The Channels.java Java example source code
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
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* published by the Free Software Foundation. Oracle designates this
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*
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
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package java.nio.channels;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.Reader;
import java.io.Writer;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.UnsupportedCharsetException;
import java.nio.channels.spi.AbstractInterruptibleChannel;
import java.util.concurrent.ExecutionException;
import sun.nio.ch.ChannelInputStream;
import sun.nio.cs.StreamDecoder;
import sun.nio.cs.StreamEncoder;
/**
* Utility methods for channels and streams.
*
* <p> This class defines static methods that support the interoperation of the
* stream classes of the <tt>{@link java.io} package with the channel
* classes of this package. </p>
*
*
* @author Mark Reinhold
* @author Mike McCloskey
* @author JSR-51 Expert Group
* @since 1.4
*/
public final class Channels {
private Channels() { } // No instantiation
private static void checkNotNull(Object o, String name) {
if (o == null)
throw new NullPointerException("\"" + name + "\" is null!");
}
/**
* Write all remaining bytes in buffer to the given channel.
* If the channel is selectable then it must be configured blocking.
*/
private static void writeFullyImpl(WritableByteChannel ch, ByteBuffer bb)
throws IOException
{
while (bb.remaining() > 0) {
int n = ch.write(bb);
if (n <= 0)
throw new RuntimeException("no bytes written");
}
}
/**
* Write all remaining bytes in buffer to the given channel.
*
* @throws IllegalBlockingModeException
* If the channel is selectable and configured non-blocking.
*/
private static void writeFully(WritableByteChannel ch, ByteBuffer bb)
throws IOException
{
if (ch instanceof SelectableChannel) {
SelectableChannel sc = (SelectableChannel)ch;
synchronized (sc.blockingLock()) {
if (!sc.isBlocking())
throw new IllegalBlockingModeException();
writeFullyImpl(ch, bb);
}
} else {
writeFullyImpl(ch, bb);
}
}
// -- Byte streams from channels --
/**
* Constructs a stream that reads bytes from the given channel.
*
* <p> The read methods of the resulting stream will throw an
* {@link IllegalBlockingModeException} if invoked while the underlying
* channel is in non-blocking mode. The stream will not be buffered, and
* it will not support the {@link InputStream#mark mark} or {@link
* InputStream#reset reset} methods. The stream will be safe for access by
* multiple concurrent threads. Closing the stream will in turn cause the
* channel to be closed. </p>
*
* @param ch
* The channel from which bytes will be read
*
* @return A new input stream
*/
public static InputStream newInputStream(ReadableByteChannel ch) {
checkNotNull(ch, "ch");
return new sun.nio.ch.ChannelInputStream(ch);
}
/**
* Constructs a stream that writes bytes to the given channel.
*
* <p> The write methods of the resulting stream will throw an
* {@link IllegalBlockingModeException} if invoked while the underlying
* channel is in non-blocking mode. The stream will not be buffered. The
* stream will be safe for access by multiple concurrent threads. Closing
* the stream will in turn cause the channel to be closed. </p>
*
* @param ch
* The channel to which bytes will be written
*
* @return A new output stream
*/
public static OutputStream newOutputStream(final WritableByteChannel ch) {
checkNotNull(ch, "ch");
return new OutputStream() {
private ByteBuffer bb = null;
private byte[] bs = null; // Invoker's previous array
private byte[] b1 = null;
public synchronized void write(int b) throws IOException {
if (b1 == null)
b1 = new byte[1];
b1[0] = (byte)b;
this.write(b1);
}
public synchronized void write(byte[] bs, int off, int len)
throws IOException
{
if ((off < 0) || (off > bs.length) || (len < 0) ||
((off + len) > bs.length) || ((off + len) < 0)) {
throw new IndexOutOfBoundsException();
} else if (len == 0) {
return;
}
ByteBuffer bb = ((this.bs == bs)
? this.bb
: ByteBuffer.wrap(bs));
bb.limit(Math.min(off + len, bb.capacity()));
bb.position(off);
this.bb = bb;
this.bs = bs;
Channels.writeFully(ch, bb);
}
public void close() throws IOException {
ch.close();
}
};
}
/**
* Constructs a stream that reads bytes from the given channel.
*
* <p> The stream will not be buffered, and it will not support the {@link
* InputStream#mark mark} or {@link InputStream#reset reset} methods. The
* stream will be safe for access by multiple concurrent threads. Closing
* the stream will in turn cause the channel to be closed. </p>
*
* @param ch
* The channel from which bytes will be read
*
* @return A new input stream
*
* @since 1.7
*/
public static InputStream newInputStream(final AsynchronousByteChannel ch) {
checkNotNull(ch, "ch");
return new InputStream() {
private ByteBuffer bb = null;
private byte[] bs = null; // Invoker's previous array
private byte[] b1 = null;
@Override
public synchronized int read() throws IOException {
if (b1 == null)
b1 = new byte[1];
int n = this.read(b1);
if (n == 1)
return b1[0] & 0xff;
return -1;
}
@Override
public synchronized int read(byte[] bs, int off, int len)
throws IOException
{
if ((off < 0) || (off > bs.length) || (len < 0) ||
((off + len) > bs.length) || ((off + len) < 0)) {
throw new IndexOutOfBoundsException();
} else if (len == 0)
return 0;
ByteBuffer bb = ((this.bs == bs)
? this.bb
: ByteBuffer.wrap(bs));
bb.position(off);
bb.limit(Math.min(off + len, bb.capacity()));
this.bb = bb;
this.bs = bs;
boolean interrupted = false;
try {
for (;;) {
try {
return ch.read(bb).get();
} catch (ExecutionException ee) {
throw new IOException(ee.getCause());
} catch (InterruptedException ie) {
interrupted = true;
}
}
} finally {
if (interrupted)
Thread.currentThread().interrupt();
}
}
@Override
public void close() throws IOException {
ch.close();
}
};
}
/**
* Constructs a stream that writes bytes to the given channel.
*
* <p> The stream will not be buffered. The stream will be safe for access
* by multiple concurrent threads. Closing the stream will in turn cause
* the channel to be closed. </p>
*
* @param ch
* The channel to which bytes will be written
*
* @return A new output stream
*
* @since 1.7
*/
public static OutputStream newOutputStream(final AsynchronousByteChannel ch) {
checkNotNull(ch, "ch");
return new OutputStream() {
private ByteBuffer bb = null;
private byte[] bs = null; // Invoker's previous array
private byte[] b1 = null;
@Override
public synchronized void write(int b) throws IOException {
if (b1 == null)
b1 = new byte[1];
b1[0] = (byte)b;
this.write(b1);
}
@Override
public synchronized void write(byte[] bs, int off, int len)
throws IOException
{
if ((off < 0) || (off > bs.length) || (len < 0) ||
((off + len) > bs.length) || ((off + len) < 0)) {
throw new IndexOutOfBoundsException();
} else if (len == 0) {
return;
}
ByteBuffer bb = ((this.bs == bs)
? this.bb
: ByteBuffer.wrap(bs));
bb.limit(Math.min(off + len, bb.capacity()));
bb.position(off);
this.bb = bb;
this.bs = bs;
boolean interrupted = false;
try {
while (bb.remaining() > 0) {
try {
ch.write(bb).get();
} catch (ExecutionException ee) {
throw new IOException(ee.getCause());
} catch (InterruptedException ie) {
interrupted = true;
}
}
} finally {
if (interrupted)
Thread.currentThread().interrupt();
}
}
@Override
public void close() throws IOException {
ch.close();
}
};
}
// -- Channels from streams --
/**
* Constructs a channel that reads bytes from the given stream.
*
* <p> The resulting channel will not be buffered; it will simply redirect
* its I/O operations to the given stream. Closing the channel will in
* turn cause the stream to be closed. </p>
*
* @param in
* The stream from which bytes are to be read
*
* @return A new readable byte channel
*/
public static ReadableByteChannel newChannel(final InputStream in) {
checkNotNull(in, "in");
if (in instanceof FileInputStream &&
FileInputStream.class.equals(in.getClass())) {
return ((FileInputStream)in).getChannel();
}
return new ReadableByteChannelImpl(in);
}
private static class ReadableByteChannelImpl
extends AbstractInterruptibleChannel // Not really interruptible
implements ReadableByteChannel
{
InputStream in;
private static final int TRANSFER_SIZE = 8192;
private byte buf[] = new byte[0];
private boolean open = true;
private Object readLock = new Object();
ReadableByteChannelImpl(InputStream in) {
this.in = in;
}
public int read(ByteBuffer dst) throws IOException {
int len = dst.remaining();
int totalRead = 0;
int bytesRead = 0;
synchronized (readLock) {
while (totalRead < len) {
int bytesToRead = Math.min((len - totalRead),
TRANSFER_SIZE);
if (buf.length < bytesToRead)
buf = new byte[bytesToRead];
if ((totalRead > 0) && !(in.available() > 0))
break; // block at most once
try {
begin();
bytesRead = in.read(buf, 0, bytesToRead);
} finally {
end(bytesRead > 0);
}
if (bytesRead < 0)
break;
else
totalRead += bytesRead;
dst.put(buf, 0, bytesRead);
}
if ((bytesRead < 0) && (totalRead == 0))
return -1;
return totalRead;
}
}
protected void implCloseChannel() throws IOException {
in.close();
open = false;
}
}
/**
* Constructs a channel that writes bytes to the given stream.
*
* <p> The resulting channel will not be buffered; it will simply redirect
* its I/O operations to the given stream. Closing the channel will in
* turn cause the stream to be closed. </p>
*
* @param out
* The stream to which bytes are to be written
*
* @return A new writable byte channel
*/
public static WritableByteChannel newChannel(final OutputStream out) {
checkNotNull(out, "out");
if (out instanceof FileOutputStream &&
FileOutputStream.class.equals(out.getClass())) {
return ((FileOutputStream)out).getChannel();
}
return new WritableByteChannelImpl(out);
}
private static class WritableByteChannelImpl
extends AbstractInterruptibleChannel // Not really interruptible
implements WritableByteChannel
{
OutputStream out;
private static final int TRANSFER_SIZE = 8192;
private byte buf[] = new byte[0];
private boolean open = true;
private Object writeLock = new Object();
WritableByteChannelImpl(OutputStream out) {
this.out = out;
}
public int write(ByteBuffer src) throws IOException {
int len = src.remaining();
int totalWritten = 0;
synchronized (writeLock) {
while (totalWritten < len) {
int bytesToWrite = Math.min((len - totalWritten),
TRANSFER_SIZE);
if (buf.length < bytesToWrite)
buf = new byte[bytesToWrite];
src.get(buf, 0, bytesToWrite);
try {
begin();
out.write(buf, 0, bytesToWrite);
} finally {
end(bytesToWrite > 0);
}
totalWritten += bytesToWrite;
}
return totalWritten;
}
}
protected void implCloseChannel() throws IOException {
out.close();
open = false;
}
}
// -- Character streams from channels --
/**
* Constructs a reader that decodes bytes from the given channel using the
* given decoder.
*
* <p> The resulting stream will contain an internal input buffer of at
* least <tt>minBufferCap bytes. The stream's read methods
* will, as needed, fill the buffer by reading bytes from the underlying
* channel; if the channel is in non-blocking mode when bytes are to be
* read then an {@link IllegalBlockingModeException} will be thrown. The
* resulting stream will not otherwise be buffered, and it will not support
* the {@link Reader#mark mark} or {@link Reader#reset reset} methods.
* Closing the stream will in turn cause the channel to be closed. </p>
*
* @param ch
* The channel from which bytes will be read
*
* @param dec
* The charset decoder to be used
*
* @param minBufferCap
* The minimum capacity of the internal byte buffer,
* or <tt>-1 if an implementation-dependent
* default capacity is to be used
*
* @return A new reader
*/
public static Reader newReader(ReadableByteChannel ch,
CharsetDecoder dec,
int minBufferCap)
{
checkNotNull(ch, "ch");
return StreamDecoder.forDecoder(ch, dec.reset(), minBufferCap);
}
/**
* Constructs a reader that decodes bytes from the given channel according
* to the named charset.
*
* <p> An invocation of this method of the form
*
* <blockquote> * Channels.newReader(ch, csname)</pre>
*
* behaves in exactly the same way as the expression
*
* <blockquote> * Channels.newReader(ch,
* Charset.forName(csName)
* .newDecoder(),
* -1);</pre>
*
* @param ch
* The channel from which bytes will be read
*
* @param csName
* The name of the charset to be used
*
* @return A new reader
*
* @throws UnsupportedCharsetException
* If no support for the named charset is available
* in this instance of the Java virtual machine
*/
public static Reader newReader(ReadableByteChannel ch,
String csName)
{
checkNotNull(csName, "csName");
return newReader(ch, Charset.forName(csName).newDecoder(), -1);
}
/**
* Constructs a writer that encodes characters using the given encoder and
* writes the resulting bytes to the given channel.
*
* <p> The resulting stream will contain an internal output buffer of at
* least <tt>minBufferCap bytes. The stream's write methods
* will, as needed, flush the buffer by writing bytes to the underlying
* channel; if the channel is in non-blocking mode when bytes are to be
* written then an {@link IllegalBlockingModeException} will be thrown.
* The resulting stream will not otherwise be buffered. Closing the stream
* will in turn cause the channel to be closed. </p>
*
* @param ch
* The channel to which bytes will be written
*
* @param enc
* The charset encoder to be used
*
* @param minBufferCap
* The minimum capacity of the internal byte buffer,
* or <tt>-1 if an implementation-dependent
* default capacity is to be used
*
* @return A new writer
*/
public static Writer newWriter(final WritableByteChannel ch,
final CharsetEncoder enc,
final int minBufferCap)
{
checkNotNull(ch, "ch");
return StreamEncoder.forEncoder(ch, enc.reset(), minBufferCap);
}
/**
* Constructs a writer that encodes characters according to the named
* charset and writes the resulting bytes to the given channel.
*
* <p> An invocation of this method of the form
*
* <blockquote> * Channels.newWriter(ch, csname)</pre>
*
* behaves in exactly the same way as the expression
*
* <blockquote> * Channels.newWriter(ch,
* Charset.forName(csName)
* .newEncoder(),
* -1);</pre>
*
* @param ch
* The channel to which bytes will be written
*
* @param csName
* The name of the charset to be used
*
* @return A new writer
*
* @throws UnsupportedCharsetException
* If no support for the named charset is available
* in this instance of the Java virtual machine
*/
public static Writer newWriter(WritableByteChannel ch,
String csName)
{
checkNotNull(csName, "csName");
return newWriter(ch, Charset.forName(csName).newEncoder(), -1);
}
}
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