src/tim/prune/gui/map/DiskTileCacher.java

   1 package tim.prune.gui.map;
   2
   3 import java.awt.Image;
   4 import java.awt.Toolkit;
   5 import java.awt.image.ImageObserver;
   6 import java.io.File;
   7 import java.io.FileOutputStream;
   8 import java.io.IOException;
   9 import java.io.InputStream;
  10 import java.net.URL;
  11 import java.net.URLConnection;
  12 import java.util.HashSet;
  13
  14 import tim.prune.GpsPrune;
  15
  16 /**
  17  * Class to control the reading and saving of map tiles
  18  * to a cache on disk
  19  */
  20 public class DiskTileCacher implements Runnable
  21 {
  22         /** URL to get image from */
  23         private URL _url = null;
  24         /** File to save image to */
  25         private File _file = null;
  26         /** Observer to be notified */
  27         private ImageObserver _observer = null;
  28         /** Time limit to cache images for */
  29         private static final long CACHE_TIME_LIMIT = 20 * 24 * 60 * 60 * 1000; // 20 days in ms
  30         /** Hashset of all blocked / 404 tiles to avoid requesting them again */
  31         private static final HashSet<String> BLOCKED_URLS = new HashSet<String>();
  32
  33         /**
  34          * Private constructor
  35          * @param inUrl URL to get
  36          * @param inFile file to save to
  37          */
  38         private DiskTileCacher(URL inUrl, File inFile, ImageObserver inObserver)
  39         {
  40                 _url = inUrl;
  41                 _file = inFile;
  42                 _observer = inObserver;
  43         }
  44
  45         /**
  46          * Get the specified tile from the disk cache
  47          * @param inBasePath base path to whole disk cache
  48          * @param inTilePath relative path to requested tile
  49          * @return tile image if available, or null if not there
  50          */
  51         public static MapTile getTile(String inBasePath, String inTilePath)
  52         {
  53                 if (inBasePath == null) {return null;}
  54                 File tileFile = new File(inBasePath, inTilePath);
  55                 Image image = null;
  56                 if (tileFile.exists() && tileFile.canRead() && tileFile.length() > 0)
  57                 {
  58                         long fileStamp = tileFile.lastModified();
  59                         boolean isExpired = ((System.currentTimeMillis()-fileStamp) > CACHE_TIME_LIMIT);
  60                         try
  61                         {
  62                                 image = Toolkit.getDefaultToolkit().createImage(tileFile.getAbsolutePath());
  63                                 return new MapTile(image, isExpired);
  64                         }
  65                         catch (Exception e) {
  66                                 System.err.println("createImage: " + e.getClass().getName() + " _ " + e.getMessage());
  67                         }
  68                 }
  69                 return null;
  70         }
  71
  72         /**
  73          * Save the specified image tile to disk
  74          * @param inUrl url to get image from
  75          * @param inBasePath base path to disk cache
  76          * @param inTilePath relative path to this tile
  77          * @param inObserver observer to inform when load complete
  78          */
  79         public static void saveTile(URL inUrl, String inBasePath, String inTilePath, ImageObserver inObserver)
  80         {
  81                 if (inBasePath == null || inTilePath == null) {return;}
  82                 // save file if possible
  83                 File basePath = new File(inBasePath);
  84                 if (!basePath.exists() || !basePath.isDirectory() || !basePath.canWrite()) {
  85                         // Can't write to base path
  86                         return;
  87                 }
  88                 File tileFile = new File(basePath, inTilePath);
  89                 // Check if this file is already being loaded
  90                 if (isBeingLoaded(tileFile)) {return;}
  91                 // Check if it has already failed
  92                 if (BLOCKED_URLS.contains(inUrl.toString())) {return;}
  93
  94                 File dir = tileFile.getParentFile();
  95                 // Start a new thread to load the image if necessary
  96                 if ((dir.exists() || dir.mkdirs()) && dir.canWrite())
  97                 {
  98                         new Thread(new DiskTileCacher(inUrl, tileFile, inObserver)).start();
  99                 }
 100         }
 101
 102         /**
 103          * Check whether the given tile is already being loaded
 104          * @param inFile desired file
 105          * @return true if temporary file with this name exists
 106          */
 107         private static boolean isBeingLoaded(File inFile)
 108         {
 109                 File tempFile = new File(inFile.getAbsolutePath() + ".temp");
 110                 if (!tempFile.exists()) {
 111                         return false;
 112                 }
 113                 // File exists, so check if it was created recently
 114                 final long fileAge = System.currentTimeMillis() - tempFile.lastModified();
 115                 return fileAge < 1000000L; // overwrite if the temp file is still there after 1000s
 116         }
 117
 118         /**
 119          * Run method for loading URL asynchronously and saving to file
 120          */
 121         public void run()
 122         {
 123                 boolean finished = false;
 124                 InputStream in = null;
 125                 FileOutputStream out = null;
 126                 File tempFile = new File(_file.getAbsolutePath() + ".temp");
 127                 // Use a synchronized block across all threads to make sure this url is only fetched once
 128                 synchronized (DiskTileCacher.class)
 129                 {
 130                         if (tempFile.exists()) {tempFile.delete();}
 131                         try {
 132                                 if (!tempFile.createNewFile()) {return;}
 133                         }
 134                         catch (Exception e) {return;}
 135                 }
 136                 try
 137                 {
 138                         // Open streams from URL and to file
 139                         out = new FileOutputStream(tempFile);
 140                         //System.out.println("Opening URL: " + _url.toString());
 141                         // Set http user agent on connection
 142                         URLConnection conn = _url.openConnection();
 143                         conn.setRequestProperty("User-Agent", "GpsPrune v" + GpsPrune.VERSION_NUMBER);
 144                         in = conn.getInputStream();
 145                         int d = 0;
 146                         // Loop over each byte in the stream (maybe buffering is more efficient?)
 147                         while ((d = in.read()) >= 0) {
 148                                 out.write(d);
 149                         }
 150                         finished = true;
 151                 } catch (IOException e) {
 152                         System.err.println("ioe: " + e.getClass().getName() + " - " + e.getMessage());
 153                         BLOCKED_URLS.add(_url.toString());
 154                 }
 155                 finally
 156                 {
 157                         // clean up files
 158                         try {in.close();} catch (Exception e) {} // ignore
 159                         try {out.close();} catch (Exception e) {} // ignore
 160                         if (!finished) {
 161                                 tempFile.delete();
 162                         }
 163                 }
 164                 // Move temp file to desired file location
 165                 if (tempFile.exists() && !tempFile.renameTo(_file))
 166                 {
 167                         // File couldn't be moved - delete both to be sure
 168                         tempFile.delete();
 169                         _file.delete();
 170                 }
 171                 // Tell parent that load is finished (parameters ignored)
 172                 _observer.imageUpdate(null, ImageObserver.ALLBITS, 0, 0, 0, 0);
 173         }
 174 }