[p5sagit/p5-mst-13.2.git] / ext / SDBM_File / sdbm / sdbm.c

/*
 * sdbm - ndbm work-alike hashed database library
 * based on Per-Aake Larson's Dynamic Hashing algorithms. BIT 18 (1978).
 * author: oz@nexus.yorku.ca
 * status: public domain.
 *
 * core routines
 */

#include "INTERN.h"
#include "config.h"
#ifdef WIN32
#include "io.h"
#endif
#include "sdbm.h"
#include "tune.h"
#include "pair.h"

#ifdef I_FCNTL
# include <fcntl.h>
#endif
#ifdef I_SYS_FILE
# include <sys/file.h>
#endif

#ifdef I_STRING
# include <string.h>
#else
# include <strings.h>
#endif

/*
 * externals
 */
#ifndef WIN32
#ifndef sun
extern int errno;
#endif

extern Malloc_t malloc proto((MEM_SIZE));
extern Free_t free proto((Malloc_t));

#endif

/*
 * forward
 */
static int getdbit proto((DBM *, long));
static int setdbit proto((DBM *, long));
static int getpage proto((DBM *, long));
static datum getnext proto((DBM *));
static int makroom proto((DBM *, long, int));

/*
 * useful macros
 */
#define bad(x)		((x).dptr == NULL || (x).dsize < 0)
#define exhash(item)	sdbm_hash((item).dptr, (item).dsize)
#define ioerr(db)	((db)->flags |= DBM_IOERR)

#define OFF_PAG(off)	(long) (off) * PBLKSIZ
#define OFF_DIR(off)	(long) (off) * DBLKSIZ

static long masks[] = {
	000000000000, 000000000001, 000000000003, 000000000007,
	000000000017, 000000000037, 000000000077, 000000000177,
	000000000377, 000000000777, 000000001777, 000000003777,
	000000007777, 000000017777, 000000037777, 000000077777,
	000000177777, 000000377777, 000000777777, 000001777777,
	000003777777, 000007777777, 000017777777, 000037777777,
	000077777777, 000177777777, 000377777777, 000777777777,
	001777777777, 003777777777, 007777777777, 017777777777
};

DBM *
sdbm_open(register char *file, register int flags, register int mode)
{
	register DBM *db;
	register char *dirname;
	register char *pagname;
	register int n;

	if (file == NULL || !*file)
		return errno = EINVAL, (DBM *) NULL;
/*
 * need space for two seperate filenames
 */
	n = strlen(file) * 2 + strlen(DIRFEXT) + strlen(PAGFEXT) + 2;

	if ((dirname = (char *) malloc((unsigned) n)) == NULL)
		return errno = ENOMEM, (DBM *) NULL;
/*
 * build the file names
 */
	dirname = strcat(strcpy(dirname, file), DIRFEXT);
	pagname = strcpy(dirname + strlen(dirname) + 1, file);
	pagname = strcat(pagname, PAGFEXT);

	db = sdbm_prep(dirname, pagname, flags, mode);
	free((char *) dirname);
	return db;
}

DBM *
sdbm_prep(char *dirname, char *pagname, int flags, int mode)
{
	register DBM *db;
	struct stat dstat;

	if ((db = (DBM *) malloc(sizeof(DBM))) == NULL)
		return errno = ENOMEM, (DBM *) NULL;

        db->flags = 0;
        db->hmask = 0;
        db->blkptr = 0;
        db->keyptr = 0;
/*
 * adjust user flags so that WRONLY becomes RDWR, 
 * as required by this package. Also set our internal
 * flag for RDONLY if needed.
 */
	if (flags & O_WRONLY)
		flags = (flags & ~O_WRONLY) | O_RDWR;

	else if ((flags & 03) == O_RDONLY)
		db->flags = DBM_RDONLY;
/*
 * open the files in sequence, and stat the dirfile.
 * If we fail anywhere, undo everything, return NULL.
 */
#if defined(OS2) || defined(MSDOS) || defined(WIN32) || defined(__CYGWIN__)
	flags |= O_BINARY;
#	endif
	if ((db->pagf = open(pagname, flags, mode)) > -1) {
		if ((db->dirf = open(dirname, flags, mode)) > -1) {
/*
 * need the dirfile size to establish max bit number.
 */
			if (fstat(db->dirf, &dstat) == 0) {
/*
 * zero size: either a fresh database, or one with a single,
 * unsplit data page: dirpage is all zeros.
 */
				db->dirbno = (!dstat.st_size) ? 0 : -1;
				db->pagbno = -1;
				db->maxbno = dstat.st_size * BYTESIZ;

				(void) memset(db->pagbuf, 0, PBLKSIZ);
				(void) memset(db->dirbuf, 0, DBLKSIZ);
			/*
			 * success
			 */
				return db;
			}
			(void) close(db->dirf);
		}
		(void) close(db->pagf);
	}
	free((char *) db);
	return (DBM *) NULL;
}

void
sdbm_close(register DBM *db)
{
	if (db == NULL)
		errno = EINVAL;
	else {
		(void) close(db->dirf);
		(void) close(db->pagf);
		free((char *) db);
	}
}

datum
sdbm_fetch(register DBM *db, datum key)
{
	if (db == NULL || bad(key))
		return errno = EINVAL, nullitem;

	if (getpage(db, exhash(key)))
		return getpair(db->pagbuf, key);

	return ioerr(db), nullitem;
}

int
sdbm_exists(register DBM *db, datum key)
{
	if (db == NULL || bad(key))
		return errno = EINVAL, -1;

	if (getpage(db, exhash(key)))
		return exipair(db->pagbuf, key);

	return ioerr(db), -1;
}

int
sdbm_delete(register DBM *db, datum key)
{
	if (db == NULL || bad(key))
		return errno = EINVAL, -1;
	if (sdbm_rdonly(db))
		return errno = EPERM, -1;

	if (getpage(db, exhash(key))) {
		if (!delpair(db->pagbuf, key))
			return -1;
/*
 * update the page file
 */
		if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
		    || write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
			return ioerr(db), -1;

		return 0;
	}

	return ioerr(db), -1;
}

int
sdbm_store(register DBM *db, datum key, datum val, int flags)
{
	int need;
	register long hash;

	if (db == NULL || bad(key))
		return errno = EINVAL, -1;
	if (sdbm_rdonly(db))
		return errno = EPERM, -1;

	need = key.dsize + val.dsize;
/*
 * is the pair too big (or too small) for this database ??
 */
	if (need < 0 || need > PAIRMAX)
		return errno = EINVAL, -1;

	if (getpage(db, (hash = exhash(key)))) {
/*
 * if we need to replace, delete the key/data pair
 * first. If it is not there, ignore.
 */
		if (flags == DBM_REPLACE)
			(void) delpair(db->pagbuf, key);
#ifdef SEEDUPS
		else if (duppair(db->pagbuf, key))
			return 1;
#endif
/*
 * if we do not have enough room, we have to split.
 */
		if (!fitpair(db->pagbuf, need))
			if (!makroom(db, hash, need))
				return ioerr(db), -1;
/*
 * we have enough room or split is successful. insert the key,
 * and update the page file.
 */
		(void) putpair(db->pagbuf, key, val);

		if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
		    || write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
			return ioerr(db), -1;
	/*
	 * success
	 */
		return 0;
	}

	return ioerr(db), -1;
}

/*
 * makroom - make room by splitting the overfull page
 * this routine will attempt to make room for SPLTMAX times before
 * giving up.
 */
static int
makroom(register DBM *db, long int hash, int need)
{
	long newp;
	char twin[PBLKSIZ];
	char *pag = db->pagbuf;
	char *New = twin;
	register int smax = SPLTMAX;

	do {
/*
 * split the current page
 */
		(void) splpage(pag, New, db->hmask + 1);
/*
 * address of the new page
 */
		newp = (hash & db->hmask) | (db->hmask + 1);

/*
 * write delay, read avoidence/cache shuffle:
 * select the page for incoming pair: if key is to go to the new page,
 * write out the previous one, and copy the new one over, thus making
 * it the current page. If not, simply write the new page, and we are
 * still looking at the page of interest. current page is not updated
 * here, as sdbm_store will do so, after it inserts the incoming pair.
 */
		if (hash & (db->hmask + 1)) {
			if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
			    || write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
				return 0;
			db->pagbno = newp;
			(void) memcpy(pag, New, PBLKSIZ);
		}
		else if (lseek(db->pagf, OFF_PAG(newp), SEEK_SET) < 0
			 || write(db->pagf, New, PBLKSIZ) < 0)
			return 0;

		if (!setdbit(db, db->curbit))
			return 0;
/*
 * see if we have enough room now
 */
		if (fitpair(pag, need))
			return 1;
/*
 * try again... update curbit and hmask as getpage would have
 * done. because of our update of the current page, we do not
 * need to read in anything. BUT we have to write the current
 * [deferred] page out, as the window of failure is too great.
 */
		db->curbit = 2 * db->curbit +
			((hash & (db->hmask + 1)) ? 2 : 1);
		db->hmask |= db->hmask + 1;

		if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
		    || write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
			return 0;

	} while (--smax);
/*
 * if we are here, this is real bad news. After SPLTMAX splits,
 * we still cannot fit the key. say goodnight.
 */
#ifdef BADMESS
	(void) write(2, "sdbm: cannot insert after SPLTMAX attempts.\n", 44);
#endif
	return 0;

}

/*
 * the following two routines will break if
 * deletions aren't taken into account. (ndbm bug)
 */
datum
sdbm_firstkey(register DBM *db)
{
	if (db == NULL)
		return errno = EINVAL, nullitem;
/*
 * start at page 0
 */
	if (lseek(db->pagf, OFF_PAG(0), SEEK_SET) < 0
	    || read(db->pagf, db->pagbuf, PBLKSIZ) < 0)
		return ioerr(db), nullitem;
	db->pagbno = 0;
	db->blkptr = 0;
	db->keyptr = 0;

	return getnext(db);
}

datum
sdbm_nextkey(register DBM *db)
{
	if (db == NULL)
		return errno = EINVAL, nullitem;
	return getnext(db);
}

/*
 * all important binary trie traversal
 */
static int
getpage(register DBM *db, register long int hash)
{
	register int hbit;
	register long dbit;
	register long pagb;

	dbit = 0;
	hbit = 0;
	while (dbit < db->maxbno && getdbit(db, dbit))
		dbit = 2 * dbit + ((hash & (1 << hbit++)) ? 2 : 1);

	debug(("dbit: %d...", dbit));

	db->curbit = dbit;
	db->hmask = masks[hbit];

	pagb = hash & db->hmask;
/*
 * see if the block we need is already in memory.
 * note: this lookaside cache has about 10% hit rate.
 */
	if (pagb != db->pagbno) { 
/*
 * note: here, we assume a "hole" is read as 0s.
 * if not, must zero pagbuf first.
 */
		if (lseek(db->pagf, OFF_PAG(pagb), SEEK_SET) < 0
		    || read(db->pagf, db->pagbuf, PBLKSIZ) < 0)
			return 0;
		if (!chkpage(db->pagbuf))
			return 0;
		db->pagbno = pagb;

		debug(("pag read: %d\n", pagb));
	}
	return 1;
}

static int
getdbit(register DBM *db, register long int dbit)
{
	register long c;
	register long dirb;

	c = dbit / BYTESIZ;
	dirb = c / DBLKSIZ;

	if (dirb != db->dirbno) {
		int got;
		if (lseek(db->dirf, OFF_DIR(dirb), SEEK_SET) < 0
		    || (got=read(db->dirf, db->dirbuf, DBLKSIZ)) < 0)
			return 0;
		if (got==0) 
			memset(db->dirbuf,0,DBLKSIZ);
		db->dirbno = dirb;

		debug(("dir read: %d\n", dirb));
	}

	return db->dirbuf[c % DBLKSIZ] & (1 << dbit % BYTESIZ);
}

static int
setdbit(register DBM *db, register long int dbit)
{
	register long c;
	register long dirb;

	c = dbit / BYTESIZ;
	dirb = c / DBLKSIZ;

	if (dirb != db->dirbno) {
		int got;
		if (lseek(db->dirf, OFF_DIR(dirb), SEEK_SET) < 0
		    || (got=read(db->dirf, db->dirbuf, DBLKSIZ)) < 0)
			return 0;
		if (got==0) 
			memset(db->dirbuf,0,DBLKSIZ);
		db->dirbno = dirb;

		debug(("dir read: %d\n", dirb));
	}

	db->dirbuf[c % DBLKSIZ] |= (1 << dbit % BYTESIZ);

#if 0
	if (dbit >= db->maxbno)
		db->maxbno += DBLKSIZ * BYTESIZ;
#else
	if (OFF_DIR((dirb+1))*BYTESIZ > db->maxbno) 
		db->maxbno=OFF_DIR((dirb+1))*BYTESIZ;
#endif

	if (lseek(db->dirf, OFF_DIR(dirb), SEEK_SET) < 0
	    || write(db->dirf, db->dirbuf, DBLKSIZ) < 0)
		return 0;

	return 1;
}

/*
 * getnext - get the next key in the page, and if done with
 * the page, try the next page in sequence
 */
static datum
getnext(register DBM *db)
{
	datum key;

	for (;;) {
		db->keyptr++;
		key = getnkey(db->pagbuf, db->keyptr);
		if (key.dptr != NULL)
			return key;
/*
 * we either run out, or there is nothing on this page..
 * try the next one... If we lost our position on the
 * file, we will have to seek.
 */
		db->keyptr = 0;
		if (db->pagbno != db->blkptr++)
			if (lseek(db->pagf, OFF_PAG(db->blkptr), SEEK_SET) < 0)
				break;
		db->pagbno = db->blkptr;
		if (read(db->pagf, db->pagbuf, PBLKSIZ) <= 0)
			break;
		if (!chkpage(db->pagbuf))
			break;
	}

	return ioerr(db), nullitem;
}
Commit	Line	Data
463ee0b2	1	/*
	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.
	6	*
	7	* core routines
	8	*/
	9
17f28c40	10	#include "INTERN.h"
85e6fe83	11	#include "config.h"
4f63d024	12	#ifdef WIN32
	13	#include "io.h"
	14	#endif
463ee0b2	15	#include "sdbm.h"
	16	#include "tune.h"
	17	#include "pair.h"
	18
85e6fe83	19	#ifdef I_FCNTL
85e6fe83	20	# include <fcntl.h>
463ee0b2	21	#endif
85e6fe83	22	#ifdef I_SYS_FILE
85e6fe83	23	# include <sys/file.h>
463ee0b2	24	#endif
463ee0b2	25
85e6fe83	26	#ifdef I_STRING
	27	# include <string.h>
	28	#else
	29	# include <strings.h>
463ee0b2	30	#endif
	31
	32	/*
	33	* externals
	34	*/
137443ea	35	#ifndef WIN32
463ee0b2	36	#ifndef sun
	37	extern int errno;
	38	#endif
	39
85e6fe83	40	extern Malloc_t malloc proto((MEM_SIZE));
851efeba	41	extern Free_t free proto((Malloc_t));
bf0c440f	42
137443ea	43	#endif
463ee0b2	44
	45	/*
	46	* forward
	47	*/
	48	static int getdbit proto((DBM *, long));
	49	static int setdbit proto((DBM *, long));
	50	static int getpage proto((DBM *, long));
	51	static datum getnext proto((DBM *));
	52	static int makroom proto((DBM *, long, int));
	53
	54	/*
	55	* useful macros
	56	*/
	57	#define bad(x) ((x).dptr == NULL \|\| (x).dsize < 0)
	58	#define exhash(item) sdbm_hash((item).dptr, (item).dsize)
	59	#define ioerr(db) ((db)->flags \|= DBM_IOERR)
	60
	61	#define OFF_PAG(off) (long) (off) * PBLKSIZ
	62	#define OFF_DIR(off) (long) (off) * DBLKSIZ
	63
	64	static long masks[] = {
	65	000000000000, 000000000001, 000000000003, 000000000007,
	66	000000000017, 000000000037, 000000000077, 000000000177,
	67	000000000377, 000000000777, 000000001777, 000000003777,
	68	000000007777, 000000017777, 000000037777, 000000077777,
	69	000000177777, 000000377777, 000000777777, 000001777777,
	70	000003777777, 000007777777, 000017777777, 000037777777,
	71	000077777777, 000177777777, 000377777777, 000777777777,
	72	001777777777, 003777777777, 007777777777, 017777777777
	73	};
	74
463ee0b2	75	DBM *
f0f333f4	76	sdbm_open(register char *file, register int flags, register int mode)
463ee0b2	77	{
	78	register DBM *db;
	79	register char *dirname;
	80	register char *pagname;
	81	register int n;
	82
	83	if (file == NULL \|\| !*file)
	84	return errno = EINVAL, (DBM *) NULL;
	85	/*
	86	* need space for two seperate filenames
	87	*/
	88	n = strlen(file) * 2 + strlen(DIRFEXT) + strlen(PAGFEXT) + 2;
	89
f0f333f4	90	if ((dirname = (char *) malloc((unsigned) n)) == NULL)
463ee0b2	91	return errno = ENOMEM, (DBM *) NULL;
	92	/*
	93	* build the file names
	94	*/
	95	dirname = strcat(strcpy(dirname, file), DIRFEXT);
	96	pagname = strcpy(dirname + strlen(dirname) + 1, file);
	97	pagname = strcat(pagname, PAGFEXT);
	98
	99	db = sdbm_prep(dirname, pagname, flags, mode);
	100	free((char *) dirname);
	101	return db;
	102	}
	103
	104	DBM *
f0f333f4	105	sdbm_prep(char dirname, char pagname, int flags, int mode)
463ee0b2	106	{
	107	register DBM *db;
	108	struct stat dstat;
	109
	110	if ((db = (DBM *) malloc(sizeof(DBM))) == NULL)
	111	return errno = ENOMEM, (DBM *) NULL;
	112
	113	db->flags = 0;
	114	db->hmask = 0;
	115	db->blkptr = 0;
	116	db->keyptr = 0;
	117	/*
	118	* adjust user flags so that WRONLY becomes RDWR,
	119	* as required by this package. Also set our internal
	120	* flag for RDONLY if needed.
	121	*/
	122	if (flags & O_WRONLY)
	123	flags = (flags & ~O_WRONLY) \| O_RDWR;
	124
	125	else if ((flags & 03) == O_RDONLY)
	126	db->flags = DBM_RDONLY;
	127	/*
	128	* open the files in sequence, and stat the dirfile.
	129	* If we fail anywhere, undo everything, return NULL.
	130	*/
1761cee5	131	#if defined(OS2) \|\| defined(MSDOS) \|\| defined(WIN32) \|\| defined(__CYGWIN__)
4633a7c4	132	flags \|= O_BINARY;
4633a7c4	133	# endif
463ee0b2	134	if ((db->pagf = open(pagname, flags, mode)) > -1) {
	135	if ((db->dirf = open(dirname, flags, mode)) > -1) {
	136	/*
	137	* need the dirfile size to establish max bit number.
	138	*/
	139	if (fstat(db->dirf, &dstat) == 0) {
	140	/*
	141	* zero size: either a fresh database, or one with a single,
	142	* unsplit data page: dirpage is all zeros.
	143	*/
	144	db->dirbno = (!dstat.st_size) ? 0 : -1;
	145	db->pagbno = -1;
	146	db->maxbno = dstat.st_size * BYTESIZ;
	147
	148	(void) memset(db->pagbuf, 0, PBLKSIZ);
	149	(void) memset(db->dirbuf, 0, DBLKSIZ);
	150	/*
	151	* success
	152	*/
	153	return db;
	154	}
	155	(void) close(db->dirf);
	156	}
	157	(void) close(db->pagf);
	158	}
	159	free((char *) db);
	160	return (DBM *) NULL;
	161	}
	162
	163	void
f0f333f4	164	sdbm_close(register DBM *db)
463ee0b2	165	{
	166	if (db == NULL)
	167	errno = EINVAL;
	168	else {
	169	(void) close(db->dirf);
	170	(void) close(db->pagf);
	171	free((char *) db);
	172	}
	173	}
	174
	175	datum
f0f333f4	176	sdbm_fetch(register DBM *db, datum key)
463ee0b2	177	{
	178	if (db == NULL \|\| bad(key))
	179	return errno = EINVAL, nullitem;
	180
	181	if (getpage(db, exhash(key)))
	182	return getpair(db->pagbuf, key);
	183
	184	return ioerr(db), nullitem;
	185	}
	186
	187	int
f4b9d880	188	sdbm_exists(register DBM *db, datum key)
	189	{
	190	if (db == NULL \|\| bad(key))
	191	return errno = EINVAL, -1;
	192
	193	if (getpage(db, exhash(key)))
	194	return exipair(db->pagbuf, key);
	195
	196	return ioerr(db), -1;
	197	}
	198
	199	int
f0f333f4	200	sdbm_delete(register DBM *db, datum key)
463ee0b2	201	{
	202	if (db == NULL \|\| bad(key))
	203	return errno = EINVAL, -1;
	204	if (sdbm_rdonly(db))
	205	return errno = EPERM, -1;
	206
	207	if (getpage(db, exhash(key))) {
	208	if (!delpair(db->pagbuf, key))
	209	return -1;
	210	/*
	211	* update the page file
	212	*/
	213	if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
	214	\|\| write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
	215	return ioerr(db), -1;
	216
	217	return 0;
	218	}
	219
	220	return ioerr(db), -1;
	221	}
	222
	223	int
f0f333f4	224	sdbm_store(register DBM *db, datum key, datum val, int flags)
463ee0b2	225	{
	226	int need;
	227	register long hash;
	228
	229	if (db == NULL \|\| bad(key))
	230	return errno = EINVAL, -1;
	231	if (sdbm_rdonly(db))
	232	return errno = EPERM, -1;
	233
	234	need = key.dsize + val.dsize;
	235	/*
	236	* is the pair too big (or too small) for this database ??
	237	*/
	238	if (need < 0 \|\| need > PAIRMAX)
	239	return errno = EINVAL, -1;
	240
	241	if (getpage(db, (hash = exhash(key)))) {
	242	/*
	243	* if we need to replace, delete the key/data pair
	244	* first. If it is not there, ignore.
	245	*/
	246	if (flags == DBM_REPLACE)
	247	(void) delpair(db->pagbuf, key);
	248	#ifdef SEEDUPS
	249	else if (duppair(db->pagbuf, key))
	250	return 1;
	251	#endif
	252	/*
	253	* if we do not have enough room, we have to split.
	254	*/
	255	if (!fitpair(db->pagbuf, need))
	256	if (!makroom(db, hash, need))
	257	return ioerr(db), -1;
	258	/*
	259	* we have enough room or split is successful. insert the key,
	260	* and update the page file.
	261	*/
	262	(void) putpair(db->pagbuf, key, val);
	263
	264	if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
	265	\|\| write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
	266	return ioerr(db), -1;
	267	/*
	268	* success
	269	*/
	270	return 0;
	271	}
	272
	273	return ioerr(db), -1;
	274	}
	275
	276	/*
	277	* makroom - make room by splitting the overfull page
	278	* this routine will attempt to make room for SPLTMAX times before
	279	* giving up.
	280	*/
	281	static int
f0f333f4	282	makroom(register DBM *db, long int hash, int need)
463ee0b2	283	{
	284	long newp;
	285	char twin[PBLKSIZ];
	286	char *pag = db->pagbuf;
f0f333f4	287	char *New = twin;
463ee0b2	288	register int smax = SPLTMAX;
	289
	290	do {
	291	/*
	292	* split the current page
	293	*/
f0f333f4	294	(void) splpage(pag, New, db->hmask + 1);
463ee0b2	295	/*
	296	* address of the new page
	297	*/
	298	newp = (hash & db->hmask) \| (db->hmask + 1);
	299
	300	/*
	301	* write delay, read avoidence/cache shuffle:
	302	* select the page for incoming pair: if key is to go to the new page,
	303	* write out the previous one, and copy the new one over, thus making
	304	* it the current page. If not, simply write the new page, and we are
	305	* still looking at the page of interest. current page is not updated
	306	* here, as sdbm_store will do so, after it inserts the incoming pair.
	307	*/
	308	if (hash & (db->hmask + 1)) {
	309	if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
	310	\|\| write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
	311	return 0;
	312	db->pagbno = newp;
f0f333f4	313	(void) memcpy(pag, New, PBLKSIZ);
463ee0b2	314	}
463ee0b2	315	else if (lseek(db->pagf, OFF_PAG(newp), SEEK_SET) < 0
f0f333f4	316	\|\| write(db->pagf, New, PBLKSIZ) < 0)
463ee0b2	317	return 0;
	318
	319	if (!setdbit(db, db->curbit))
	320	return 0;
	321	/*
	322	* see if we have enough room now
	323	*/
	324	if (fitpair(pag, need))
	325	return 1;
	326	/*
	327	* try again... update curbit and hmask as getpage would have
	328	* done. because of our update of the current page, we do not
	329	* need to read in anything. BUT we have to write the current
	330	* [deferred] page out, as the window of failure is too great.
	331	*/
	332	db->curbit = 2 * db->curbit +
	333	((hash & (db->hmask + 1)) ? 2 : 1);
	334	db->hmask \|= db->hmask + 1;
	335
	336	if (lseek(db->pagf, OFF_PAG(db->pagbno), SEEK_SET) < 0
	337	\|\| write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
	338	return 0;
	339
	340	} while (--smax);
	341	/*
	342	* if we are here, this is real bad news. After SPLTMAX splits,
	343	* we still cannot fit the key. say goodnight.
	344	*/
	345	#ifdef BADMESS
	346	(void) write(2, "sdbm: cannot insert after SPLTMAX attempts.\n", 44);
	347	#endif
	348	return 0;
	349
	350	}
	351
	352	/*
	353	* the following two routines will break if
	354	* deletions aren't taken into account. (ndbm bug)
	355	*/
	356	datum
f0f333f4	357	sdbm_firstkey(register DBM *db)
463ee0b2	358	{
	359	if (db == NULL)
	360	return errno = EINVAL, nullitem;
	361	/*
	362	* start at page 0
	363	*/
	364	if (lseek(db->pagf, OFF_PAG(0), SEEK_SET) < 0
	365	\|\| read(db->pagf, db->pagbuf, PBLKSIZ) < 0)
	366	return ioerr(db), nullitem;
	367	db->pagbno = 0;
	368	db->blkptr = 0;
	369	db->keyptr = 0;
	370
	371	return getnext(db);
	372	}
	373
	374	datum
f0f333f4	375	sdbm_nextkey(register DBM *db)
463ee0b2	376	{
	377	if (db == NULL)
	378	return errno = EINVAL, nullitem;
	379	return getnext(db);
	380	}
	381
	382	/*
	383	* all important binary trie traversal
	384	*/
	385	static int
f0f333f4	386	getpage(register DBM *db, register long int hash)
463ee0b2	387	{
	388	register int hbit;
	389	register long dbit;
	390	register long pagb;
	391
	392	dbit = 0;
	393	hbit = 0;
	394	while (dbit < db->maxbno && getdbit(db, dbit))
	395	dbit = 2 * dbit + ((hash & (1 << hbit++)) ? 2 : 1);
	396
	397	debug(("dbit: %d...", dbit));
	398
	399	db->curbit = dbit;
	400	db->hmask = masks[hbit];
	401
	402	pagb = hash & db->hmask;
	403	/*
	404	* see if the block we need is already in memory.
	405	* note: this lookaside cache has about 10% hit rate.
	406	*/
	407	if (pagb != db->pagbno) {
	408	/*
	409	* note: here, we assume a "hole" is read as 0s.
	410	* if not, must zero pagbuf first.
	411	*/
	412	if (lseek(db->pagf, OFF_PAG(pagb), SEEK_SET) < 0
	413	\|\| read(db->pagf, db->pagbuf, PBLKSIZ) < 0)
	414	return 0;
	415	if (!chkpage(db->pagbuf))
	416	return 0;
	417	db->pagbno = pagb;
	418
	419	debug(("pag read: %d\n", pagb));
	420	}
	421	return 1;
	422	}
	423
	424	static int
f0f333f4	425	getdbit(register DBM *db, register long int dbit)
463ee0b2	426	{
	427	register long c;
	428	register long dirb;
	429
	430	c = dbit / BYTESIZ;
	431	dirb = c / DBLKSIZ;
	432
	433	if (dirb != db->dirbno) {
98627ae8	434	int got;
463ee0b2	435	if (lseek(db->dirf, OFF_DIR(dirb), SEEK_SET) < 0
98627ae8	436	\|\| (got=read(db->dirf, db->dirbuf, DBLKSIZ)) < 0)
463ee0b2	437	return 0;
98627ae8	438	if (got==0)
98627ae8	439	memset(db->dirbuf,0,DBLKSIZ);
463ee0b2	440	db->dirbno = dirb;
	441
	442	debug(("dir read: %d\n", dirb));
	443	}
	444
	445	return db->dirbuf[c % DBLKSIZ] & (1 << dbit % BYTESIZ);
	446	}
	447
	448	static int
f0f333f4	449	setdbit(register DBM *db, register long int dbit)
463ee0b2	450	{
	451	register long c;
	452	register long dirb;
	453
	454	c = dbit / BYTESIZ;
	455	dirb = c / DBLKSIZ;
	456
	457	if (dirb != db->dirbno) {
98627ae8	458	int got;
463ee0b2	459	if (lseek(db->dirf, OFF_DIR(dirb), SEEK_SET) < 0
98627ae8	460	\|\| (got=read(db->dirf, db->dirbuf, DBLKSIZ)) < 0)
463ee0b2	461	return 0;
98627ae8	462	if (got==0)
98627ae8	463	memset(db->dirbuf,0,DBLKSIZ);
463ee0b2	464	db->dirbno = dirb;
	465
	466	debug(("dir read: %d\n", dirb));
	467	}
	468
	469	db->dirbuf[c % DBLKSIZ] \|= (1 << dbit % BYTESIZ);
	470
98627ae8	471	#if 0
463ee0b2	472	if (dbit >= db->maxbno)
463ee0b2	473	db->maxbno += DBLKSIZ * BYTESIZ;
98627ae8	474	#else
	475	if (OFF_DIR((dirb+1))*BYTESIZ > db->maxbno)
	476	db->maxbno=OFF_DIR((dirb+1))*BYTESIZ;
	477	#endif
463ee0b2	478
	479	if (lseek(db->dirf, OFF_DIR(dirb), SEEK_SET) < 0
	480	\|\| write(db->dirf, db->dirbuf, DBLKSIZ) < 0)
	481	return 0;
	482
	483	return 1;
	484	}
	485
	486	/*
	487	* getnext - get the next key in the page, and if done with
	488	* the page, try the next page in sequence
	489	*/
	490	static datum
f0f333f4	491	getnext(register DBM *db)
463ee0b2	492	{
	493	datum key;
	494
	495	for (;;) {
	496	db->keyptr++;
	497	key = getnkey(db->pagbuf, db->keyptr);
	498	if (key.dptr != NULL)
	499	return key;
	500	/*
	501	* we either run out, or there is nothing on this page..
	502	* try the next one... If we lost our position on the
	503	* file, we will have to seek.
	504	*/
	505	db->keyptr = 0;
	506	if (db->pagbno != db->blkptr++)
	507	if (lseek(db->pagf, OFF_PAG(db->blkptr), SEEK_SET) < 0)
	508	break;
	509	db->pagbno = db->blkptr;
	510	if (read(db->pagf, db->pagbuf, PBLKSIZ) <= 0)
	511	break;
	512	if (!chkpage(db->pagbuf))
	513	break;
	514	}
	515
	516	return ioerr(db), nullitem;
	517	}
85e6fe83	518