src/tim/prune/function/srtm/SrtmSource.java

   1 package tim.prune.function.srtm;
   2
   3 import java.io.File;
   4 import java.io.FileInputStream;
   5 import java.io.FileOutputStream;
   6 import java.io.IOException;
   7 import java.util.zip.ZipEntry;
   8 import java.util.zip.ZipInputStream;
   9
  10 public abstract class SrtmSource {
  11         public abstract String getName();
  12         public abstract boolean isReadyToUse();
  13         public abstract boolean downloadTile(SrtmTile inTile)
  14                 throws SrtmSourceException;
  15         public abstract int getRowSize(SrtmTile inTile);
  16         protected abstract String getSourceExtension();
  17
  18         public int[] getTileHeights(SrtmTile inTile)
  19                 throws SrtmSourceException
  20         {
  21                 File cacheFileName = getCacheFileName(inTile);
  22                 if (cacheFileName == null)
  23                 {
  24                         throw new SrtmSourceException("Tile "+inTile.getTileName()+" not in cache");
  25                 }
  26                 try
  27                 {
  28                         ZipInputStream inStream = new ZipInputStream(new FileInputStream(cacheFileName));
  29                         ZipEntry entry = inStream.getNextEntry();
  30                         int rowSize = getRowSize(inTile);
  31                         int tileSize = rowSize * rowSize;
  32                         if (entry.getSize() != 2 * tileSize)
  33                         {
  34                                 throw new SrtmSourceException("Tile file "+cacheFileName+" does not have the expected size");
  35                         }
  36                         int[] heights = new int[tileSize];
  37                         // Read entire file contents into one byte array
  38                         for (int i = 0; i < heights.length; i++)
  39                         {
  40                                 heights[i] = inStream.read() * 256 + inStream.read();
  41                                 if (heights[i] >= 32768) {heights[i] -= 65536;}
  42                         }
  43                         // Close stream
  44                         inStream.close();
  45                         return heights;
  46                 }
  47                 catch (IOException e)
  48                 {
  49                         throw new SrtmSourceException("Failure opening "+cacheFileName+" for reading:"+e.getMessage());
  50                 }
  51
  52         }
  53
  54         protected File getCacheDir()
  55         {
  56                 return SrtmDiskCache.getCacheDir(getName());
  57         }
  58
  59         protected File getCacheFileName(SrtmTile inTile)
  60         {
  61                 String fileName = inTile.getTileName() + getSourceExtension();
  62                 return new File(getCacheDir(), fileName);
  63         }
  64
  65         public boolean isCached(SrtmTile inTile)
  66         {
  67                 return getCacheFileName(inTile).exists();
  68         }
  69 }