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.InputStream;
   7 import java.io.IOException;
   8 import java.util.zip.ZipEntry;
   9 import java.util.zip.ZipInputStream;
  10
  11 public abstract class SrtmSource {
  12         // methods implemented by each source
  13         public abstract String getName();
  14         public abstract boolean isReadyToUse();
  15         public abstract boolean downloadTile(SrtmTile inTile)
  16                 throws SrtmSourceException;
  17         public abstract int getRowSize(SrtmTile inTile);
  18         protected abstract String getSourceExtension();
  19
  20         protected boolean downloadToFile(InputStream inStream, File outputFile)
  21                 throws IOException
  22         {
  23                 FileOutputStream outStream = new FileOutputStream(outputFile);
  24
  25                 byte[] buffer = new byte[4096];
  26                 int read = 0;
  27                 while ((read = inStream.read(buffer)) != -1)
  28                 {
  29                         outStream.write(buffer, 0, read);
  30                 }
  31                 // Make sure streams are closed
  32                 try {inStream.close();} catch (Exception e) {}
  33                 try {outStream.close();} catch (Exception e) {}
  34                 return true;
  35
  36         }
  37
  38         protected int[] slurpTileHeigths(ZipInputStream inStream, int tileSize)
  39                 throws IOException
  40         {
  41                 int[] heights = new int[tileSize];
  42                 int dataSize = 2 * tileSize;
  43                 byte[] buffer = new byte[dataSize];
  44                 // Read entire file contents into one byte array
  45                 int alreadyRead = 0;
  46                 while (alreadyRead < dataSize)
  47                 {
  48                         alreadyRead += inStream.read(buffer, alreadyRead, dataSize - alreadyRead);
  49                 }
  50                 for (int i = 0; i < tileSize; i++)
  51                 {
  52                         // Bytes are signed. Cast high-order to int with sign
  53                         // extension, and clamp low-order to its unsigned range
  54                         heights[i] = buffer[2 * i] * 256 + (0xff & buffer[2 * i + 1]);
  55                 }
  56                 // Close stream
  57                 inStream.close();
  58                 return heights;
  59         }
  60
  61         public int[] getTileHeights(SrtmTile inTile)
  62                 throws SrtmSourceException
  63         {
  64                 File cacheFileName = getCacheFileName(inTile);
  65                 if (cacheFileName == null)
  66                 {
  67                         throw new SrtmSourceException("Tile "+inTile.getTileName()+" not in cache");
  68                 }
  69                 try
  70                 {
  71                         ZipInputStream inStream = new ZipInputStream(new FileInputStream(cacheFileName));
  72                         ZipEntry entry = inStream.getNextEntry();
  73                         int rowSize = getRowSize(inTile);
  74                         int tileSize = rowSize * rowSize;
  75                         if (entry.getSize() != 2 * tileSize)
  76                         {
  77                                 throw new SrtmSourceException("Tile file "+cacheFileName+" does not have the expected size");
  78                         }
  79                         return slurpTileHeigths(inStream, tileSize);
  80                 }
  81                 catch (IOException e)
  82                 {
  83                         throw new SrtmSourceException("Failure opening "+cacheFileName+" for reading:"+e.getMessage());
  84                 }
  85
  86         }
  87
  88         protected File getCacheDir()
  89         {
  90                 return SrtmDiskCache.getCacheDir(getName());
  91         }
  92
  93         protected File getCacheFileName(SrtmTile inTile)
  94         {
  95                 String fileName = inTile.getTileName() + getSourceExtension();
  96                 return new File(getCacheDir(), fileName);
  97         }
  98
  99         public boolean isCached(SrtmTile inTile)
 100         {
 101                 File cachedFileName = getCacheFileName(inTile);
 102                 return cachedFileName != null &&
 103                         getCacheFileName(inTile).exists();
 104         }
 105 }