1/*
2 * Copyright (c) 1994, 1995, 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 read 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 TelnetInputStream extends FilterInputStream {
73    /** If stickyCRLF is true, then we're a machine, like an IBM PC,
74        where a Newline is a CR followed by LF.  On UNIX, this is false
75        because Newline is represented with just a LF character. */
76    boolean         stickyCRLF = false;
77    boolean         seenCR = false;
78
79    public boolean  binaryMode = false;
80
81    public TelnetInputStream(InputStream fd, boolean binary) {
82        super(fd);
83        binaryMode = binary;
84    }
85
86    public void setStickyCRLF(boolean on) {
87        stickyCRLF = on;
88    }
89
90    public int read() throws IOException {
91        if (binaryMode)
92            return super.read();
93
94        int c;
95
96        /* If last time we determined we saw a CRLF pair, and we're
97           not turning that into just a Newline (that is, we're
98           stickyCRLF), then return the LF part of that sticky
99           pair now. */
100
101        if (seenCR) {
102            seenCR = false;
103            return '\n';
104        }
105
106        if ((c = super.read()) == '\r') {    /* CR */
107            switch (c = super.read()) {
108            default:
109            case -1:                        /* this is an error */
110                throw new TelnetProtocolException("misplaced CR in input");
111
112            case 0:                         /* NUL - treat CR as CR */
113                return '\r';
114
115            case '\n':                      /* CRLF - treat as NL */
116                if (stickyCRLF) {
117                    seenCR = true;
118                    return '\r';
119                } else {
120                    return '\n';
121                }
122            }
123        }
124        return c;
125    }
126
127    /** read into a byte array */
128    public int read(byte bytes[]) throws IOException {
129        return read(bytes, 0, bytes.length);
130    }
131
132    /**
133     * Read into a byte array at offset <i>off</i> for length <i>length</i>
134     * bytes.
135     */
136    public int read(byte bytes[], int off, int length) throws IOException {
137        if (binaryMode)
138            return super.read(bytes, off, length);
139
140        int c;
141        int offStart = off;
142
143        while (--length >= 0) {
144            c = read();
145            if (c == -1)
146                break;
147            bytes[off++] = (byte)c;
148        }
149        return (off > offStart) ? off - offStart : -1;
150    }
151}
152