/*

 * Copyright 1994-1995 Sun Microsystems, Inc.  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.  Sun designates this

 * particular file as subject to the "Classpath" exception as provided

 * by Sun 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

 * CA 95054 USA or visit www.sun.com if you need additional information or

 * have any questions.

 */

package sun.net;

import java.io.*;

/**

 * This class provides input and output streams for telnet clients.

 * This class overrides read to do CRLF processing as specified in

 * RFC 854. The class assumes it is running on a system where lines

 * are terminated with a single newline <LF> character.

 *

 * This is the relevant section of RFC 824 regarding CRLF processing:

 *

 * <pre>

 * The sequence "CR LF", as defined, will cause the NVT to be

 * positioned at the left margin of the next print line (as would,

 * for example, the sequence "LF CR").  However, many systems and

 * terminals do not treat CR and LF independently, and will have to

 * go to some effort to simulate their effect.  (For example, some

 * terminals do not have a CR independent of the LF, but on such

 * terminals it may be possible to simulate a CR by backspacing.)

 * Therefore, the sequence "CR LF" must be treated as a single "new

 * line" character and used whenever their combined action is

 * intended; the sequence "CR NUL" must be used where a carriage

 * return alone is actually desired; and the CR character must be

 * avoided in other contexts.  This rule gives assurance to systems

 * which must decide whether to perform a "new line" function or a

 * multiple-backspace that the TELNET stream contains a character

 * following a CR that will allow a rational decision.

 *

 *    Note that "CR LF" or "CR NUL" is required in both directions

 *    (in the default ASCII mode), to preserve the symmetry of the

 *    NVT model.  Even though it may be known in some situations

 *    (e.g., with remote echo and suppress go ahead options in

 *    effect) that characters are not being sent to an actual

 *    printer, nonetheless, for the sake of consistency, the protocol

 *    requires that a NUL be inserted following a CR not followed by

 *    a LF in the data stream.  The converse of this is that a NUL

 *    received in the data stream after a CR (in the absence of

 *    options negotiations which explicitly specify otherwise) should

 *    be stripped out prior to applying the NVT to local character

 *    set mapping.

 * </pre>

 *

 * @author      Jonathan Payne

 */

public class TelnetInputStream extends FilterInputStream {

    /** If stickyCRLF is true, then we're a machine, like an IBM PC,

        where a Newline is a CR followed by LF.  On UNIX, this is false

        because Newline is represented with just a LF character. */

    boolean         stickyCRLF = false;

    boolean         seenCR = false;

    public boolean  binaryMode = false;

    public TelnetInputStream(InputStream fd, boolean binary) {

        super(fd);

        binaryMode = binary;

    }

    public void setStickyCRLF(boolean on) {

        stickyCRLF = on;

    }

    public int read() throws IOException {

        if (binaryMode)

            return super.read();

        int c;

        /* If last time we determined we saw a CRLF pair, and we're

           not turning that into just a Newline (that is, we're

           stickyCRLF), then return the LF part of that sticky

           pair now. */

        if (seenCR) {

            seenCR = false;

            return '\n';

        }

        if ((c = super.read()) == '\r') {    /* CR */

            switch (c = super.read()) {

            default:

            case -1:                        /* this is an error */

                throw new TelnetProtocolException("misplaced CR in input");

            case 0:                         /* NUL - treat CR as CR */

                return '\r';

            case '\n':                      /* CRLF - treat as NL */

                if (stickyCRLF) {

                    seenCR = true;

                    return '\r';

                } else {

                    return '\n';

                }

            }

        }

        return c;

    }

    /** read into a byte array */

    public int read(byte bytes[]) throws IOException {

        return read(bytes, 0, bytes.length);

    }

    /**

     * Read into a byte array at offset <i>off</i> for length <i>length</i>

     * bytes.

     */

    public int read(byte bytes[], int off, int length) throws IOException {

        if (binaryMode)

            return super.read(bytes, off, length);

        int c;

        int offStart = off;

        while (--length >= 0) {

            c = read();

            if (c == -1)

                break;

            bytes[off++] = (byte)c;

        }

        return (off > offStart) ? off - offStart : -1;

    }

}