/*

 * Copyright 1995-2023 The OpenSSL Project Authors. All Rights Reserved.

 *

 * Licensed under the Apache License 2.0 (the "License").  You may not use

 * this file except in compliance with the License.  You can obtain a copy

 * in the file LICENSE in the source distribution or at

 * https://www.openssl.org/source/license.html

 */

#include <stdio.h>

#include <string.h>

#include <stdlib.h>

#include <openssl/crypto.h>

#include <openssl/lhash.h>

#include <openssl/err.h>

#include "crypto/ctype.h"

#include "crypto/lhash.h"

#include "lhash_local.h"

/*

 * A hashing implementation that appears to be based on the linear hashing

 * algorithm:

 * 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

 * https://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

 */

#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(OPENSSL_LHASH *lh);

static void contract(OPENSSL_LHASH *lh);

static OPENSSL_LH_NODE **getrn(OPENSSL_LHASH *lh, const void *data, unsigned long *rhash);

OPENSSL_LHASH *OPENSSL_LH_new(OPENSSL_LH_HASHFUNC h, OPENSSL_LH_COMPFUNC c)

{

    OPENSSL_LHASH *ret;

    if ((ret = OPENSSL_zalloc(sizeof(*ret))) == NULL) {

        /*

         * Do not set the error code, because the ERR code uses LHASH

         * and we want to avoid possible endless error loop.

         * ERR_raise(ERR_LIB_CRYPTO, ERR_R_MALLOC_FAILURE);

         */

        return NULL;

    }

    if ((ret->b = OPENSSL_zalloc(sizeof(*ret->b) * MIN_NODES)) == NULL)

        goto err;

    ret->comp = ((c == NULL) ? (OPENSSL_LH_COMPFUNC)strcmp : c);

    ret->hash = ((h == NULL) ? (OPENSSL_LH_HASHFUNC)OPENSSL_LH_strhash : h);

    ret->num_nodes = MIN_NODES / 2;

    ret->num_alloc_nodes = MIN_NODES;

    ret->pmax = MIN_NODES / 2;

    ret->up_load = UP_LOAD;

    ret->down_load = DOWN_LOAD;

    return ret;

err:

    OPENSSL_free(ret->b);

    OPENSSL_free(ret);

    return NULL;

}

void OPENSSL_LH_free(OPENSSL_LHASH *lh)

{

    if (lh == NULL)

        return;

    OPENSSL_LH_flush(lh);

    OPENSSL_free(lh->b);

    OPENSSL_free(lh);

}

void OPENSSL_LH_flush(OPENSSL_LHASH *lh)

{

    unsigned int i;

    OPENSSL_LH_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;

        }

        lh->b[i] = NULL;

    }

    lh->num_items = 0;

}

void *OPENSSL_LH_insert(OPENSSL_LHASH *lh, void *data)

{

    unsigned long hash;

    OPENSSL_LH_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;        /* 'lh->error++' already done in 'expand' */

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

    if (*rn == NULL) {

        if ((nn = OPENSSL_malloc(sizeof(*nn))) == NULL) {

            lh->error++;

            return NULL;

        }

        nn->data = data;

        nn->next = NULL;

        nn->hash = hash;

        *rn = nn;

        ret = NULL;

        lh->num_items++;

    } else {                    /* replace same key */

        ret = (*rn)->data;

        (*rn)->data = data;

    }

    return ret;

}

void *OPENSSL_LH_delete(OPENSSL_LHASH *lh, const void *data)

{

    unsigned long hash;

    OPENSSL_LH_NODE *nn, **rn;

    void *ret;

    lh->error = 0;

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

    if (*rn == NULL) {

        return NULL;

    } else {

        nn = *rn;

        *rn = nn->next;

        ret = nn->data;

        OPENSSL_free(nn);

    }

    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 *OPENSSL_LH_retrieve(OPENSSL_LHASH *lh, const void *data)

{

    unsigned long hash;

    OPENSSL_LH_NODE **rn;

    if (lh->error != 0)

        lh->error = 0;

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

    return *rn == NULL ? NULL : (*rn)->data;

}

static void doall_util_fn(OPENSSL_LHASH *lh, int use_arg,

                          OPENSSL_LH_DOALL_FUNC func,

                          OPENSSL_LH_DOALL_FUNCARG func_arg, void *arg)

{

    int i;

    OPENSSL_LH_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) {

            n = a->next;

            if (use_arg)

                func_arg(a->data, arg);

            else

                func(a->data);

            a = n;

        }

    }

}

void OPENSSL_LH_doall(OPENSSL_LHASH *lh, OPENSSL_LH_DOALL_FUNC func)

{

    doall_util_fn(lh, 0, func, (OPENSSL_LH_DOALL_FUNCARG)0, NULL);

}

void OPENSSL_LH_doall_arg(OPENSSL_LHASH *lh, OPENSSL_LH_DOALL_FUNCARG func, void *arg)

{

    doall_util_fn(lh, 1, (OPENSSL_LH_DOALL_FUNC)0, func, arg);

}

static int expand(OPENSSL_LHASH *lh)

{

    OPENSSL_LH_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, sizeof(OPENSSL_LH_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->p = 0;

    } else {

        lh->p++;

    }

    lh->num_nodes++;

    n1 = &(lh->b[p]);

    n2 = &(lh->b[p + pmax]);

    *n2 = NULL;

    for (np = *n1; np != NULL;) {

        hash = np->hash;

        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(OPENSSL_LHASH *lh)

{

    OPENSSL_LH_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 = OPENSSL_realloc(lh->b,

                            (unsigned int)(sizeof(OPENSSL_LH_NODE *) * lh->pmax));

        if (n == NULL) {

            /* fputs("realloc error in lhash",stderr); */

            lh->error++;

        } else {

            lh->b = n;

        }

        lh->num_alloc_nodes /= 2;

        lh->pmax /= 2;

        lh->p = lh->pmax - 1;

    } else

        lh->p--;

    lh->num_nodes--;

    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 OPENSSL_LH_NODE **getrn(OPENSSL_LHASH *lh,

                               const void *data, unsigned long *rhash)

{

    OPENSSL_LH_NODE **ret, *n1;

    unsigned long hash, nn;

    OPENSSL_LH_COMPFUNC cf;

    hash = (*(lh->hash)) (data);

    *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) {

        if (n1->hash != hash) {

            ret = &(n1->next);

            continue;

        }

        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 OPENSSL_LH_strhash(const char *c)

{

    unsigned long ret = 0;

    long n;

    unsigned long v;

    int r;

    if ((c == NULL) || (*c == '\0'))

        return ret;

    n = 0x100;

    while (*c) {

        v = n | (*c);

        n += 0x100;

        r = (int)((v >> 2) ^ v) & 0x0f;

        /* cast to uint64_t to avoid 32 bit shift of 32 bit value */

        ret = (ret << r) | (unsigned long)((uint64_t)ret >> (32 - r));

        ret &= 0xFFFFFFFFL;

        ret ^= v * v;

        c++;

    }

    return (ret >> 16) ^ ret;

}

unsigned long ossl_lh_strcasehash(const char *c)

{

    unsigned long ret = 0;

    long n;

    unsigned long v;

    int r;

    if (c == NULL || *c == '\0')

        return ret;

    for (n = 0x100; *c != '\0'; n += 0x100) {

        v = n | ossl_tolower(*c);

        r = (int)((v >> 2) ^ v) & 0x0f;

        /* cast to uint64_t to avoid 32 bit shift of 32 bit value */

        ret = (ret << r) | (unsigned long)((uint64_t)ret >> (32 - r));

        ret &= 0xFFFFFFFFL;

        ret ^= v * v;

        c++;

    }

    return (ret >> 16) ^ ret;

}

unsigned long OPENSSL_LH_num_items(const OPENSSL_LHASH *lh)

{

    return lh ? lh->num_items : 0;

}

unsigned long OPENSSL_LH_get_down_load(const OPENSSL_LHASH *lh)

{

    return lh->down_load;

}

void OPENSSL_LH_set_down_load(OPENSSL_LHASH *lh, unsigned long down_load)

{

    lh->down_load = down_load;

}

int OPENSSL_LH_error(OPENSSL_LHASH *lh)

{

    return lh->error;

}