/* crypto/lhash/lhash.c */
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
 * All rights reserved.
 *
 * This package is an SSL implementation written
 * by Eric Young (eay@cryptsoft.com).
 * The implementation was written so as to conform with Netscapes SSL.
 *
 * This library is free for commercial and non-commercial use as long as
 * the following conditions are aheared to.  The following conditions
 * apply to all code found in this distribution, be it the RC4, RSA,
 * lhash, DES, etc., code; not just the SSL code.  The SSL documentation
 * included with this distribution is covered by the same copyright terms
 * except that the holder is Tim Hudson (tjh@cryptsoft.com).
 *
 * Copyright remains Eric Young's, and as such any Copyright notices in
 * the code are not to be removed.
 * If this package is used in a product, Eric Young should be given attribution
 * as the author of the parts of the library used.
 * This can be in the form of a textual message at program startup or
 * in documentation (online or textual) provided with the package.
 *
 * 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 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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *    "This product includes cryptographic software written by
 *     Eric Young (eay@cryptsoft.com)"
 *    The word 'cryptographic' can be left out if the rouines from the library
 *    being used are not cryptographic related :-).
 * 4. If you include any Windows specific code (or a derivative thereof) from
 *    the apps directory (application code) you must include an acknowledgement:
 *    "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
 *
 * THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``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 OR CONTRIBUTORS 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.
 *
 * The licence and distribution terms for any publically available version or
 * derivative of this code cannot be changed.  i.e. this code cannot simply be
 * copied and put under another distribution licence
 * [including the GNU Public Licence.]
 */

/*-
 * Code for dynamic hash table routines
 * Author - Eric Young v 2.0
 *
 * 2.2 eay - added #include "crypto.h" so the memory leak checking code is
 *           present. eay 18-Jun-98
 *
 * 2.1 eay - Added an 'error in last operation' flag. eay 6-May-98
 *
 * 2.0 eay - Fixed a bug that occurred when using lh_delete
 *           from inside lh_doall().  As entries were deleted,
 *           the 'table' was 'contract()ed', making some entries
 *           jump from the end of the table to the start, there by
 *           skipping the lh_doall() processing. eay - 4/12/95
 *
 * 1.9 eay - Fixed a memory leak in lh_free, the LHASH_NODEs
 *           were not being free()ed. 21/11/95
 *
 * 1.8 eay - Put the stats routines into a separate file, lh_stats.c
 *           19/09/95
 *
 * 1.7 eay - Removed the fputs() for realloc failures - the code
 *           should silently tolerate them.  I have also fixed things
 *           lint complained about 04/05/95
 *
 * 1.6 eay - Fixed an invalid pointers in contract/expand 27/07/92
 *
 * 1.5 eay - Fixed a misuse of realloc in expand 02/03/1992
 *
 * 1.4 eay - Fixed lh_doall so the function can call lh_delete 28/05/91
 *
 * 1.3 eay - Fixed a few lint problems 19/3/1991
 *
 * 1.2 eay - Fixed lh_doall problem 13/3/1991
 *
 * 1.1 eay - Added lh_doall
 *
 * 1.0 eay - First version
 */
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <openssl/crypto.h>
#include <openssl/lhash.h>

/*
 * A hashing implementation that appears to be based on the linear hashing
 * alogrithm:
 * https://en.wikipedia.org/wiki/Linear_hashing
 *
 * Litwin, Witold (1980), "Linear hashing: A new tool for file and table
 * addressing", Proc. 6th Conference on Very Large Databases: 212-223
 * http://hackthology.com/pdfs/Litwin-1980-Linear_Hashing.pdf
 *
 * From the wikipedia article "Linear hashing is used in the BDB Berkeley
 * database system, which in turn is used by many software systems such as
 * OpenLDAP, using a C implementation derived from the CACM article and first
 * published on the Usenet in 1988 by Esmond Pitt."
 *
 * The CACM paper is available here:
 * https://pdfs.semanticscholar.org/ff4d/1c5deca6269cc316bfd952172284dbf610ee.pdf
 */

const char lh_version[] = "lhash" OPENSSL_VERSION_PTEXT;

#undef MIN_NODES
#define MIN_NODES       16
#define UP_LOAD         (2*LH_LOAD_MULT) /* load times 256 (default 2) */
#define DOWN_LOAD       (LH_LOAD_MULT) /* load times 256 (default 1) */

static int expand(_LHASH *lh);
static void contract(_LHASH *lh);
static LHASH_NODE **getrn(_LHASH *lh, const void *data, unsigned long *rhash);

_LHASH *lh_new(LHASH_HASH_FN_TYPE h, LHASH_COMP_FN_TYPE c)
{
    _LHASH *ret;
    int i;

    if ((ret = OPENSSL_malloc(sizeof(_LHASH))) == NULL)
        goto err0;
    if ((ret->b = OPENSSL_malloc(sizeof(LHASH_NODE *) * MIN_NODES)) == NULL)
        goto err1;
    for (i = 0; i < MIN_NODES; i++)
        ret->b[i] = NULL;
    ret->comp = ((c == NULL) ? (LHASH_COMP_FN_TYPE)strcmp : c);
    ret->hash = ((h == NULL) ? (LHASH_HASH_FN_TYPE)lh_strhash : h);
    ret->num_nodes = MIN_NODES / 2;
    ret->num_alloc_nodes = MIN_NODES;
    ret->p = 0;
    ret->pmax = MIN_NODES / 2;
    ret->up_load = UP_LOAD;
    ret->down_load = DOWN_LOAD;
    ret->num_items = 0;

    ret->num_expands = 0;
    ret->num_expand_reallocs = 0;
    ret->num_contracts = 0;
    ret->num_contract_reallocs = 0;
    ret->num_hash_calls = 0;
    ret->num_comp_calls = 0;
    ret->num_insert = 0;
    ret->num_replace = 0;
    ret->num_delete = 0;
    ret->num_no_delete = 0;
    ret->num_retrieve = 0;
    ret->num_retrieve_miss = 0;
    ret->num_hash_comps = 0;

    ret->error = 0;
    return (ret);
 err1:
    OPENSSL_free(ret);
 err0:
    return (NULL);
}

void lh_free(_LHASH *lh)
{
    unsigned int i;
    LHASH_NODE *n, *nn;

    if (lh == NULL)
        return;

    for (i = 0; i < lh->num_nodes; i++) {
        n = lh->b[i];
        while (n != NULL) {
            nn = n->next;
            OPENSSL_free(n);
            n = nn;
        }
    }
    OPENSSL_free(lh->b);
    OPENSSL_free(lh);
}

void *lh_insert(_LHASH *lh, void *data)
{
    unsigned long hash;
    LHASH_NODE *nn, **rn;
    void *ret;

    lh->error = 0;
    if (lh->up_load <= (lh->num_items * LH_LOAD_MULT / lh->num_nodes)
            && !expand(lh))
        return NULL;

    rn = getrn(lh, data, &hash);

    if (*rn == NULL) {
        if ((nn = (LHASH_NODE *)OPENSSL_malloc(sizeof(LHASH_NODE))) == NULL) {
            lh->error++;
            return (NULL);
        }
        nn->data = data;
        nn->next = NULL;
#ifndef OPENSSL_NO_HASH_COMP
        nn->hash = hash;
#endif
        *rn = nn;
        ret = NULL;
        lh->num_insert++;
        lh->num_items++;
    } else {                    /* replace same key */

        ret = (*rn)->data;
        (*rn)->data = data;
        lh->num_replace++;
    }
    return (ret);
}

void *lh_delete(_LHASH *lh, const void *data)
{
    unsigned long hash;
    LHASH_NODE *nn, **rn;
    void *ret;

    lh->error = 0;
    rn = getrn(lh, data, &hash);

    if (*rn == NULL) {
        lh->num_no_delete++;
        return (NULL);
    } else {
        nn = *rn;
        *rn = nn->next;
        ret = nn->data;
        OPENSSL_free(nn);
        lh->num_delete++;
    }

    lh->num_items--;
    if ((lh->num_nodes > MIN_NODES) &&
        (lh->down_load >= (lh->num_items * LH_LOAD_MULT / lh->num_nodes)))
        contract(lh);

    return (ret);
}

void *lh_retrieve(_LHASH *lh, const void *data)
{
    unsigned long hash;
    LHASH_NODE **rn;
    void *ret;

    lh->error = 0;
    rn = getrn(lh, data, &hash);

    if (*rn == NULL) {
        lh->num_retrieve_miss++;
        return (NULL);
    } else {
        ret = (*rn)->data;
        lh->num_retrieve++;
    }
    return (ret);
}

static void doall_util_fn(_LHASH *lh, int use_arg, LHASH_DOALL_FN_TYPE func,
                          LHASH_DOALL_ARG_FN_TYPE func_arg, void *arg)
{
    int i;
    LHASH_NODE *a, *n;

    if (lh == NULL)
        return;

    /*
     * reverse the order so we search from 'top to bottom' We were having
     * memory leaks otherwise
     */
    for (i = lh->num_nodes - 1; i >= 0; i--) {
        a = lh->b[i];
        while (a != NULL) {
            /*
             * 28/05/91 - eay - n added so items can be deleted via lh_doall
             */
            /*
             * 22/05/08 - ben - eh? since a is not passed, this should not be
             * needed
             */
            n = a->next;
            if (use_arg)
                func_arg(a->data, arg);
            else
                func(a->data);
            a = n;
        }
    }
}

void lh_doall(_LHASH *lh, LHASH_DOALL_FN_TYPE func)
{
    doall_util_fn(lh, 0, func, (LHASH_DOALL_ARG_FN_TYPE)0, NULL);
}

void lh_doall_arg(_LHASH *lh, LHASH_DOALL_ARG_FN_TYPE func, void *arg)
{
    doall_util_fn(lh, 1, (LHASH_DOALL_FN_TYPE)0, func, arg);
}

static int expand(_LHASH *lh)
{
    LHASH_NODE **n, **n1, **n2, *np;
    unsigned int p, pmax, nni, j;
    unsigned long hash;

    nni = lh->num_alloc_nodes;
    p = lh->p;
    pmax = lh->pmax;
    if (p + 1 >= pmax) {
        j = nni * 2;
        n = OPENSSL_realloc(lh->b, (int)(sizeof(LHASH_NODE *) * j));
        if (n == NULL) {
            lh->error++;
            return 0;
        }
        lh->b = n;
        memset(n + nni, 0, sizeof(*n) * (j - nni));
        lh->pmax = nni;
        lh->num_alloc_nodes = j;
        lh->num_expand_reallocs++;
        lh->p = 0;
    } else {
        lh->p++;
    }

    lh->num_nodes++;
    lh->num_expands++;
    n1 = &(lh->b[p]);
    n2 = &(lh->b[p + pmax]);
    *n2 = NULL;

    for (np = *n1; np != NULL;) {
#ifndef OPENSSL_NO_HASH_COMP
        hash = np->hash;
#else
        hash = lh->hash(np->data);
        lh->num_hash_calls++;
#endif
        if ((hash % nni) != p) { /* move it */
            *n1 = (*n1)->next;
            np->next = *n2;
            *n2 = np;
        } else
            n1 = &((*n1)->next);
        np = *n1;
    }

    return 1;
}

static void contract(_LHASH *lh)
{
    LHASH_NODE **n, *n1, *np;

    np = lh->b[lh->p + lh->pmax - 1];
    lh->b[lh->p + lh->pmax - 1] = NULL; /* 24/07-92 - eay - weird but :-( */
    if (lh->p == 0) {
        n = (LHASH_NODE **)OPENSSL_realloc(lh->b,
                                           (unsigned int)(sizeof(LHASH_NODE *)
                                                          * lh->pmax));
        if (n == NULL) {
/*                      fputs("realloc error in lhash",stderr); */
            lh->error++;
            return;
        }
        lh->num_contract_reallocs++;
        lh->num_alloc_nodes /= 2;
        lh->pmax /= 2;
        lh->p = lh->pmax - 1;
        lh->b = n;
    } else
        lh->p--;

    lh->num_nodes--;
    lh->num_contracts++;

    n1 = lh->b[(int)lh->p];
    if (n1 == NULL)
        lh->b[(int)lh->p] = np;
    else {
        while (n1->next != NULL)
            n1 = n1->next;
        n1->next = np;
    }
}

static LHASH_NODE **getrn(_LHASH *lh, const void *data, unsigned long *rhash)
{
    LHASH_NODE **ret, *n1;
    unsigned long hash, nn;
    LHASH_COMP_FN_TYPE cf;

    hash = (*(lh->hash)) (data);
    lh->num_hash_calls++;
    *rhash = hash;

    nn = hash % lh->pmax;
    if (nn < lh->p)
        nn = hash % lh->num_alloc_nodes;

    cf = lh->comp;
    ret = &(lh->b[(int)nn]);
    for (n1 = *ret; n1 != NULL; n1 = n1->next) {
#ifndef OPENSSL_NO_HASH_COMP
        lh->num_hash_comps++;
        if (n1->hash != hash) {
            ret = &(n1->next);
            continue;
        }
#endif
        lh->num_comp_calls++;
        if (cf(n1->data, data) == 0)
            break;
        ret = &(n1->next);
    }
    return (ret);
}

/*
 * The following hash seems to work very well on normal text strings no
 * collisions on /usr/dict/words and it distributes on %2^n quite well, not
 * as good as MD5, but still good.
 */
unsigned long lh_strhash(const char *c)
{
    unsigned long ret = 0;
    long n;
    unsigned long v;
    int r;

    if ((c == NULL) || (*c == '\0'))
        return (ret);
/*-
    unsigned char b[16];
    MD5(c,strlen(c),b);
    return(b[0]|(b[1]<<8)|(b[2]<<16)|(b[3]<<24));
*/

    n = 0x100;
    while (*c) {
        v = n | (*c);
        n += 0x100;
        r = (int)((v >> 2) ^ v) & 0x0f;
        ret = (ret << r) | (ret >> (32 - r));
        ret &= 0xFFFFFFFFL;
        ret ^= v * v;
        c++;
    }
    return ((ret >> 16) ^ ret);
}

unsigned long lh_num_items(const _LHASH *lh)
{
    return lh ? lh->num_items : 0;
}
