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package org.apache.http.conn;

import java.io.IOException;
import java.io.InputStream;

import org.apache.http.util.Args;

A stream wrapper that triggers actions on close() and EOF. Primarily used to auto-release an underlying managed connection when the response body is consumed or no longer needed. 
See Also:
EofSensorWatcher
Since:
4.0/**
 * A stream wrapper that triggers actions on {@link #close close()} and EOF.
 * Primarily used to auto-release an underlying managed connection when the response
 * body is consumed or no longer needed.
 *
 * @see EofSensorWatcher
 *
 * @since 4.0
 */
// don't use FilterInputStream as the base class, we'd have to
// override markSupported(), mark(), and reset() to disable them
public class EofSensorInputStream extends InputStream implements ConnectionReleaseTrigger {

    
The wrapped input stream, while accessible. The value changes to null when the wrapped stream becomes inaccessible. /**
     * The wrapped input stream, while accessible.
     * The value changes to {@code null} when the wrapped stream
     * becomes inaccessible.
     */
    protected InputStream wrappedStream;

    
Indicates whether this stream itself is closed. If it isn't, but wrappedStream is null, we're running in EOF mode. All read operations will indicate EOF without accessing the underlying stream. After closing this stream, read operations will trigger an IOException. 
See Also:
isReadAllowed/**
     * Indicates whether this stream itself is closed.
     * If it isn't, but {@link #wrappedStream wrappedStream}
     * is {@code null}, we're running in EOF mode.
     * All read operations will indicate EOF without accessing
     * the underlying stream. After closing this stream, read
     * operations will trigger an {@link IOException IOException}.
     *
     * @see #isReadAllowed isReadAllowed
     */
    private boolean selfClosed;

    
The watcher to be notified, if any. /** The watcher to be notified, if any. */
    private final EofSensorWatcher eofWatcher;

    
Creates a new EOF sensor. If no watcher is passed, the underlying stream will simply be closed when EOF is detected or close is called. Otherwise, the watcher decides whether the underlying stream should be closed before detaching from it. 
Params:
in –        the wrapped stream
watcher –  the watcher for events, or null for auto-close behavior without notification/**
     * Creates a new EOF sensor.
     * If no watcher is passed, the underlying stream will simply be
     * closed when EOF is detected or {@link #close close} is called.
     * Otherwise, the watcher decides whether the underlying stream
     * should be closed before detaching from it.
     *
     * @param in        the wrapped stream
     * @param watcher   the watcher for events, or {@code null} for
     *                  auto-close behavior without notification
     */
    public EofSensorInputStream(final InputStream in,
                                final EofSensorWatcher watcher) {
        Args.notNull(in, "Wrapped stream");
        wrappedStream = in;
        selfClosed = false;
        eofWatcher = watcher;
    }

    boolean isSelfClosed() {
        return selfClosed;
    }

    InputStream getWrappedStream() {
        return wrappedStream;
    }

    
Checks whether the underlying stream can be read from.
Throws:
IOException –      if this stream is already closed
Returns:
 true if the underlying stream is accessible, false if this stream is in EOF mode and detached from the underlying stream/**
     * Checks whether the underlying stream can be read from.
     *
     * @return  {@code true} if the underlying stream is accessible,
     *          {@code false} if this stream is in EOF mode and
     *          detached from the underlying stream
     *
     * @throws IOException      if this stream is already closed
     */
    protected boolean isReadAllowed() throws IOException {
        if (selfClosed) {
            throw new IOException("Attempted read on closed stream.");
        }
        return (wrappedStream != null);
    }

    @Override
    public int read() throws IOException {
        int readLen = -1;

        if (isReadAllowed()) {
            try {
                readLen = wrappedStream.read();
                checkEOF(readLen);
            } catch (final IOException ex) {
                checkAbort();
                throw ex;
            }
        }

        return readLen;
    }

    @Override
    public int read(final byte[] b, final int off, final int len) throws IOException {
        int readLen = -1;

        if (isReadAllowed()) {
            try {
                readLen = wrappedStream.read(b,  off,  len);
                checkEOF(readLen);
            } catch (final IOException ex) {
                checkAbort();
                throw ex;
            }
        }

        return readLen;
    }

    @Override
    public int read(final byte[] b) throws IOException {
        return read(b, 0, b.length);
    }

    @Override
    public int available() throws IOException {
        int a = 0; // not -1

        if (isReadAllowed()) {
            try {
                a = wrappedStream.available();
                // no checkEOF() here, available() can't trigger EOF
            } catch (final IOException ex) {
                checkAbort();
                throw ex;
            }
        }

        return a;
    }

    @Override
    public void close() throws IOException {
        // tolerate multiple calls to close()
        selfClosed = true;
        checkClose();
    }

    
Detects EOF and notifies the watcher. This method should only be called while the underlying stream is still accessible. Use isReadAllowed to check that condition. 

If EOF is detected, the watcher will be notified and this stream
is detached from the underlying stream. This prevents multiple
notifications from this stream.

Params:
eof –       the result of the calling read operation.
                 A negative value indicates that EOF is reached.
Throws:
IOException – 
         in case of an IO problem on closing the underlying stream/**
     * Detects EOF and notifies the watcher.
     * This method should only be called while the underlying stream is
     * still accessible. Use {@link #isReadAllowed isReadAllowed} to
     * check that condition.
     * <p>
     * If EOF is detected, the watcher will be notified and this stream
     * is detached from the underlying stream. This prevents multiple
     * notifications from this stream.
     * </p>
     *
     * @param eof       the result of the calling read operation.
     *                  A negative value indicates that EOF is reached.
     *
     * @throws IOException
     *          in case of an IO problem on closing the underlying stream
     */
    protected void checkEOF(final int eof) throws IOException {

        final InputStream toCheckStream = wrappedStream;
        if ((toCheckStream != null) && (eof < 0)) {
            try {
                boolean scws = true; // should close wrapped stream?
                if (eofWatcher != null) {
                    scws = eofWatcher.eofDetected(toCheckStream);
                }
                if (scws) {
                    toCheckStream.close();
                }
            } finally {
                wrappedStream = null;
            }
        }
    }

    
Detects stream close and notifies the watcher. There's not much to detect since this is called by close. The watcher will only be notified if this stream is closed for the first time and before EOF has been detected. This stream will be detached from the underlying stream to prevent multiple notifications to the watcher. 
Throws:
IOException – 
         in case of an IO problem on closing the underlying stream/**
     * Detects stream close and notifies the watcher.
     * There's not much to detect since this is called by {@link #close close}.
     * The watcher will only be notified if this stream is closed
     * for the first time and before EOF has been detected.
     * This stream will be detached from the underlying stream to prevent
     * multiple notifications to the watcher.
     *
     * @throws IOException
     *          in case of an IO problem on closing the underlying stream
     */
    protected void checkClose() throws IOException {

        final InputStream toCloseStream = wrappedStream;
        if (toCloseStream != null) {
            try {
                boolean scws = true; // should close wrapped stream?
                if (eofWatcher != null) {
                    scws = eofWatcher.streamClosed(toCloseStream);
                }
                if (scws) {
                    toCloseStream.close();
                }
            } finally {
                wrappedStream = null;
            }
        }
    }

    
Detects stream abort and notifies the watcher. There's not much to detect since this is called by abortConnection. The watcher will only be notified if this stream is aborted for the first time and before EOF has been detected or the stream has been closed gracefully. This stream will be detached from the underlying stream to prevent multiple notifications to the watcher. 
Throws:
IOException – 
         in case of an IO problem on closing the underlying stream/**
     * Detects stream abort and notifies the watcher.
     * There's not much to detect since this is called by
     * {@link #abortConnection abortConnection}.
     * The watcher will only be notified if this stream is aborted
     * for the first time and before EOF has been detected or the
     * stream has been {@link #close closed} gracefully.
     * This stream will be detached from the underlying stream to prevent
     * multiple notifications to the watcher.
     *
     * @throws IOException
     *          in case of an IO problem on closing the underlying stream
     */
    protected void checkAbort() throws IOException {

        final InputStream toAbortStream = wrappedStream;
        if (toAbortStream != null) {
            try {
                boolean scws = true; // should close wrapped stream?
                if (eofWatcher != null) {
                    scws = eofWatcher.streamAbort(toAbortStream);
                }
                if (scws) {
                    toAbortStream.close();
                }
            } finally {
                wrappedStream = null;
            }
        }
    }

    
Same as close(). /**
     * Same as {@link #close close()}.
     */
    @Override
    public void releaseConnection() throws IOException {
        close();
    }

    
Aborts this stream. This is a special version of close() which prevents re-use of the underlying connection, if any. Calling this method indicates that there should be no attempt to read until the end of the stream. /**
     * Aborts this stream.
     * This is a special version of {@link #close close()} which prevents
     * re-use of the underlying connection, if any. Calling this method
     * indicates that there should be no attempt to read until the end of
     * the stream.
     */
    @Override
    public void abortConnection() throws IOException {
        // tolerate multiple calls
        selfClosed = true;
        checkAbort();
    }

}