1
/* Copyright 2000-2005 The Apache Software Foundation or its licensors, as
4
* Licensed under the Apache License, Version 2.0 (the "License");
5
* you may not use this file except in compliance with the License.
6
* You may obtain a copy of the License at
8
* http://www.apache.org/licenses/LICENSE-2.0
10
* Unless required by applicable law or agreed to in writing, software
11
* distributed under the License is distributed on an "AS IS" BASIS,
12
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13
* See the License for the specific language governing permissions and
14
* limitations under the License.
18
* sdbm - ndbm work-alike hashed database library
19
* based on Per-Aake Larson's Dynamic Hashing algorithms. BIT 18 (1978).
20
* author: oz@nexus.yorku.ca
21
* ex-public domain, ported to APR for Apache 2
26
#include "apr_file_io.h"
27
#include "apr_strings.h"
28
#include "apr_errno.h"
31
#include "sdbm_tune.h"
32
#include "sdbm_pair.h"
33
#include "sdbm_private.h"
35
#include <string.h> /* for memset() */
36
#include <stdlib.h> /* for malloc() and free() */
41
static int getdbit (apr_sdbm_t *, long);
42
static apr_status_t setdbit(apr_sdbm_t *, long);
43
static apr_status_t getpage(apr_sdbm_t *db, long);
44
static apr_status_t getnext(apr_sdbm_datum_t *key, apr_sdbm_t *db);
45
static apr_status_t makroom(apr_sdbm_t *, long, int);
50
#define bad(x) ((x).dptr == NULL || (x).dsize <= 0)
51
#define exhash(item) sdbm_hash((item).dptr, (item).dsize)
53
/* ### Does anything need these externally? */
54
#define sdbm_dirfno(db) ((db)->dirf)
55
#define sdbm_pagfno(db) ((db)->pagf)
57
#define OFF_PAG(off) (apr_off_t) (off) * PBLKSIZ
58
#define OFF_DIR(off) (apr_off_t) (off) * DBLKSIZ
60
static long masks[] = {
61
000000000000, 000000000001, 000000000003, 000000000007,
62
000000000017, 000000000037, 000000000077, 000000000177,
63
000000000377, 000000000777, 000000001777, 000000003777,
64
000000007777, 000000017777, 000000037777, 000000077777,
65
000000177777, 000000377777, 000000777777, 000001777777,
66
000003777777, 000007777777, 000017777777, 000037777777,
67
000077777777, 000177777777, 000377777777, 000777777777,
68
001777777777, 003777777777, 007777777777, 017777777777
71
const apr_sdbm_datum_t sdbm_nullitem = { NULL, 0 };
73
static apr_status_t database_cleanup(void *data)
75
apr_sdbm_t *db = data;
78
* Can't rely on apr_sdbm_unlock, since it will merely
79
* decrement the refcnt if several locks are held.
81
if (db->flags & (SDBM_SHARED_LOCK | SDBM_EXCLUSIVE_LOCK))
82
(void) apr_file_unlock(db->dirf);
83
(void) apr_file_close(db->dirf);
84
(void) apr_file_close(db->pagf);
90
static apr_status_t prep(apr_sdbm_t **pdb, const char *dirname, const char *pagname,
91
apr_int32_t flags, apr_fileperms_t perms, apr_pool_t *p)
98
db = malloc(sizeof(*db));
99
memset(db, 0, sizeof(*db));
104
* adjust user flags so that WRONLY becomes RDWR,
105
* as required by this package. Also set our internal
106
* flag for RDONLY if needed.
108
if (!(flags & APR_WRITE)) {
109
db->flags |= SDBM_RDONLY;
113
* adjust the file open flags so that we handle locking
114
* on our own (don't rely on any locking behavior within
115
* an apr_file_t, in case it's ever introduced, and set
118
if (flags & APR_SHARELOCK) {
119
db->flags |= SDBM_SHARED;
120
flags &= ~APR_SHARELOCK;
123
flags |= APR_BINARY | APR_READ;
126
* open the files in sequence, and stat the dirfile.
127
* If we fail anywhere, undo everything, return NULL.
130
if ((status = apr_file_open(&db->dirf, dirname, flags, perms, p))
134
if ((status = apr_file_open(&db->pagf, pagname, flags, perms, p))
138
if ((status = apr_sdbm_lock(db, (db->flags & SDBM_RDONLY)
140
: APR_FLOCK_EXCLUSIVE))
144
/* apr_pcalloc zeroed the buffers
145
* apr_sdbm_lock stated the dirf->size and invalidated the cache
149
* if we are opened in SHARED mode, unlock ourself
151
if (db->flags & SDBM_SHARED)
152
if ((status = apr_sdbm_unlock(db)) != APR_SUCCESS)
155
/* make sure that we close the database at some point */
156
apr_pool_cleanup_register(p, db, database_cleanup, apr_pool_cleanup_null);
163
if (db->dirf && db->pagf)
164
(void) apr_sdbm_unlock(db);
165
if (db->dirf != NULL)
166
(void) apr_file_close(db->dirf);
167
if (db->pagf != NULL) {
168
(void) apr_file_close(db->pagf);
174
APU_DECLARE(apr_status_t) apr_sdbm_open(apr_sdbm_t **db, const char *file,
176
apr_fileperms_t perms, apr_pool_t *p)
178
char *dirname = apr_pstrcat(p, file, APR_SDBM_DIRFEXT, NULL);
179
char *pagname = apr_pstrcat(p, file, APR_SDBM_PAGFEXT, NULL);
181
return prep(db, dirname, pagname, flags, perms, p);
184
APU_DECLARE(apr_status_t) apr_sdbm_close(apr_sdbm_t *db)
186
return apr_pool_cleanup_run(db->pool, db, database_cleanup);
189
APU_DECLARE(apr_status_t) apr_sdbm_fetch(apr_sdbm_t *db, apr_sdbm_datum_t *val,
190
apr_sdbm_datum_t key)
194
if (db == NULL || bad(key))
197
if ((status = apr_sdbm_lock(db, APR_FLOCK_SHARED)) != APR_SUCCESS)
200
if ((status = getpage(db, exhash(key))) == APR_SUCCESS) {
201
*val = getpair(db->pagbuf, key);
202
/* ### do we want a not-found result? */
205
(void) apr_sdbm_unlock(db);
210
static apr_status_t write_page(apr_sdbm_t *db, const char *buf, long pagno)
213
apr_off_t off = OFF_PAG(pagno);
215
if ((status = apr_file_seek(db->pagf, APR_SET, &off)) == APR_SUCCESS)
216
status = apr_file_write_full(db->pagf, buf, PBLKSIZ, NULL);
221
APU_DECLARE(apr_status_t) apr_sdbm_delete(apr_sdbm_t *db,
222
const apr_sdbm_datum_t key)
226
if (db == NULL || bad(key))
228
if (apr_sdbm_rdonly(db))
231
if ((status = apr_sdbm_lock(db, APR_FLOCK_EXCLUSIVE)) != APR_SUCCESS)
234
if ((status = getpage(db, exhash(key))) == APR_SUCCESS) {
235
if (!delpair(db->pagbuf, key))
236
/* ### should we define some APRUTIL codes? */
237
status = APR_EGENERAL;
239
status = write_page(db, db->pagbuf, db->pagbno);
242
(void) apr_sdbm_unlock(db);
247
APU_DECLARE(apr_status_t) apr_sdbm_store(apr_sdbm_t *db, apr_sdbm_datum_t key,
248
apr_sdbm_datum_t val, int flags)
254
if (db == NULL || bad(key))
256
if (apr_sdbm_rdonly(db))
258
need = key.dsize + val.dsize;
260
* is the pair too big (or too small) for this database ??
262
if (need < 0 || need > PAIRMAX)
265
if ((status = apr_sdbm_lock(db, APR_FLOCK_EXCLUSIVE)) != APR_SUCCESS)
268
if ((status = getpage(db, (hash = exhash(key)))) == APR_SUCCESS) {
271
* if we need to replace, delete the key/data pair
272
* first. If it is not there, ignore.
274
if (flags == APR_SDBM_REPLACE)
275
(void) delpair(db->pagbuf, key);
276
else if (!(flags & APR_SDBM_INSERTDUP) && duppair(db->pagbuf, key)) {
281
* if we do not have enough room, we have to split.
283
if (!fitpair(db->pagbuf, need))
284
if ((status = makroom(db, hash, need)) != APR_SUCCESS)
287
* we have enough room or split is successful. insert the key,
288
* and update the page file.
290
(void) putpair(db->pagbuf, key, val);
292
status = write_page(db, db->pagbuf, db->pagbno);
296
(void) apr_sdbm_unlock(db);
302
* makroom - make room by splitting the overfull page
303
* this routine will attempt to make room for SPLTMAX times before
306
static apr_status_t makroom(apr_sdbm_t *db, long hash, int need)
310
char *pag = db->pagbuf;
312
register int smax = SPLTMAX;
317
* split the current page
319
(void) splpage(pag, new, db->hmask + 1);
321
* address of the new page
323
newp = (hash & db->hmask) | (db->hmask + 1);
326
* write delay, read avoidence/cache shuffle:
327
* select the page for incoming pair: if key is to go to the new page,
328
* write out the previous one, and copy the new one over, thus making
329
* it the current page. If not, simply write the new page, and we are
330
* still looking at the page of interest. current page is not updated
331
* here, as sdbm_store will do so, after it inserts the incoming pair.
333
if (hash & (db->hmask + 1)) {
334
if ((status = write_page(db, db->pagbuf, db->pagbno))
339
(void) memcpy(pag, new, PBLKSIZ);
342
if ((status = write_page(db, new, newp)) != APR_SUCCESS)
346
if ((status = setdbit(db, db->curbit)) != APR_SUCCESS)
349
* see if we have enough room now
351
if (fitpair(pag, need))
354
* try again... update curbit and hmask as getpage would have
355
* done. because of our update of the current page, we do not
356
* need to read in anything. BUT we have to write the current
357
* [deferred] page out, as the window of failure is too great.
359
db->curbit = 2 * db->curbit
360
+ ((hash & (db->hmask + 1)) ? 2 : 1);
361
db->hmask |= db->hmask + 1;
363
if ((status = write_page(db, db->pagbuf, db->pagbno))
370
* if we are here, this is real bad news. After SPLTMAX splits,
371
* we still cannot fit the key. say goodnight.
374
(void) write(2, "sdbm: cannot insert after SPLTMAX attempts.\n", 44);
376
/* ### ENOSPC not really appropriate but better than nothing */
381
/* Reads 'len' bytes from file 'f' at offset 'off' into buf.
382
* 'off' is given relative to the start of the file.
383
* If EOF is returned while reading, this is taken as success.
385
static apr_status_t read_from(apr_file_t *f, void *buf,
386
apr_off_t off, apr_size_t len)
390
if ((status = apr_file_seek(f, APR_SET, &off)) != APR_SUCCESS ||
391
((status = apr_file_read_full(f, buf, len, NULL)) != APR_SUCCESS)) {
392
/* if EOF is reached, pretend we read all zero's */
393
if (status == APR_EOF) {
395
status = APR_SUCCESS;
403
* the following two routines will break if
404
* deletions aren't taken into account. (ndbm bug)
406
APU_DECLARE(apr_status_t) apr_sdbm_firstkey(apr_sdbm_t *db,
407
apr_sdbm_datum_t *key)
411
if ((status = apr_sdbm_lock(db, APR_FLOCK_SHARED)) != APR_SUCCESS)
417
if ((status = read_from(db->pagf, db->pagbuf, OFF_PAG(0), PBLKSIZ))
422
status = getnext(key, db);
425
(void) apr_sdbm_unlock(db);
430
APU_DECLARE(apr_status_t) apr_sdbm_nextkey(apr_sdbm_t *db,
431
apr_sdbm_datum_t *key)
435
if ((status = apr_sdbm_lock(db, APR_FLOCK_SHARED)) != APR_SUCCESS)
438
status = getnext(key, db);
440
(void) apr_sdbm_unlock(db);
446
* all important binary tree traversal
448
static apr_status_t getpage(apr_sdbm_t *db, long hash)
457
while (dbit < db->maxbno && getdbit(db, dbit))
458
dbit = 2 * dbit + ((hash & (1 << hbit++)) ? 2 : 1);
460
debug(("dbit: %d...", dbit));
463
db->hmask = masks[hbit];
465
pagb = hash & db->hmask;
467
* see if the block we need is already in memory.
468
* note: this lookaside cache has about 10% hit rate.
470
if (pagb != db->pagbno) {
472
* note: here, we assume a "hole" is read as 0s.
473
* if not, must zero pagbuf first.
474
* ### joe: this assumption was surely never correct? but
475
* ### we make it so in read_from anyway.
477
if ((status = read_from(db->pagf, db->pagbuf, OFF_PAG(pagb), PBLKSIZ))
481
if (!chkpage(db->pagbuf))
482
return APR_ENOSPC; /* ### better error? */
485
debug(("pag read: %d\n", pagb));
490
static int getdbit(apr_sdbm_t *db, long dbit)
498
if (dirb != db->dirbno) {
499
if (read_from(db->dirf, db->dirbuf, OFF_DIR(dirb), DBLKSIZ)
505
debug(("dir read: %d\n", dirb));
508
return db->dirbuf[c % DBLKSIZ] & (1 << dbit % BYTESIZ);
511
static apr_status_t setdbit(apr_sdbm_t *db, long dbit)
521
if (dirb != db->dirbno) {
522
if ((status = read_from(db->dirf, db->dirbuf, OFF_DIR(dirb), DBLKSIZ))
528
debug(("dir read: %d\n", dirb));
531
db->dirbuf[c % DBLKSIZ] |= (1 << dbit % BYTESIZ);
533
if (dbit >= db->maxbno)
534
db->maxbno += DBLKSIZ * BYTESIZ;
537
if ((status = apr_file_seek(db->dirf, APR_SET, &off)) == APR_SUCCESS)
538
status = apr_file_write_full(db->dirf, db->dirbuf, DBLKSIZ, NULL);
544
* getnext - get the next key in the page, and if done with
545
* the page, try the next page in sequence
547
static apr_status_t getnext(apr_sdbm_datum_t *key, apr_sdbm_t *db)
552
*key = getnkey(db->pagbuf, db->keyptr);
553
if (key->dptr != NULL)
556
* we either run out, or there is nothing on this page..
557
* try the next one... If we lost our position on the
558
* file, we will have to seek.
561
if (db->pagbno != db->blkptr++) {
562
apr_off_t off = OFF_PAG(db->blkptr);
563
if ((status = apr_file_seek(db->pagf, APR_SET, &off)
568
db->pagbno = db->blkptr;
569
/* ### EOF acceptable here too? */
570
if ((status = apr_file_read_full(db->pagf, db->pagbuf, PBLKSIZ, NULL))
573
if (!chkpage(db->pagbuf))
574
return APR_EGENERAL; /* ### need better error */
581
APU_DECLARE(int) apr_sdbm_rdonly(apr_sdbm_t *db)
583
/* ### Should we return true if the first lock is a share lock,
584
* to reflect that apr_sdbm_store and apr_sdbm_delete will fail?
586
return (db->flags & SDBM_RDONLY) != 0;