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
26 package sun.net;
27
28 import 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 <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
72 public 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 }