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 * Copyright (c) 1995, 2021, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 */

package java.net;

import java.io.FileDescriptor;
import java.io.FileInputStream;
import java.io.IOException;
import java.nio.channels.FileChannel;

import sun.net.ConnectionResetException;

/**
 * This stream extends FileInputStream to implement a
 * SocketInputStream. Note that this class should <b>NOT</b> be
 * public.
 *
 * @author      Jonathan Payne
 * @author      Arthur van Hoff
 */
class SocketInputStream extends FileInputStream {
    static {
        init();
    }

    private boolean eof;
    private AbstractPlainSocketImpl impl = null;
    private byte temp[];

    /**
     * Creates a new SocketInputStream. Can only be called
     * by a Socket. This method needs to hang on to the owner Socket so
     * that the fd will not be closed.
     * @param impl the implemented socket input stream
     */
    SocketInputStream(AbstractPlainSocketImpl impl) throws IOException {
        super(impl.getFileDescriptor());
        this.impl = impl;
    }

    /**
     * Returns the unique {@link java.nio.channels.FileChannel FileChannel}
     * object associated with this file input stream.</p>
     *
     * The {@code getChannel} method of {@code SocketInputStream}
     * returns {@code null} since it is a socket based stream.</p>
     *
     * @return  the file channel associated with this file input stream
     *
     * @since 1.4
     */
    public final FileChannel getChannel() {
        return null;
    }

    /**
     * Reads into an array of bytes at the specified offset using
     * the received socket primitive.
     * @param fd the FileDescriptor
     * @param b the buffer into which the data is read
     * @param off the start offset of the data
     * @param len the maximum number of bytes read
     * @param timeout the read timeout in ms
     * @return the actual number of bytes read, -1 is
     *          returned when the end of the stream is reached.
     * @throws    IOException If an I/O error has occurred.
     */
    private native int socketRead0(FileDescriptor fd,
                                   byte b[], int off, int len,
                                   int timeout)
        throws IOException;

    // wrap native call to allow instrumentation
    /**
     * Reads into an array of bytes at the specified offset using
     * the received socket primitive.
     * @param fd the FileDescriptor
     * @param b the buffer into which the data is read
     * @param off the start offset of the data
     * @param len the maximum number of bytes read
     * @param timeout the read timeout in ms
     * @return the actual number of bytes read, -1 is
     *          returned when the end of the stream is reached.
     * @throws    IOException If an I/O error has occurred.
     */
    private int socketRead(FileDescriptor fd,
                           byte b[], int off, int len,
                           int timeout)
        throws IOException {
        return socketRead0(fd, b, off, len, timeout);
    }

    /**
     * Reads into a byte array data from the socket.
     * @param b the buffer into which the data is read
     * @return the actual number of bytes read, -1 is
     *          returned when the end of the stream is reached.
     * @throws    IOException If an I/O error has occurred.
     */
    public int read(byte b[]) throws IOException {
        return read(b, 0, b.length);
    }

    /**
     * Reads into a byte array <i>b</i> at offset <i>off</i>,
     * <i>length</i> bytes of data.
     * @param b the buffer into which the data is read
     * @param off the start offset of the data
     * @param length the maximum number of bytes read
     * @return the actual number of bytes read, -1 is
     *          returned when the end of the stream is reached.
     * @throws    IOException If an I/O error has occurred.
     */
    public int read(byte b[], int off, int length) throws IOException {
        return read(b, off, length, impl.getTimeout());
    }

    int read(byte b[], int off, int length, int timeout) throws IOException {
        int n;

        // EOF already encountered
        if (eof) {
            return -1;
        }

        // connection reset
        if (impl.isConnectionReset()) {
            throw new SocketException("Connection reset");
        }

        // bounds check
        if (length <= 0 || off < 0 || length > b.length - off) {
            if (length == 0) {
                return 0;
            }
            throw new ArrayIndexOutOfBoundsException("length == " + length
                    + " off == " + off + " buffer length == " + b.length);
        }

        // acquire file descriptor and do the read
        FileDescriptor fd = impl.acquireFD();
        try {
            n = socketRead(fd, b, off, length, timeout);
            if (n > 0) {
                return n;
            }
        } catch (ConnectionResetException rstExc) {
            impl.setConnectionReset();
        } finally {
            impl.releaseFD();
        }

        /*
         * If we get here we are at EOF, the socket has been closed,
         * or the connection has been reset.
         */
        if (impl.isClosedOrPending()) {
            throw new SocketException("Socket closed");
        }
        if (impl.isConnectionReset()) {
            throw new SocketException("Connection reset");
        }
        eof = true;
        return -1;
    }

    /**
     * Reads a single byte from the socket.
     */
    public int read() throws IOException {
        if (eof) {
            return -1;
        }
        temp = new byte[1];
        int n = read(temp, 0, 1);
        if (n <= 0) {
            return -1;
        }
        return temp[0] & 0xff;
    }

    /**
     * Skips n bytes of input.
     * @param numbytes the number of bytes to skip
     * @return  the actual number of bytes skipped.
     * @throws    IOException If an I/O error has occurred.
     */
    public long skip(long numbytes) throws IOException {
        if (numbytes <= 0) {
            return 0;
        }
        long n = numbytes;
        int buflen = (int) Math.min(1024, n);
        byte data[] = new byte[buflen];
        while (n > 0) {
            int r = read(data, 0, (int) Math.min((long) buflen, n));
            if (r < 0) {
                break;
            }
            n -= r;
        }
        return numbytes - n;
    }

    /**
     * Returns the number of bytes that can be read without blocking.
     * @return the number of immediately available bytes
     */
    public int available() throws IOException {
        int available = impl.available();
        return eof ? 0 : available;
    }

    void setEOF(boolean eof) {
        this.eof = eof;
    }

    public void close() throws IOException {
        // No longer used. Socket.getInputStream returns an
        // InputStream which calls Socket.close directly
        assert false;
    }

    /**
     * Perform class load-time initializations.
     */
    private static native void init();
}
