1 /* Licensed to the Apache Software Foundation (ASF) under one or more
2 * contributor license agreements. See the NOTICE file distributed with
3 * this work for additional information regarding copyright ownership.
4 * The ASF licenses this file to You under the Apache License, Version 2.0
5 * (the "License"); you may not use this file except in compliance with
6 * the License. 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 #define OFF_PAG(off) (apr_off_t) (off) * PBLKSIZ
54 #define OFF_DIR(off) (apr_off_t) (off) * DBLKSIZ
56 static const long masks[] = {
57 000000000000, 000000000001, 000000000003, 000000000007,
58 000000000017, 000000000037, 000000000077, 000000000177,
59 000000000377, 000000000777, 000000001777, 000000003777,
60 000000007777, 000000017777, 000000037777, 000000077777,
61 000000177777, 000000377777, 000000777777, 000001777777,
62 000003777777, 000007777777, 000017777777, 000037777777,
63 000077777777, 000177777777, 000377777777, 000777777777,
64 001777777777, 003777777777, 007777777777, 017777777777
67 const apr_sdbm_datum_t sdbm_nullitem = { NULL, 0 };
69 static apr_status_t database_cleanup(void *data)
71 apr_sdbm_t *db = data;
74 * Can't rely on apr_sdbm_unlock, since it will merely
75 * decrement the refcnt if several locks are held.
77 if (db->flags & (SDBM_SHARED_LOCK | SDBM_EXCLUSIVE_LOCK))
78 (void) apr_file_unlock(db->dirf);
79 (void) apr_file_close(db->dirf);
80 (void) apr_file_close(db->pagf);
86 static apr_status_t prep(apr_sdbm_t **pdb, const char *dirname, const char *pagname,
87 apr_int32_t flags, apr_fileperms_t perms, apr_pool_t *p)
94 db = malloc(sizeof(*db));
95 memset(db, 0, sizeof(*db));
100 * adjust user flags so that WRONLY becomes RDWR,
101 * as required by this package. Also set our internal
102 * flag for RDONLY if needed.
104 if (!(flags & APR_FOPEN_WRITE)) {
105 db->flags |= SDBM_RDONLY;
109 * adjust the file open flags so that we handle locking
110 * on our own (don't rely on any locking behavior within
111 * an apr_file_t, in case it's ever introduced, and set
114 if (flags & APR_FOPEN_SHARELOCK) {
115 db->flags |= SDBM_SHARED;
116 flags &= ~APR_FOPEN_SHARELOCK;
119 flags |= APR_FOPEN_BINARY | APR_FOPEN_READ;
122 * open the files in sequence, and stat the dirfile.
123 * If we fail anywhere, undo everything, return NULL.
126 if ((status = apr_file_open(&db->dirf, dirname, flags, perms, p))
130 if ((status = apr_file_open(&db->pagf, pagname, flags, perms, p))
134 if ((status = apr_sdbm_lock(db, (db->flags & SDBM_RDONLY)
136 : APR_FLOCK_EXCLUSIVE))
140 /* apr_pcalloc zeroed the buffers
141 * apr_sdbm_lock stated the dirf->size and invalidated the cache
145 * if we are opened in SHARED mode, unlock ourself
147 if (db->flags & SDBM_SHARED)
148 if ((status = apr_sdbm_unlock(db)) != APR_SUCCESS)
151 /* make sure that we close the database at some point */
152 apr_pool_cleanup_register(p, db, database_cleanup, apr_pool_cleanup_null);
159 if (db->dirf && db->pagf)
160 (void) apr_sdbm_unlock(db);
161 if (db->dirf != NULL)
162 (void) apr_file_close(db->dirf);
163 if (db->pagf != NULL) {
164 (void) apr_file_close(db->pagf);
170 APU_DECLARE(apr_status_t) apr_sdbm_open(apr_sdbm_t **db, const char *file,
172 apr_fileperms_t perms, apr_pool_t *p)
174 char *dirname = apr_pstrcat(p, file, APR_SDBM_DIRFEXT, NULL);
175 char *pagname = apr_pstrcat(p, file, APR_SDBM_PAGFEXT, NULL);
177 return prep(db, dirname, pagname, flags, perms, p);
180 APU_DECLARE(apr_status_t) apr_sdbm_close(apr_sdbm_t *db)
182 return apr_pool_cleanup_run(db->pool, db, database_cleanup);
185 APU_DECLARE(apr_status_t) apr_sdbm_fetch(apr_sdbm_t *db, apr_sdbm_datum_t *val,
186 apr_sdbm_datum_t key)
190 if (db == NULL || bad(key))
193 if ((status = apr_sdbm_lock(db, APR_FLOCK_SHARED)) != APR_SUCCESS)
196 if ((status = getpage(db, exhash(key))) == APR_SUCCESS) {
197 *val = getpair(db->pagbuf, key);
198 /* ### do we want a not-found result? */
201 (void) apr_sdbm_unlock(db);
206 static apr_status_t write_page(apr_sdbm_t *db, const char *buf, long pagno)
209 apr_off_t off = OFF_PAG(pagno);
211 if ((status = apr_file_seek(db->pagf, APR_SET, &off)) == APR_SUCCESS)
212 status = apr_file_write_full(db->pagf, buf, PBLKSIZ, NULL);
217 APU_DECLARE(apr_status_t) apr_sdbm_delete(apr_sdbm_t *db,
218 const apr_sdbm_datum_t key)
222 if (db == NULL || bad(key))
224 if (apr_sdbm_rdonly(db))
227 if ((status = apr_sdbm_lock(db, APR_FLOCK_EXCLUSIVE)) != APR_SUCCESS)
230 if ((status = getpage(db, exhash(key))) == APR_SUCCESS) {
231 if (!delpair(db->pagbuf, key))
232 /* ### should we define some APRUTIL codes? */
233 status = APR_EGENERAL;
235 status = write_page(db, db->pagbuf, db->pagbno);
238 (void) apr_sdbm_unlock(db);
243 APU_DECLARE(apr_status_t) apr_sdbm_store(apr_sdbm_t *db, apr_sdbm_datum_t key,
244 apr_sdbm_datum_t val, int flags)
250 if (db == NULL || bad(key))
252 if (apr_sdbm_rdonly(db))
254 need = key.dsize + val.dsize;
256 * is the pair too big (or too small) for this database ??
258 if (need < 0 || need > PAIRMAX)
261 if ((status = apr_sdbm_lock(db, APR_FLOCK_EXCLUSIVE)) != APR_SUCCESS)
264 if ((status = getpage(db, (hash = exhash(key)))) == APR_SUCCESS) {
267 * if we need to replace, delete the key/data pair
268 * first. If it is not there, ignore.
270 if (flags == APR_SDBM_REPLACE)
271 (void) delpair(db->pagbuf, key);
272 else if (!(flags & APR_SDBM_INSERTDUP) && duppair(db->pagbuf, key)) {
277 * if we do not have enough room, we have to split.
279 if (!fitpair(db->pagbuf, need))
280 if ((status = makroom(db, hash, need)) != APR_SUCCESS)
283 * we have enough room or split is successful. insert the key,
284 * and update the page file.
286 (void) putpair(db->pagbuf, key, val);
288 status = write_page(db, db->pagbuf, db->pagbno);
292 (void) apr_sdbm_unlock(db);
298 * makroom - make room by splitting the overfull page
299 * this routine will attempt to make room for SPLTMAX times before
302 static apr_status_t makroom(apr_sdbm_t *db, long hash, int need)
306 char *pag = db->pagbuf;
308 register int smax = SPLTMAX;
313 * split the current page
315 (void) splpage(pag, new, db->hmask + 1);
317 * address of the new page
319 newp = (hash & db->hmask) | (db->hmask + 1);
322 * write delay, read avoidence/cache shuffle:
323 * select the page for incoming pair: if key is to go to the new page,
324 * write out the previous one, and copy the new one over, thus making
325 * it the current page. If not, simply write the new page, and we are
326 * still looking at the page of interest. current page is not updated
327 * here, as sdbm_store will do so, after it inserts the incoming pair.
329 if (hash & (db->hmask + 1)) {
330 if ((status = write_page(db, db->pagbuf, db->pagbno))
335 (void) memcpy(pag, new, PBLKSIZ);
338 if ((status = write_page(db, new, newp)) != APR_SUCCESS)
342 if ((status = setdbit(db, db->curbit)) != APR_SUCCESS)
345 * see if we have enough room now
347 if (fitpair(pag, need))
350 * try again... update curbit and hmask as getpage would have
351 * done. because of our update of the current page, we do not
352 * need to read in anything. BUT we have to write the current
353 * [deferred] page out, as the window of failure is too great.
355 db->curbit = 2 * db->curbit
356 + ((hash & (db->hmask + 1)) ? 2 : 1);
357 db->hmask |= db->hmask + 1;
359 if ((status = write_page(db, db->pagbuf, db->pagbno))
366 * if we are here, this is real bad news. After SPLTMAX splits,
367 * we still cannot fit the key. say goodnight.
370 (void) write(2, "sdbm: cannot insert after SPLTMAX attempts.\n", 44);
372 /* ### ENOSPC not really appropriate but better than nothing */
377 /* Reads 'len' bytes from file 'f' at offset 'off' into buf.
378 * 'off' is given relative to the start of the file.
379 * If EOF is returned while reading, this is taken as success.
381 static apr_status_t read_from(apr_file_t *f, void *buf,
382 apr_off_t off, apr_size_t len)
386 if ((status = apr_file_seek(f, APR_SET, &off)) != APR_SUCCESS ||
387 ((status = apr_file_read_full(f, buf, len, NULL)) != APR_SUCCESS)) {
388 /* if EOF is reached, pretend we read all zero's */
389 if (status == APR_EOF) {
391 status = APR_SUCCESS;
399 * the following two routines will break if
400 * deletions aren't taken into account. (ndbm bug)
402 APU_DECLARE(apr_status_t) apr_sdbm_firstkey(apr_sdbm_t *db,
403 apr_sdbm_datum_t *key)
407 if ((status = apr_sdbm_lock(db, APR_FLOCK_SHARED)) != APR_SUCCESS)
413 if ((status = read_from(db->pagf, db->pagbuf, OFF_PAG(0), PBLKSIZ))
418 status = getnext(key, db);
421 (void) apr_sdbm_unlock(db);
426 APU_DECLARE(apr_status_t) apr_sdbm_nextkey(apr_sdbm_t *db,
427 apr_sdbm_datum_t *key)
431 if ((status = apr_sdbm_lock(db, APR_FLOCK_SHARED)) != APR_SUCCESS)
434 status = getnext(key, db);
436 (void) apr_sdbm_unlock(db);
442 * all important binary tree traversal
444 static apr_status_t getpage(apr_sdbm_t *db, long hash)
453 while (dbit < db->maxbno && getdbit(db, dbit))
454 dbit = 2 * dbit + ((hash & (1 << hbit++)) ? 2 : 1);
456 debug(("dbit: %d...", dbit));
459 db->hmask = masks[hbit];
461 pagb = hash & db->hmask;
463 * see if the block we need is already in memory.
464 * note: this lookaside cache has about 10% hit rate.
466 if (pagb != db->pagbno) {
468 * note: here, we assume a "hole" is read as 0s.
469 * if not, must zero pagbuf first.
470 * ### joe: this assumption was surely never correct? but
471 * ### we make it so in read_from anyway.
473 if ((status = read_from(db->pagf, db->pagbuf, OFF_PAG(pagb), PBLKSIZ))
477 if (!chkpage(db->pagbuf))
478 return APR_ENOSPC; /* ### better error? */
481 debug(("pag read: %d\n", pagb));
486 static int getdbit(apr_sdbm_t *db, long dbit)
494 if (dirb != db->dirbno) {
495 if (read_from(db->dirf, db->dirbuf, OFF_DIR(dirb), DBLKSIZ)
501 debug(("dir read: %d\n", dirb));
504 return db->dirbuf[c % DBLKSIZ] & (1 << dbit % BYTESIZ);
507 static apr_status_t setdbit(apr_sdbm_t *db, long dbit)
517 if (dirb != db->dirbno) {
518 if ((status = read_from(db->dirf, db->dirbuf, OFF_DIR(dirb), DBLKSIZ))
524 debug(("dir read: %d\n", dirb));
527 db->dirbuf[c % DBLKSIZ] |= (1 << dbit % BYTESIZ);
529 if (dbit >= db->maxbno)
530 db->maxbno += DBLKSIZ * BYTESIZ;
533 if ((status = apr_file_seek(db->dirf, APR_SET, &off)) == APR_SUCCESS)
534 status = apr_file_write_full(db->dirf, db->dirbuf, DBLKSIZ, NULL);
540 * getnext - get the next key in the page, and if done with
541 * the page, try the next page in sequence
543 static apr_status_t getnext(apr_sdbm_datum_t *key, apr_sdbm_t *db)
548 *key = getnkey(db->pagbuf, db->keyptr);
549 if (key->dptr != NULL)
552 * we either run out, or there is nothing on this page..
553 * try the next one... If we lost our position on the
554 * file, we will have to seek.
557 if (db->pagbno != db->blkptr++) {
558 apr_off_t off = OFF_PAG(db->blkptr);
559 if ((status = apr_file_seek(db->pagf, APR_SET, &off))
564 db->pagbno = db->blkptr;
565 /* ### EOF acceptable here too? */
566 if ((status = apr_file_read_full(db->pagf, db->pagbuf, PBLKSIZ, NULL))
569 if (!chkpage(db->pagbuf))
570 return APR_EGENERAL; /* ### need better error */
577 APU_DECLARE(int) apr_sdbm_rdonly(apr_sdbm_t *db)
579 /* ### Should we return true if the first lock is a share lock,
580 * to reflect that apr_sdbm_store and apr_sdbm_delete will fail?
582 return (db->flags & SDBM_RDONLY) != 0;