Working in a more robust implementation of fetchMagnet, still with a …

…multithreading errors.

src/main/java/com/frostwire/jlibtorrent/Downloader.java

@@ -17,6 +17,8 @@
  */
 public final class Downloader {
 
+    private static final Logger LOG = Logger.getLogger(Downloader.class);
+
     private static final int[] LISTENER_TYPES = new int[]{AlertType.METADATA_RECEIVED.getSwig()};
 
     private final Session s;
@@ -60,8 +62,6 @@ public void download(TorrentInfo ti, File saveDir) {
     }
 
     /**
-     * This method is not thread safe.
-     *
      * @param uri
      * @param timeout in milliseconds
      * @return
@@ -77,11 +77,10 @@ public byte[] fetchMagnet(String uri, long timeout) {
 
         final sha1_hash info_hash = p.getInfo_hash();
 
-        torrent_handle th = s.getSwig().find_torrent(info_hash);
-
         boolean add = true;
 
-        if (th != null && th.is_valid()) {
+        torrent_handle th = null;//s.getSwig().find_torrent(info_hash);
+        /*if (th != null && th.is_valid()) {
             // we have a download with the same info-hash, let's see if we have the torrent info
             torrent_info ti = th.get_torrent_copy();
             if (ti != null && ti.is_valid()) {
@@ -90,9 +89,10 @@ public byte[] fetchMagnet(String uri, long timeout) {
             } else {
                 add = false;
             }
-        }
+        }*/
 
         final CountDownLatch signal = new CountDownLatch(1);
+        final byte[][] data = new byte[1][];
 
         AlertListener l = new AlertListener() {
             @Override
@@ -102,13 +102,24 @@ public int[] types() {
 
             @Override
             public void alert(Alert<?> alert) {
-                if (!(alert instanceof MetadataReceivedAlert)) {
-                    return;
-                }
-
-                MetadataReceivedAlert mr = (MetadataReceivedAlert) alert;
-
-                if (mr.getSwig().getHandle().info_hash().op_eq(info_hash)) {
+                try {
+                    if (!(alert instanceof MetadataReceivedAlert)) {
+                        return;
+                    }
+
+                    MetadataReceivedAlert mr = (MetadataReceivedAlert) alert;
+                    torrent_handle th = mr.getHandle().getSwig();
+
+                    if (th.info_hash().op_eq(info_hash)) {
+                        try {
+                            data[0] = new TorrentInfo(th.get_torrent_copy()).bencode();
+                        } catch (Throwable e) {
+                            LOG.error("Error encoding torrent info", e);
+                        }
+                        signal.countDown();
+                    }
+                } catch (Throwable e) {
+                    LOG.error("Error in fetch magnet internal listener", e);
                     signal.countDown();
                 }
             }
@@ -117,7 +128,8 @@ public void alert(Alert<?> alert) {
         s.addListener(l);
 
         if (add) {
-            p.setName("fetchMagnet - " + uri);
+            p.setName("fetch_magnet:" + uri);
+            p.setSave_path("fetch_magnet/" + uri);
 
             long flags = p.get_flags();
             flags &= ~add_torrent_params.flags_t.flag_auto_managed.swigValue();
@@ -135,21 +147,10 @@ public void alert(Alert<?> alert) {
 
         s.removeListener(l);
 
-        try {
-            th = s.getSwig().find_torrent(info_hash);
-            if (th != null && th.is_valid()) {
-                // we have a download with the same info-hash, let's see if we have the torrent info
-                torrent_info ti = th.get_torrent_copy();
-                if (ti != null && ti.is_valid()) {
-                    // ok. we have it, ready to return the data
-                    return new TorrentInfo(th.get_torrent_copy()).bencode();
-                }
-            }
-
-        } finally {
+        if (add && th != null && th.is_valid()) {
             s.getSwig().remove_torrent(th);
         }
 
-        return null;
+        return data[0];
     }
 }

src/test/java/com/frostwire/jlibtorrent/demo/GetMagnet2.java

@@ -0,0 +1,97 @@
+package com.frostwire.jlibtorrent.demo;
+
+import com.frostwire.jlibtorrent.AlertListener;
+import com.frostwire.jlibtorrent.Downloader;
+import com.frostwire.jlibtorrent.Entry;
+import com.frostwire.jlibtorrent.Session;
+import com.frostwire.jlibtorrent.alerts.Alert;
+import com.frostwire.jlibtorrent.alerts.AlertType;
+import com.frostwire.jlibtorrent.alerts.DhtStatsAlert;
+
+import java.util.concurrent.CountDownLatch;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicInteger;
+
+/**
+ * @author gubatron
+ * @author aldenml
+ */
+public final class GetMagnet2 {
+
+    public static void main(String[] args) throws Throwable {
+
+        final String uri = "magnet:?xt=urn:btih:a83cc13bf4a07e85b938dcf06aa707955687ca7c";
+
+        final Session s = new Session();
+
+        final CountDownLatch signal = new CountDownLatch(1);
+
+        // the session stats are posted about once per second.
+        AlertListener l = new AlertListener() {
+            @Override
+            public int[] types() {
+                return new int[]{AlertType.SESSION_STATS.getSwig(), AlertType.DHT_STATS.getSwig()};
+            }
+
+            @Override
+            public void alert(Alert<?> alert) {
+                if (alert.getType().equals(AlertType.SESSION_STATS)) {
+                    s.postDHTStats();
+                }
+
+                if (alert.getType().equals(AlertType.DHT_STATS)) {
+
+                    long nodes = ((DhtStatsAlert) alert).totalNodes();
+                    // wait for at least 10 nodes in the DHT.
+                    if (nodes >= 10) {
+                        System.out.println("DHT contains " + nodes + " nodes");
+                        signal.countDown();
+                    }
+                }
+            }
+        };
+
+        s.addListener(l);
+        s.postDHTStats();
+
+        final Downloader d = new Downloader(s);
+
+        System.out.println("Waiting for nodes in DHT (10 seconds)...");
+        boolean r = signal.await(10, TimeUnit.SECONDS);
+        if (!r) {
+            System.out.println("DHT bootstrap timeout");
+            System.exit(0);
+        }
+
+        // no more trigger of DHT stats
+        s.removeListener(l);
+
+        System.out.println("Fetching the magnet uri (multi thread), please wait...");
+
+        final AtomicInteger counter = new AtomicInteger(0);
+        for (int i = 0; i < 3; i++) {
+            final int index = i;
+            Thread t = new Thread() {
+                @Override
+                public void run() {
+                    byte[] data = d.fetchMagnet(uri, 30000);
+
+                    int count = counter.incrementAndGet();
+                    if (data != null) {
+                        System.out.println("Success fetching magnet: " + index + "/" + count);
+                    } else {
+                        System.out.println("Failed to retrieve the magnet: " + index + "/" + count);
+                    }
+                }
+            };
+
+            t.start();
+            //t.join();
+        }
+
+        System.out.println("Press ENTER to exit");
+        System.in.read();
+
+        s.abort();
+    }
+}