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 this notice is preserved and that due credit is given
   7:  * to the University of California at Berkeley. The name of the University
   8:  * may not be used to endorse or promote products derived from this
   9:  * software without specific prior written permission. This software
  10:  * is provided ``as is'' without express or implied warranty.
  11:  */
  12: 
  13: #if defined(DOSCCS) && !defined(lint)
  14: static char sccsid[] = "@(#)db_lookup.c	4.14.1 (2.11BSD GTE) 1/1/94";
  15: #endif
  16: 
  17: /*
  18:  * Table lookup routines.
  19:  */
  20: 
  21: #include <sys/types.h>
  22: #include <stdio.h>
  23: #include <arpa/nameser.h>
  24: #include "db.h"
  25: 
  26: struct hashbuf *hashtab;    /* root hash table */
  27: struct hashbuf *fcachetab;  /* hash table of cache read from file */
  28: 
  29: #ifdef DEBUG
  30: extern int debug;
  31: extern FILE *ddt;
  32: #endif
  33: 
  34: /*
  35:  * Lookup 'name' and return a pointer to the namebuf;
  36:  * NULL otherwise. If 'insert', insert name into tables.
  37:  * Wildcard lookups are handled.
  38:  */
  39: struct namebuf *
  40: nlookup(name, htpp, fname, insert)
  41:     char *name;
  42:     struct hashbuf **htpp;
  43:     char **fname;
  44:     int insert;
  45: {
  46:     register struct namebuf *np;
  47:     register char *cp;
  48:     register int c;
  49:     register unsigned hval;
  50:     register struct hashbuf *htp;
  51:     struct namebuf *parent = NULL;
  52: 
  53:     htp = *htpp;
  54:     hval = 0;
  55:     *fname = "???";
  56:     for (cp = name; c = *cp++; ) {
  57:         if (c == '.') {
  58:             parent = np = nlookup(cp, htpp, fname, insert);
  59:             if (np == NULL)
  60:                 return (NULL);
  61:             if (*fname != cp)
  62:                 return (np);
  63:             if ((htp = np->n_hash) == NULL) {
  64:                 if (!insert) {
  65:                     if (np->n_dname[0] == '*' &&
  66:                         np->n_dname[1] == '\0')
  67:                         *fname = name;
  68:                     return (np);
  69:                 }
  70:                 htp = savehash((struct hashbuf *)NULL);
  71:                 np->n_hash = htp;
  72:             }
  73:             *htpp = htp;
  74:             break;
  75:         }
  76:         hval <<= HASHSHIFT;
  77:         hval += c & HASHMASK;
  78:     }
  79:     c = *--cp;
  80:     *cp = '\0';
  81:     /*
  82: 	 * Lookup this label in current hash table.
  83: 	 */
  84:     for (np = htp->h_tab[hval % htp->h_size]; np != NULL; np = np->n_next) {
  85: 
  86: #ifdef ALLOW_UPDATES
  87:         /* Note: at this point, if np->n_data is NULL, we could be in
  88: 		   one of two situations: Either we have come across a name
  89: 		   for which all the RRs have been (dynamically) deleted, or
  90: 		   else we have come across a name which has no RRs
  91: 		   associated with it because it is just a place holder
  92: 		   (e.g., EDU).  In the former case, we would like to delete
  93: 		   the namebuf, since it is no longer of use, but in the
  94: 		   latter case we need to hold on to it, so future lookups
  95: 		   that depend on it don't fail.  The only way I can see of
  96: 		   doing this is to always leave the namebufs around
  97: 		   (although then the memory usage continues to grow whenever
  98: 		   names are added, and can never shrink back down completely
  99: 		   when all their associated RRs are deleted). */
 100: #endif ALLOW_UPDATES
 101: 
 102:         if (np->n_hashval == hval &&
 103:             strcasecmp(name, np->n_dname) == 0) {
 104:             *cp = c;
 105:             *fname = name;
 106:             return (np);
 107:         }
 108:     }
 109:     if (!insert) {
 110:         /*
 111: 		 * look for wildcard in this hash table
 112: 		 */
 113:         hval = ('*' & HASHMASK)  % htp->h_size;
 114:         for (np = htp->h_tab[hval]; np != NULL; np = np->n_next) {
 115:             if (np->n_dname[0] == '*'  && np->n_dname[1] == '\0') {
 116:                 *cp = c;
 117:                 *fname = name;
 118:                 return (np);
 119:             }
 120:         }
 121:         *cp = c;
 122:         return (parent);
 123:     }
 124:     np = savename(name);
 125:     np->n_parent = parent;
 126:     np->n_hashval = hval;
 127:     hval %= htp->h_size;
 128:     np->n_next = htp->h_tab[hval];
 129:     htp->h_tab[hval] = np;
 130:     /* increase hash table size */
 131:     if (++htp->h_cnt > htp->h_size * 2) {
 132:         *htpp = savehash(htp);
 133:         if (parent == NULL) {
 134:             if (htp == hashtab)
 135:                 hashtab = *htpp;
 136:             else
 137:                 fcachetab = *htpp;
 138:         }
 139:         else
 140:             parent->n_hash = *htpp;
 141:         htp = *htpp;
 142:     }
 143:     *cp = c;
 144:     *fname = name;
 145:     return (np);
 146: }
 147: 
 148: /*
 149:  * Does the data record match the class and type?
 150:  */
 151: match(dp, class, type)
 152:     register struct databuf *dp;
 153:     register int class, type;
 154: {
 155: #ifdef DEBUG
 156:     if (debug >= 5)
 157:         fprintf(ddt,"match(0x%x, %d, %d) %d, %d\n", dp, class, type,
 158:             dp->d_class, dp->d_type);
 159: #endif
 160:     if (dp->d_class != class && class != C_ANY)
 161:         return (0);
 162:     if (dp->d_type != type && type != T_ANY)
 163:         return (0);
 164:     return (1);
 165: }

Defined functions

Defined variables

sccsid defined in line 14; never used
Last modified: 1994-01-11
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