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