ref: e09adf59442cd36888eaea1d76e66ff3259d16b8
dir: /sys/src/cmd/ndb/mkhash.c/
#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); }