org.glassfish.jersey.internal.util.collection.NonBlockingInputStream Maven / Gradle / Ivy
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package org.glassfish.jersey.internal.util.collection;
import java.io.IOException;
import java.io.InputStream;
/**
* An abstract {@link InputStream} extension that defines contract for non-blocking
* streaming {@code read} operations.
*
* @author Marek Potociar (marek.potociar at oracle.com)
*/
public abstract class NonBlockingInputStream extends InputStream {
/**
* Constant used as a return value from {@link #tryRead()} method, to indicate that nothing
* has been read.
*/
public static final int NOTHING = Integer.MIN_VALUE;
/**
* Returns an estimate of the number of bytes that can be read (or
* skipped over) from this input stream without blocking by the next
* invocation of a method for this input stream. The next invocation
* might be the same thread or another thread. A single read or skip of this
* many bytes will not block, but may read or skip fewer bytes.
*
* Note that while some implementations of {@code InputStream} will return
* the total number of bytes in the stream, many will not. It is
* never correct to use the return value of this method to allocate
* a buffer intended to hold all data in this stream.
*
*
* A subclass' implementation of this method may choose to throw an
* {@link java.io.IOException} if this input stream has been closed by
* invoking the {@link #close()} method.
*
*
* The default implementation of this method in {@code NonBlockingInputStream}
* throws an {@link UnsupportedOperationException}. This method must be overridden
* by subclasses. The overriding implementations must guarantee non-blocking behavior
* of the method. The overriding implementation must also guarantee that a non-empty
* stream does not return zero from the method. IOW, it must be possible to use the
* method for empty check: {@code stream.available() == 0}
*
*
* @return an estimate of the number of bytes that can be read (or skipped
* over) from this input stream without blocking or {@code 0} when
* it reaches the end of the input stream or the stream is empty.
* @throws java.io.IOException if an I/O error occurs.
*/
@Override
public int available() throws IOException {
throw new UnsupportedOperationException();
}
/**
* Behaves mostly like {@link java.io.InputStream#read()}.
*
* The main difference is that this method is non-blocking. In case there are no
* data available to be read, the method returns {@link #NOTHING} immediately.
*
* @return next byte of data, {@code -1} if end of the stream has been reached or
* {@link #NOTHING} in case no data are available to be read at the moment.
* @throws java.io.IOException if an I/O error occurs.
*/
public abstract int tryRead() throws IOException;
/**
* Behaves mostly like {@link java.io.InputStream#read(byte[])}.
*
* The main difference is that this method is non-blocking. In case there are no
* data available to be read, the method returns zero immediately.
*
* @param b the buffer into which the data is read.
* @return the total number of bytes read into the buffer or {@code -1} if end of the
* stream has been reached or {@code 0} in case no data are available to be
* read at the moment.
* @throws java.io.IOException if an I/O error occurs.
*/
public abstract int tryRead(byte b[]) throws IOException;
/**
* Behaves mostly like {@link java.io.InputStream#read(byte[], int, int)}.
*
* The main difference is that this method is non-blocking. In case there are no
* data available to be read, the method returns zero immediately.
*
* @param b the buffer into which the data is read.
* @param off the start offset in array {@code b}
* at which the data is written.
* @param len the maximum number of bytes to read.
* @return the total number of bytes read into the buffer or {@code -1} if end of the
* stream has been reached or {@code 0} in case no data are available to be
* read at the moment.
* @throws java.io.IOException if an I/O error occurs.
*/
public abstract int tryRead(byte b[], int off, int len) throws IOException;
}