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         protected int[] slurpTileHeigths(ZipInputStream inStream, int tileSize)
  19                 throws IOException
  20         {
  21                 int[] heights = new int[tileSize];
  22                 // Read entire file contents into one byte array
  23                 for (int i = 0; i < heights.length; i++)
  24                 {
  25                         heights[i] = inStream.read() * 256 + inStream.read();
  26                         if (heights[i] >= 32768) {heights[i] -= 65536;}
  27                 }
  28                 // Close stream
  29                 inStream.close();
  30                 return heights;
  31         }
  32
  33         public int[] getTileHeights(SrtmTile inTile)
  34                 throws SrtmSourceException
  35         {
  36                 File cacheFileName = getCacheFileName(inTile);
  37                 if (cacheFileName == null)
  38                 {
  39                         throw new SrtmSourceException("Tile "+inTile.getTileName()+" not in cache");
  40                 }
  41                 try
  42                 {
  43                         ZipInputStream inStream = new ZipInputStream(new FileInputStream(cacheFileName));
  44                         ZipEntry entry = inStream.getNextEntry();
  45                         int rowSize = getRowSize(inTile);
  46                         int tileSize = rowSize * rowSize;
  47                         if (entry.getSize() != 2 * tileSize)
  48                         {
  49                                 throw new SrtmSourceException("Tile file "+cacheFileName+" does not have the expected size");
  50                         }
  51                         return slurpTileHeigths(inStream, tileSize);
  52                 }
  53                 catch (IOException e)
  54                 {
  55                         throw new SrtmSourceException("Failure opening "+cacheFileName+" for reading:"+e.getMessage());
  56                 }
  57
  58         }
  59
  60         protected File getCacheDir()
  61         {
  62                 return SrtmDiskCache.getCacheDir(getName());
  63         }
  64
  65         protected File getCacheFileName(SrtmTile inTile)
  66         {
  67                 String fileName = inTile.getTileName() + getSourceExtension();
  68                 return new File(getCacheDir(), fileName);
  69         }
  70
  71         public boolean isCached(SrtmTile inTile)
  72         {
  73                 File cachedFileName = getCacheFileName(inTile);
  74                 return cachedFileName != null &&
  75                         getCacheFileName(inTile).exists();
  76         }
  77 }