/* $NetBSD: hcreate.c,v 1.13 2022/03/13 01:44:37 kre Exp $ */

/*
 * Copyright (c) 2001 Christopher G. Demetriou
 * All rights reserved.
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 * 
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 * 
 * <<Id: LICENSE,v 1.2 2000/06/14 15:57:33 cgd Exp>>
 */

/*
 * hcreate() / hsearch() / hdestroy()
 *
 * SysV/XPG4 hash table functions.
 *
 * Implementation done based on NetBSD manual page and Solaris manual page,
 * plus my own personal experience about how they're supposed to work.
 *
 * I tried to look at Knuth (as cited by the Solaris manual page), but
 * nobody had a copy in the office, so...
 */

#include <sys/cdefs.h>
#if defined(LIBC_SCCS) && !defined(lint)
__RCSID("$NetBSD: hcreate.c,v 1.13 2022/03/13 01:44:37 kre Exp $");
#endif /* LIBC_SCCS and not lint */

#if !defined(lint)
__COPYRIGHT("@(#) Copyright (c) 2001\
 Christopher G. Demetriou.  All rights reserved.");
#endif /* not lint */

#include "namespace.h"
#include <assert.h>
#include <errno.h>
#include <inttypes.h>
#include <search.h>
#include <stdlib.h>
#include <string.h>
#include <sys/queue.h>

/*
 * DO NOT MAKE THIS STRUCTURE LARGER THAN 32 BYTES (4 ptrs on 64-bit
 * ptr machine) without adjusting MAX_BUCKETS_LG2 below.
 */
struct internal_entry {
        SLIST_ENTRY(internal_entry) link;
        ENTRY ent;
};
SLIST_HEAD(internal_head, internal_entry);

#define MIN_BUCKETS_LG2 4
#define MIN_BUCKETS     (1 << MIN_BUCKETS_LG2)

/*
 * max * sizeof internal_entry must fit into size_t.
 * assumes internal_entry is <= 32 (2^5) bytes.
 */
#define MAX_BUCKETS_LG2 (sizeof (size_t) * 8 - 1 - 5)
#define MAX_BUCKETS     ((size_t)1 << MAX_BUCKETS_LG2)

/* Default hash function, from db/hash/hash_func.c */
extern u_int32_t (*__default_hash)(const void *, size_t);

static struct hsearch_data htable;

int
hcreate(size_t nel)
{
        _DIAGASSERT(htable.table == NULL);

        /* Make sure this isn't called when a table already exists. */
        if (htable.table != NULL) {
                errno = EINVAL;
                return 0;
        }
        return hcreate_r(nel, &htable);
}

int
hcreate_r(size_t nel, struct hsearch_data *head)
{
        struct internal_head *table;
        size_t idx;
        unsigned int p2;

        /* If nel is too small, make it min sized. */
        if (nel < MIN_BUCKETS)
                nel = MIN_BUCKETS;

        /* If it's too large, cap it. */
        if (nel > MAX_BUCKETS)
                nel = MAX_BUCKETS;

        /* If it's is not a power of two in size, round up. */
        if ((nel & (nel - 1)) != 0) {
                for (p2 = 0; nel != 0; p2++)
                        nel >>= 1;
                _DIAGASSERT(p2 <= MAX_BUCKETS_LG2);
                nel = 1 << p2;
        }
        
        /* Allocate the table. */
        head->size = nel;
        head->filled = 0;
        table = NULL;
        errno = reallocarr(&table, nel, sizeof(*table));
        if (errno)
                return 0;
        head->table = (void *)table;

        /* Initialize it. */
        for (idx = 0; idx < nel; idx++)
                SLIST_INIT(&table[idx]);

        return 1;
}

void
hdestroy1(void (*freekey)(void *), void (*freedata)(void *))
{
        _DIAGASSERT(htable.table != NULL);
        hdestroy1_r(&htable, freekey, freedata);
}

void
hdestroy(void)
{
        hdestroy1(NULL, NULL);
}

void
hdestroy1_r(struct hsearch_data *head, void (*freekey)(void *),
    void (*freedata)(void *))
{
        struct internal_entry *ie;
        size_t idx;
        void *p;
        struct internal_head *table;

        if (head == NULL)
                return;

        p = head->table;
        head->table = NULL;
        table = p;

        for (idx = 0; idx < head->size; idx++) {
                while (!SLIST_EMPTY(&table[idx])) {
                        ie = SLIST_FIRST(&table[idx]);
                        SLIST_REMOVE_HEAD(&table[idx], link);
                        if (freekey)
                                (*freekey)(ie->ent.key);
                        if (freedata)
                                (*freedata)(ie->ent.data);
                        free(ie);
                }
        }
        free(table);
}

void
hdestroy_r(struct hsearch_data *head)
{
        hdestroy1_r(head, NULL, NULL);
}

ENTRY *
hsearch(ENTRY item, ACTION action)
{
        ENTRY *ep;
        _DIAGASSERT(htable.table != NULL);
        (void)hsearch_r(item, action, &ep, &htable);
        return ep;
}

int
hsearch_r(ENTRY item, ACTION action, ENTRY **itemp, struct hsearch_data *head)
{
        struct internal_head *table, *chain;
        struct internal_entry *ie;
        uint32_t hashval;
        size_t len;
        void *p;

        _DIAGASSERT(item.key != NULL);
        _DIAGASSERT(action == ENTER || action == FIND);

        p = head->table;
        table = p;

        len = strlen(item.key);
        hashval = (*__default_hash)(item.key, len);

        chain = &table[hashval & (head->size - 1)];
        ie = SLIST_FIRST(chain);
        while (ie != NULL) {
                if (strcmp(ie->ent.key, item.key) == 0)
                        break;
                ie = SLIST_NEXT(ie, link);
        }

        if (ie != NULL) {
                *itemp = &ie->ent;
                return 1;
        } else if (action == FIND) {
                *itemp = NULL;
                errno = ESRCH;
                return 1;
        }

        ie = malloc(sizeof *ie);
        if (ie == NULL)
                return 0;
        ie->ent.key = item.key;
        ie->ent.data = item.data;

        SLIST_INSERT_HEAD(chain, ie, link);
        *itemp = &ie->ent;
        head->filled++;
        return 1;
}