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1 /* |
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2 * Copyright 1994-1995 Sun Microsystems, Inc. All Rights Reserved. |
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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4 * |
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5 * This code is free software; you can redistribute it and/or modify it |
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6 * under the terms of the GNU General Public License version 2 only, as |
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7 * published by the Free Software Foundation. Sun designates this |
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8 * particular file as subject to the "Classpath" exception as provided |
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9 * by Sun in the LICENSE file that accompanied this code. |
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10 * |
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11 * This code is distributed in the hope that it will be useful, but WITHOUT |
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12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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14 * version 2 for more details (a copy is included in the LICENSE file that |
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15 * accompanied this code). |
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16 * |
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17 * You should have received a copy of the GNU General Public License version |
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18 * 2 along with this work; if not, write to the Free Software Foundation, |
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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20 * |
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21 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, |
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22 * CA 95054 USA or visit www.sun.com if you need additional information or |
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23 * have any questions. |
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24 */ |
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25 |
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26 package sun.net; |
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27 |
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28 import java.io.*; |
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29 |
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30 /** |
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31 * This class provides input and output streams for telnet clients. |
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32 * This class overrides read to do CRLF processing as specified in |
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33 * RFC 854. The class assumes it is running on a system where lines |
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34 * are terminated with a single newline <LF> character. |
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35 * |
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36 * This is the relevant section of RFC 824 regarding CRLF processing: |
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37 * |
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38 * <pre> |
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39 * The sequence "CR LF", as defined, will cause the NVT to be |
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40 * positioned at the left margin of the next print line (as would, |
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41 * for example, the sequence "LF CR"). However, many systems and |
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42 * terminals do not treat CR and LF independently, and will have to |
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43 * go to some effort to simulate their effect. (For example, some |
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44 * terminals do not have a CR independent of the LF, but on such |
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45 * terminals it may be possible to simulate a CR by backspacing.) |
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46 * Therefore, the sequence "CR LF" must be treated as a single "new |
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47 * line" character and used whenever their combined action is |
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48 * intended; the sequence "CR NUL" must be used where a carriage |
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49 * return alone is actually desired; and the CR character must be |
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50 * avoided in other contexts. This rule gives assurance to systems |
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51 * which must decide whether to perform a "new line" function or a |
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52 * multiple-backspace that the TELNET stream contains a character |
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53 * following a CR that will allow a rational decision. |
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54 * |
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55 * Note that "CR LF" or "CR NUL" is required in both directions |
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56 * (in the default ASCII mode), to preserve the symmetry of the |
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57 * NVT model. Even though it may be known in some situations |
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58 * (e.g., with remote echo and suppress go ahead options in |
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59 * effect) that characters are not being sent to an actual |
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60 * printer, nonetheless, for the sake of consistency, the protocol |
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61 * requires that a NUL be inserted following a CR not followed by |
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62 * a LF in the data stream. The converse of this is that a NUL |
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63 * received in the data stream after a CR (in the absence of |
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64 * options negotiations which explicitly specify otherwise) should |
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65 * be stripped out prior to applying the NVT to local character |
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66 * set mapping. |
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67 * </pre> |
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68 * |
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69 * @author Jonathan Payne |
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70 */ |
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71 |
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72 public class TelnetInputStream extends FilterInputStream { |
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73 /** If stickyCRLF is true, then we're a machine, like an IBM PC, |
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74 where a Newline is a CR followed by LF. On UNIX, this is false |
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75 because Newline is represented with just a LF character. */ |
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76 boolean stickyCRLF = false; |
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77 boolean seenCR = false; |
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78 |
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79 public boolean binaryMode = false; |
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80 |
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81 public TelnetInputStream(InputStream fd, boolean binary) { |
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82 super(fd); |
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83 binaryMode = binary; |
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84 } |
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85 |
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86 public void setStickyCRLF(boolean on) { |
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87 stickyCRLF = on; |
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88 } |
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89 |
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90 public int read() throws IOException { |
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91 if (binaryMode) |
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92 return super.read(); |
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93 |
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94 int c; |
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95 |
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96 /* If last time we determined we saw a CRLF pair, and we're |
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97 not turning that into just a Newline (that is, we're |
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98 stickyCRLF), then return the LF part of that sticky |
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99 pair now. */ |
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100 |
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101 if (seenCR) { |
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102 seenCR = false; |
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103 return '\n'; |
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104 } |
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105 |
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106 if ((c = super.read()) == '\r') { /* CR */ |
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107 switch (c = super.read()) { |
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108 default: |
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109 case -1: /* this is an error */ |
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110 throw new TelnetProtocolException("misplaced CR in input"); |
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111 |
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112 case 0: /* NUL - treat CR as CR */ |
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113 return '\r'; |
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114 |
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115 case '\n': /* CRLF - treat as NL */ |
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116 if (stickyCRLF) { |
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117 seenCR = true; |
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118 return '\r'; |
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119 } else { |
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120 return '\n'; |
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121 } |
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122 } |
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123 } |
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124 return c; |
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125 } |
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126 |
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127 /** read into a byte array */ |
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128 public int read(byte bytes[]) throws IOException { |
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129 return read(bytes, 0, bytes.length); |
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130 } |
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131 |
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132 /** |
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133 * Read into a byte array at offset <i>off</i> for length <i>length</i> |
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134 * bytes. |
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135 */ |
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136 public int read(byte bytes[], int off, int length) throws IOException { |
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137 if (binaryMode) |
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138 return super.read(bytes, off, length); |
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139 |
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140 int c; |
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141 int offStart = off; |
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142 |
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143 while (--length >= 0) { |
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144 c = read(); |
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145 if (c == -1) |
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146 break; |
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147 bytes[off++] = (byte)c; |
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148 } |
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149 return (off > offStart) ? off - offStart : -1; |
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150 } |
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151 } |