path: root/ext/SDBM_File/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 "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

#include <string.h>

/*
 * externals
 */

#include <errno.h> /* See notes in perl.h about avoiding
                        extern int errno; */
#ifdef __cplusplus
extern "C" {
#endif

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

#ifdef __cplusplus
}
#endif

const datum nullitem = {0, 0};

/*
 * forward
 */
static int getdbit(DBM *, long);
static int setdbit(DBM *, long);
static int getpage(DBM *, long);
static datum getnext(DBM *);
static int makroom(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 const 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(char *file, int flags, int mode)
{
        DBM *db;
        char *dirname;
        char *pagname;
        size_t filelen;
        const size_t dirfext_size = sizeof(DIRFEXT "");
        const size_t pagfext_size = sizeof(PAGFEXT "");

        if (file == NULL || !*file)
                return errno = EINVAL, (DBM *) NULL;
/*
 * need space for two separate filenames
 */
        filelen = strlen(file);

        if ((dirname = (char *) malloc(filelen + dirfext_size
                                       + filelen + pagfext_size)) == NULL)
                return errno = ENOMEM, (DBM *) NULL;
/*
 * build the file names
 */
        memcpy(dirname, file, filelen);
        memcpy(dirname + filelen, DIRFEXT, dirfext_size);
        pagname = dirname + filelen + dirfext_size;
        memcpy(pagname, file, filelen);
        memcpy(pagname + filelen, PAGFEXT, pagfext_size);

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

DBM *
sdbm_prep(char *dirname, char *pagname, int flags, int mode)
{
        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(DBM *db)
{
        if (db == NULL)
                errno = EINVAL;
        else {
                (void) close(db->dirf);
                (void) close(db->pagf);
                free((char *) db);
        }
}

datum
sdbm_fetch(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(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(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(DBM *db, datum key, datum val, int flags)
{
        int need;
        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(DBM *db, long int hash, int need)
{
        long newp;
        char twin[PBLKSIZ];
#if defined(DOSISH) || defined(WIN32)
        char zer[PBLKSIZ];
        long oldtail;
#endif
        char *pag = db->pagbuf;
        char *New = twin;
        int smax = SPLTMAX;
#ifdef BADMESS
        int rc;
#endif

        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 avoidance/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 defined(DOSISH) || defined(WIN32)
                /*
                 * Fill hole with 0 if made it.
                 * (hole is NOT read as 0)
                 */
                oldtail = lseek(db->pagf, 0L, SEEK_END);
                memset(zer, 0, PBLKSIZ);
                while (OFF_PAG(newp) > oldtail) {
                        if (lseek(db->pagf, 0L, SEEK_END) < 0 ||
                            write(db->pagf, zer, PBLKSIZ) < 0) {

                                return 0;
                        }
                        oldtail += PBLKSIZ;
                }
#endif
                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
        rc = write(2, "sdbm: cannot insert after SPLTMAX attempts.\n", 44);
        /* PERL_UNUSED_VAR() or PERL_UNUSED_RESULT() would be
         * useful here but that would mean pulling in perl.h */
        (void)rc;
#endif
        return 0;

}

/*
 * the following two routines will break if
 * deletions aren't taken into account. (ndbm bug)
 */
datum
sdbm_firstkey(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;
        if (!chkpage(db->pagbuf)) {
            errno = EINVAL;
            ioerr(db);
            db->pagbno = -1;
            return nullitem;
        }
        db->pagbno = 0;
        db->blkptr = 0;
        db->keyptr = 0;

        return getnext(db);
}

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

/*
 * all important binary trie traversal
 */
static int
getpage(DBM *db, long int hash)
{
        int hbit;
        long dbit;
        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)) {
                    errno = EINVAL;
                    db->pagbno = -1;
                    ioerr(db);
                    return 0;
                }
                db->pagbno = pagb;

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

static int
getdbit(DBM *db, long int dbit)
{
        long c;
        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(DBM *db, long int dbit)
{
        long c;
        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(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)) {
                    errno = EINVAL;
                    db->pagbno = -1;
                    ioerr(db);
                    break;
                }
        }

        return ioerr(db), nullitem;
}