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[unix-history] / usr.bin / m4 / look.c

/*  File   : look.c
   Author : Ozan Yigit
   Updated: 4 May 1992
   Purpose: Hash table for M4 
*/

#include "mdef.h"
#include "extr.h"

ndptr hashtab[HASHSIZE];


/*
* hash - get a hash value for string s
*/
int
hash(name)
char *name;
{
       register unsigned long h = 0;

       while (*name)
               h = (h << 5) + h + *name++;

       return h % HASHSIZE;
}

/* 
* lookup(name) - find name in the hash table
*/
ndptr lookup(name)
   char *name;
   {
       register ndptr p;

       for (p = hashtab[hash(name)]; p != nil; p = p->nxtptr)
           if (strcmp(name, p->name) == 0)
               break;
       return p;
   }

/*  
* addent(name) - hash and create an entry in the hash table.
* The new entry is added at the front of a hash bucket.
* BEWARE: the type and defn fields are UNDEFINED.
*/
ndptr addent(name)
   char *name;
   {
       register ndptr p, *h;

       p = (ndptr)malloc(sizeof *p);
       if (p == NULL) error("m4: no more memory.");
       h = &hashtab[hash(name)];
       p->name = strsave(name);
       p->defn = null;
       p->nxtptr = *h;
       *h = p;
       return p;
   }


/*  
* addkywd(name, type) - stores a keyword in the hash table.
*/
void addkywd(name, type)
   char *name;
   int type;
   {
       register ndptr p = addent(name);
       p->type = type | STATIC;
   }


/* 
* remhash(name, all)
* remove one entry (all==0) or all entries (all!=0) for a given name
* from the hash table.  All hash table entries must have been obtained
* from malloc(), so it is safe to free the records themselves.
* However, the ->name and ->defn fields might point to storage which
* was obtained from strsave() -- in which case they may be freed -- or
* to static storage -- in which case they must not be freed.  If the
* STATIC bit is set, the fields are not to be freed.
*/
void remhash(name, all)
   char *name;
   int all;
   {
       register ndptr p, *h;
       /*  h always points to the pointer to p  */

       h = &hashtab[hash(name)];
       while ((p = *h) != nil) {
           if (strcmp(p->name, name) == 0) {
               *h = p->nxtptr;                 /* delink this record */                
               if (!(p->type & STATIC)) {      /* free the name and defn */
                   free(p->name);              /* if they came from strsave */
                   if (p->defn != null) free(p->defn);
               }                               /* otherwise leave them */
               free(p);                        /* free the record itself */
               if (!all) return;               /* first occurrence has gone */
           } else {
               h = &(p->nxtptr);
           }
       }
   }