/*
 * 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 "sdbm.h"
#include "sdbm_tune.h"
#include "sdbm_pair.h"
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <stdlib.h>
#ifdef WIN32
#include <io.h>
#include <stdio.h>
#else
#include <unistd.h>       /* for lseek() */
#endif
#ifdef NETWARE
#include <nwsemaph.h>
#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
};
datum nullitem = {NULL, 0};
#ifdef NETWARE
extern LONG locking_sem;
#endif
DBM *
sdbm_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);
#ifdef NETWARE
        locking_sem = OpenLocalSemaphore (1);
#endif
        db = sdbm_prep(dirname, pagname, flags, mode);
        free((char *) dirname);
        return db;
}
DBM *
sdbm_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;
        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(NETWARE)
        flags |= O_BINARY;
#endif
        if ((db->pagf = open(pagname, flags, mode)) > -1) {
            if ( sdbm_fd_lock(db->pagf, sdbm_rdonly(db)) > -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) sdbm_fd_unlock(db->pagf);
            }
            (void) close(db->pagf);
        }
        free((char *) db);
        return (DBM *) NULL;
}
void
sdbm_close(db)
register DBM *db;
{
        if (db == NULL)
                errno = EINVAL;
        else {
                (void) close(db->dirf);
                (void) sdbm_fd_unlock(db->pagf);
                (void) close(db->pagf);
                free((char *) db);
#ifdef NETWARE
                CloseLocalSemaphore (locking_sem);
#endif
        }
}
datum
sdbm_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 ioerr(db), nullitem;
}
int
sdbm_delete(db, key)
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(db, key, val, flags)
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(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 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(db)
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(db)
register DBM *db;
{
        if (db == NULL)
                return errno = EINVAL, nullitem;
        return getnext(db);
}
/*
 * all important binary trie traversal
 */
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 + ((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(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), SEEK_SET) < 0
                    || read(db->dirf, db->dirbuf, DBLKSIZ) < 0)
                        return 0;
                db->dirbno = dirb;
                debug(("dir read: %d\n", dirb));
        }
        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), SEEK_SET) < 0
                    || read(db->dirf, db->dirbuf, DBLKSIZ) < 0)
                        return 0;
                db->dirbno = dirb;
                debug(("dir read: %d\n", dirb));
        }
        db->dirbuf[c % DBLKSIZ] |= (1 << dbit % BYTESIZ);
        if (dbit >= db->maxbno)
                db->maxbno += DBLKSIZ * BYTESIZ;
        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(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), 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;
}