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1 ;;; multicast.el --- lisp frontend for multicast connections in XEmacs
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2
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3 ;; Copyright (C) 1997-2000 Didier Verna.
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4 ;; Copyright (C) 2002 Ben Wing.
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5
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6 ;; Author: Didier Verna <didier@xemacs.org>
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7 ;; Maintainer: Didier Verna <didier@xemacs.org>
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8 ;; Created: Thu Dec 4 16:37:39 1997
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9 ;; Last Revision: Mon Jan 19 19:10:50 1998
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10 ;; Current Version: 0.4
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11 ;; Keywords: dumped comm processes
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12
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13 ;; This file is part of XEmacs.
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14
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15 ;; XEmacs is free software; you can redistribute it and/or modify
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16 ;; it under the terms of the GNU General Public License as published by
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17 ;; the Free Software Foundation; either version 2 of the License, or
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18 ;; (at your option) any later version.
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19
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20 ;; XEmacs is distributed in the hope that it will be useful,
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21 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
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22 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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23 ;; GNU General Public License for more details.
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24
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25 ;; You should have received a copy of the GNU General Public License
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26 ;; along with this program; if not, write to the Free Software
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27 ;; Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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28
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29
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30 ;;; Commentary:
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31
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32 ;; This file just contains a lisp frontend to the internal function
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33 ;; open-multicast-group-internal written in C and belonging to process.c
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34 ;; Well, nothing much to say about it ... read the doc string.
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35
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36
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37 ;;; Change Log:
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38
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39 ;; Rev. of Mon Jan 19 19:04:44 1998 : packaging cleanup
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40 ;; Rev. of Thu Dec 11 13:54:26 1997 : updated the docstring
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41 ;; Rev. of Mon Dec 8 15:28:47 1997 : Improved the doc string
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42 ;; Rev. of Thu Dec 4 16:38:09 1997 : Initial Version.
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43
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44
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45 ;;; Code:
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46
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47 (defun open-multicast-group (name buffer address)
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48 "Open a multicast connection on the specified address.
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49 Returns a process object to represent the connection.
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50 Input and output work as for subprocesses; `delete-process' closes it.
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51 NAME is a name for the process. It is modified if necessary to make it unique.
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52 BUFFER is the buffer (or buffer-name) to associate with the process.
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53 Process output goes at the end of that buffer, unless you specify an output
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54 stream or filter function to handle the output.
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55 BUFFER may be also nil, meaning that this process is not associated with any
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56 buffer.
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57 ADDRESS specifies a standard multicast address \"dest/port/ttl\":
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58 dest is an internet address between 224.0.0.0 and 239.255.255.255
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59 port is a communication port like in traditional unicast
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60 ttl is the time-to-live (15 for site, 63 for region and 127 for world).
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61
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62 WARNING: it is *strongly* recommended to avoid using groups beginning with
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63 224 or 239. Such groups are considered 'admin' groups, and may
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64 behave in a surprising way ...
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65
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66 The read/write coding systems used for process I/O on the process are
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67 determined as follows:
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68
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69 1. `coding-system-for-read', `coding-system-for-write', if non-nil.
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70 (Intended as a temporary overriding mechanism for use by Lisp
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71 code.)
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72 2. The matching value for the port from `network-coding-system-alist',
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73 if any, and if non-nil. The value may be either a single coding
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74 system, used for both read and write; or a cons of read/write; or a
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75 function, called to get one of the other two values.
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76 3. The value of `default-network-coding-system', which should be a cons
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77 of read/write coding systems, if the values are non-nil.
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78 4. The coding system `undecided' for read, and `raw-text' for write.
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79
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80 Note that the processes of determining the read and write coding systems
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81 proceed essentially independently one from the other, as in `start-process'.
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82
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83 You can change the coding systems later on using
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84 `set-process-coding-system', `set-process-input-coding-system', or
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85 `set-process-output-coding-system'."
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86 (let (dest port ttl)
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87 ;; We check only the general form of the multicast address.
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88 ;; The rest will be handled by the internal function.
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89 (string-match "^\\([0-9\\.]+\\)/\\([0-9]+\\)/\\([0-9]+\\)$" address)
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90 (and (not (and (= (match-beginning 0) 0)
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91 (= (match-end 0) (length address))))
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92 (error "malformed multicast address: %s" address))
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93 (and (not (setq dest (match-string 1 address)))
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94 (error "invalid destination specification."))
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95 (and (= 0 (setq port (string-to-int (match-string 2 address))))
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96 (error "invalid port specification."))
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97 (and (= 0 (setq ttl (string-to-int (match-string 3 address))))
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98 (error "invalid ttl specification."))
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99 (let (cs-r cs-w)
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100 (let (ret)
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101 (catch 'found
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102 (let ((alist network-coding-system-alist)
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103 (case-fold-search nil)
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104 pattern)
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105 (while alist
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106 (setq pattern (car (car alist)))
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107 (and
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108 (cond ((numberp pattern)
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109 (and (numberp port)
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110 (eq pattern port)))
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111 ((stringp pattern)
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112 (or (and (stringp port)
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113 (string-match pattern port))
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114 (and (numberp port)
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115 (string-match pattern
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116 (number-to-string port))))))
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117 (throw 'found (setq ret (cdr (car alist)))))
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118 (setq alist (cdr alist))
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119 )))
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120 (if (functionp ret)
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121 (setq ret (funcall ret 'open-multicast-group port)))
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122 (cond ((consp ret)
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123 (setq cs-r (car ret)
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124 cs-w (cdr ret)))
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125 ((and ret (find-coding-system ret))
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126 (setq cs-r ret
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127 cs-w ret))))
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128 (let ((coding-system-for-read
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129 (or coding-system-for-read cs-r
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130 (car default-network-coding-system)
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131 'undecided))
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132 (coding-system-for-write
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133 (or coding-system-for-write cs-w
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134 (cdr default-network-coding-system)
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135 'raw-text)))
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136 (declare-fboundp (open-multicast-group-internal name buffer dest port
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137 ttl))))))
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139 ;;; multicast.el ends here
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