001: /*
002: * @(#)TelnetOutputStream.java 1.25 06/10/10
003: *
004: * Copyright 1990-2006 Sun Microsystems, Inc. All Rights Reserved.
005: * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
006: *
007: * This program is free software; you can redistribute it and/or
008: * modify it under the terms of the GNU General Public License version
009: * 2 only, as published by the Free Software Foundation.
010: *
011: * This program is distributed in the hope that it will be useful, but
012: * WITHOUT ANY WARRANTY; without even the implied warranty of
013: * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
014: * General Public License version 2 for more details (a copy is
015: * included at /legal/license.txt).
016: *
017: * You should have received a copy of the GNU General Public License
018: * version 2 along with this work; if not, write to the Free Software
019: * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
020: * 02110-1301 USA
021: *
022: * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
023: * Clara, CA 95054 or visit www.sun.com if you need additional
024: * information or have any questions.
025: *
026: */
027:
028: package sun.net;
029:
030: import java.io.*;
031:
032: /**
033: * This class provides input and output streams for telnet clients.
034: * This class overrides write to do CRLF processing as specified in
035: * RFC 854. The class assumes it is running on a system where lines
036: * are terminated with a single newline <LF> character.
037: *
038: * This is the relevant section of RFC 824 regarding CRLF processing:
039: *
040: * <pre>
041: * The sequence "CR LF", as defined, will cause the NVT to be
042: * positioned at the left margin of the next print line (as would,
043: * for example, the sequence "LF CR"). However, many systems and
044: * terminals do not treat CR and LF independently, and will have to
045: * go to some effort to simulate their effect. (For example, some
046: * terminals do not have a CR independent of the LF, but on such
047: * terminals it may be possible to simulate a CR by backspacing.)
048: * Therefore, the sequence "CR LF" must be treated as a single "new
049: * line" character and used whenever their combined action is
050: * intended; the sequence "CR NUL" must be used where a carriage
051: * return alone is actually desired; and the CR character must be
052: * avoided in other contexts. This rule gives assurance to systems
053: * which must decide whether to perform a "new line" function or a
054: * multiple-backspace that the TELNET stream contains a character
055: * following a CR that will allow a rational decision.
056: *
057: * Note that "CR LF" or "CR NUL" is required in both directions
058: * (in the default ASCII mode), to preserve the symmetry of the
059: * NVT model. Even though it may be known in some situations
060: * (e.g., with remote echo and suppress go ahead options in
061: * effect) that characters are not being sent to an actual
062: * printer, nonetheless, for the sake of consistency, the protocol
063: * requires that a NUL be inserted following a CR not followed by
064: * a LF in the data stream. The converse of this is that a NUL
065: * received in the data stream after a CR (in the absence of
066: * options negotiations which explicitly specify otherwise) should
067: * be stripped out prior to applying the NVT to local character
068: * set mapping.
069: * </pre>
070: *
071: * @version 1.21, 08/19/02
072: * @author Jonathan Payne
073: */
074:
075: public class TelnetOutputStream extends BufferedOutputStream {
076: boolean stickyCRLF = false;
077: boolean seenCR = false;
078: public boolean binaryMode = false;
079:
080: public TelnetOutputStream(OutputStream fd, boolean binary) {
081: super (fd);
082: binaryMode = binary;
083: }
084:
085: /**
086: * Writes the int to the stream and does CR LF processing if necessary.
087: */
088: public void write(int c) throws IOException {
089: if (binaryMode)
090: super .write(c);
091: else {
092: if (seenCR) {
093: if (c != '\n')
094: super .write(0);
095: } else if (c == '\r') {
096: if (stickyCRLF)
097: seenCR = true;
098: else {
099: super .write('\r');
100: c = 0;
101: }
102: }
103: super .write(c);
104: }
105: }
106:
107: /**
108: * Write the bytes at offset <i>off</i> in buffer <i>bytes</i> for
109: * <i>length</i> bytes.
110: */
111: public void write(byte bytes[], int off, int length)
112: throws IOException {
113: if (binaryMode) {
114: super .write(bytes, off, length);
115: return;
116: }
117: while (--length >= 0) {
118: write(bytes[off++]);
119: }
120: }
121: }
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