Mega Code Archive
ReadableByteChannel
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/*
* Copyright (c) 2004 David Flanagan. All rights reserved.
* This code is from the book Java Examples in a Nutshell, 3nd Edition.
* It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
* You may study, use, and modify it for any non-commercial purpose,
* including teaching and use in open-source projects.
* You may distribute it non-commercially as long as you retain this notice.
* For a commercial use license, or to purchase the book,
* please visit http://www.davidflanagan.com/javaexamples3.
*/
//package je3.nio;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.Channels;
import java.nio.channels.ReadableByteChannel;
import java.nio.channels.WritableByteChannel;
public class Main {
public static void main(String[] args) throws IOException {
// Open file streams and get channels for them.
ReadableByteChannel in = new FileInputStream(args[0]).getChannel();
WritableByteChannel out;
if (args.length > 1)
out = new FileOutputStream(args[1]).getChannel();
else
out = Channels.newChannel(System.out);
// Do the copy
copy(in, out);
// Exception handling and stream-closing code has been omitted.
}
// Read all available bytes from one channel and copy them to the other.
public static void copy(ReadableByteChannel in, WritableByteChannel out) throws IOException {
// First, we need a buffer to hold blocks of copied bytes.
ByteBuffer buffer = ByteBuffer.allocateDirect(32 * 1024);
// Now loop until no more bytes to read and the buffer is empty
while (in.read(buffer) != -1 || buffer.position() > 0) {
// The read() call leaves the buffer in "fill mode". To prepare
// to write bytes from the bufferwe have to put it in "drain mode"
// by flipping it: setting limit to position and position to zero
buffer.flip();
// Now write some or all of the bytes out to the output channel
out.write(buffer);
// Compact the buffer by discarding bytes that were written,
// and shifting any remaining bytes. This method also
// prepares the buffer for the next call to read() by setting the
// position to the limit and the limit to the buffer capacity.
buffer.compact();
}
}
}
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