1 | /* dbmopen.c - Open the file for dbm operations. This looks like the
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2 | NDBM interface for dbm use. */
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3 |
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4 | /* This file is part of GDBM, the GNU data base manager, by Philip A. Nelson.
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5 | Copyright (C) 1990, 1991, 1993 Free Software Foundation, Inc.
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6 |
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7 | GDBM is free software; you can redistribute it and/or modify
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8 | it under the terms of the GNU General Public License as published by
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9 | the Free Software Foundation; either version 2, or (at your option)
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10 | any later version.
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11 |
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12 | GDBM is distributed in the hope that it will be useful,
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13 | but WITHOUT ANY WARRANTY; without even the implied warranty of
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14 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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15 | GNU General Public License for more details.
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16 |
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17 | You should have received a copy of the GNU General Public License
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18 | along with GDBM; see the file COPYING. If not, write to
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19 | the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
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20 |
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21 | You may contact the author by:
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22 | e-mail: [email protected]
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23 | us-mail: Philip A. Nelson
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24 | Computer Science Department
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25 | Western Washington University
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26 | Bellingham, WA 98226
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27 |
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28 | *************************************************************************/
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29 |
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30 |
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31 | /* include system configuration before all else. */
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32 | #include "autoconf.h"
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33 |
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34 | #include "gdbmdefs.h"
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35 | #include "gdbmerrno.h"
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36 | #include "extern.h"
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37 |
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38 | /* Initialize ndbm system. FILE is a pointer to the file name. In
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39 | standard dbm, the database is found in files called FILE.pag and
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40 | FILE.dir. To make gdbm compatable with dbm using the dbminit call,
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41 | the same file names are used. Specifically, dbminit will use the file
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42 | name FILE.pag in its call to gdbm open. If the file (FILE.pag) has a
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43 | size of zero bytes, a file initialization procedure is performed,
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44 | setting up the initial structure in the file. Any error detected will
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45 | cause a return value of -1. No errors cause the return value of 0.
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46 | NOTE: file.dir will be ignored and will always have a size of zero.
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47 | FLAGS and MODE are the same as the open (2) call. This call will
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48 | look at the FLAGS and decide what call to make to gdbm_open. For
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49 | FLAGS == O_RDONLY, it will be a GDBM_READER, if FLAGS == O_RDWR|O_CREAT,
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50 | it will be a GDBM_WRCREAT (creater and writer) and if the FLAGS == O_RDWR,
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51 | it will be a GDBM_WRITER and if FLAGS contain O_TRUNC then it will be
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52 | a GDBM_NEWDB. All other values of FLAGS in the flags are
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53 | ignored. */
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54 |
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55 | gdbm_file_info *
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56 | dbm_open (file, flags, mode)
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57 | char *file;
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58 | int flags;
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59 | int mode;
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60 | {
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61 | char* pag_file; /* Used to construct "file.pag". */
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62 | char* dir_file; /* Used to construct "file.dir". */
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63 | struct stat dir_stat; /* Stat information for "file.dir". */
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64 | gdbm_file_info *temp_dbf; /* Temporary file pointer storage. */
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65 |
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66 |
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67 | /* Prepare the correct names of "file.pag" and "file.dir". */
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68 | pag_file = (char *) malloc (strlen (file)+5);
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69 | dir_file = (char *) malloc (strlen (file)+5);
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70 | if ((pag_file == NULL) || (dir_file == NULL))
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71 | {
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72 | gdbm_errno = GDBM_MALLOC_ERROR; /* For the hell of it. */
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73 | return NULL;
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74 | }
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75 |
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76 | strcpy (pag_file, file);
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77 | strcat (pag_file, ".pag");
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78 | strcpy (dir_file, file);
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79 | strcat (dir_file, ".dir");
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80 |
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81 |
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82 | /* Call the actual routine, saving the pointer to the file information. */
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83 | flags &= O_RDONLY | O_RDWR | O_CREAT | O_TRUNC;
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84 | if (flags == O_RDONLY)
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85 | {
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86 | temp_dbf = gdbm_open (pag_file, 0, GDBM_READER, 0, NULL);
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87 | }
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88 | else if (flags == (O_RDWR | O_CREAT))
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89 | {
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90 | temp_dbf = gdbm_open (pag_file, 0, GDBM_WRCREAT, mode, NULL);
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91 | }
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92 | else if ( (flags & O_TRUNC) == O_TRUNC)
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93 | {
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94 | temp_dbf = gdbm_open (pag_file, 0, GDBM_NEWDB, mode, NULL);
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95 | }
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96 | else
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97 | {
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98 | temp_dbf = gdbm_open (pag_file, 0, GDBM_WRITER, 0, NULL);
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99 | }
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100 |
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101 | /* Did we successfully open the file? */
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102 | if (temp_dbf == NULL)
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103 | {
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104 | gdbm_errno = GDBM_FILE_OPEN_ERROR;
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105 | goto done;
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106 | }
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107 |
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108 | /* If the database is new, link "file.dir" to "file.pag". This is done
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109 | so the time stamp on both files is the same. */
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110 | if (stat (dir_file, &dir_stat) == 0)
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111 | {
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112 | if (dir_stat.st_size == 0)
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113 | if (unlink (dir_file) != 0 || link (pag_file, dir_file) != 0)
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114 | {
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115 | gdbm_errno = GDBM_FILE_OPEN_ERROR;
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116 | gdbm_close (temp_dbf);
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117 | temp_dbf = NULL;
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118 | goto done;
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119 | }
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120 | }
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121 | else
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122 | {
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123 | /* Since we can't stat it, we assume it is not there and try
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124 | to link the dir_file to the pag_file. */
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125 | if (link (pag_file, dir_file) != 0)
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126 | {
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127 | gdbm_errno = GDBM_FILE_OPEN_ERROR;
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128 | gdbm_close (temp_dbf);
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129 | temp_dbf = NULL;
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130 | goto done;
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131 | }
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132 | }
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133 |
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134 | done:
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135 | free (pag_file);
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136 | free (dir_file);
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137 | return temp_dbf;
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138 | }
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