in<0 implies the buffer is empty,
* in==out implies the buffer is full
*/
int in = -1;
/**
* The index of the position in the circular buffer at which the next
* character of data will be read by this piped reader.
*/
int out = 0;
/**
* Creates a PipedReader so
* that it is connected to the piped writer
* src. Data written to src
* will then be available as input from this stream.
*
* @param src the stream to connect to.
* @exception IOException if an I/O error occurs.
*/
public PipedReader(PipedWriter src) throws IOException {
connect(src);
}
/**
* Creates a PipedReader so
* that it is not yet connected. It must be
* connected to a PipedWriter
* before being used.
*
* @see java.io.PipedReader#connect(java.io.PipedWriter)
* @see java.io.PipedWriter#connect(java.io.PipedReader)
*/
public PipedReader() {
}
/**
* Causes this piped reader to be connected
* to the piped writer src.
* If this object is already connected to some
* other piped writer, an IOException
* is thrown.
*
* If src is an
* unconnected piped writer and snk
* is an unconnected piped reader, they
* may be connected by either the call:
*
*
snk.connect(src) * or the call: *
*
src.connect(snk)
* The two
* calls have the same effect.
*
* @param src The piped writer to connect to.
* @exception IOException if an I/O error occurs.
*/
public void connect(PipedWriter src) throws IOException {
src.connect(this);
}
/**
* Receives a char of data. This method will block if no input is
* available.
*/
synchronized void receive(int c) throws IOException {
if (!connected) {
throw new IOException("Pipe not connected");
} else if (closedByWriter || closedByReader) {
throw new IOException("Pipe closed");
} else if (readSide != null && !readSide.isAlive()) {
throw new IOException("Read end dead");
}
writeSide = Thread.currentThread();
while (in == out) {
if ((readSide != null) && !readSide.isAlive()) {
throw new IOException("Pipe broken");
}
/* full: kick any waiting readers */
notifyAll();
try {
wait(1000);
} catch (InterruptedException ex) {
throw new java.io.InterruptedIOException();
}
}
if (in < 0) {
in = 0;
out = 0;
}
buffer[in++] = (char) c;
if (in >= buffer.length) {
in = 0;
}
}
/**
* Receives data into an array of characters. This method will
* block until some input is available.
*/
synchronized void receive(char c[], int off, int len) throws IOException {
while (--len >= 0) {
receive(c[off++]);
}
}
/**
* Notifies all waiting threads that the last character of data has been
* received.
*/
synchronized void receivedLast() {
closedByWriter = true;
notifyAll();
}
/**
* Reads the next character of data from this piped stream.
* If no character is available because the end of the stream
* has been reached, the value -1 is returned.
* This method blocks until input data is available, the end of
* the stream is detected, or an exception is thrown.
*
* If a thread was providing data characters
* to the connected piped writer, but
* the thread is no longer alive, then an
* IOException is thrown.
*
* @return the next character of data, or -1 if the end of the
* stream is reached.
* @exception IOException if the pipe is broken.
*/
public synchronized int read() throws IOException {
if (!connected) {
throw new IOException("Pipe not connected");
} else if (closedByReader) {
throw new IOException("Pipe closed");
} else if (writeSide != null && !writeSide.isAlive()
&& !closedByWriter && (in < 0)) {
throw new IOException("Write end dead");
}
readSide = Thread.currentThread();
int trials = 2;
while (in < 0) {
if (closedByWriter) {
/* closed by writer, return EOF */
return -1;
}
if ((writeSide != null) && (!writeSide.isAlive()) && (--trials < 0)) {
throw new IOException("Pipe broken");
}
/* might be a writer waiting */
notifyAll();
try {
wait(1000);
} catch (InterruptedException ex) {
throw new java.io.InterruptedIOException();
}
}
int ret = buffer[out++];
if (out >= buffer.length) {
out = 0;
}
if (in == out) {
/* now empty */
in = -1;
}
return ret;
}
/**
* Reads up to len characters of data from this piped
* stream into an array of characters. Less than len characters
* will be read if the end of the data stream is reached. This method
* blocks until at least one character of input is available.
* If a thread was providing data characters to the connected piped output,
* but the thread is no longer alive, then an IOException
* is thrown.
*
* @param cbuf the buffer into which the data is read.
* @param off the start offset of the data.
* @param len the maximum number of characters read.
* @return the total number of characters read into the buffer, or
* -1 if there is no more data because the end of
* the stream has been reached.
* @exception IOException if an I/O error occurs.
*/
public synchronized int read(char cbuf[], int off, int len) throws IOException {
if (!connected) {
throw new IOException("Pipe not connected");
} else if (closedByReader) {
throw new IOException("Pipe closed");
} else if (writeSide != null && !writeSide.isAlive()
&& !closedByWriter && (in < 0)) {
throw new IOException("Write end dead");
}
if ((off < 0) || (off > cbuf.length) || (len < 0) ||
((off + len) > cbuf.length) || ((off + len) < 0)) {
throw new IndexOutOfBoundsException();
} else if (len == 0) {
return 0;
}
/* possibly wait on the first character */
int c = read();
if (c < 0) {
return -1;
}
cbuf[off] = (char)c;
int rlen = 1;
while ((in >= 0) && (--len > 0)) {
cbuf[off + rlen] = buffer[out++];
rlen++;
if (out >= buffer.length) {
out = 0;
}
if (in == out) {
/* now empty */
in = -1;
}
}
return rlen;
}
/**
* Tell whether this stream is ready to be read. A piped character
* stream is ready if the circular buffer is not empty.
*
* @exception IOException If an I/O error occurs
*/
public synchronized boolean ready() throws IOException {
if (!connected) {
throw new IOException("Pipe not connected");
} else if (closedByReader) {
throw new IOException("Pipe closed");
} else if (writeSide != null && !writeSide.isAlive()
&& !closedByWriter && (in < 0)) {
throw new IOException("Write end dead");
}
if (in < 0) {
return false;
} else {
return true;
}
}
/**
* Closes this piped stream and releases any system resources
* associated with the stream.
*
* @exception IOException if an I/O error occurs.
*/
public void close() throws IOException {
in = -1;
closedByReader = true;
}
}