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Annotation of 43BSDTahoe/etc/named/db_lookup.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (c) 1986 Regents of the University of California.
        !             3:  * All rights reserved.
        !             4:  *
        !             5:  * Redistribution and use in source and binary forms are permitted
        !             6:  * provided that the above copyright notice and this paragraph are
        !             7:  * duplicated in all such forms and that any documentation,
        !             8:  * advertising materials, and other materials related to such
        !             9:  * distribution and use acknowledge that the software was developed
        !            10:  * by the University of California, Berkeley.  The name of the
        !            11:  * University may not be used to endorse or promote products derived
        !            12:  * from this software without specific prior written permission.
        !            13:  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
        !            14:  * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
        !            15:  * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
        !            16:  */
        !            17: 
        !            18: #ifndef lint
        !            19: static char sccsid[] = "@(#)db_lookup.c        4.15 (Berkeley) 6/18/88";
        !            20: #endif /* not lint */
        !            21: 
        !            22: /*
        !            23:  * Table lookup routines.
        !            24:  */
        !            25: 
        !            26: #include <sys/types.h>
        !            27: #include <stdio.h>
        !            28: #include <arpa/nameser.h>
        !            29: #include "db.h"
        !            30: 
        !            31: struct hashbuf *hashtab;       /* root hash table */
        !            32: struct hashbuf *fcachetab;     /* hash table of cache read from file */
        !            33: 
        !            34: #ifdef DEBUG
        !            35: extern int debug;
        !            36: extern FILE *ddt;
        !            37: #endif
        !            38: 
        !            39: /* 
        !            40:  * Lookup 'name' and return a pointer to the namebuf;
        !            41:  * NULL otherwise. If 'insert', insert name into tables.
        !            42:  * Wildcard lookups are handled.
        !            43:  */
        !            44: struct namebuf *
        !            45: nlookup(name, htpp, fname, insert)
        !            46:        char *name;
        !            47:        struct hashbuf **htpp;
        !            48:        char **fname;
        !            49:        int insert;
        !            50: {
        !            51:        register struct namebuf *np;
        !            52:        register char *cp;
        !            53:        register int c;
        !            54:        register unsigned hval;
        !            55:        register struct hashbuf *htp;
        !            56:        struct namebuf *parent = NULL;
        !            57: 
        !            58:        htp = *htpp;
        !            59:        hval = 0;
        !            60:        *fname = "???";
        !            61:        for (cp = name; c = *cp++; ) {
        !            62:                if (c == '.') {
        !            63:                        parent = np = nlookup(cp, htpp, fname, insert);
        !            64:                        if (np == NULL)
        !            65:                                return (NULL);
        !            66:                        if (*fname != cp)
        !            67:                                return (np);
        !            68:                        if ((htp = np->n_hash) == NULL) {
        !            69:                                if (!insert) {
        !            70:                                        if (np->n_dname[0] == '*' && 
        !            71:                                            np->n_dname[1] == '\0')
        !            72:                                                *fname = name;
        !            73:                                        return (np);
        !            74:                                }
        !            75:                                htp = savehash((struct hashbuf *)NULL);
        !            76:                                np->n_hash = htp;
        !            77:                        }
        !            78:                        *htpp = htp;
        !            79:                        break;
        !            80:                }
        !            81:                hval <<= HASHSHIFT;
        !            82:                hval += c & HASHMASK;
        !            83:        }
        !            84:        c = *--cp;
        !            85:        *cp = '\0';
        !            86:        /*
        !            87:         * Lookup this label in current hash table.
        !            88:         */
        !            89:        for (np = htp->h_tab[hval % htp->h_size]; np != NULL; np = np->n_next) {
        !            90: 
        !            91: #ifdef ALLOW_UPDATES
        !            92:                /* Note: at this point, if np->n_data is NULL, we could be in
        !            93:                   one of two situations: Either we have come across a name
        !            94:                   for which all the RRs have been (dynamically) deleted, or
        !            95:                   else we have come across a name which has no RRs
        !            96:                   associated with it because it is just a place holder
        !            97:                   (e.g., EDU).  In the former case, we would like to delete
        !            98:                   the namebuf, since it is no longer of use, but in the
        !            99:                   latter case we need to hold on to it, so future lookups
        !           100:                   that depend on it don't fail.  The only way I can see of
        !           101:                   doing this is to always leave the namebufs around
        !           102:                   (although then the memory usage continues to grow whenever
        !           103:                   names are added, and can never shrink back down completely
        !           104:                   when all their associated RRs are deleted). */
        !           105: #endif ALLOW_UPDATES
        !           106: 
        !           107:                if (np->n_hashval == hval &&
        !           108:                    strcasecmp(name, np->n_dname) == 0) {
        !           109:                        *cp = c;
        !           110:                        *fname = name;
        !           111:                        return (np);
        !           112:                }
        !           113:        }
        !           114:        if (!insert) {
        !           115:                /*
        !           116:                 * look for wildcard in this hash table
        !           117:                 */
        !           118:                hval = ('*' & HASHMASK)  % htp->h_size;
        !           119:                for (np = htp->h_tab[hval]; np != NULL; np = np->n_next) {
        !           120:                        if (np->n_dname[0] == '*'  && np->n_dname[1] == '\0') {
        !           121:                                *cp = c;
        !           122:                                *fname = name;
        !           123:                                return (np);
        !           124:                        }
        !           125:                }
        !           126:                *cp = c;
        !           127:                return (parent);
        !           128:        }
        !           129:        np = savename(name);
        !           130:        np->n_parent = parent;
        !           131:        np->n_hashval = hval;
        !           132:        hval %= htp->h_size;
        !           133:        np->n_next = htp->h_tab[hval];
        !           134:        htp->h_tab[hval] = np;
        !           135:        /* increase hash table size */
        !           136:        if (++htp->h_cnt > htp->h_size * 2) {
        !           137:                *htpp = savehash(htp);
        !           138:                if (parent == NULL) {
        !           139:                        if (htp == hashtab)
        !           140:                            hashtab = *htpp;
        !           141:                        else
        !           142:                            fcachetab = *htpp;
        !           143:                }
        !           144:                else
        !           145:                        parent->n_hash = *htpp;
        !           146:                htp = *htpp;
        !           147:        }
        !           148:        *cp = c;
        !           149:        *fname = name;
        !           150:        return (np);
        !           151: }
        !           152: 
        !           153: /*
        !           154:  * Does the data record match the class and type?
        !           155:  */
        !           156: match(dp, class, type)
        !           157:        register struct databuf *dp;
        !           158:        register int class, type;
        !           159: {
        !           160: #ifdef DEBUG
        !           161:        if (debug >= 5)
        !           162:                fprintf(ddt,"match(0x%x, %d, %d) %d, %d\n", dp, class, type,
        !           163:                        dp->d_class, dp->d_type);
        !           164: #endif
        !           165:        if (dp->d_class != class && class != C_ANY)
        !           166:                return (0);
        !           167:        if (dp->d_type != type && type != T_ANY)
        !           168:                return (0);
        !           169:        return (1);
        !           170: }

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