X-Git-Url: http://gitweb.fperrin.net/?a=blobdiff_plain;f=src%2Ftim%2Fprune%2Ffunction%2Fsrtm%2FSrtmSource.java;h=44ceccfab52a13a5ced20108ad539cafbf2c6fb2;hb=8f45a9f2289e01d4f6eee6036f7fc3c4a92e3024;hp=5651a3f314656b155e979056ba1deafd0a6cb671;hpb=94113b9f5f037cd56c07cca5f69f7f56620d84ef;p=GpsPrune.git

diff --git a/src/tim/prune/function/srtm/SrtmSource.java b/src/tim/prune/function/srtm/SrtmSource.java
index 5651a3f..44ceccf 100644
--- a/src/tim/prune/function/srtm/SrtmSource.java
+++ b/src/tim/prune/function/srtm/SrtmSource.java
@@ -15,6 +15,29 @@ public abstract class SrtmSource {
 	public abstract int getRowSize(SrtmTile inTile);
 	protected abstract String getSourceExtension();
 
+	protected int[] slurpTileHeigths(ZipInputStream inStream, int tileSize)
+		throws IOException
+	{
+		int[] heights = new int[tileSize];
+		int dataSize = 2 * tileSize;
+		byte[] buffer = new byte[dataSize];
+		// Read entire file contents into one byte array
+		int alreadyRead = 0;
+		while (alreadyRead < dataSize)
+		{
+			alreadyRead += inStream.read(buffer, alreadyRead, dataSize - alreadyRead);
+		}
+		for (int i = 0; i < tileSize; i++)
+		{
+			// Bytes are signed. Cast high-order to int with sign
+			// extension, and clamp low-order to its unsigned range
+			heights[i] = buffer[2 * i] * 256 + (0xff & buffer[2 * i + 1]);
+		}
+		// Close stream
+		inStream.close();
+		return heights;
+	}
+
 	public int[] getTileHeights(SrtmTile inTile)
 		throws SrtmSourceException
 	{
@@ -33,16 +56,7 @@ public abstract class SrtmSource {
 			{
 				throw new SrtmSourceException("Tile file "+cacheFileName+" does not have the expected size");
 			}
-			int[] heights = new int[tileSize];
-			// Read entire file contents into one byte array
-			for (int i = 0; i < heights.length; i++)
-			{
-				heights[i] = inStream.read() * 256 + inStream.read();
-				if (heights[i] >= 32768) {heights[i] -= 65536;}
-			}
-			// Close stream
-			inStream.close();
-			return heights;
+			return slurpTileHeigths(inStream, tileSize);
 		}
 		catch (IOException e)
 		{
@@ -64,6 +78,8 @@ public abstract class SrtmSource {
 
 	public boolean isCached(SrtmTile inTile)
 	{
-		return getCacheFileName(inTile).exists();
+		File cachedFileName = getCacheFileName(inTile);
+		return cachedFileName != null &&
+			getCacheFileName(inTile).exists();
 	}
 }