java.io.PipedOutputStream Maven / Gradle / Ivy
/*
* 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 java.io;
/**
* Places information on a communications pipe. When two threads want to pass
* data back and forth, one creates a piped output stream and the other one
* creates a piped input stream.
*
* @see PipedInputStream
*/
public class PipedOutputStream extends OutputStream {
/**
* The destination PipedInputStream
*/
private PipedInputStream target;
/**
* Constructs a new unconnected {@code PipedOutputStream}. The resulting
* stream must be connected to a {@link PipedInputStream} before data can be
* written to it.
*/
public PipedOutputStream() {
}
/**
* Constructs a new {@code PipedOutputStream} connected to the
* {@link PipedInputStream} {@code target}. Any data written to this stream
* can be read from the target stream.
*
* @param target
* the piped input stream to connect to.
* @throws IOException
* if this stream or {@code target} are already connected.
*/
public PipedOutputStream(PipedInputStream target) throws IOException {
connect(target);
}
/**
* Closes this stream. If this stream is connected to an input stream, the
* input stream is closed and the pipe is disconnected.
*
* @throws IOException
* if an error occurs while closing this stream.
*/
@Override
public void close() throws IOException {
// Is the pipe connected?
PipedInputStream stream = target;
if (stream != null) {
stream.done();
target = null;
}
}
/**
* Connects this stream to a {@link PipedInputStream}. Any data written to
* this output stream becomes readable in the input stream.
*
* @param stream
* the piped input stream to connect to.
* @throws IOException
* if either stream is already connected.
*/
public void connect(PipedInputStream stream) throws IOException {
if (stream == null) {
throw new NullPointerException("stream == null");
}
synchronized (stream) {
if (this.target != null) {
throw new IOException("Already connected");
}
if (stream.isConnected) {
throw new IOException("Pipe already connected");
}
stream.establishConnection();
this.target = stream;
}
}
/**
* Notifies the readers of this {@link PipedInputStream} that bytes can be
* read. This method does nothing if this stream is not connected.
*
* @throws IOException
* if an I/O error occurs while flushing this stream.
*/
@Override
public void flush() throws IOException {
PipedInputStream stream = target;
if (stream == null) {
return;
}
synchronized (stream) {
stream.notifyAll();
}
}
/**
* Writes {@code count} bytes from the byte array {@code buffer} starting at
* {@code offset} to this stream. The written data can then be read from the
* connected input stream.
*
* Separate threads should be used to write to a {@code PipedOutputStream}
* and to read from the connected {@link PipedInputStream}. If the same
* thread is used, a deadlock may occur.
*
* @param buffer
* the buffer to write.
* @param offset
* the index of the first byte in {@code buffer} to write.
* @param count
* the number of bytes from {@code buffer} to write to this
* stream.
* @throws IndexOutOfBoundsException
* if {@code offset < 0} or {@code count < 0}, or if {@code
* offset + count} is bigger than the length of {@code buffer}.
* @throws InterruptedIOException
* if the pipe is full and the current thread is interrupted
* waiting for space to write data. This case is not currently
* handled correctly.
* @throws IOException
* if this stream is not connected, if the target stream is
* closed or if the thread reading from the target stream is no
* longer alive. This case is currently not handled correctly.
*/
@Override
public void write(byte[] buffer, int offset, int count) throws IOException {
super.write(buffer, offset, count);
}
/**
* Writes a single byte to this stream. Only the least significant byte of
* the integer {@code oneByte} is written. The written byte can then be read
* from the connected input stream.
*
* Separate threads should be used to write to a {@code PipedOutputStream}
* and to read from the connected {@link PipedInputStream}. If the same
* thread is used, a deadlock may occur.
*
* @param oneByte
* the byte to write.
* @throws InterruptedIOException
* if the pipe is full and the current thread is interrupted
* waiting for space to write data. This case is not currently
* handled correctly.
* @throws IOException
* if this stream is not connected, if the target stream is
* closed or if the thread reading from the target stream is no
* longer alive. This case is currently not handled correctly.
*/
@Override
public void write(int oneByte) throws IOException {
PipedInputStream stream = target;
if (stream == null) {
throw new IOException("Pipe not connected");
}
stream.receive(oneByte);
}
}