1/* gdbmdelete.c - Remove the key and its associated data from the database. */
2
3/*  This file is part of GDBM, the GNU data base manager, by Philip A. Nelson.
4    Copyright (C) 1990, 1991, 1993  Free Software Foundation, Inc.
5
6    GDBM is free software; you can redistribute it and/or modify
7    it under the terms of the GNU General Public License as published by
8    the Free Software Foundation; either version 2, or (at your option)
9    any later version.
10
11    GDBM is distributed in the hope that it will be useful,
12    but WITHOUT ANY WARRANTY; without even the implied warranty of
13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14    GNU General Public License for more details.
15
16    You should have received a copy of the GNU General Public License
17    along with GDBM; see the file COPYING.  If not, write to
18    the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
19
20    You may contact the author by:
21       e-mail:  phil@cs.wwu.edu
22      us-mail:  Philip A. Nelson
23                Computer Science Department
24                Western Washington University
25                Bellingham, WA 98226
26
27*************************************************************************/
28
29
30/* include system configuration before all else. */
31#include "autoconf.h"
32
33#include "gdbmdefs.h"
34#include "gdbmerrno.h"
35
36/* Remove the KEYed item and the KEY from the database DBF.  The file on disk
37   is updated to reflect the structure of the new database before returning
38   from this procedure.  */
39
40int
41gdbm_delete (dbf, key)
42     gdbm_file_info *dbf;
43     datum key;
44{
45  int elem_loc;		/* The location in the current hash bucket. */
46  int last_loc;		/* Last location emptied by the delete.  */
47  int home;		/* Home position of an item. */
48  bucket_element elem;  /* The element to be deleted. */
49  char *find_data;	/* Return pointer from findkey. */
50  int   hash_val;	/* Returned by findkey. */
51  off_t free_adr;       /* Temporary stroage for address and size. */
52  int   free_size;
53
54  /* First check to make sure this guy is a writer. */
55  if (dbf->read_write == GDBM_READER)
56    {
57      gdbm_errno = GDBM_READER_CANT_DELETE;
58      return -1;
59    }
60
61  /* Initialize the gdbm_errno variable. */
62  gdbm_errno = GDBM_NO_ERROR;
63
64  /* Find the item. */
65  elem_loc = _gdbm_findkey (dbf, key, &find_data, &hash_val);
66  if (elem_loc == -1)
67    {
68      gdbm_errno = GDBM_ITEM_NOT_FOUND;
69      return -1;
70    }
71
72  /* Save the element.  */
73  elem = dbf->bucket->h_table[elem_loc];
74
75  /* Delete the element.  */
76  dbf->bucket->h_table[elem_loc].hash_value = -1;
77  dbf->bucket->count -= 1;
78
79  /* Move other elements to guarantee that they can be found. */
80  last_loc = elem_loc;
81  elem_loc = (elem_loc + 1) % dbf->header->bucket_elems;
82  while (elem_loc != last_loc
83	 && dbf->bucket->h_table[elem_loc].hash_value != -1)
84    {
85      home = dbf->bucket->h_table[elem_loc].hash_value
86	     % dbf->header->bucket_elems;
87      if ( (last_loc < elem_loc && (home <= last_loc || home > elem_loc))
88	  || (last_loc > elem_loc && home <= last_loc && home > elem_loc))
89
90	{
91	  dbf->bucket->h_table[last_loc] = dbf->bucket->h_table[elem_loc];
92	  dbf->bucket->h_table[elem_loc].hash_value = -1;
93	  last_loc = elem_loc;
94	}
95      elem_loc = (elem_loc + 1) % dbf->header->bucket_elems;
96    }
97
98  /* Free the file space. */
99  free_adr = elem.data_pointer;
100  free_size = elem.key_size + elem.data_size;
101  _gdbm_free (dbf, free_adr, free_size);
102
103  /* Set the flags. */
104  dbf->bucket_changed = TRUE;
105
106  /* Clear out the data cache for the current bucket. */
107  if (dbf->cache_entry->ca_data.dptr != NULL)
108    {
109      free (dbf->cache_entry->ca_data.dptr);
110      dbf->cache_entry->ca_data.dptr = NULL;
111    }
112  dbf->cache_entry->ca_data.hash_val = -1;
113  dbf->cache_entry->ca_data.key_size = 0;
114  dbf->cache_entry->ca_data.elem_loc = -1;
115
116  /* Do the writes. */
117  _gdbm_end_update (dbf);
118  return 0;
119}
120