/*
 * sdbm - ndbm work-alike hashed database library
 * based on Per-Ake Larson's Dynamic Hashing algorithms. BIT 18 (1978).
 * author: oz@nexus.yorku.ca
 *
 * Copyright 1989, Ozan S. Yigit
 * When it is officially released, this code will be in Public Domain.
 * Until that time, only those who have received this code directly
 * from the author have the right to modify and use it in a form suitable
 * to a beta-test release. Please especially note the following:
 *
 * - The author is not responsible for the consequences of use of
 *   this software, no matter how awful, even if they arise from defects
 *   in it.
 *
 * - This code must NOT be distributed without prior permission from
 *   the author.
 */

#ifndef lint
static char rcsid[] = "$Id: sdbm.c,v 1.3 90/10/05 23:52:55 lee Exp $";
#endif

#include "sdbm.h"
#include "port.h" /* this may need SVID to be defined... */
#include "pair.h"

#define SPLTMAX		8	       /* maximum number of split attempts */

#include <sys/types.h>
#include <sys/stat.h>
#ifdef SYSV
# include <fcntl.h>
#else
# include <sys/file.h>
#endif
#include <errno.h>
#include <string.h>
#ifndef BSD42
#include <memory.h>
#endif

#ifdef __STDC__
#include <stddef.h>
#endif

#ifndef NULL
#define NULL	0
#endif

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

extern char *malloc proto((unsigned int));
extern void free proto((void *));
extern long lseek();

/*
 * 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)	dbm_hash((item).dptr, (item).dsize)

#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
};

datum nullitem = {NULL, 0};

DBM *
dbm_open(file, flags, mode)
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 = 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 = dbm_prep(dirname, pagname, flags, mode);
	free((char *) dirname);
	return (db);
}

DBM *
dbm_prep(dirname, pagname, flags, mode)
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);

	/* Liam Quin (lee@sq.com): initialise the new structure: */
	db->dirf = db->pagf = -1; /* paranoia on this one! */
	db->flags = 0; /* but this is very important! */
	db->curbit = 0;
	db->hmask = 0;
	db->blkptr = 0;
	db->keyptr = 0;
	db->blkno = 0L; /* I think this is unused actually. */
	db->pagbno = -1;
	db->dirbno = -1;
	/* End of Liam's change */
/*
 * adjust user flags so that WRONLY becomes RDWR, 
 * as required by this package. Also set our internal
 * flag for RDONLY.
 */
	if (flags & O_WRONLY)
		flags = (flags & ~O_WRONLY) | O_RDWR;
	if (flags & O_RDONLY)
		db->flags = DBM_RDONLY;
/*
 * open the files in sequence, and stat the dirfile.
 * If we fail anywhere, undo everything, return NULL.
 */
	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
dbm_close(db)
register DBM *db;
{
	if (db == NULL)
		errno = EINVAL;
	else {
		(void) close(db->dirf);
		(void) close(db->pagf);
		free((char *) db);
	}
}

datum
dbm_fetch(db, key)
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 (nullitem);
}

int
dbm_delete(db, key)
register DBM *db;
datum key;
{
	if (db == NULL || bad(key))
		return (errno = EINVAL, -1);
	if (dbm_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), L_SET) < 0 ||
		    write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
			return (-1);

		return (0);
	}

	return (-1);
}

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

	errno = 0; /* Liam, to assist debugging */
	if (db == NULL || bad(key))
		return (errno = EINVAL, -1);
	if (dbm_rdonly(db))
		return (errno = EPERM, -1);
/*
 * is the pair too big for this database ??
 */
	if ((need = key.dsize + val.dsize) > PAIRMAX)
		return (-1);

	if (!getpage(db, (hash = exhash(key))))
		return (-1);
/*
 * 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 DUPERROR
	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 (-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), L_SET) < 0 ||
	    write(db->pagf, db->pagbuf, PBLKSIZ) < 0)
		return (-1);

	return (0);
}

/*
 * makroom - make room by splitting the overfull page
 * this routine will attempt to split for SPLTMAX times before
 * giving up.
 */
static int
makroom(db, hash, need)
register DBM *db;
long 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 dbm_store will do so, after it inserts the incoming pair.
 */
		if (hash & (db->hmask + 1)) {
			if (lseek(db->pagf, OFF_PAG(db->pagbno), L_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), L_SET) < 0 ||
			 write(db->pagf, new, PBLKSIZ) < 0)
			return (0);

		if (!setdbit(db, db->curbit))
			return (0);

		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 + 1 +
			((hash & (db->hmask + 1)) ? 1 : 0);
		db->hmask |= (db->hmask + 1);

		if (lseek(db->pagf, OFF_PAG(db->pagbno), L_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 SPLITERROR
	printf("sdbm: cannot make room after %d splits.\n", SPLTMAX);
#endif
	return (0);

}

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

	return (getnext(db));
}

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

static int
getpage(db, hash)
register DBM *db;
register long hash;
{
	register int hbit;
	register long dbit;
	register long pagb;

	dbit = 0;
	hbit = 0;
	while (dbit < db->maxbno && getdbit(db, dbit))
		dbit = 2 * dbit + 1 + ((hash & (1 << hbit++)) ? 1 : 0);
#ifdef DEBUG
	printf("dbit: %d...", dbit);
#endif
	db->curbit = dbit;
	pagb = hash & (db->hmask = masks[hbit]);
/*
 * note: here, we assume a "hole" is read as 0s.
 * if not, must zero pagbuf first.
 */
	if (pagb != db->pagbno) {
		if (lseek(db->pagf, OFF_PAG(pagb), L_SET) < 0 ||
		    read(db->pagf, db->pagbuf, PBLKSIZ) < 0)
			return (0);
		if (!chkpage(db->pagbuf))
			return (0);
		db->pagbno = pagb;
#ifdef DEBUG
		printf("pag read: %d\n", pagb);
#endif
	}
	return (1);
}

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

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

	if (dirb != db->dirbno) {
		if (lseek(db->dirf, OFF_DIR(dirb), L_SET) < 0 ||
		    read(db->dirf, db->dirbuf, DBLKSIZ) < 0)
			return (0);
		db->dirbno = dirb;
#ifdef DEBUG
		printf("dir read: %d\n", dirb);
#endif
	}

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

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

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

	if (dirb != db->dirbno) {
		if (lseek(db->dirf, OFF_DIR(dirb), L_SET) < 0 ||
		    read(db->dirf, db->dirbuf, DBLKSIZ) < 0)
			return (0);
		db->dirbno = dirb;
#ifdef DEBUG
		printf("dir read: %d\n", dirb);
#endif
	}

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

	if (dbit >= db->maxbno)
		db->maxbno += DBLKSIZ * BYTESIZ;

	if (lseek(db->dirf, OFF_DIR(dirb), L_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(db)
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), L_SET) < 0)
				break;
		db->pagbno = db->blkptr;
		if (read(db->pagf, db->pagbuf, PBLKSIZ) <= 0)
			break;
		if (!chkpage(db->pagbuf))
			break;
	}

	return (nullitem);
}