/*
 *  hashtable management 
 * 
 *  Copyright (c) 1997 Alfredo K. Kojima
 * 
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */


#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>

extern void* safemalloc(size_t size);
#include "hashtable.h"


#define INIT_TABLE_SIZE	239


/*
 *----------------------------------------------------------------------
 * table_init--
 * 	Initializes a hashtable with a initial size = INIT_TABLE_SIZE
 * The table must already be allocated.
 * 
 * Returns:
 * 	The table.
 *---------------------------------------------------------------------- 
 */
HashTable *
table_init(HashTable *table)
{
    table->elements = 0;
    table->size = INIT_TABLE_SIZE;
    table->table = safemalloc(INIT_TABLE_SIZE*sizeof(HashEntry*));
    table->last = NULL;
    memset(table->table, 0, INIT_TABLE_SIZE*sizeof(HashEntry*));

    return table;
}

static unsigned long
hash_ikey(unsigned long key)
{
    unsigned long h = 0, g;
    int i;
    char skey[sizeof(int)];
    
    memcpy(skey, &key, sizeof(unsigned long));
    for (i=0; i<sizeof(unsigned long); i++) {
	h = (h<<4) + skey[i];
	if ((g = h & 0xf0000000))
	  h ^=g >> 24;
	h &= ~g;
    }
    return h;
}



static void
rebuild_itable(HashTable *table)
{
    HashTable newtable;
    HashEntry *entry;
    int i;

    newtable.last = NULL;
    newtable.elements = 0;
    newtable.size = table->size*2;
    newtable.table = safemalloc(newtable.size * sizeof(HashEntry*));
    memset(newtable.table, 0, newtable.size * sizeof(HashEntry*));
    for (i=0; i<table->size; i++) {
	entry = table->table[i];
	while (entry) {
	    table_iput(&newtable, entry->key, entry->data);
	    entry=entry->next;
	}
    }
    table_idestroy(table);
    table->elements = newtable.elements;
    table->size = newtable.size;
    table->table = newtable.table;
}


void
table_iput(HashTable *table, unsigned long key, unsigned long data)
{
    unsigned long hkey;
    HashEntry *nentry;
    
    nentry = safemalloc(sizeof(HashEntry));
    nentry->key = key;
    nentry->data = data;
    hkey = hash_ikey(key) % table->size;
    /* collided */
    if (table->table[hkey]!=NULL) {
	nentry->next = table->table[hkey];
	table->table[hkey] = nentry;
    } else {
	nentry->next = NULL;
	table->table[hkey] = nentry;
    }
    table->elements++;
    
    nentry->nptr = NULL;
    nentry->pptr = table->last;
    if (table->last)
      table->last->nptr = nentry;
    table->last = nentry;
    
    if (table->elements>(table->size*3)/2) {
#ifdef DEBUG
	printf("rebuilding hash table...\n");
#endif
	rebuild_itable(table);
    }
}


int
table_iget(HashTable *table, unsigned long key, unsigned long *data)
{
    unsigned long hkey;
    HashEntry *entry;
    
    hkey = hash_ikey(key)%table->size;
    entry = table->table[hkey];
    while (entry!=NULL) {
	if (entry->key==key) {
	    *data=entry->data;
	    return 1;
	}
	entry = entry->next;
    }
    return 0;
}



static HashEntry *
delete_fromilist(HashTable *table, HashEntry *entry, unsigned long key)
{
    HashEntry *next;

    if (entry==NULL) return NULL;
    if (entry->key==key) {
	if (table->last == entry)
	  table->last = entry->pptr;
	if (entry->nptr)
	  entry->nptr->pptr = entry->pptr;
	if (entry->pptr)
	  entry->pptr->nptr = entry->nptr;
	next = entry->next;
	free(entry);
	return next;
    }
    entry->next = delete_fromilist(table, entry->next, key);
    return entry;
}

void
table_idelete(HashTable *table, unsigned long key)
{
    unsigned long hkey;
    
    hkey = hash_ikey(key)%table->size;
    table->table[hkey] = delete_fromilist(table, table->table[hkey], key);
    table->elements--;
}


void
table_idestroy(HashTable *table)
{
    HashEntry *entry, *next;
    int i;

    for (i=0; i<table->size; i++) {
	entry=table->table[i];
	while (entry) {
	    next = entry->next;
	    entry = next;
	}
    }
    free(table->table);
}

