d30c24cdde5cc837dd849a4eec2662dc2ef75dee
[ccan] / ccan / tdb2 / traverse.c
1  /* 
2    Trivial Database 2: traverse function.
3    Copyright (C) Rusty Russell 2010
4    
5    This library is free software; you can redistribute it and/or
6    modify it under the terms of the GNU Lesser General Public
7    License as published by the Free Software Foundation; either
8    version 3 of the License, or (at your option) any later version.
9
10    This library is distributed in the hope that it will be useful,
11    but WITHOUT ANY WARRANTY; without even the implied warranty of
12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
13    Lesser General Public License for more details.
14
15    You should have received a copy of the GNU Lesser General Public
16    License along with this library; if not, see <http://www.gnu.org/licenses/>.
17 */
18 #include "private.h"
19 #include <ccan/likely/likely.h>
20
21 static int64_t traverse(struct tdb_context *tdb, int ltype,
22                         tdb_traverse_func fn, void *p)
23 {
24         uint64_t i, num, count = 0;
25         tdb_off_t off, prev_bucket;
26         struct tdb_used_record rec;
27         struct tdb_data k, d;
28         bool finish = false;
29
30         /* FIXME: Do we need to start at 0? */
31         prev_bucket = tdb_lock_list(tdb, 0, ltype, TDB_LOCK_WAIT);
32         if (prev_bucket != 0)
33                 return -1;
34
35         num = (1ULL << tdb->header.v.hash_bits);
36
37         for (i = tdb_find_nonzero_off(tdb, hash_off(tdb, 0), num);
38              i != num && !finish;
39              i += tdb_find_nonzero_off(tdb, hash_off(tdb, i), num - i)) {
40                 if (tdb_lock_list(tdb, i, ltype, TDB_LOCK_WAIT) != i)
41                         goto fail;
42
43                 off = tdb_read_off(tdb, hash_off(tdb, i));
44                 if (off == TDB_OFF_ERR) {
45                         tdb_unlock_list(tdb, i, ltype);
46                         goto fail;
47                 }
48
49                 /* This race can happen, but look again. */
50                 if (off == 0) {
51                         tdb_unlock_list(tdb, i, ltype);
52                         continue;
53                 }
54
55                 /* Drop previous lock. */
56                 tdb_unlock_list(tdb, prev_bucket, ltype);
57                 prev_bucket = i;
58
59                 if (tdb_read_convert(tdb, off, &rec, sizeof(rec)) != 0)
60                         goto fail;
61
62                 k.dsize = rec_key_length(&rec);
63                 d.dsize = rec_data_length(&rec);
64                 if (ltype == F_RDLCK) {
65                         /* Read traverses can keep the lock. */
66                         k.dptr = (void *)tdb_access_read(tdb,
67                                                          off + sizeof(rec),
68                                                          k.dsize + d.dsize,
69                                                          false);
70                 } else {
71                         k.dptr = tdb_alloc_read(tdb, off + sizeof(rec),
72                                                 k.dsize + d.dsize);
73                 }
74                 if (!k.dptr)
75                         goto fail;
76                 d.dptr = k.dptr + k.dsize;
77                 count++;
78
79                 if (ltype == F_WRLCK) {
80                         /* Drop lock before calling out. */
81                         tdb_unlock_list(tdb, i, ltype);
82                 }
83
84                 if (fn && fn(tdb, k, d, p))
85                         finish = true;
86
87                 if (ltype == F_WRLCK) {
88                         free(k.dptr);
89                         /* Regain lock.  FIXME: Is this necessary? */
90                         if (tdb_lock_list(tdb, i, ltype, TDB_LOCK_WAIT) != i)
91                                 return -1;
92
93                         /* This makes deleting under ourselves a bit nicer. */
94                         if (tdb_read_off(tdb, hash_off(tdb, i)) == off)
95                                 i++;
96                 } else {
97                         tdb_access_release(tdb, k.dptr);
98                         i++;
99                 }
100         }
101
102         /* Drop final lock. */
103         tdb_unlock_list(tdb, prev_bucket, ltype);
104         return count;
105
106 fail:
107         tdb_unlock_list(tdb, prev_bucket, ltype);
108         return -1;
109 }
110
111 int64_t tdb_traverse(struct tdb_context *tdb, tdb_traverse_func fn, void *p)
112 {
113         return traverse(tdb, F_WRLCK, fn, p);
114 }
115         
116 int64_t tdb_traverse_read(struct tdb_context *tdb,
117                           tdb_traverse_func fn, void *p)
118 {
119         int64_t ret;
120         bool was_ro = tdb->read_only;
121         tdb->read_only = true;
122         ret = traverse(tdb, F_RDLCK, fn, p);
123         tdb->read_only = was_ro;
124         return ret;
125 }