Version 20, March 2020

[GpsPrune.git] / src / tim / prune / function / olc / OlcDecoder.java

diff --git a/src/tim/prune/function/olc/OlcDecoder.java b/src/tim/prune/function/olc/OlcDecoder.java
new file mode 100644 (file)
index 0000000..122f6fe
--- /dev/null
+++ b/src/tim/prune/function/olc/OlcDecoder.java
@@ -0,0 +1,101 @@
+package tim.prune.function.olc;
+
+
+/**
+ * Decoder of OLC (Open Location Code) strings
+ */
+public class OlcDecoder
+{
+       /**
+        * Decode the given String into an OlcArea object
+        * @param inCode code representing an OLC
+        * @return an OlcArea object, or null if parsing failed
+        */
+       public static OlcArea decode(String inCode)
+       {
+               if (inCode == null || inCode.length() < 8) {
+                       return null;
+               }
+               String code = inCode.trim().toUpperCase();
+               if (code.length() < 8 || code.length() > 12) {
+                       return null;
+               }
+               double lat = 0.0, lon = 0.0;
+               double resolution = 400.0;
+               int charPos = 0;
+               int numSteps = 0;
+               boolean amPadding = false;
+               try
+               {
+                       while (charPos < inCode.length())
+                       {
+                               if (charPos == 0 || charPos == 2 || charPos == 4 || charPos == 6 || charPos == 9)
+                               {
+                                       // take next two characters, make pair, position += 2
+                                       CoordPair pair = CoordPair.decode(code.charAt(charPos), code.charAt(charPos+1));
+                                       if (pair == CoordPair.PADDING) {
+                                               amPadding = true;
+                                       }
+                                       else if (amPadding)
+                                       {
+                                               return null;
+                                       }
+                                       else
+                                       {
+                                               // Add to current lat, lon
+                                               lat += (pair.lat * resolution);
+                                               lon += (pair.lon * resolution);
+                                               numSteps++;
+                                               resolution /= 20.0;
+                                       }
+                                       charPos += 2;
+                               }
+                               else if (charPos == 8)
+                               {
+                                       if (code.charAt(charPos) != '+')
+                                       {
+                                               return null;
+                                       }
+                                       charPos += 1;
+                               }
+                               else if (charPos == 11)
+                               {
+                                       // take next character, make pair
+                                       CoordPair pair = CoordPair.decode(code.charAt(charPos));
+                                       // Add to current lat, lon
+                                       lat += (pair.lat * resolution);
+                                       lon += (pair.lon * resolution);
+                                       charPos += 1;
+                                       numSteps++;
+                                       resolution /= 20.0;
+                               }
+                               else
+                               {
+                                       return null;
+                               }
+                       }
+
+                       // Make OlcArea object and return it
+                       if (numSteps < 1)
+                       {
+                               return null;
+                       }
+                       else if (numSteps < 6)
+                       {
+                               // make four points
+                               lat -= 90.0;
+                               lon -= 180.0;
+                               return new OlcArea(lat, lon, lat+resolution, lon+resolution);
+                       }
+                       else
+                       {
+                               // make single point:
+                               lat -= 90.0;
+                               lon -= 180.0;
+                               return new OlcArea(lat, lon, lat+resolution*2.5, lon+resolution*2.0);
+                       }
+               }
+               catch (ParseException e) {}
+               return null;
+       }
+}
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