/* $XConsortium: ut_htab.c,v 5.2 94/04/17 20:42:20 rws Exp $ */

/***********************************************************

Copyright (c) 1989, 1990, 1991  X Consortium

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Except as contained in this notice, the name of the X Consortium shall not be
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Copyright 1989, 1990, 1991 by Sun Microsystems, Inc. 

                        All Rights Reserved

Permission to use, copy, modify, and distribute this software and its 
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provided that the above copyright notice appear in all copies and that
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******************************************************************/

/* Hash table code. */

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


typedef struct _Htab_entry {
    int			key;
    caddr_t		cdata;	/* client data */
    struct _Htab_entry	*next;
} Htab_entry;

typedef struct _Htab {
    int		num_entries;	/* in table */
    int		hash_size;
    Htab_entry	**tbl;		/* *tbl[num_entries] */
    int		search_used;	/* non-zero if first/next search ever used*/
    int		cur_list;	/* for first and next searches only */
    Htab_entry	*next_entry;	/* for first and next searches only */
} Htab;

#ifndef _ABS
#define _ABS(x) ((x) < 0 ? -(x) : (x))
#endif

static Htab_entry**
get_entry( htab, key )
    Htab	*htab;
    int		key;
{
    Htab_entry	**entry_p;

    /* Returns either a pointer to the pointer to the entry (not a pointer
     * to the entry itself) or a pointer to the place the pointer to the
     * entry should exist if it were to be added.
     */
    entry_p = &htab->tbl[_ABS(key) % htab->hash_size];
    for ( ; *entry_p && (*entry_p)->key != key; entry_p = &(*entry_p)->next )
	;
    return entry_p;
}


/* Public functions. */
Htab*
phg_ut_htab_create( hash_size )
    int		hash_size;
{
    Htab	*htab;

    /* Get a block of memory for the Htab structure and the table. */
    if ( hash_size <= 0 )
	hash_size = 1;	/* makes it an essentially linear table. */

    if ( htab = (Htab *)calloc( 1, sizeof(Htab)
	    + sizeof(Htab_entry *)* (unsigned)hash_size ) ) {
	htab->tbl = (Htab_entry **)(htab + 1);
	/* Initialize the table. */
	htab->num_entries = 0;
	htab->hash_size = hash_size;
    } else
	htab = (Htab *)NULL;

    return htab;
}

void
phg_ut_htab_destroy( htab, destroy_entry )
    Htab	*htab;
    void	(*destroy_entry)();
{
    register int	i;
    register Htab_entry	*entry, *next;

    for ( i = 0; i < htab->hash_size; i++ ) {
	for ( entry = htab->tbl[i]; entry; entry = next ) {
	    next = entry->next;
	    if ( destroy_entry )
		(*destroy_entry)( entry->key, entry->cdata );
	    free( (char *)entry );
	}
    }
    free( (char *)htab );
}

caddr_t
phg_ut_htab_delete_entry( htab, key )
    Htab	*htab;
    int		key;
{
    caddr_t	cdata;
    Htab_entry	**entry_p, *tmp;

    /* If the entry exists, free it return the client's data. */
    if ( *(entry_p = get_entry( htab, key )) ) {
	cdata = (*entry_p)->cdata;
	tmp = *entry_p;
	*entry_p = tmp->next;
	/* Update the first/next search field. */
	if ( tmp == htab->next_entry )
	    htab->next_entry = tmp->next;
	free( (char *)tmp );
	--htab->num_entries;
    } else
	cdata = (caddr_t)NULL;

    return cdata;
}

int
phg_ut_htab_add_entry( htab, key, cdata )
    Htab	*htab;
    int		key;
    caddr_t	cdata;
{
    Htab_entry	**entry_p;

    /* If found, just replace the client data. */
    if ( *(entry_p = get_entry( htab, key )) ) {
	(*entry_p)->cdata = cdata;

    } else {
	/* Create the entry and link it into the table. */
	if ( *entry_p = (Htab_entry *)malloc( sizeof(Htab_entry) ) ) {
	    (*entry_p)->key = key;
	    (*entry_p)->cdata = cdata;
	    (*entry_p)->next = (Htab_entry *)NULL;
	    ++htab->num_entries;

	    /* Update the first/next search fields if the "next_entry" is
	     * the end of the list this entry was added to.
	     */
	    if ( htab->search_used && !htab->next_entry
		    && ( _ABS(key) % htab->hash_size == htab->cur_list ) )
		htab->next_entry = *entry_p;
	}
    }

    return (*entry_p ? 1 : 0);
}

int
phg_ut_htab_get_entry( htab, key, cdata_p )
    Htab	*htab;
    int		key;
    caddr_t	*cdata_p;
{
    Htab_entry	**entry_p;

    if ( *(entry_p = get_entry( htab, key )) )
	if ( cdata_p )
	    *cdata_p = (*entry_p)->cdata;

    return (*entry_p ? 1 : 0);
}

void
phg_ut_htab_change_data( htab, key, cdata )
    Htab	*htab;
    int		key;
    caddr_t	cdata;
{
    Htab_entry	**entry_p;

    if ( *(entry_p = get_entry( htab, key )) )
	(*entry_p)->cdata = cdata;
}

int
phg_ut_htab_num_entries( htab )
    Htab	*htab;
{
    return htab->num_entries;
}

int
phg_ut_htab_first_entry( htab, key, cdata )
    Htab	*htab;
    int		*key;
    caddr_t	*cdata;
{
    htab->search_used = 1;	/* this is never reset to 0 */
    for ( htab->cur_list = 0; htab->cur_list < htab->hash_size;
	    htab->cur_list++ ) {
	if ( htab->tbl[htab->cur_list] ) {
	    htab->next_entry = htab->tbl[htab->cur_list]->next;
	    if ( cdata ) *cdata = htab->tbl[htab->cur_list]->cdata;
	    if ( key ) *key = htab->tbl[htab->cur_list]->key;
	    return 1;
	}
    }

    return 0;
}

int
phg_ut_htab_next_entry( htab, key, cdata )
    Htab	*htab;
    int		*key;
    caddr_t	*cdata;
{
    int		status = 0;

    if ( htab->next_entry ) {
	if ( cdata ) *cdata = htab->next_entry->cdata;
	if ( key ) *key = htab->next_entry->key;
	htab->next_entry = htab->next_entry->next;
	status = 1;

    } else {
	++htab->cur_list;
	for ( ; htab->cur_list < htab->hash_size; htab->cur_list++ ) {
	    if ( htab->tbl[htab->cur_list] ) {
		htab->next_entry = htab->tbl[htab->cur_list]->next;
		if ( cdata) *cdata = htab->tbl[htab->cur_list]->cdata;
		if ( key ) *key = htab->tbl[htab->cur_list]->key;
		status = 1;
		break;
	    }
	}

    }

    return status;
}