1 | /* gdbmdelete.c - Remove the key and its associated data from the database. */
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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 | /* Remove the KEYed item and the KEY from the database DBF. The file on disk
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37 | is updated to reflect the structure of the new database before returning
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38 | from this procedure. */
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39 |
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40 | int
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41 | gdbm_delete (dbf, key)
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42 | gdbm_file_info *dbf;
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43 | datum key;
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44 | {
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45 | int elem_loc; /* The location in the current hash bucket. */
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46 | int last_loc; /* Last location emptied by the delete. */
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47 | int home; /* Home position of an item. */
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48 | bucket_element elem; /* The element to be deleted. */
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49 | char *find_data; /* Return pointer from findkey. */
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50 | int hash_val; /* Returned by findkey. */
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51 | off_t free_adr; /* Temporary stroage for address and size. */
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52 | int free_size;
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53 |
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54 | /* First check to make sure this guy is a writer. */
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55 | if (dbf->read_write == GDBM_READER)
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56 | {
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57 | gdbm_errno = GDBM_READER_CANT_DELETE;
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58 | return -1;
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59 | }
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60 |
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61 | /* Initialize the gdbm_errno variable. */
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62 | gdbm_errno = GDBM_NO_ERROR;
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63 |
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64 | /* Find the item. */
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65 | elem_loc = _gdbm_findkey (dbf, key, &find_data, &hash_val);
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66 | if (elem_loc == -1)
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67 | {
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68 | gdbm_errno = GDBM_ITEM_NOT_FOUND;
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69 | return -1;
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70 | }
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71 |
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72 | /* Save the element. */
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73 | elem = dbf->bucket->h_table[elem_loc];
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74 |
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75 | /* Delete the element. */
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76 | dbf->bucket->h_table[elem_loc].hash_value = -1;
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77 | dbf->bucket->count -= 1;
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78 |
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79 | /* Move other elements to guarantee that they can be found. */
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80 | last_loc = elem_loc;
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81 | elem_loc = (elem_loc + 1) % dbf->header->bucket_elems;
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82 | while (elem_loc != last_loc
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83 | && dbf->bucket->h_table[elem_loc].hash_value != -1)
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84 | {
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85 | home = dbf->bucket->h_table[elem_loc].hash_value
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86 | % dbf->header->bucket_elems;
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87 | if ( (last_loc < elem_loc && (home <= last_loc || home > elem_loc))
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88 | || (last_loc > elem_loc && home <= last_loc && home > elem_loc))
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89 |
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90 | {
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91 | dbf->bucket->h_table[last_loc] = dbf->bucket->h_table[elem_loc];
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92 | dbf->bucket->h_table[elem_loc].hash_value = -1;
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93 | last_loc = elem_loc;
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94 | }
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95 | elem_loc = (elem_loc + 1) % dbf->header->bucket_elems;
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96 | }
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97 |
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98 | /* Free the file space. */
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99 | free_adr = elem.data_pointer;
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100 | free_size = elem.key_size + elem.data_size;
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101 | _gdbm_free (dbf, free_adr, free_size);
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102 |
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103 | /* Set the flags. */
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104 | dbf->bucket_changed = TRUE;
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105 |
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106 | /* Clear out the data cache for the current bucket. */
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107 | if (dbf->cache_entry->ca_data.dptr != NULL)
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108 | {
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109 | free (dbf->cache_entry->ca_data.dptr);
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110 | dbf->cache_entry->ca_data.dptr = NULL;
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111 | }
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112 | dbf->cache_entry->ca_data.hash_val = -1;
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113 | dbf->cache_entry->ca_data.key_size = 0;
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114 | dbf->cache_entry->ca_data.elem_loc = -1;
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115 |
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116 | /* Do the writes. */
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117 | _gdbm_end_update (dbf);
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118 | return 0;
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119 | }
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