[18019] | 1 | /* bucket.c - The routines for playing with hash buckets. */
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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 |
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[18038] | 35 | #include "gsdlmods.h"
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[18019] | 36 |
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[18038] | 37 |
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[18019] | 38 | /* Initializing a new hash buckets sets all bucket entries to -1 hash value. */
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| 39 | void
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| 40 | _gdbm_new_bucket (dbf, bucket, bits)
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| 41 | gdbm_file_info *dbf;
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| 42 | hash_bucket *bucket;
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| 43 | int bits;
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| 44 | {
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| 45 | int index;
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| 46 |
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| 47 | /* Initialize the avail block. */
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| 48 | bucket->av_count = 0;
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| 49 |
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| 50 | /* Set the information fields first. */
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| 51 | bucket->bucket_bits = bits;
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| 52 | bucket->count = 0;
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| 53 |
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| 54 | /* Initialize all bucket elements. */
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| 55 | for (index = 0; index < dbf->header->bucket_elems; index++)
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| 56 | bucket->h_table[index].hash_value = -1;
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| 57 | }
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| 58 |
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| 59 |
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| 60 |
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| 61 | /* Find a bucket for DBF that is pointed to by the bucket directory from
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| 62 | location DIR_INDEX. The bucket cache is first checked to see if it
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| 63 | is already in memory. If not, a bucket may be tossed to read the new
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| 64 | bucket. In any case, the requested bucket is make the "current" bucket
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| 65 | and dbf->bucket points to the correct bucket. */
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| 66 |
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| 67 | void
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| 68 | _gdbm_get_bucket (dbf, dir_index)
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| 69 | gdbm_file_info *dbf;
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| 70 | int dir_index;
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| 71 | {
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| 72 | off_t bucket_adr; /* The address of the correct hash bucket. */
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| 73 | int num_bytes; /* The number of bytes read. */
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| 74 | off_t file_pos; /* The return address for lseek. */
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| 75 | register int index; /* Loop index. */
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| 76 |
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| 77 | /* Initial set up. */
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| 78 | dbf->bucket_dir = dir_index;
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| 79 | bucket_adr = dbf->dir [dir_index];
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| 80 |
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| 81 | if (dbf->bucket_cache == NULL)
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| 82 | {
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| 83 | if(_gdbm_init_cache(dbf, DEFAULT_CACHESIZE) == -1)
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| 84 | _gdbm_fatal(dbf, "couldn't init cache");
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| 85 | }
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| 86 |
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| 87 | /* Is that one is not already current, we must find it. */
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| 88 | if (dbf->cache_entry->ca_adr != bucket_adr)
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| 89 | {
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| 90 | /* Look in the cache. */
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| 91 | for (index = 0; index < dbf->cache_size; index++)
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| 92 | {
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| 93 | if (dbf->bucket_cache[index].ca_adr == bucket_adr)
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| 94 | {
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| 95 | dbf->bucket = dbf->bucket_cache[index].ca_bucket;
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| 96 | dbf->cache_entry = &dbf->bucket_cache[index];
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| 97 | return;
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| 98 | }
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| 99 | }
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| 100 |
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| 101 | /* It is not in the cache, read it from the disk. */
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| 102 | dbf->last_read = (dbf->last_read + 1) % dbf->cache_size;
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| 103 | if (dbf->bucket_cache[dbf->last_read].ca_changed)
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| 104 | _gdbm_write_bucket (dbf, &dbf->bucket_cache[dbf->last_read]);
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| 105 | dbf->bucket_cache[dbf->last_read].ca_adr = bucket_adr;
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| 106 | dbf->bucket = dbf->bucket_cache[dbf->last_read].ca_bucket;
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| 107 | dbf->cache_entry = &dbf->bucket_cache[dbf->last_read];
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| 108 | dbf->cache_entry->ca_data.elem_loc = -1;
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| 109 | dbf->cache_entry->ca_changed = FALSE;
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| 110 |
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| 111 | /* Read the bucket. */
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| 112 | file_pos = lseek (dbf->desc, bucket_adr, L_SET);
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| 113 | if (file_pos != bucket_adr)
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| 114 | _gdbm_fatal (dbf, "lseek error");
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| 115 |
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| 116 | num_bytes = read (dbf->desc, dbf->bucket, dbf->header->bucket_size);
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| 117 | if (num_bytes != dbf->header->bucket_size)
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| 118 | _gdbm_fatal (dbf, "read error");
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[18038] | 119 |
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| 120 | // GREENSTONE CUSTOMISATION: Swap each value in the bucket if the GDBM file is the wrong endianness
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| 121 | if (wrong_endianness)
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| 122 | {
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| 123 | endian_swap_array((int*) dbf->bucket, dbf->header->bucket_size);
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[18039] | 124 |
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| 125 | // There is a 4-byte string in each hash table entry that we need to leave alone (because character
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| 126 | // strings are not affected by endianness), so convert these back to how they were originally
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| 127 | int b;
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| 128 | for (b = 0; b < dbf->bucket->count; b++)
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| 129 | {
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| 130 | int* key_start = (int*) dbf->bucket->h_table[b].key_start;
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| 131 | *key_start = endian_swap (*key_start);
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| 132 | }
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[18038] | 133 | }
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[18019] | 134 | }
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| 135 |
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| 136 | return;
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| 137 | }
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| 138 |
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| 139 |
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| 140 | /* Split the current bucket. This includes moving all items in the bucket to
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| 141 | a new bucket. This doesn't require any disk reads because all hash values
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| 142 | are stored in the buckets. Splitting the current bucket may require
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| 143 | doubling the size of the hash directory. */
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| 144 | void
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| 145 | _gdbm_split_bucket (dbf, next_insert)
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| 146 | gdbm_file_info *dbf;
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| 147 | int next_insert;
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| 148 | {
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| 149 | hash_bucket *bucket[2]; /* Pointers to the new buckets. */
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| 150 |
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| 151 | int new_bits; /* The number of bits for the new buckets. */
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| 152 | int cache_0; /* Location in the cache for the buckets. */
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| 153 | int cache_1;
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| 154 | off_t adr_0; /* File address of the new bucket 0. */
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| 155 | off_t adr_1; /* File address of the new bucket 1. */
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| 156 | avail_elem old_bucket; /* Avail Struct for the old bucket. */
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| 157 |
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| 158 | off_t dir_start0; /* Used in updating the directory. */
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| 159 | off_t dir_start1;
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| 160 | off_t dir_end;
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| 161 |
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| 162 | off_t *new_dir; /* Pointer to the new directory. */
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| 163 | off_t dir_adr; /* Address of the new directory. */
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| 164 | int dir_size; /* Size of the new directory. */
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| 165 | off_t old_adr[31]; /* Address of the old directories. */
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| 166 | int old_size[31]; /* Size of the old directories. */
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| 167 | int old_count; /* Number of old directories. */
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| 168 |
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| 169 | int index; /* Used in array indexing. */
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| 170 | int index1; /* Used in array indexing. */
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| 171 | int elem_loc; /* Location in new bucket to put element. */
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| 172 | bucket_element *old_el; /* Pointer into the old bucket. */
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| 173 | int select; /* Used to index bucket during movement. */
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| 174 |
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| 175 |
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| 176 | /* No directories are yet old. */
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| 177 | old_count = 0;
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| 178 |
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| 179 | if (dbf->bucket_cache == NULL)
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| 180 | {
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| 181 | if(_gdbm_init_cache(dbf, DEFAULT_CACHESIZE) == -1)
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| 182 | _gdbm_fatal(dbf, "couldn't init cache");
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| 183 | }
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| 184 |
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| 185 | while (dbf->bucket->count == dbf->header->bucket_elems)
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| 186 | {
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| 187 | /* Initialize the "new" buckets in the cache. */
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| 188 | do
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| 189 | {
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| 190 | dbf->last_read = (dbf->last_read + 1) % dbf->cache_size;
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| 191 | cache_0 = dbf->last_read;
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| 192 | }
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| 193 | while (dbf->bucket_cache[cache_0].ca_bucket == dbf->bucket);
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| 194 | bucket[0] = dbf->bucket_cache[cache_0].ca_bucket;
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| 195 | if (dbf->bucket_cache[cache_0].ca_changed)
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| 196 | _gdbm_write_bucket (dbf, &dbf->bucket_cache[cache_0]);
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| 197 | do
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| 198 | {
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| 199 | dbf->last_read = (dbf->last_read + 1) % dbf->cache_size;
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| 200 | cache_1 = dbf->last_read;
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| 201 | }
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| 202 | while (dbf->bucket_cache[cache_1].ca_bucket == dbf->bucket);
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| 203 | bucket[1] = dbf->bucket_cache[cache_1].ca_bucket;
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| 204 | if (dbf->bucket_cache[cache_1].ca_changed)
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| 205 | _gdbm_write_bucket (dbf, &dbf->bucket_cache[cache_1]);
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| 206 | new_bits = dbf->bucket->bucket_bits+1;
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| 207 | _gdbm_new_bucket (dbf, bucket[0], new_bits);
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| 208 | _gdbm_new_bucket (dbf, bucket[1], new_bits);
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| 209 | adr_0 = _gdbm_alloc (dbf, dbf->header->bucket_size);
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| 210 | dbf->bucket_cache[cache_0].ca_adr = adr_0;
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| 211 | adr_1 = _gdbm_alloc (dbf, dbf->header->bucket_size);
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| 212 | dbf->bucket_cache[cache_1].ca_adr = adr_1;
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| 213 |
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| 214 |
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| 215 |
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| 216 | /* Double the directory size if necessary. */
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| 217 | if (dbf->header->dir_bits == dbf->bucket->bucket_bits)
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| 218 | {
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| 219 | dir_size = dbf->header->dir_size * 2;
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| 220 | dir_adr = _gdbm_alloc (dbf, dir_size);
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| 221 | new_dir = (off_t *) malloc (dir_size);
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| 222 | if (new_dir == NULL) _gdbm_fatal (dbf, "malloc error");
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| 223 | for (index = 0;
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| 224 | index < dbf->header->dir_size/sizeof (off_t); index++)
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| 225 | {
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| 226 | new_dir[2*index] = dbf->dir[index];
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| 227 | new_dir[2*index+1] = dbf->dir[index];
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| 228 | }
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| 229 |
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| 230 | /* Update header. */
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| 231 | old_adr[old_count] = dbf->header->dir;
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| 232 | dbf->header->dir = dir_adr;
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| 233 | old_size[old_count] = dbf->header->dir_size;
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| 234 | dbf->header->dir_size = dir_size;
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| 235 | dbf->header->dir_bits = new_bits;
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| 236 | old_count++;
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| 237 |
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| 238 | /* Now update dbf. */
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| 239 | dbf->header_changed = TRUE;
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| 240 | dbf->bucket_dir *= 2;
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| 241 | free (dbf->dir);
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| 242 | dbf->dir = new_dir;
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| 243 | }
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| 244 |
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| 245 | /* Copy all elements in dbf->bucket into the new buckets. */
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| 246 | for (index = 0; index < dbf->header->bucket_elems; index++)
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| 247 | {
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| 248 | old_el = & (dbf->bucket->h_table[index]);
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| 249 | select = (old_el->hash_value >> (31-new_bits)) & 1;
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| 250 | elem_loc = old_el->hash_value % dbf->header->bucket_elems;
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| 251 | while (bucket[select]->h_table[elem_loc].hash_value != -1)
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| 252 | elem_loc = (elem_loc + 1) % dbf->header->bucket_elems;
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| 253 | bucket[select]->h_table[elem_loc] = *old_el;
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| 254 | bucket[select]->count += 1;
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| 255 | }
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| 256 |
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| 257 | /* Allocate avail space for the bucket[1]. */
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| 258 | bucket[1]->bucket_avail[0].av_adr
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| 259 | = _gdbm_alloc (dbf, dbf->header->block_size);
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| 260 | bucket[1]->bucket_avail[0].av_size = dbf->header->block_size;
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| 261 | bucket[1]->av_count = 1;
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| 262 |
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| 263 | /* Copy the avail elements in dbf->bucket to bucket[0]. */
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| 264 | bucket[0]->av_count = dbf->bucket->av_count;
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| 265 | index = 0;
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| 266 | index1 = 0;
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| 267 | if (bucket[0]->av_count == BUCKET_AVAIL)
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| 268 | {
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| 269 | /* The avail is full, move the first one to bucket[1]. */
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| 270 | _gdbm_put_av_elem (dbf->bucket->bucket_avail[0],
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| 271 | bucket[1]->bucket_avail,
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| 272 | &bucket[1]->av_count, FALSE);
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| 273 | index = 1;
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| 274 | bucket[0]->av_count --;
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| 275 | }
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| 276 | for (; index < dbf->bucket->av_count; index++)
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| 277 | {
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| 278 | bucket[0]->bucket_avail[index1++] = dbf->bucket->bucket_avail[index];
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| 279 | }
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| 280 |
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| 281 | /* Update the directory. We have new file addresses for both buckets. */
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| 282 | dir_start1 = (dbf->bucket_dir >> (dbf->header->dir_bits - new_bits)) | 1;
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| 283 | dir_end = (dir_start1 + 1) << (dbf->header->dir_bits - new_bits);
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| 284 | dir_start1 = dir_start1 << (dbf->header->dir_bits - new_bits);
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| 285 | dir_start0 = dir_start1 - (dir_end - dir_start1);
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| 286 | for (index = dir_start0; index < dir_start1; index++)
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| 287 | dbf->dir[index] = adr_0;
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| 288 | for (index = dir_start1; index < dir_end; index++)
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| 289 | dbf->dir[index] = adr_1;
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| 290 |
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| 291 |
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| 292 | /* Set changed flags. */
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| 293 | dbf->bucket_cache[cache_0].ca_changed = TRUE;
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| 294 | dbf->bucket_cache[cache_1].ca_changed = TRUE;
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| 295 | dbf->bucket_changed = TRUE;
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| 296 | dbf->directory_changed = TRUE;
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| 297 | dbf->second_changed = TRUE;
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| 298 |
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| 299 | /* Update the cache! */
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| 300 | dbf->bucket_dir = next_insert >> (31-dbf->header->dir_bits);
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| 301 |
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| 302 | /* Invalidate old cache entry. */
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| 303 | old_bucket.av_adr = dbf->cache_entry->ca_adr;
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| 304 | old_bucket.av_size = dbf->header->bucket_size;
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| 305 | dbf->cache_entry->ca_adr = 0;
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| 306 | dbf->cache_entry->ca_changed = FALSE;
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| 307 |
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| 308 | /* Set dbf->bucket to the proper bucket. */
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| 309 | if (dbf->dir[dbf->bucket_dir] == adr_0)
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| 310 | {
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| 311 | dbf->bucket = bucket[0];
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| 312 | dbf->cache_entry = &dbf->bucket_cache[cache_0];
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| 313 | _gdbm_put_av_elem (old_bucket,
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| 314 | bucket[1]->bucket_avail,
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| 315 | &bucket[1]->av_count, FALSE);
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| 316 | }
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| 317 | else
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| 318 | {
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| 319 | dbf->bucket = bucket[1];
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| 320 | dbf->cache_entry = &dbf->bucket_cache[cache_1];
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| 321 | _gdbm_put_av_elem (old_bucket,
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| 322 | bucket[0]->bucket_avail,
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| 323 | &bucket[0]->av_count, FALSE);
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| 324 | }
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| 325 |
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| 326 | }
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| 327 |
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| 328 | /* Get rid of old directories. */
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| 329 | for (index = 0; index < old_count; index++)
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| 330 | _gdbm_free (dbf, old_adr[index], old_size[index]);
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| 331 | }
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| 332 |
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| 333 |
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| 334 | /* The only place where a bucket is written. CA_ENTRY is the
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| 335 | cache entry containing the bucket to be written. */
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| 336 |
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| 337 | void
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| 338 | _gdbm_write_bucket (dbf, ca_entry)
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| 339 | gdbm_file_info *dbf;
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| 340 | cache_elem *ca_entry;
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| 341 | {
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| 342 | int num_bytes; /* The return value for write. */
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| 343 | off_t file_pos; /* The return value for lseek. */
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| 344 |
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| 345 | file_pos = lseek (dbf->desc, ca_entry->ca_adr, L_SET);
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| 346 | if (file_pos != ca_entry->ca_adr)
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| 347 | _gdbm_fatal (dbf, "lseek error");
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| 348 | num_bytes = write (dbf->desc, ca_entry->ca_bucket, dbf->header->bucket_size);
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| 349 | if (num_bytes != dbf->header->bucket_size)
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| 350 | _gdbm_fatal (dbf, "write error");
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| 351 | ca_entry->ca_changed = FALSE;
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| 352 | ca_entry->ca_data.hash_val = -1;
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| 353 | ca_entry->ca_data.elem_loc = -1;
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| 354 | }
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