util/ncgg/lookup.c

   1 /*
   2  * (c) copyright 1987 by the Vrije Universiteit, Amsterdam, The Netherlands.
   3  * See the copyright notice in the ACK home directory, in the file "Copyright".
   4  */
   5 #ifndef NORCSID
   6 static char rcsid[]= "$Id: lookup.c,v 0.3 1994/06/24 10:37:40 ceriel Exp $";
   7 #endif
   8
   9 #include "assert.h"
  10 #include "param.h"
  11 #include "lookup.h"
  12
  13 char *myalloc();
  14 char *mystrcpy();
  15
  16 symbol dumsym;  /* dummy to return in case of error */
  17
  18 symbol *lookup(name,type,style)
  19 char *name;
  20 symtype type;
  21 lookupstyle style;
  22 {
  23         symbol *sy_p,**sy_pp;
  24
  25         for (sy_pp = &symhash[hashvalue(name)];(sy_p= *sy_pp) != 0;sy_pp= &sy_p->sy_next) {
  26                 if (strcmp(sy_p->sy_name,name)!=0)
  27                         continue;
  28                 switch(style) {
  29                 default:
  30                         assert(0);
  31                 case justlooking:
  32                 case mustexist:
  33                 case makeexist:
  34                         if (type==symany || type==sy_p->sy_type)
  35                                 return(sy_p);
  36                         continue;
  37                 case newsymbol:
  38                         error("%s already defined",name);
  39                         return(&dumsym);
  40                 }
  41         }
  42         switch(style) {
  43         default:
  44                 assert(0);
  45         case justlooking:
  46                 return((symbol *) 0);
  47         case mustexist:
  48                 fatal("%s is unknown symbol",name);
  49                 /* NOTREACHED */
  50         case newsymbol:
  51         case makeexist:
  52                 NEW(sy_p,symbol);
  53                 sy_p->sy_next = 0;
  54                 sy_p->sy_name = mystrcpy(name);
  55                 assert(type!=symany);
  56                 sy_p->sy_type = type;
  57                 *sy_pp = sy_p;
  58                 return(sy_p);
  59         }
  60 }
  61
  62 hashvalue(s) register char *s; {
  63         register unsigned sum=0;
  64         register i;
  65
  66         for(i=0;*s;s++,i=(i+3)&07)
  67                 sum += *s<<i;
  68         return(sum%NSYMHASH);
  69 }