Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You 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.github.sparkfy.network.buffer; import com.github.sparkfy.util.JavaUtils; import com.google.common.base.Objects; import io.netty.channel.FileRegion; import io.netty.util.AbstractReferenceCounted; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.nio.channels.FileChannel; import java.nio.channels.WritableByteChannel; /** * A FileRegion implementation that only creates the file descriptor when the region is being * transferred. This cannot be used with Epoll because there is no native support for it. * * This is mostly copied from DefaultFileRegion implementation in Netty. In the future, we * should push this into Netty so the native Epoll transport can support this feature. */ public final class LazyFileRegion extends AbstractReferenceCounted implements FileRegion { private final File file; private final long position; private final long count; private FileChannel channel; private long numBytesTransferred = 0L; /** * @param file file to transfer. * @param position start position for the transfer. * @param count number of bytes to transfer starting from position. */ public LazyFileRegion(File file, long position, long count) { this.file = file; this.position = position; this.count = count; } @Override protected void deallocate() { JavaUtils.closeQuietly(channel); } @Override public long position() { return position; } @Override public long transfered() { return numBytesTransferred; } @Override public long count() { return count; } @Override public long transferTo(WritableByteChannel target, long position) throws IOException { if (channel == null) { channel = new FileInputStream(file).getChannel(); } long count = this.count - position; if (count < 0 || position < 0) { throw new IllegalArgumentException( "position out of range: " + position + " (expected: 0 - " + (count - 1) + ')'); } if (count == 0) { return 0L; } long written = channel.transferTo(this.position + position, count, target); if (written > 0) { numBytesTransferred += written; } return written; } @Override public String toString() { return Objects.toStringHelper(this).add("file", file).add("position", position).add("count", count) .toString(); } }