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          * @param inCheckAge true to check age of file, false to ignore
  50          * @return tile image if available, or null if not there
  51          */
  52         public static Image getTile(String inBasePath, String inTilePath, boolean inCheckAge)
  53         {
  54                 if (inBasePath == null) {return null;}
  55                 File tileFile = new File(inBasePath, inTilePath);
  56                 Image image = null;
  57                 if (tileFile.exists() && tileFile.canRead() && tileFile.length() > 0)
  58                 {
  59                         long fileStamp = tileFile.lastModified();
  60                         if (!inCheckAge || ((System.currentTimeMillis()-fileStamp) < CACHE_TIME_LIMIT))
  61                         {
  62                                 try {
  63                                         image = Toolkit.getDefaultToolkit().createImage(tileFile.getAbsolutePath());
  64                                 }
  65                                 catch (Exception e) {
  66                                         System.err.println("createImage: " + e.getClass().getName() + " _ " + e.getMessage());
  67                                 }
  68                         }
  69                 }
  70                 return image;
  71         }
  72
  73         /**
  74          * Save the specified image tile to disk
  75          * @param inUrl url to get image from
  76          * @param inBasePath base path to disk cache
  77          * @param inTilePath relative path to this tile
  78          * @param inObserver observer to inform when load complete
  79          * @return true if successful, false for failure
  80          */
  81         public static boolean saveTile(URL inUrl, String inBasePath, String inTilePath, ImageObserver inObserver)
  82         {
  83                 if (inBasePath == null || inTilePath == null) {return false;}
  84                 // save file if possible
  85                 File basePath = new File(inBasePath);
  86                 if (!basePath.exists() || !basePath.isDirectory() || !basePath.canWrite()) {
  87                         // Can't write to base path
  88                         return false;
  89                 }
  90                 File tileFile = new File(basePath, inTilePath);
  91                 // Check if this file is already being loaded
  92                 if (isBeingLoaded(tileFile)) {return true;}
  93                 // Check if it has already failed
  94                 if (BLOCKED_URLS.contains(inUrl.toString())) {return true;}
  95
  96                 File dir = tileFile.getParentFile();
  97                 // Start a new thread to load the image if necessary
  98                 if ((dir.exists() || dir.mkdirs()) && dir.canWrite())
  99                 {
 100                         new Thread(new DiskTileCacher(inUrl, tileFile, inObserver)).start();
 101                         return true;
 102                 }
 103                 return false; // couldn't write the file
 104         }
 105
 106         /**
 107          * Check whether the given tile is already being loaded
 108          * @param inFile desired file
 109          * @return true if temporary file with this name exists
 110          */
 111         private static boolean isBeingLoaded(File inFile)
 112         {
 113                 File tempFile = new File(inFile.getAbsolutePath() + ".temp");
 114                 if (!tempFile.exists()) {
 115                         return false;
 116                 }
 117                 // File exists, so check if it was created recently
 118                 final long fileAge = System.currentTimeMillis() - tempFile.lastModified();
 119                 return fileAge < 1000000L; // overwrite if the temp file is still there after 1000s
 120         }
 121
 122         /**
 123          * Run method for loading URL asynchronously and saving to file
 124          */
 125         public void run()
 126         {
 127                 boolean finished = false;
 128                 InputStream in = null;
 129                 FileOutputStream out = null;
 130                 File tempFile = new File(_file.getAbsolutePath() + ".temp");
 131                 // Use a synchronized block across all threads to make sure this url is only fetched once
 132                 synchronized (DiskTileCacher.class)
 133                 {
 134                         if (tempFile.exists()) {tempFile.delete();}
 135                         try {
 136                                 if (!tempFile.createNewFile()) {return;}
 137                         }
 138                         catch (Exception e) {return;}
 139                 }
 140                 try
 141                 {
 142                         // Open streams from URL and to file
 143                         out = new FileOutputStream(tempFile);
 144                         // Set http user agent on connection
 145                         URLConnection conn = _url.openConnection();
 146                         conn.setRequestProperty("User-Agent", "GpsPrune v" + GpsPrune.VERSION_NUMBER);
 147                         in = conn.getInputStream();
 148                         int d = 0;
 149                         // Loop over each byte in the stream (maybe buffering is more efficient?)
 150                         while ((d = in.read()) >= 0) {
 151                                 out.write(d);
 152                         }
 153                         finished = true;
 154                 } catch (IOException e) {
 155                         System.err.println("ioe: " + e.getClass().getName() + " - " + e.getMessage());
 156                         BLOCKED_URLS.add(_url.toString());
 157                 }
 158                 finally
 159                 {
 160                         // clean up files
 161                         try {in.close();} catch (Exception e) {} // ignore
 162                         try {out.close();} catch (Exception e) {} // ignore
 163                         if (!finished) {
 164                                 tempFile.delete();
 165                         }
 166                 }
 167                 // Move temp file to desired file location
 168                 if (!tempFile.renameTo(_file))
 169                 {
 170                         // File couldn't be moved - delete both to be sure
 171                         tempFile.delete();
 172                         _file.delete();
 173                 }
 174                 // Tell parent that load is finished (parameters ignored)
 175                 _observer.imageUpdate(null, ImageObserver.ALLBITS, 0, 0, 0, 0);
 176         }
 177 }