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Java 1.8+ Library with tons of utility classes required in all projects
/*
* Copyright (C) 2014-2022 Philip Helger (www.helger.com)
* philip[at]helger[dot]com
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.helger.commons.io.channel;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.Channel;
import java.nio.channels.FileLock;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.WritableByteChannel;
import javax.annotation.Nonnegative;
import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.annotation.WillNotClose;
import javax.annotation.concurrent.Immutable;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.helger.commons.ValueEnforcer;
import com.helger.commons.annotation.PresentForCodeCoverage;
import com.helger.commons.exception.mock.IMockException;
import com.helger.commons.io.stream.StreamHelper;
import com.helger.commons.state.ESuccess;
/**
* Some very basic NIO channel utility stuff.
*
* @author Philip Helger
*/
@Immutable
public final class ChannelHelper
{
/** The logger to use. */
private static final Logger LOGGER = LoggerFactory.getLogger (ChannelHelper.class);
// Use version 1 as it seems to be faster
private static final boolean USE_COPY_V1 = true;
@PresentForCodeCoverage
private static final ChannelHelper INSTANCE = new ChannelHelper ();
private ChannelHelper ()
{}
/**
* Copy all content from the source channel to the destination channel.
*
* @param aSrc
* Source channel. May not be null. Is not closed after
* the operation.
* @param aDest
* Destination channel. May not be null. Is not closed
* after the operation.
* @return The number of bytes written.
* @throws IOException
* In case of IO error
*/
@Nonnegative
public static long channelCopy (@Nonnull @WillNotClose final ReadableByteChannel aSrc,
@Nonnull @WillNotClose final WritableByteChannel aDest) throws IOException
{
ValueEnforcer.notNull (aSrc, "SourceChannel");
ValueEnforcer.isTrue (aSrc.isOpen (), "SourceChannel is not open!");
ValueEnforcer.notNull (aDest, "DestinationChannel");
ValueEnforcer.isTrue (aDest.isOpen (), "DestinationChannel is not open!");
long nBytesWritten;
if (USE_COPY_V1)
nBytesWritten = _channelCopy1 (aSrc, aDest);
else
nBytesWritten = _channelCopy2 (aSrc, aDest);
return nBytesWritten;
}
/**
* Channel copy method 1. This method copies data from the src channel and
* writes it to the dest channel until EOF on src. This implementation makes
* use of compact( ) on the temp buffer to pack down the data if the buffer
* wasn't fully drained. This may result in data copying, but minimizes system
* calls. It also requires a cleanup loop to make sure all the data gets sent.
*
* Source: Java NIO, page 60
*
* @param aSrc
* Source channel. May not be null. Is not closed after
* the operation.
* @param aDest
* Destination channel. May not be null. Is not closed
* after the operation.
* @return The number of bytes written.
*/
@Nonnegative
private static long _channelCopy1 (@Nonnull @WillNotClose final ReadableByteChannel aSrc,
@Nonnull @WillNotClose final WritableByteChannel aDest) throws IOException
{
long nBytesWritten = 0;
final ByteBuffer aBuffer = ByteBuffer.allocateDirect (16 * 1024);
while (aSrc.read (aBuffer) != -1)
{
// Prepare the buffer to be drained
aBuffer.flip ();
// Write to the channel; may block
nBytesWritten += aDest.write (aBuffer);
// If partial transfer, shift remainder down
// If buffer is empty, same as doing clear()
aBuffer.compact ();
}
// EOF will leave buffer in fill state
aBuffer.flip ();
// Make sure that the buffer is fully drained
while (aBuffer.hasRemaining ())
nBytesWritten += aDest.write (aBuffer);
return nBytesWritten;
}
/**
* Channel copy method 2. This method performs the same copy, but assures the
* temporary buffer is empty before reading more data. This never requires
* data copying but may result in more systems calls. No post-loop cleanup is
* needed because the buffer will be empty when the loop is exited.
* Source: Java NIO, page 60
*
* @param aSrc
* Source channel. May not be null. Is not closed after
* the operation.
* @param aDest
* Destination channel. May not be null. Is not closed
* after the operation.
* @return The number of bytes written.
*/
private static long _channelCopy2 (@Nonnull @WillNotClose final ReadableByteChannel aSrc,
@Nonnull @WillNotClose final WritableByteChannel aDest) throws IOException
{
long nBytesWritten = 0;
final ByteBuffer aBuffer = ByteBuffer.allocateDirect (16 * 1024);
while (aSrc.read (aBuffer) != -1)
{
// Prepare the buffer to be drained
aBuffer.flip ();
// Make sure that the buffer was fully drained
while (aBuffer.hasRemaining ())
nBytesWritten += aDest.write (aBuffer);
// Make the buffer empty, ready for filling
aBuffer.clear ();
}
return nBytesWritten;
}
@Nonnull
public static ESuccess close (@Nullable final Channel aChannel)
{
if (aChannel != null && aChannel.isOpen ())
return StreamHelper.close (aChannel);
return ESuccess.FAILURE;
}
@Nonnull
public static ESuccess release (@Nullable final FileLock aFileLock)
{
if (aFileLock != null)
{
try
{
aFileLock.release ();
return ESuccess.SUCCESS;
}
catch (final IOException ex)
{
if (LOGGER.isErrorEnabled ())
LOGGER.error ("Failed to release object " + aFileLock, ex instanceof IMockException ? null : ex);
}
}
return ESuccess.FAILURE;
}
}