work on partial piece persistence

core/src/main/groovy/com/muwire/core/download/DownloadSession.groovy

@@ -69,21 +69,22 @@ class DownloadSession {
         OutputStream os = endpoint.getOutputStream()
         InputStream is = endpoint.getInputStream()
 
-        int piece
+        int[] pieceAndPosition
         if (available.isEmpty())
-            piece = pieces.claim()
+            pieceAndPosition = pieces.claim()
         else
-            piece = pieces.claim(new HashSet<>(available))
-        if (piece == -1)
+            pieceAndPosition = pieces.claim(new HashSet<>(available))
+        if (pieceAndPosition == null)
             return false
+        int piece = pieceAndPosition[0]
+        int position = pieceAndPosition[1]
         boolean unclaim = true
 
-        log.info("will download piece $piece")
-
-        long start = piece * pieceSize
-        long end = Math.min(fileLength, start + pieceSize) - 1
-        long length = end - start + 1
+        log.info("will download piece $piece from position $position")
 
+        long pieceStart = piece * pieceSize
+        long end = Math.min(fileLength, pieceStart + pieceSize) - 1
+        long start = pieceStart + position
         String root = Base64.encode(infoHash.getRoot())
 
         try {
@@ -172,8 +173,9 @@ class DownloadSession {
             FileChannel channel
             try {
                 channel = Files.newByteChannel(file.toPath(), EnumSet.of(StandardOpenOption.READ, StandardOpenOption.WRITE,
-                        StandardOpenOption.SPARSE, StandardOpenOption.CREATE)) // TODO: double-check, maybe CREATE_NEW
-                mapped = channel.map(FileChannel.MapMode.READ_WRITE, start, end - start + 1)
+                        StandardOpenOption.SPARSE, StandardOpenOption.CREATE)) 
+                mapped = channel.map(FileChannel.MapMode.READ_WRITE, pieceStart, end - start + 1)
+                mapped.position(position)
 
                 byte[] tmp = new byte[0x1 << 13]
                 while(mapped.hasRemaining()) {
@@ -185,6 +187,7 @@ class DownloadSession {
                     synchronized(this) {
                         mapped.put(tmp, 0, read)
                         dataSinceLastRead += read
+                        pieces.markPartial(piece, mapped.position())
                     }
                 }
 
@@ -194,8 +197,10 @@ class DownloadSession {
                 byte [] hash = digest.digest()
                 byte [] expected = new byte[32]
                 System.arraycopy(infoHash.getHashList(), piece * 32, expected, 0, 32)
-                if (hash != expected)
+                if (hash != expected) {
+                    pieces.markPartial(piece, 0)
                     throw new BadHashException()
+                }
             } finally {
                 try { channel?.close() } catch (IOException ignore) {}
             }

core/src/main/groovy/com/muwire/core/download/Downloader.groovy

@@ -111,8 +111,14 @@ public class Downloader {
         if (!piecesFile.exists())
             return
         piecesFile.eachLine {
-            int piece = Integer.parseInt(it)
-            pieces.markDownloaded(piece)
+            String [] split = it.split(",")
+            int piece = Integer.parseInt(split[0])
+            if (split.length == 1)
+                pieces.markDownloaded(piece)
+            else {
+                int position = Integer.parseInt(split[1])
+                pieces.markPartial(piece, position)
+            }
         }
     }
 
@@ -121,9 +127,7 @@ public class Downloader {
             if (piecesFileClosed)
                 return
             piecesFile.withPrintWriter { writer ->
-                pieces.getDownloaded().each { piece ->
-                    writer.println(piece)
-                }
+                pieces.write(writer)
             }
         }
     }

core/src/main/groovy/com/muwire/core/download/Pieces.groovy

@@ -5,6 +5,7 @@ class Pieces {
     private final int nPieces
     private final float ratio
     private final Random random = new Random()
+    private final Map<Integer,Integer> partials = new HashMap<>()
 
     Pieces(int nPieces) {
         this(nPieces, 1.0f)
@@ -17,16 +18,16 @@ class Pieces {
         claimed = new BitSet(nPieces)
     }
 
-    synchronized int claim() {
+    synchronized int[] claim() {
         int claimedCardinality = claimed.cardinality()
         if (claimedCardinality == nPieces)
-            return -1
+            return null
 
         // if fuller than ratio just do sequential
         if ( (1.0f * claimedCardinality) / nPieces > ratio) {
             int rv = claimed.nextClearBit(0)
             claimed.set(rv)
-            return rv
+            return [rv, partials.getOrDefault(rv, 0)]
         }
 
         while(true) {
@@ -34,11 +35,11 @@ class Pieces {
             if (claimed.get(start))
                 continue
             claimed.set(start)
-            return start
+            return [start, partials.getOrDefault(start,0)]
         }
     }
 
-    synchronized int claim(Set<Integer> available) {
+    synchronized int[] claim(Set<Integer> available) {
         for (int i = claimed.nextSetBit(0); i >= 0; i = claimed.nextSetBit(i+1))
             available.remove(i)
         if (available.isEmpty())
@@ -47,7 +48,7 @@ class Pieces {
         Collections.shuffle(toList)
         int rv = toList[0]
         claimed.set(rv)
-        rv
+        [rv, partials.getOrDefault(rv, 0)]
     }
 
     synchronized def getDownloaded() {
@@ -61,6 +62,11 @@ class Pieces {
     synchronized void markDownloaded(int piece) {
         done.set(piece)
         claimed.set(piece)
+        partials.remove(piece)
+    }
+    
+    synchronized void markPartial(int piece, int position) {
+        partials.put(piece, position)
     }
 
     synchronized void unclaim(int piece) {
@@ -82,5 +88,15 @@ class Pieces {
     synchronized void clearAll() {
         done.clear()
         claimed.clear()
+        partials.clear()
+    }
+    
+    synchronized void write(PrintWriter writer) {
+        for (int i = done.nextSetBit(0); i >= 0; i = done.nextSetBit(i+1)) {
+            writer.println(i)
+        }
+        partials.each { piece, position ->
+            writer.println("$piece,$position")
+        }
     }
 }