1 | /* gdbmopen.c - Open the dbm file and initialize data structures for use. */
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2 |
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3 | /* This file is part of GDBM, the GNU data base manager, by Philip A. Nelson.
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4 | Copyright (C) 1990, 1991, 1993 Free Software Foundation, Inc.
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5 |
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6 | GDBM 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, or (at your option)
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9 | any later version.
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10 |
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11 | GDBM 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 GDBM; see the file COPYING. If not, write to
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18 | the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
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19 |
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20 | You may contact the author by:
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21 | e-mail: [email protected]
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22 | us-mail: Philip A. Nelson
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23 | Computer Science Department
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24 | Western Washington University
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25 | Bellingham, WA 98226
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26 |
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27 | *************************************************************************/
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28 |
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29 |
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30 | /* include system configuration before all else. */
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31 | #include "autoconf.h"
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32 |
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33 | #include "gdbmdefs.h"
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34 | #include "gdbmerrno.h"
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35 |
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36 | #include "gsdlmods.h"
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37 |
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38 |
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39 | /* Initialize dbm system. FILE is a pointer to the file name. If the file
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40 | has a size of zero bytes, a file initialization procedure is performed,
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41 | setting up the initial structure in the file. BLOCK_SIZE is used during
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42 | initialization to determine the size of various constructs. If the value
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43 | is less than 512, the file system blocksize is used, otherwise the value
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44 | of BLOCK_SIZE is used. BLOCK_SIZE is ignored if the file has previously
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45 | initialized. If FLAGS is set to GDBM_READ the user wants to just
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46 | read the database and any call to dbm_store or dbm_delete will fail. Many
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47 | readers can access the database at the same time. If FLAGS is set to
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48 | GDBM_WRITE, the user wants both read and write access to the database and
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49 | requires exclusive access. If FLAGS is GDBM_WRCREAT, the user wants
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50 | both read and write access to the database and if the database does not
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51 | exist, create a new one. If FLAGS is GDBM_NEWDB, the user want a
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52 | new database created, regardless of whether one existed, and wants read
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53 | and write access to the new database. Any error detected will cause a
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54 | return value of null and an approprate value will be in gdbm_errno. If
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55 | no errors occur, a pointer to the "gdbm file descriptor" will be
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56 | returned. */
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57 |
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58 |
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59 | gdbm_file_info *
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60 | #ifdef MSDOS
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61 | gdbm_open (file, block_size, flags, mode, fatal_func, need_filelock)
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62 | #else
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63 | gdbm_open (file, block_size, flags, mode, fatal_func)
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64 | #endif
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65 | char *file;
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66 | int block_size;
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67 | int flags;
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68 | int mode;
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69 | void (*fatal_func) ();
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70 | #ifdef MSDOS
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71 | int need_filelock;
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72 | #endif
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73 | {
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74 | gdbm_file_info *dbf; /* The record to return. */
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75 | struct stat file_stat; /* Space for the stat information. */
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76 | int len; /* Length of the file name. */
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77 | int num_bytes; /* Used in reading and writing. */
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78 | off_t file_pos; /* Used with seeks. */
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79 | int lock_val; /* Returned by the flock call. */
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80 | int file_block_size; /* Block size to use for a new file. */
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81 | int index; /* Used as a loop index. */
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82 | char need_trunc; /* Used with GDBM_NEWDB and locking to avoid
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83 | truncating a file from under a reader. */
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84 |
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85 | /* Initialize the gdbm_errno variable. */
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86 | gdbm_errno = GDBM_NO_ERROR;
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87 |
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88 | /* Allocate new info structure. */
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89 | dbf = (gdbm_file_info *) malloc (sizeof (gdbm_file_info));
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90 | if (dbf == NULL)
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91 | {
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92 | gdbm_errno = GDBM_MALLOC_ERROR;
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93 | return NULL;
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94 | }
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95 |
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96 | /* Initialize some fields for known values. This is done so gdbm_close
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97 | will work if called before allocating some structures. */
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98 | #ifdef MSDOS
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99 | dbf->need_filelock = need_filelock;
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100 | #endif
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101 | dbf->dir = NULL;
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102 | dbf->bucket = NULL;
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103 | dbf->header = NULL;
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104 | dbf->bucket_cache = NULL;
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105 | dbf->cache_size = 0;
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106 |
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107 | /* Save name of file. */
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108 | len = strlen (file);
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109 | dbf->name = (char *) malloc (len + 1);
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110 | if (dbf->name == NULL)
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111 | {
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112 | free (dbf);
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113 | gdbm_errno = GDBM_MALLOC_ERROR;
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114 | return NULL;
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115 | }
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116 | strcpy (dbf->name, file);
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117 |
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118 | /* Initialize the fatal error routine. */
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119 | dbf->fatal_err = fatal_func;
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120 |
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121 | dbf->fast_write = TRUE; /* Default to setting fast_write. */
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122 | dbf->file_locking = TRUE; /* Default to doing file locking. */
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123 | dbf->central_free = FALSE; /* Default to not using central_free. */
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124 | dbf->coalesce_blocks = FALSE; /* Default to not coalescing blocks. */
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125 |
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126 | /* GDBM_FAST used to determine whethere or not we set fast_write. */
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127 | if (flags & GDBM_SYNC)
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128 | {
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129 | /* If GDBM_SYNC has been requested, don't do fast_write. */
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130 | dbf->fast_write = FALSE;
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131 | }
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132 | if (flags & GDBM_NOLOCK)
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133 | {
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134 | dbf->file_locking = FALSE;
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135 | }
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136 |
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137 | /* Open the file. */
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138 | need_trunc = FALSE;
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139 | switch (flags & GDBM_OPENMASK)
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140 | {
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141 | case GDBM_READER:
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142 | #ifdef MSDOS
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143 | dbf->desc = open (dbf->name, O_RDONLY|O_BINARY, 0);
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144 | #else
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145 | dbf->desc = open (dbf->name, O_RDONLY, 0);
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146 | #endif
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147 | break;
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148 |
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149 | case GDBM_WRITER:
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150 | #ifdef MSDOS
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151 | dbf->desc = open (dbf->name, O_RDWR|O_BINARY, 0);
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152 | #else
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153 | dbf->desc = open (dbf->name, O_RDWR, 0);
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154 | #endif
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155 | break;
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156 |
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157 | case GDBM_NEWDB:
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158 | #ifdef MSDOS
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159 | dbf->desc = open (dbf->name, O_RDWR|O_CREAT|O_BINARY, mode);
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160 | #else
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161 | dbf->desc = open (dbf->name, O_RDWR|O_CREAT, mode);
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162 | #endif
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163 | need_trunc = TRUE;
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164 | break;
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165 |
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166 | default:
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167 | #ifdef MSDOS
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168 | dbf->desc = open (dbf->name, O_RDWR|O_CREAT|O_BINARY, mode);
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169 | #else
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170 | dbf->desc = open (dbf->name, O_RDWR|O_CREAT, mode);
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171 | #endif
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172 | break;
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173 |
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174 | }
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175 | if (dbf->desc < 0)
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176 | {
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177 | free (dbf->name);
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178 | free (dbf);
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179 | gdbm_errno = GDBM_FILE_OPEN_ERROR;
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180 | return NULL;
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181 | }
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182 |
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183 | /* Get the status of the file. */
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184 | fstat (dbf->desc, &file_stat);
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185 |
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186 | /* Lock the file in the approprate way. */
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187 | if ((flags & GDBM_OPENMASK) == GDBM_READER)
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188 | {
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189 | if (file_stat.st_size == 0)
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190 | {
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191 | close (dbf->desc);
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192 | free (dbf->name);
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193 | free (dbf);
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194 | gdbm_errno = GDBM_EMPTY_DATABASE;
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195 | return NULL;
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196 | }
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197 | if (dbf->file_locking)
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198 | {
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199 | /* Sets lock_val to 0 for success. See systems.h. */
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200 | #ifdef MSDOS
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201 | if (dbf->need_filelock) {
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202 | READLOCK_FILE(dbf);
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203 | }
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204 | else {
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205 | lock_val = 0;
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206 | }
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207 | #else
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208 | READLOCK_FILE(dbf);
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209 | #endif
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210 | }
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211 | }
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212 | else if (dbf->file_locking)
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213 | {
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214 | /* Sets lock_val to 0 for success. See systems.h. */
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215 | #ifdef MSDOS
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216 | if (dbf->need_filelock) {
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217 | WRITELOCK_FILE(dbf);
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218 | }
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219 | else {
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220 | lock_val = 0;
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221 | }
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222 | #else
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223 | WRITELOCK_FILE(dbf);
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224 | #endif
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225 | }
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226 | if (dbf->file_locking && (lock_val != 0))
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227 | {
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228 | close (dbf->desc);
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229 | free (dbf->name);
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230 | free (dbf);
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231 | if ((flags & GDBM_OPENMASK) == GDBM_READER)
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232 | gdbm_errno = GDBM_CANT_BE_READER;
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233 | else
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234 | gdbm_errno = GDBM_CANT_BE_WRITER;
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235 | return NULL;
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236 | }
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237 |
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238 | /* Record the kind of user. */
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239 | dbf->read_write = (flags & GDBM_OPENMASK);
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240 |
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241 | /* If we do have a write lock and it was a GDBM_NEWDB, it is
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242 | now time to truncate the file. */
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243 | if (need_trunc && file_stat.st_size != 0)
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244 | {
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245 | TRUNCATE (dbf);
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246 | fstat (dbf->desc, &file_stat);
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247 | }
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248 |
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249 | /* Decide if this is a new file or an old file. */
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250 | if (file_stat.st_size == 0)
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251 | {
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252 |
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253 | /* This is a new file. Create an empty database. */
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254 |
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255 | /* Start with the blocksize. */
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256 | if (block_size < 512)
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257 | file_block_size = STATBLKSIZE;
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258 | else
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259 | file_block_size = block_size;
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260 |
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261 | /* Get space for the file header. */
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262 | dbf->header = (gdbm_file_header *) malloc (file_block_size);
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263 | if (dbf->header == NULL)
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264 | {
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265 | gdbm_close (dbf);
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266 | gdbm_errno = GDBM_MALLOC_ERROR;
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267 | return NULL;
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268 | }
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269 |
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270 | /* Set the magic number and the block_size. */
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271 | dbf->header->header_magic = 0x13579ace;
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272 | dbf->header->block_size = file_block_size;
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273 |
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274 | /* Create the initial hash table directory. */
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275 | dbf->header->dir_size = 8 * sizeof (off_t);
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276 | dbf->header->dir_bits = 3;
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277 | while (dbf->header->dir_size < dbf->header->block_size)
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278 | {
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279 | dbf->header->dir_size <<= 1;
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280 | dbf->header->dir_bits += 1;
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281 | }
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282 |
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283 | /* Check for correct block_size. */
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284 | if (dbf->header->dir_size != dbf->header->block_size)
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285 | {
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286 | gdbm_close (dbf);
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287 | gdbm_errno = GDBM_BLOCK_SIZE_ERROR;
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288 | return NULL;
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289 | }
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290 |
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291 | /* Allocate the space for the directory. */
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292 | dbf->dir = (off_t *) malloc (dbf->header->dir_size);
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293 | if (dbf->dir == NULL)
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294 | {
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295 | gdbm_close (dbf);
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296 | gdbm_errno = GDBM_MALLOC_ERROR;
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297 | return NULL;
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298 | }
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299 | dbf->header->dir = dbf->header->block_size;
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300 |
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301 | /* Create the first and only hash bucket. */
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302 | dbf->header->bucket_elems =
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303 | (dbf->header->block_size - sizeof (hash_bucket))
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304 | / sizeof (bucket_element) + 1;
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305 | dbf->header->bucket_size = dbf->header->block_size;
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306 | dbf->bucket = (hash_bucket *) malloc (dbf->header->bucket_size);
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307 | if (dbf->bucket == NULL)
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308 | {
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309 | gdbm_close (dbf);
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310 | gdbm_errno = GDBM_MALLOC_ERROR;
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311 | return NULL;
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312 | }
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313 | _gdbm_new_bucket (dbf, dbf->bucket, 0);
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314 | dbf->bucket->av_count = 1;
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315 | dbf->bucket->bucket_avail[0].av_adr = 3*dbf->header->block_size;
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316 | dbf->bucket->bucket_avail[0].av_size = dbf->header->block_size;
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317 |
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318 | /* Set table entries to point to hash buckets. */
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319 | for (index = 0; index < dbf->header->dir_size / sizeof (off_t); index++)
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320 | dbf->dir[index] = 2*dbf->header->block_size;
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321 |
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322 | /* Initialize the active avail block. */
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323 | dbf->header->avail.size
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324 | = ( (dbf->header->block_size - sizeof (gdbm_file_header))
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325 | / sizeof (avail_elem)) + 1;
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326 | dbf->header->avail.count = 0;
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327 | dbf->header->avail.next_block = 0;
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328 | dbf->header->next_block = 4*dbf->header->block_size;
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329 |
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330 | /* Write initial configuration to the file. */
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331 | /* Block 0 is the file header and active avail block. */
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332 | num_bytes = write (dbf->desc, dbf->header, dbf->header->block_size);
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333 | if (num_bytes != dbf->header->block_size)
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334 | {
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335 | gdbm_close (dbf);
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336 | gdbm_errno = GDBM_FILE_WRITE_ERROR;
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337 | return NULL;
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338 | }
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339 |
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340 | /* Block 1 is the initial bucket directory. */
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341 | num_bytes = write (dbf->desc, dbf->dir, dbf->header->dir_size);
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342 | if (num_bytes != dbf->header->dir_size)
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343 | {
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344 | gdbm_close (dbf);
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345 | gdbm_errno = GDBM_FILE_WRITE_ERROR;
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346 | return NULL;
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347 | }
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348 |
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349 | /* Block 2 is the only bucket. */
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350 | num_bytes = write (dbf->desc, dbf->bucket, dbf->header->bucket_size);
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351 | if (num_bytes != dbf->header->bucket_size)
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352 | {
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353 | gdbm_close (dbf);
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354 | gdbm_errno = GDBM_FILE_WRITE_ERROR;
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355 | return NULL;
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356 | }
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357 |
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358 | /* Wait for initial configuration to be written to disk. */
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359 | fsync (dbf->desc);
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360 |
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361 | free (dbf->bucket);
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362 | }
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363 | else
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364 | {
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365 | /* This is an old database. Read in the information from the file
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366 | header and initialize the hash directory. */
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367 |
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368 | gdbm_file_header partial_header; /* For the first part of it. */
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369 |
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370 | /* Read the partial file header. */
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371 | num_bytes = read (dbf->desc, &partial_header, sizeof (gdbm_file_header));
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372 | if (num_bytes != sizeof (gdbm_file_header))
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373 | {
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374 | gdbm_close (dbf);
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375 | gdbm_errno = GDBM_FILE_READ_ERROR;
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376 | return NULL;
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377 | }
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378 |
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379 | // GREENSTONE CUSTOMISATION: Check if the magic number is reversed
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380 | // If it is then the GDBM file is the wrong endianness for the current machine
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381 | wrong_endianness = (partial_header.header_magic == 0xCE9A5713);
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382 |
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383 | // GREENSTONE CUSTOMISATION (thanks to Andrew Brooks): prevent write access to wrong-byte-order databases
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384 | if (wrong_endianness && ((flags & GDBM_OPENMASK) != GDBM_READER))
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385 | {
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386 | gdbm_close (dbf);
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387 | gdbm_errno = GDBM_CANT_BE_WRITER;
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388 | return NULL;
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389 | }
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390 |
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391 | // GREENSTONE CUSTOMISATION: Swap each value in the partial header if the GDBM file is the wrong endianness
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392 | if (wrong_endianness)
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393 | {
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394 | endian_swap_array((int*) &partial_header, sizeof (gdbm_file_header));
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395 | }
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396 |
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397 | /* Is the magic number good? */
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398 | if (partial_header.header_magic != 0x13579ace)
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399 | {
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400 | gdbm_close (dbf);
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401 | gdbm_errno = GDBM_BAD_MAGIC_NUMBER;
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402 | return NULL;
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403 | }
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404 |
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405 | /* GREENSTONE CUSTOMISATION: Debugging output
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406 | printf("\n");
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407 | printf("Header magic: %x\n", partial_header.header_magic);
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408 | printf("Block size: %d\n", partial_header.block_size);
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409 | printf("Dir: %d\n", partial_header.dir);
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410 | printf("Dir size: %d\n", partial_header.dir_size);
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411 | printf("Dir bits: %d\n", partial_header.dir_bits);
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412 | printf("Bucket size: %d\n", partial_header.bucket_size);
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413 | printf("Bucket elems: %d\n", partial_header.bucket_elems);
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414 | printf("Next block: %d\n", partial_header.next_block);
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415 | printf("\n");
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416 | */
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417 |
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418 | /* It is a good database, read the entire header. */
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419 | dbf->header = (gdbm_file_header *) malloc (partial_header.block_size);
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420 | if (dbf->header == NULL)
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421 | {
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422 | gdbm_close (dbf);
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423 | gdbm_errno = GDBM_MALLOC_ERROR;
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424 | return NULL;
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425 | }
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426 | bcopy (&partial_header, dbf->header, sizeof (gdbm_file_header));
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427 | num_bytes = read (dbf->desc, &dbf->header->avail.av_table[1],
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428 | dbf->header->block_size-sizeof (gdbm_file_header));
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429 |
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430 | // GREENSTONE CUSTOMISATION: Swap each value in the header if the GDBM file is the wrong endianness
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431 | if (wrong_endianness)
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432 | {
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433 | endian_swap_array((int*) &dbf->header->avail.av_table[1],
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434 | dbf->header->block_size-sizeof(gdbm_file_header));
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435 | }
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436 |
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437 | if (num_bytes != dbf->header->block_size-sizeof (gdbm_file_header))
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438 | {
|
---|
439 | gdbm_close (dbf);
|
---|
440 | gdbm_errno = GDBM_FILE_READ_ERROR;
|
---|
441 | return NULL;
|
---|
442 | }
|
---|
443 |
|
---|
444 | /* Allocate space for the hash table directory. */
|
---|
445 | dbf->dir = (off_t *) malloc (dbf->header->dir_size);
|
---|
446 | if (dbf->dir == NULL)
|
---|
447 | {
|
---|
448 | gdbm_close (dbf);
|
---|
449 | gdbm_errno = GDBM_MALLOC_ERROR;
|
---|
450 | return NULL;
|
---|
451 | }
|
---|
452 |
|
---|
453 | /* Read the hash table directory. */
|
---|
454 | file_pos = lseek (dbf->desc, dbf->header->dir, L_SET);
|
---|
455 | if (file_pos != dbf->header->dir)
|
---|
456 | {
|
---|
457 | gdbm_close (dbf);
|
---|
458 | gdbm_errno = GDBM_FILE_SEEK_ERROR;
|
---|
459 | return NULL;
|
---|
460 | }
|
---|
461 |
|
---|
462 | num_bytes = read (dbf->desc, dbf->dir, dbf->header->dir_size);
|
---|
463 | if (num_bytes != dbf->header->dir_size)
|
---|
464 | {
|
---|
465 | gdbm_close (dbf);
|
---|
466 | gdbm_errno = GDBM_FILE_READ_ERROR;
|
---|
467 | return NULL;
|
---|
468 | }
|
---|
469 |
|
---|
470 | // GREENSTONE CUSTOMISATION: Swap each value in the directory if the GDBM file is the wrong endianness
|
---|
471 | if (wrong_endianness)
|
---|
472 | {
|
---|
473 | endian_swap_array((int*) dbf->dir, dbf->header->dir_size);
|
---|
474 | }
|
---|
475 | }
|
---|
476 |
|
---|
477 | /* Finish initializing dbf. */
|
---|
478 | dbf->last_read = -1;
|
---|
479 | dbf->bucket = NULL;
|
---|
480 | dbf->bucket_dir = 0;
|
---|
481 | dbf->cache_entry = NULL;
|
---|
482 | dbf->header_changed = FALSE;
|
---|
483 | dbf->directory_changed = FALSE;
|
---|
484 | dbf->bucket_changed = FALSE;
|
---|
485 | dbf->second_changed = FALSE;
|
---|
486 |
|
---|
487 | /* Everything is fine, return the pointer to the file
|
---|
488 | information structure. */
|
---|
489 | return dbf;
|
---|
490 |
|
---|
491 | }
|
---|
492 |
|
---|
493 | /* initialize the bucket cache. */
|
---|
494 | int
|
---|
495 | _gdbm_init_cache(dbf, size)
|
---|
496 | gdbm_file_info *dbf;
|
---|
497 | int size;
|
---|
498 | {
|
---|
499 | register int index;
|
---|
500 |
|
---|
501 | if (dbf->bucket_cache == NULL)
|
---|
502 | {
|
---|
503 | dbf->bucket_cache = (cache_elem *) malloc(sizeof(cache_elem) * size);
|
---|
504 | if(dbf->bucket_cache == NULL)
|
---|
505 | {
|
---|
506 | gdbm_errno = GDBM_MALLOC_ERROR;
|
---|
507 | return(-1);
|
---|
508 | }
|
---|
509 | dbf->cache_size = size;
|
---|
510 |
|
---|
511 | for(index = 0; index < size; index++)
|
---|
512 | {
|
---|
513 | (dbf->bucket_cache[index]).ca_bucket
|
---|
514 | = (hash_bucket *) malloc (dbf->header->bucket_size);
|
---|
515 | if ((dbf->bucket_cache[index]).ca_bucket == NULL)
|
---|
516 | {
|
---|
517 | gdbm_errno = GDBM_MALLOC_ERROR;
|
---|
518 | return(-1);
|
---|
519 | }
|
---|
520 | (dbf->bucket_cache[index]).ca_adr = 0;
|
---|
521 | (dbf->bucket_cache[index]).ca_changed = FALSE;
|
---|
522 | (dbf->bucket_cache[index]).ca_data.hash_val = -1;
|
---|
523 | (dbf->bucket_cache[index]).ca_data.elem_loc = -1;
|
---|
524 | (dbf->bucket_cache[index]).ca_data.dptr = NULL;
|
---|
525 | }
|
---|
526 | dbf->bucket = dbf->bucket_cache[0].ca_bucket;
|
---|
527 | dbf->cache_entry = &dbf->bucket_cache[0];
|
---|
528 | }
|
---|
529 | return(0);
|
---|
530 | }
|
---|