' - 17));
-			} else if (pBytes[i] <= 20) {
-				buffer.append((char) (pBytes[i] + 'j' - 19));
-			} else if (pBytes[i] <= 32) {
-				buffer.append((char) (pBytes[i] + 'p' - 21));
-			} else {
-				throw new IllegalArgumentException("Must not have a value greater than 32 in Base32 encoding!");
-			}
+			byte b = pBytes[i];
+			buffer.append(encodeByte(b));
 		}
 		return buffer.toString();
 	}
 
+	private static char encodeByte(byte b) {
+		if (b <= 9) {
+			return (char) (b + '0');
+		} else if (b <= 16) {
+			return (char) (b + 'b' - 10);
+		} else if (b <= 18) {
+			return (char) (b + 'j' - 17);
+		} else if (b <= 20) {
+			return (char) (b + 'm' - 19);
+		} else if (b <= 32) {
+			return (char) (b + 'p' - 21);
+		} else {
+			throw new IllegalArgumentException("Must not have a value greater than 32 in Base32 encoding!");
+		}
+	}
+
+	private static byte decodeByte(char c) {
+		if (c >= 'p') {
+			return (byte) (c - 'p' + 21);
+		} else if (c >= 'm') {
+			return (byte) (c - 'm' + 19);
+		} else if (c >= 'j') {
+			return (byte) (c - 'j' + 17);
+		} else if (c >= 'b') {
+			return (byte) (c - 'b' + 10);
+		} else if (c >= '0') {
+			return (byte) (c - '0' + 0);
+		}
+		return -1;
+	}
+
+	public static byte[] decode(String pGeohash) {
+		byte[] bytes = new byte[pGeohash.length()];
+
+		for (int i = 0; i < pGeohash.length(); i++) {
+			bytes[i] = decodeByte(pGeohash.charAt(i));
+		}
+
+		return bytes;
+	}
+
 	private static boolean getNextBit(double currentCellPosition, double currentCellSize) {
 	    double border = currentCellSize / 2.0;