2 * sdbm - ndbm work-alike hashed database library
3 * based on Per-Aake Larson's Dynamic Hashing algorithms. BIT 18 (1978).
4 * author: oz@nexus.yorku.ca
5 * status: public domain.
23 # include <sys/file.h>
38 #include <errno.h> /* See notes in perl.h about avoiding
41 extern Malloc_t malloc proto((MEM_SIZE));
42 extern Free_t free proto((Malloc_t));
47 static int getdbit proto((DBM *, long));
48 static int setdbit proto((DBM *, long));
49 static int getpage proto((DBM *, long));
50 static datum getnext proto((DBM *));
51 static int makroom proto((DBM *, long, int));
56 #define bad(x) ((x).dptr == NULL || (x).dsize < 0)
57 #define exhash(item) sdbm_hash((item).dptr, (item).dsize)
58 #define ioerr(db) ((db)->flags |= DBM_IOERR)
60 #define OFF_PAG(off) (long) (off) * PBLKSIZ
61 #define OFF_DIR(off) (long) (off) * DBLKSIZ
63 static const long masks[] = {
64 000000000000, 000000000001, 000000000003, 000000000007,
65 000000000017, 000000000037, 000000000077, 000000000177,
66 000000000377, 000000000777, 000000001777, 000000003777,
67 000000007777, 000000017777, 000000037777, 000000077777,
68 000000177777, 000000377777, 000000777777, 000001777777,
69 000003777777, 000007777777, 000017777777, 000037777777,
70 000077777777, 000177777777, 000377777777, 000777777777,
71 001777777777, 003777777777, 007777777777, 017777777777
75 sdbm_open(register char *file, register int flags, register int mode)
78 register char *dirname;
79 register char *pagname;
82 if (file == NULL || !*file)
83 return errno = EINVAL, (DBM *) NULL;
85 * need space for two seperate filenames
87 n = strlen(file) * 2 + strlen(DIRFEXT) + strlen(PAGFEXT) + 2;
89 if ((dirname = (char *) malloc((unsigned) n)) == NULL)
90 return errno = ENOMEM, (DBM *) NULL;
92 * build the file names
94 dirname = strcat(strcpy(dirname, file), DIRFEXT);
95 pagname = strcpy(dirname + strlen(dirname) + 1, file);
96 pagname = strcat(pagname, PAGFEXT);
98 db = sdbm_prep(dirname, pagname, flags, mode);
99 free((char *) dirname);
104 sdbm_prep(char *dirname, char *pagname, int flags, int mode)
109 if ((db = (DBM *) malloc(sizeof(DBM))) == NULL)
110 return errno = ENOMEM, (DBM *) NULL;
117 * adjust user flags so that WRONLY becomes RDWR,
118 * as required by this package. Also set our internal
119 * flag for RDONLY if needed.
121 if (flags & O_WRONLY)
122 flags = (flags & ~O_WRONLY) | O_RDWR;
124 else if ((flags & 03) == O_RDONLY)
125 db->flags = DBM_RDONLY;
127 * open the files in sequence, and stat the dirfile.
128 * If we fail anywhere, undo everything, return NULL.
130 #if defined(OS2) || defined(MSDOS) || defined(WIN32) || defined(__CYGWIN__)
133 if ((db->pagf = open(pagname, flags, mode)) > -1) {
134 if ((db->dirf = open(dirname, flags, mode)) > -1) {
136 * need the dirfile size to establish max bit number.
138 if (fstat(db->dirf, &dstat) == 0) {
140 * zero size: either a fresh database, or one with a single,
141 * unsplit data page: dirpage is all zeros.
143 db->dirbno = (!dstat.st_size) ? 0 : -1;
145 db->maxbno = dstat.st_size * BYTESIZ;
147 (void) memset(db->pagbuf, 0, PBLKSIZ);
148 (void) memset(db->dirbuf, 0, DBLKSIZ);
154 (void) close(db->dirf);
156 (void) close(db->pagf);
163 sdbm_close(register DBM *db)
168 (void) close(db->dirf);
169 (void) close(db->pagf);
175 sdbm_fetch(register DBM *db, datum key)
177 if (db == NULL || bad(key))
178 return errno = EINVAL, nullitem;
180 if (getpage(db, exhash(key)))
181 return getpair(db->pagbuf, key);
183 return ioerr(db), nullitem;
187 sdbm_exists(register DBM *db, datum key)
189 if (db == NULL || bad(key))
190 return errno = EINVAL, -1;
192 if (getpage(db, exhash(key)))
193 return exipair(db->pagbuf, key);
195 return ioerr(db), -1;
199 sdbm_delete(register DBM *db, datum key)
201 if (db == NULL || bad(key))
202 return errno = EINVAL, -1;
204 return errno = EPERM, -1;
206 if (getpage(db, exhash(key))) {
207 if (!delpair(db->pagbuf, key))
210 * update the page file
212 if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
213 || write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
214 return ioerr(db), -1;
219 return ioerr(db), -1;
223 sdbm_store(register DBM *db, datum key, datum val, int flags)
228 if (db == NULL || bad(key))
229 return errno = EINVAL, -1;
231 return errno = EPERM, -1;
233 need = key.dsize + val.dsize;
235 * is the pair too big (or too small) for this database ??
237 if (need < 0 || need > PAIRMAX)
238 return errno = EINVAL, -1;
240 if (getpage(db, (hash = exhash(key)))) {
242 * if we need to replace, delete the key/data pair
243 * first. If it is not there, ignore.
245 if (flags == DBM_REPLACE)
246 (void) delpair(db->pagbuf, key);
248 else if (duppair(db->pagbuf, key))
252 * if we do not have enough room, we have to split.
254 if (!fitpair(db->pagbuf, need))
255 if (!makroom(db, hash, need))
256 return ioerr(db), -1;
258 * we have enough room or split is successful. insert the key,
259 * and update the page file.
261 (void) putpair(db->pagbuf, key, val);
263 if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
264 || write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
265 return ioerr(db), -1;
272 return ioerr(db), -1;
276 * makroom - make room by splitting the overfull page
277 * this routine will attempt to make room for SPLTMAX times before
281 makroom(register DBM *db, long int hash, int need)
285 #if defined(DOSISH) || defined(WIN32)
289 char *pag = db->pagbuf;
291 register int smax = SPLTMAX;
295 * split the current page
297 (void) splpage(pag, New, db->hmask + 1);
299 * address of the new page
301 newp = (hash & db->hmask) | (db->hmask + 1);
304 * write delay, read avoidence/cache shuffle:
305 * select the page for incoming pair: if key is to go to the new page,
306 * write out the previous one, and copy the new one over, thus making
307 * it the current page. If not, simply write the new page, and we are
308 * still looking at the page of interest. current page is not updated
309 * here, as sdbm_store will do so, after it inserts the incoming pair.
312 #if defined(DOSISH) || defined(WIN32)
314 * Fill hole with 0 if made it.
315 * (hole is NOT read as 0)
317 oldtail = lseek(db->pagf, 0L, SEEK_END);
318 memset(zer, 0, PBLKSIZ);
319 while (OFF_PAG(newp) > oldtail) {
320 if (lseek(db->pagf, 0L, SEEK_END) < 0 ||
321 write(db->pagf, zer, PBLKSIZ) < 0) {
328 if (hash & (db->hmask + 1)) {
329 if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
330 || write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
333 (void) memcpy(pag, New, PBLKSIZ);
335 else if (lseek(db->pagf, OFF_PAG(newp), SEEK_SET) < 0
336 || write(db->pagf, New, PBLKSIZ) < 0)
339 if (!setdbit(db, db->curbit))
342 * see if we have enough room now
344 if (fitpair(pag, need))
347 * try again... update curbit and hmask as getpage would have
348 * done. because of our update of the current page, we do not
349 * need to read in anything. BUT we have to write the current
350 * [deferred] page out, as the window of failure is too great.
352 db->curbit = 2 * db->curbit +
353 ((hash & (db->hmask + 1)) ? 2 : 1);
354 db->hmask |= db->hmask + 1;
356 if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
357 || write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
362 * if we are here, this is real bad news. After SPLTMAX splits,
363 * we still cannot fit the key. say goodnight.
366 (void) write(2, "sdbm: cannot insert after SPLTMAX attempts.\n", 44);
373 * the following two routines will break if
374 * deletions aren't taken into account. (ndbm bug)
377 sdbm_firstkey(register DBM *db)
380 return errno = EINVAL, nullitem;
384 if (lseek(db->pagf, OFF_PAG(0), SEEK_SET) < 0
385 || read(db->pagf, db->pagbuf, PBLKSIZ) < 0)
386 return ioerr(db), nullitem;
395 sdbm_nextkey(register DBM *db)
398 return errno = EINVAL, nullitem;
403 * all important binary trie traversal
406 getpage(register DBM *db, register long int hash)
414 while (dbit < db->maxbno && getdbit(db, dbit))
415 dbit = 2 * dbit + ((hash & (1 << hbit++)) ? 2 : 1);
417 debug(("dbit: %d...", dbit));
420 db->hmask = masks[hbit];
422 pagb = hash & db->hmask;
424 * see if the block we need is already in memory.
425 * note: this lookaside cache has about 10% hit rate.
427 if (pagb != db->pagbno) {
429 * note: here, we assume a "hole" is read as 0s.
430 * if not, must zero pagbuf first.
432 if (lseek(db->pagf, OFF_PAG(pagb), SEEK_SET) < 0
433 || read(db->pagf, db->pagbuf, PBLKSIZ) < 0)
435 if (!chkpage(db->pagbuf))
439 debug(("pag read: %d\n", pagb));
445 getdbit(register DBM *db, register long int dbit)
453 if (dirb != db->dirbno) {
455 if (lseek(db->dirf, OFF_DIR(dirb), SEEK_SET) < 0
456 || (got=read(db->dirf, db->dirbuf, DBLKSIZ)) < 0)
459 memset(db->dirbuf,0,DBLKSIZ);
462 debug(("dir read: %d\n", dirb));
465 return db->dirbuf[c % DBLKSIZ] & (1 << dbit % BYTESIZ);
469 setdbit(register DBM *db, register long int dbit)
477 if (dirb != db->dirbno) {
479 if (lseek(db->dirf, OFF_DIR(dirb), SEEK_SET) < 0
480 || (got=read(db->dirf, db->dirbuf, DBLKSIZ)) < 0)
483 memset(db->dirbuf,0,DBLKSIZ);
486 debug(("dir read: %d\n", dirb));
489 db->dirbuf[c % DBLKSIZ] |= (1 << dbit % BYTESIZ);
492 if (dbit >= db->maxbno)
493 db->maxbno += DBLKSIZ * BYTESIZ;
495 if (OFF_DIR((dirb+1))*BYTESIZ > db->maxbno)
496 db->maxbno=OFF_DIR((dirb+1))*BYTESIZ;
499 if (lseek(db->dirf, OFF_DIR(dirb), SEEK_SET) < 0
500 || write(db->dirf, db->dirbuf, DBLKSIZ) < 0)
507 * getnext - get the next key in the page, and if done with
508 * the page, try the next page in sequence
511 getnext(register DBM *db)
517 key = getnkey(db->pagbuf, db->keyptr);
518 if (key.dptr != NULL)
521 * we either run out, or there is nothing on this page..
522 * try the next one... If we lost our position on the
523 * file, we will have to seek.
526 if (db->pagbno != db->blkptr++)
527 if (lseek(db->pagf, OFF_PAG(db->blkptr), SEEK_SET) < 0)
529 db->pagbno = db->blkptr;
530 if (read(db->pagf, db->pagbuf, PBLKSIZ) <= 0)
532 if (!chkpage(db->pagbuf))
536 return ioerr(db), nullitem;