src/tim/prune/function/olc/OlcDecoder.java

   1 package tim.prune.function.olc;
   2
   3
   4 /**
   5  * Decoder of OLC (Open Location Code) strings
   6  */
   7 public class OlcDecoder
   8 {
   9         /**
  10          * Decode the given String into an OlcArea object
  11          * @param inCode code representing an OLC
  12          * @return an OlcArea object, or null if parsing failed
  13          */
  14         public static OlcArea decode(String inCode)
  15         {
  16                 if (inCode == null || inCode.length() < 8) {
  17                         return null;
  18                 }
  19                 String code = inCode.trim().toUpperCase();
  20                 if (code.length() < 8 || code.length() > 12) {
  21                         return null;
  22                 }
  23                 double lat = 0.0, lon = 0.0;
  24                 double resolution = 400.0;
  25                 int charPos = 0;
  26                 int numSteps = 0;
  27                 boolean amPadding = false;
  28                 try
  29                 {
  30                         while (charPos < inCode.length())
  31                         {
  32                                 if (charPos == 0 || charPos == 2 || charPos == 4 || charPos == 6 || charPos == 9)
  33                                 {
  34                                         // take next two characters, make pair, position += 2
  35                                         CoordPair pair = CoordPair.decode(code.charAt(charPos), code.charAt(charPos+1));
  36                                         if (pair == CoordPair.PADDING) {
  37                                                 amPadding = true;
  38                                         }
  39                                         else if (amPadding)
  40                                         {
  41                                                 return null;
  42                                         }
  43                                         else
  44                                         {
  45                                                 // Add to current lat, lon
  46                                                 lat += (pair.lat * resolution);
  47                                                 lon += (pair.lon * resolution);
  48                                                 numSteps++;
  49                                                 resolution /= 20.0;
  50                                         }
  51                                         charPos += 2;
  52                                 }
  53                                 else if (charPos == 8)
  54                                 {
  55                                         if (code.charAt(charPos) != '+')
  56                                         {
  57                                                 return null;
  58                                         }
  59                                         charPos += 1;
  60                                 }
  61                                 else if (charPos == 11)
  62                                 {
  63                                         // take next character, make pair
  64                                         CoordPair pair = CoordPair.decode(code.charAt(charPos));
  65                                         // Add to current lat, lon
  66                                         lat += (pair.lat * resolution);
  67                                         lon += (pair.lon * resolution);
  68                                         charPos += 1;
  69                                         numSteps++;
  70                                         resolution /= 20.0;
  71                                 }
  72                                 else
  73                                 {
  74                                         return null;
  75                                 }
  76                         }
  77
  78                         // Make OlcArea object and return it
  79                         if (numSteps < 1)
  80                         {
  81                                 return null;
  82                         }
  83                         else if (numSteps < 6)
  84                         {
  85                                 // make four points
  86                                 lat -= 90.0;
  87                                 lon -= 180.0;
  88                                 return new OlcArea(lat, lon, lat+resolution, lon+resolution);
  89                         }
  90                         else
  91                         {
  92                                 // make single point:
  93                                 lat -= 90.0;
  94                                 lon -= 180.0;
  95                                 return new OlcArea(lat, lon, lat+resolution*2.5, lon+resolution*2.0);
  96                         }
  97                 }
  98                 catch (ParseException e) {}
  99                 return null;
 100         }
 101 }