close the file before marking pieces complete

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

@@ -66,6 +66,8 @@ class DownloadSession {
         int piece
         while(true) {
             piece = downloaded.getRandomPiece()
+            if (piece == -1)
+                return false
             if (claimed.isMarked(piece)) {
                 if (downloaded.donePieces() + claimed.donePieces() == downloaded.nPieces) {
                     log.info("all pieces claimed")
@@ -85,7 +87,6 @@ class DownloadSession {
         
         String root = Base64.encode(infoHash.getRoot())
                 
-        FileChannel channel
         try {
             os.write("GET $root\r\n".getBytes(StandardCharsets.US_ASCII))
             os.write("Range: $start-$end\r\n".getBytes(StandardCharsets.US_ASCII))
@@ -135,6 +136,8 @@ class DownloadSession {
             }
             
             // start the download
+            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)
@@ -165,11 +168,12 @@ class DownloadSession {
                 System.arraycopy(infoHash.getHashList(), piece * 32, expected, 0, 32)
                 if (hash != expected)
                     throw new BadHashException()
-            
+            } finally {
+                try { channel?.close() } catch (IOException ignore) {}
+            }
             downloaded.markDownloaded(piece)
         } finally {
             claimed.clear(piece)
-            try { channel?.close() } catch (IOException ignore) {}
         }
         return true
     }