1/*
2 * Copyright (c) 1994, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26package sun.net;
27
28import java.io.*;
29
30/**
31 * This class provides input and output streams for telnet clients.
32 * This class overrides write to do CRLF processing as specified in
33 * RFC 854. The class assumes it is running on a system where lines
34 * are terminated with a single newline {@literal <LF>} character.
35 *
36 * This is the relevant section of RFC 824 regarding CRLF processing:
37 *
38 * <pre>
39 * The sequence "CR LF", as defined, will cause the NVT to be
40 * positioned at the left margin of the next print line (as would,
41 * for example, the sequence "LF CR").  However, many systems and
42 * terminals do not treat CR and LF independently, and will have to
43 * go to some effort to simulate their effect.  (For example, some
44 * terminals do not have a CR independent of the LF, but on such
45 * terminals it may be possible to simulate a CR by backspacing.)
46 * Therefore, the sequence "CR LF" must be treated as a single "new
47 * line" character and used whenever their combined action is
48 * intended; the sequence "CR NUL" must be used where a carriage
49 * return alone is actually desired; and the CR character must be
50 * avoided in other contexts.  This rule gives assurance to systems
51 * which must decide whether to perform a "new line" function or a
52 * multiple-backspace that the TELNET stream contains a character
53 * following a CR that will allow a rational decision.
54 *
55 *    Note that "CR LF" or "CR NUL" is required in both directions
56 *    (in the default ASCII mode), to preserve the symmetry of the
57 *    NVT model.  Even though it may be known in some situations
58 *    (e.g., with remote echo and suppress go ahead options in
59 *    effect) that characters are not being sent to an actual
60 *    printer, nonetheless, for the sake of consistency, the protocol
61 *    requires that a NUL be inserted following a CR not followed by
62 *    a LF in the data stream.  The converse of this is that a NUL
63 *    received in the data stream after a CR (in the absence of
64 *    options negotiations which explicitly specify otherwise) should
65 *    be stripped out prior to applying the NVT to local character
66 *    set mapping.
67 * </pre>
68 *
69 * @author      Jonathan Payne
70 */
71
72public class TelnetOutputStream extends BufferedOutputStream {
73    boolean         stickyCRLF = false;
74    boolean         seenCR = false;
75
76    public boolean  binaryMode = false;
77
78    public TelnetOutputStream(OutputStream fd, boolean binary) {
79        super(fd);
80        binaryMode = binary;
81    }
82
83    /**
84     * set the stickyCRLF flag. Tells whether the terminal considers CRLF as a single
85     * char.
86     *
87     * @param   on      the <code>boolean</code> to set the flag to.
88     */
89    public void setStickyCRLF(boolean on) {
90        stickyCRLF = on;
91    }
92
93    /**
94     * Writes the int to the stream and does CR LF processing if necessary.
95     */
96    public void write(int c) throws IOException {
97        if (binaryMode) {
98            super.write(c);
99            return;
100        }
101
102        if (seenCR) {
103            if (c != '\n')
104                super.write(0);
105            super.write(c);
106            if (c != '\r')
107                seenCR = false;
108        } else { // !seenCR
109            if (c == '\n') {
110                super.write('\r');
111                super.write('\n');
112                return;
113            }
114            if (c == '\r') {
115                if (stickyCRLF)
116                    seenCR = true;
117                else {
118                    super.write('\r');
119                    c = 0;
120                }
121            }
122            super.write(c);
123        }
124    }
125
126    /**
127     * Write the bytes at offset <i>off</i> in buffer <i>bytes</i> for
128     * <i>length</i> bytes.
129     */
130    public void write(byte bytes[], int off, int length) throws IOException {
131        if (binaryMode) {
132            super.write(bytes, off, length);
133            return;
134        }
135
136        while (--length >= 0) {
137            write(bytes[off++]);
138        }
139    }
140}
141