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| 1 | +/* | |
| 2 | + * Copyright (c) 1994, 2002, 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 wether 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 | +} | |