try a thing

Author: tpietzsch

src/main/java/org/janelia/saalfeldlab/n5/ChannelLock.java

@@ -29,6 +29,10 @@ public void close() throws IOException {
 		channel.close();
 	}
 
+	FileChannel getChannel() {
+		return channel;
+	}
+
 	/**
 	 * Create a {@link FileChannel} on the given {@code path} and lock it with a
 	 * system-level {@link FileLock}. If there is an existing overlapping file

src/main/java/org/janelia/saalfeldlab/n5/KeyLockState.java

@@ -76,7 +76,10 @@ LockedFileChannel acquireRead() throws IOException {
 				// We have a FileChannel.
 				// Create a LockedFileChannel that will releaseRead() when it is closed.
 				++numReaders;
-				return new LockedFileChannel(channel, this::releaseRead);
+				return new LockedFileChannel(channel, () -> {
+					channel.close();
+					releaseRead();
+				});
 			} finally {
 				readerMutex.release();
 			}
@@ -177,23 +180,8 @@ LockedFileChannel acquireWrite() throws IOException {
 			}
 
 			// We have a WRITE ChannelLock.
-			// Try to open a FileChannel.
-			final FileChannel channel;
-			try {
-				channel = FileChannel.open(path, StandardOpenOption.READ, StandardOpenOption.WRITE, StandardOpenOption.CREATE);
-			} catch (IOException e) {
-				// Something went wrong. Back off.
-				try {
-					channelLock.close();
-				} finally {
-					channelLockMutex.release();
-				}
-				throw e;
-			}
-
-			// We have a FileChannel.
 			// Create a LockedFileChannel that will releaseWrite() when it is closed.
-			return new LockedFileChannel(channel, this::releaseWrite);
+			return new LockedFileChannel(channelLock.getChannel(), this::releaseWrite);
 		} catch (InterruptedException e) {
 			throw new IOException(e);
 		}
@@ -214,22 +202,8 @@ LockedFileChannel tryAcquireWrite() {
 		}
 
 		// We have a WRITE ChannelLock.
-		// Try to open a FileChannel.
-		final FileChannel channel;
-		try {
-			channel = FileChannel.open(path, StandardOpenOption.READ, StandardOpenOption.WRITE, StandardOpenOption.CREATE);
-		} catch (IOException e) {
-			// Something went wrong. Back off.
-			try {
-				releaseChannelLock();
-			} catch (IOException ignored) {
-			}
-			return null;
-		}
-
-		// We have a FileChannel.
 		// Create a LockedFileChannel that will releaseWrite() when it is closed.
-		return new LockedFileChannel(channel, this::releaseWrite);
+		return new LockedFileChannel(channelLock.getChannel(), this::releaseWrite);
 	}
 
 	void releaseWrite() throws IOException {

src/main/java/org/janelia/saalfeldlab/n5/LockedFileChannel.java

@@ -1,6 +1,10 @@
 package org.janelia.saalfeldlab.n5;
 
-import java.io.*;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.OutputStream;
+import java.io.Reader;
+import java.io.Writer;
 import java.nio.channels.Channels;
 import java.nio.channels.FileChannel;
 import java.nio.charset.StandardCharsets;
@@ -11,7 +15,7 @@
 // TODO: This only has to be public because of a test in another package. Fix that
 public class LockedFileChannel implements LockedChannel {
 
-    private final FileChannel channel;
+	private final FileChannel channel;
 	private ReleaseLock releaseLock;
 
 	@FunctionalInterface
@@ -27,50 +31,49 @@ public interface ReleaseLock {
 	}
 
 	@Override
-    public Reader newReader() throws N5Exception.N5IOException {
+	public Reader newReader() throws N5Exception.N5IOException {
 
-        return Channels.newReader(channel, StandardCharsets.UTF_8.name());
-    }
+		return Channels.newReader(channel, StandardCharsets.UTF_8.name());
+	}
 
-    @Override
-    public InputStream newInputStream() throws N5Exception.N5IOException {
+	@Override
+	public InputStream newInputStream() throws N5Exception.N5IOException {
 
-        return Channels.newInputStream(channel);
-    }
+		return Channels.newInputStream(channel);
+	}
 
-    @Override
-    public Writer newWriter() throws N5Exception.N5IOException {
+	@Override
+	public Writer newWriter() throws N5Exception.N5IOException {
 
-        truncateChannel();
-        return Channels.newWriter(channel, StandardCharsets.UTF_8.name());
-    }
+		truncateChannel();
+		return Channels.newWriter(channel, StandardCharsets.UTF_8.name());
+	}
 
-    @Override
-    public OutputStream newOutputStream() throws N5Exception.N5IOException {
+	@Override
+	public OutputStream newOutputStream() throws N5Exception.N5IOException {
 
-        truncateChannel();
-        return Channels.newOutputStream(channel);
-    }
+		truncateChannel();
+		return Channels.newOutputStream(channel);
+	}
 
 	// TODO: This only has to be public because of a test in another package. Fix that
-    public FileChannel getFileChannel() {
+	public FileChannel getFileChannel() {
 
-        return channel;
-    }
+		return channel;
+	}
 
-    private void truncateChannel() throws N5Exception.N5IOException {
+	private void truncateChannel() throws N5Exception.N5IOException {
 
-        try {
-            channel.truncate(0);
-        } catch (final IOException e) {
-            throw new N5Exception.N5IOException("Failed to truncate channel", e);
-        }
-    }
+		try {
+			channel.truncate(0);
+		} catch (final IOException e) {
+			throw new N5Exception.N5IOException("Failed to truncate channel", e);
+		}
+	}
 
-    @Override
-    public void close() throws IOException {
+	@Override
+	public void close() throws IOException {
 
-		channel.close();
 		if (releaseLock != null) {
 			releaseLock.release();
 			releaseLock = null;