001: /*
002: * @(#)TelnetInputStream.java 1.26 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 read 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 1.22, 08/19/02
072: * @author Jonathan Payne
073: */
074:
075: public class TelnetInputStream extends FilterInputStream {
076: /** If stickyCRLF is true, then we're a machine, like an IBM PC,
077: where a Newline is a CR followed by LF. On UNIX, this is false
078: because Newline is represented with just a LF character. */
079: boolean stickyCRLF = false;
080: boolean seenCR = false;
081: public boolean binaryMode = false;
082:
083: public TelnetInputStream(InputStream fd, boolean binary) {
084: super (fd);
085: binaryMode = binary;
086: }
087:
088: public void setStickyCRLF(boolean on) {
089: stickyCRLF = on;
090: }
091:
092: public int read() throws IOException {
093: if (binaryMode)
094: return super .read();
095: int c;
096: /* If last time we determined we saw a CRLF pair, and we're
097: not turning that into just a Newline (that is, we're
098: stickyCRLF), then return the LF part of that sticky
099: pair now. */
100:
101: if (seenCR) {
102: seenCR = false;
103: return '\n';
104: }
105: if ((c = super .read()) == '\r') { /* CR */
106: switch (c = super .read()) {
107: default:
108: case -1: /* this is an error */
109: throw new TelnetProtocolException(
110: "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)
137: throws IOException {
138: if (binaryMode)
139: return super .read(bytes, off, length);
140: int c;
141: int offStart = off;
142: while (--length >= 0) {
143: c = read();
144: if (c == -1)
145: break;
146: bytes[off++] = (byte) c;
147: }
148: return (off > offStart) ? off - offStart : -1;
149: }
150: }
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