Subversion Repositories planix.SVN

#include <u.h>
#include <libc.h>
#include <bio.h>
#include <ndb.h>

/*
 *  make the hash table completely in memory and then write as a file
 */

uchar *ht;
ulong hlen;
Ndb *db;
ulong nextchain;

char*
syserr(void)
{
        static char buf[ERRMAX];

        errstr(buf, sizeof buf);
        return buf;
}

void
enter(char *val, ulong dboff)
{
        ulong h;
        uchar *last;
        ulong ptr;

        h = ndbhash(val, hlen);
        h *= NDBPLEN;
        last = &ht[h];
        ptr = NDBGETP(last);
        if(ptr == NDBNAP){
                NDBPUTP(dboff, last);
                return;
        }

        if(ptr & NDBCHAIN){
                /* walk the chain to the last entry */
                for(;;){
                        ptr &= ~NDBCHAIN;
                        last = &ht[ptr+NDBPLEN];
                        ptr = NDBGETP(last);
                        if(ptr == NDBNAP){
                                NDBPUTP(dboff, last);
                                return;
                        }
                        if(!(ptr & NDBCHAIN)){
                                NDBPUTP(nextchain|NDBCHAIN, last);
                                break;
                        }
                }
        } else
                NDBPUTP(nextchain|NDBCHAIN, last);

        /* add a chained entry */
        NDBPUTP(ptr, &ht[nextchain]);
        NDBPUTP(dboff, &ht[nextchain + NDBPLEN]);
        nextchain += 2*NDBPLEN;
}

uchar nbuf[16*1024];

void
main(int argc, char **argv)
{
        Ndbtuple *t, *nt;
        int n;
        Dir *d; 
        uchar buf[8];
        char file[128];
        int fd;
        ulong off;
        uchar *p;

        if(argc != 3){
                fprint(2, "usage: mkhash file attribute\n");
                exits("usage");
        }
        db = ndbopen(argv[1]);
        if(db == 0){
                fprint(2, "mkhash: can't open %s\n", argv[1]);
                exits(syserr());
        }

        /* try a bigger than normal buffer */
        Binits(&db->b, Bfildes(&db->b), OREAD, nbuf, sizeof(nbuf));

        /* count entries to calculate hash size */
        n = 0;

        while(nt = ndbparse(db)){
                for(t = nt; t; t = t->entry){
                        if(strcmp(t->attr, argv[2]) == 0)
                                n++;
                }
                ndbfree(nt);
        }

        /* allocate an array large enough for worst case */
        hlen = 2*n+1;
        n = hlen*NDBPLEN + hlen*2*NDBPLEN;
        ht = mallocz(n, 1);
        if(ht == 0){
                fprint(2, "mkhash: not enough memory\n");
                exits(syserr());
        }
        for(p = ht; p < &ht[n]; p += NDBPLEN)
                NDBPUTP(NDBNAP, p);
        nextchain = hlen*NDBPLEN;

        /* create the in core hash table */
        Bseek(&db->b, 0, 0);
        off = 0;
        while(nt = ndbparse(db)){
                for(t = nt; t; t = t->entry){
                        if(strcmp(t->attr, argv[2]) == 0)
                                enter(t->val, off);
                }
                ndbfree(nt);
                off = Boffset(&db->b);
        }

        /* create the hash file */
        snprint(file, sizeof(file), "%s.%s", argv[1], argv[2]);
        fd = create(file, ORDWR, 0664);
        if(fd < 0){
                fprint(2, "mkhash: can't create %s\n", file);
                exits(syserr());
        }
        NDBPUTUL(db->mtime, buf);
        NDBPUTUL(hlen, buf+NDBULLEN);
        if(write(fd, buf, NDBHLEN) != NDBHLEN){
                fprint(2, "mkhash: writing %s\n", file);
                exits(syserr());
        }
        if(write(fd, ht, nextchain) != nextchain){
                fprint(2, "mkhash: writing %s\n", file);
                exits(syserr());
        }
        close(fd);

        /* make sure file didn't change while we were making the hash */
        d = dirstat(argv[1]);
        if(d == nil || d->qid.path != db->qid.path
           || d->qid.vers != db->qid.vers){
                fprint(2, "mkhash: %s changed underfoot\n", argv[1]);
                remove(file);
                exits("changed");
        }

        exits(0);
}