prhash.c

/* prhash.c */
/* symbol table handling */

#include <stdio.h>
#include <string.h>
#include "prmachine.h"

#include "prtypes.h"


#define HASHSIZE 103 /* a prime */
#define HASHNULL ((atom_ptr_t) NULL)


static atom_ptr_t Hashtable[HASHSIZE];
atom_ptr_t intern(), make_atom(); /* forward declaration */

/**********************************************************************
			hash()
 Find the index in the hash table of the bucket in which to store
 atom corresponding to the string s;
 **********************************************************************/
int hash(s)
char *s;
{
	int ret = 0;
	while(*s)ret += *s++;
	return(ret % HASHSIZE);
}

/**********************************************************************
			ini_hash()
 Initialise the hash table.
 Call this before any call on the functions below.
 **********************************************************************/
void ini_hash()
{
	register int i;

	for(i = 0; i < HASHSIZE; i++)
		Hashtable[i] = HASHNULL;

}

/******************************************************************************
 			hash_search()
 See if a string is in the hash table and return the pointer to
 the atom if it is and NULL otherwise.
 ******************************************************************************/
atom_ptr_t hash_search(s)
char *s;
{
	int hashval;
	atom_ptr_t the_el;

	hashval = hash(s);
	the_el = Hashtable[hashval];

	if (the_el == HASHNULL)
	{
		return(HASHNULL);
	}
	else
	{
		while(the_el != HASHNULL && strcmp(s, the_el->name))
			the_el = the_el->hash_link;
	}

	if(the_el == HASHNULL)
		return(HASHNULL);
	else
		return(the_el);
}


/**********************************************************************
			intern()
 Add a new atom to the symbol table and return it.
 **********************************************************************/
atom_ptr_t intern(char *s)
{
	int hashval;
	int status = PERMANENT;
	atom_ptr_t the_el, previous = NULL;

	ENTER("intern");
	hashval = hash(s);

	the_el = Hashtable[hashval];

	if (the_el == HASHNULL)
	{
		the_el = make_atom(s, status);
		Hashtable[hashval] = the_el;
		return(the_el);
	}
	else
	{
		while(the_el!= HASHNULL && strcmp(s, the_el->name))
		{
			previous = the_el;
			the_el = the_el->hash_link;
		}
		if(the_el == HASHNULL)
		{
			the_el = make_atom(s, status);
			previous->hash_link = the_el;
		// BUGHUNT(s);
			return(the_el);
		}
		else
		{
			return(the_el);
		}
	}
}

/**********************************************************************
			make_atom()
 Makes an atom from a string. Does not insert it into hash table. 
 **********************************************************************/
atom_ptr_t make_atom(char* s,int status)
{
	string_ptr_t get_string();
	atom_ptr_t ret, get_atom();
	char *s2;

	ret = get_atom(status);

	if(ret == HASHNULL)return(HASHNULL);
	if(status == PERMANENT) status = PERM_STRING;
	s2 = get_string((my_alloc_size_t)(strlen(s) + 1), status); /* alloue pour chaine et caractere '\0' */

	if(ret == NULL)return(HASHNULL);

	strcpy(s2, s);
	ret->hash_link = HASHNULL;
	ret->name = s2;
	(ret->proc).clause = NULL;
	//	BUGHUNT(s);
	return(ret);
}

#ifndef NDEBUG

void pr_bucket(atom_ptr_t a)
{
while(a != HASHNULL)
     {
     tty_pr_string(ATOMPTR_NAME(a));
     tty_pr_string("\n");
     a = a->hash_link;
     }
}

void pr_hash_table()
{
int i;

for( i = 0; i < HASHSIZE; i++)
 {
 if(Hashtable[i] == NULL)
   continue;
 pr_bucket(Hashtable[i]);
 more_y_n();
 }
tty_pr_string("End of Hash Table!");
}

#endif

/* end of file */