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1772
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1 /* genseq.c Routine to create a unique ID for UUCP spool files.
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2 Copyright (C) 1990, 1993 Rick Adams and Bob Billson
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3
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4 This file is part of the OS-9 UUCP package, UUCPbb.
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5
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6 This program is free software; you can redistribute it and/or modify
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7 it under the terms of the GNU General Public License as published by
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8 the Free Software Foundation; either version 2 of the License, or
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9 (at your option) any later version.
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10
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11 This program is distributed in the hope that it will be useful,
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12 but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 GNU General Public License for more details.
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15
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16 You should have received a copy of the GNU General Public License
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17 along with this program; if not, write to the Free Software
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18 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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19
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20 The author of UUCPbb, Bob Billson, can be contacted at:
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21 bob@kc2wz.bubble.org or uunet!kc2wz!bob or by snail mail:
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22 21 Bates Way, Westfield, NJ 07090
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23 */
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24
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25 /* Generate a unique sequence id for spool files. The last value used is
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26 stored in the file GENSEQ (defined in uucp.h). The values run from '0000'
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27 to '0zzz'. Three places gives us 46,656 unique combinations. (26 letters
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28 plus 10 digits. -- 36^3) '0zzz' wraps around to '0000'. This should be
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29 plenty for everyday use <grin>. Of course, if you wish, you can change the
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30 value of MSB below to '0'. This will use all four places. You will then
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31 have 1,679,616 unique combinations. To use them all in one year, you will
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32 need to send about 4,600 messages/day. If you do that, you need more than
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33 a CoCo! 8-) --REB */
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34
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35 #include "uucp.h"
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36 #include <modes.h>
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37
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38 #define MSB 1 /* leftmost place of string before wrapping around */
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39
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40 EXTERN QQ unsigned myuid;
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41
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42 static char sequence[5];
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43
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44
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45 char *genseq()
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46 {
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47 char seq[5], nextseq();
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48 FILE *sfp;
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49 register int i;
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50 flag carry;
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51
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52 /* must be superuser to get at the sequence file */
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53 asetuid (0);
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54
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55 if ((sfp = fopen (GENSEQ, "r")) == NULL)
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56 strcpy (seq, "0000");
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57 else
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58 {
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59 if ((fgets (seq, sizeof (seq), sfp) == NULL) || seq[0] == '\0')
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60 /* file exists but empty? Start sequence over again */
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61 strcpy (seq, "0000");
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62
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63 fclose (sfp);
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64
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65 /* Create next sequence id. As long as we have a carry, keep moving
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66 one place to the left, up to place define by MSB. */
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67
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68 for (i = 3, carry = TRUE; carry && i >= MSB; --i)
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69 seq[i] = nextseq (seq[i], &carry);
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70 }
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71
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72 if ((sfp = fopen (GENSEQ, "w")) == NULL)
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73 fatal ("genseq() can't open spool sequence file for writing");
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74
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75 strcpy (sequence, seq);
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76 fprintf (sfp, "%s", seq);
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77
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78 /* protect the sequence file from prying eyes/hands */
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79 fixperms (sfp);
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80
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81 fclose (sfp);
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82 asetuid (myuid);
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83 return (sequence);
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84 }
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85
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86
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87
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88 /* Get the next value in the sequence which runs from 0 - 9 and a - z. Skip
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89 any non-letters/numbers. If the value is > 'Z', we wrap around to '0' and
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90 bump the next left place up one on our next pass. */
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91
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92 char nextseq (place_val, carry)
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93 char place_val;
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94 flag *carry;
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95 {
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96 ++place_val;
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97
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98 if (place_val > 'z')
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99 {
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100 place_val = '0';
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101 *carry = TRUE;
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102 }
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103 else
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104 {
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105 if (place_val == ':')
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106 place_val = 'a';
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107
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108 *carry = FALSE;
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109 }
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110 return (place_val);
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111 }
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