/*
* 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 writer and the other creates a piped
* reader.
*
* @see PipedReader
*/
public class PipedWriter extends Writer {
private PipedReader destination;
private boolean isClosed;
/**
* Constructs a new unconnected {@code PipedWriter}. The resulting writer
* must be connected to a {@code PipedReader} before data may be written to
* it.
*
* @see PipedReader
*/
public PipedWriter() {
}
/**
* Constructs a new {@code PipedWriter} connected to {@code destination}.
* Any data written to this writer can be read from {@code destination}.
*
* @param destination
* the {@code PipedReader} to connect to.
* @throws IOException
* if {@code destination} is already connected.
*/
public PipedWriter(PipedReader destination) throws IOException {
super(destination);
connect(destination);
}
/**
* Closes this writer. If a {@link PipedReader} is connected to this writer,
* it is closed as well and the pipe is disconnected. Any data buffered in
* the reader can still be read.
*
* @throws IOException
* if an error occurs while closing this writer.
*/
@Override
public void close() throws IOException {
PipedReader reader = destination;
if (reader != null) {
reader.done();
isClosed = true;
destination = null;
}
}
/**
* Connects this {@code PipedWriter} to a {@link PipedReader}. Any data
* written to this writer becomes readable in the reader.
*
* @param reader
* the reader to connect to.
* @throws IOException
* if this writer is closed or already connected, or if {@code
* reader} is already connected.
*/
public void connect(PipedReader reader) throws IOException {
if (reader == null) {
throw new NullPointerException("reader == null");
}
synchronized (reader) {
if (this.destination != null) {
throw new IOException("Pipe already connected");
}
reader.establishConnection();
this.lock = reader;
this.destination = reader;
}
}
/**
* Notifies the readers of this {@code PipedReader} that characters can be read. This
* method does nothing if this Writer is not connected.
*
* @throws IOException
* if an I/O error occurs while flushing this writer.
*/
@Override
public void flush() throws IOException {
PipedReader reader = destination;
if (isClosed) {
throw new IOException("Pipe is closed");
}
if (reader == null) {
return;
}
synchronized (reader) {
if (reader.isClosed) {
throw new IOException("Pipe is broken");
}
reader.notifyAll();
}
}
/**
* Writes {@code count} characters from the character array {@code buffer}
* starting at offset {@code index} to this writer. The written data can
* then be read from the connected {@link PipedReader} instance.
* <p>
* Separate threads should be used to write to a {@code PipedWriter} and to
* read from the connected {@code PipedReader}. If the same thread is used,
* a deadlock may occur.
*
* @param buffer
* the buffer to write.
* @param offset
* the index of the first character in {@code buffer} to write.
* @param count
* the number of characters from {@code buffer} to write to this
* writer.
* @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 writer is closed or not connected, if the target
* reader is closed or if the thread reading from the target
* reader is no longer alive. This case is currently not handled
* correctly.
* @throws NullPointerException
* if {@code buffer} is {@code null}.
*/
@Override
public void write(char[] buffer, int offset, int count) throws IOException {
PipedReader reader = destination;
if (reader == null) {
throw new IOException("Pipe not connected");
}
reader.receive(buffer, offset, count);
}
/**
* Writes a single character {@code c} to this writer. This character can
* then be read from the connected {@link PipedReader} instance.
* <p>
* Separate threads should be used to write to a {@code PipedWriter} and to
* read from the connected {@code PipedReader}. If the same thread is used,
* a deadlock may occur.
*
* @param c
* the character 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 writer is closed or not connected, if the target
* reader is closed or if the thread reading from the target
* reader is no longer alive. This case is currently not handled
* correctly.
*/
@Override
public void write(int c) throws IOException {
PipedReader reader = destination;
if (reader == null) {
throw new IOException("Pipe not connected");
}
reader.receive((char) c);
}
}