/*
 *      install --- add a symbol to the table
 */
install(str,val,override)
char    *str;
int     val;
int     override;
{
        struct link *lp;
	struct nlist *np,*p,*backp;
	struct nlist *lookup();
	int     i;

	if( !alpha(*str) ){
		error("Illegal Symbol Name");
		return(NO);
		}
	if( (np = lookup(str)) != NULL ){
	    if (override) {
		np -> def = val;
		return (YES);
		}
	    else {
		if( Pass==2 ){
			if( np->def == val )
				return(YES);
			else{
				error("Phasing Error");
				return(NO);
				}
			}
		error("Symbol Redefined");
		return(NO);
		}
	    }
	/* enter new symbol */
#ifdef DEBUG
	printf("Installing %s as %d\n",str,val);
#endif
	np = (struct nlist *) alloc(sizeof(struct nlist));
	if( np == (struct nlist *)ERR ){
		error("Symbol table full");
		return(NO);
		}
	np->name = alloc(strlen(str)+1);
	if( np->name == (char *)ERR ){
		error("Symbol table full");
		return(NO);
		}
	strcpy(np->name,str);
	np->def = val;
	np->Lnext = NULL;  
        np->Rnext = NULL;
           lp = (struct link *) alloc(sizeof(struct link));
           np->L_list = lp;
           lp->L_num = Line_num;
           lp->next = NULL;
        p = root;
          backp = NULL;
           while (p != NULL) 
            {
              backp = p;
              i = strcmp (str,p->name);
               if (i<0)
                   p=p->Lnext;
                  else p=p->Rnext;
            }
          if (backp == NULL)
              root = np;
             else if (strcmp(str,backp->name)<0)
                  backp->Lnext = np;
                 else backp->Rnext = np;
          return (YES);  
}

/*
 *      lookup --- find string in symbol table
 */
struct nlist *
lookup(name)
char    *name;
{
	struct nlist *np;
	int     i;

        np = root;
         while (np != NULL)
          {
            i = strcmp(name,np->name);
             if (i == 0)
               {
                 Last_sym = np->def;
                 return (np);
               }
             else if (i < 0)
                 np = np->Lnext;
                else np = np->Rnext;
          }
      Last_sym = 0;
      if (Pass == 2)
          error ("symbol Undefined on pass 2");
        return (NULL); 
}


#define NMNE (sizeof(table)/ sizeof(struct oper))
#define NPSE (sizeof(pseudo)/ sizeof(struct oper))
/*
 *      mne_look --- mnemonic lookup
 *
 *      Return pointer to an oper structure if found.
 *      Searches both the machine mnemonic table and the pseudo table.
 */
struct oper *
mne_look(str)
char    *str;
{
	struct oper *low,*high,*mid;
	int     cond;

	/* Search machine mnemonics first */
	low =  &table[0];
	high = &table[ NMNE-1 ];
	while (low <= high){
		mid = low + (high-low)/2;
		if( ( cond = strcmp(str,mid->mnemonic)) < 0)
			high = mid - 1;
		else if (cond > 0)
			low = mid + 1;
		else
			return(mid);
	}

	/* Check for pseudo ops */
	low =  &pseudo[0];
	high = &pseudo[ NPSE-1 ];
	while (low <= high){
		mid = low + (high-low)/2;
		if( ( cond = strcmp(str,mid->mnemonic)) < 0)
			high = mid - 1;
		else if (cond > 0)
			low = mid + 1;
		else
			return(mid);
	}

	return(NULL);
}