/* Licensed to the Apache Software Foundation (ASF) under one or more

 * contributor license agreements.  See the NOTICE file distributed with

 * this work for additional information regarding copyright ownership.

 * The ASF licenses this file to You under the Apache License, Version 2.0

 * (the "License"); you may not use this file except in compliance with

 * the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

/*

 * Copyright (C) 2019-2020 by Sukchan Lee <acetcom@gmail.com>

 *

 * This file is part of Open5GS.

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *   http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

#include "ogs-core.h"

typedef struct ogs_hash_entry_t ogs_hash_entry_t;

struct ogs_hash_entry_t {

    ogs_hash_entry_t    *next;

    unsigned int        hash;

    const void          *key;

    int                 klen;

    const void          *val;

};

struct ogs_hash_index_t {

    ogs_hash_t          *ht;

    ogs_hash_entry_t    *this, *next;

    unsigned int        index;

};

struct ogs_hash_t {

    ogs_hash_entry_t    **array;

    ogs_hash_index_t    iterator;  /* For ogs_hash_first(NULL, ...) */

    unsigned int        count, max, seed;

    ogs_hashfunc_t      hash_func;

    ogs_hash_entry_t    *free;  /* List of recycled entries */

};

#define INITIAL_MAX 15 /* tunable == 2^n - 1 */

static ogs_hash_entry_t **alloc_array(ogs_hash_t *ht, unsigned int max)

{

    ogs_hash_entry_t **ptr = ogs_calloc(1, sizeof(*ht->array) * (max + 1));

    ogs_assert(ptr);

    return ptr;

}

ogs_hash_t *ogs_hash_make(void)

{

    ogs_hash_t *ht;

    ogs_time_t now = ogs_get_monotonic_time();

    ht = ogs_malloc(sizeof(ogs_hash_t));

    if (!ht) {

        ogs_error("ogs_malloc() failed");

        return NULL;

    }

    ht->free = NULL;

    ht->count = 0;

    ht->max = INITIAL_MAX;

    ht->seed = (unsigned int)((now >> 32) ^ now ^ 

                              (uintptr_t)ht ^ (uintptr_t)&now) - 1;

    ht->array = alloc_array(ht, ht->max);

    ht->hash_func = NULL;

    return ht;

}

ogs_hash_t *ogs_hash_make_custom(ogs_hashfunc_t hash_func)

{

    ogs_hash_t *ht = ogs_hash_make();

    if (!ht) {

        ogs_error("ogs_hash_make() failed");

        return NULL;

    }

    ht->hash_func = hash_func;

    return ht;

}

void ogs_hash_destroy(ogs_hash_t *ht)

{

    ogs_hash_entry_t *he = NULL, *next_he = NULL;

    ogs_assert(ht);

    ogs_assert(ht->array);

    ogs_hash_clear(ht);

    he = ht->free;

    while(he) {

        next_he = he->next;

        ogs_free(he);

        he = next_he;

    }

    ogs_free(ht->array);

    ogs_free(ht);

}

ogs_hash_index_t *ogs_hash_next(ogs_hash_index_t *hi)

{

    ogs_assert(hi);

    hi->this = hi->next;

    while (!hi->this) {

        if (hi->index > hi->ht->max)

            return NULL;

        hi->this = hi->ht->array[hi->index++];

    }

    hi->next = hi->this->next;

    return hi;

}

ogs_hash_index_t *ogs_hash_first(ogs_hash_t *ht)

{

    ogs_hash_index_t *hi;

    ogs_assert(ht);

    hi = &ht->iterator;

    hi->ht = ht;

    hi->index = 0;

    hi->this = NULL;

    hi->next = NULL;

    return ogs_hash_next(hi);

}

void ogs_hash_this(ogs_hash_index_t *hi,

        const void **key, int *klen, void **val)

{

    ogs_assert(hi);

    if (key)  *key  = hi->this->key;

    if (klen) *klen = hi->this->klen;

    if (val)  *val  = (void *)hi->this->val;

}

const void *ogs_hash_this_key(ogs_hash_index_t *hi)

{

    const void *key;

    ogs_hash_this(hi, &key, NULL, NULL);

    return key;

}

int ogs_hash_this_key_len(ogs_hash_index_t *hi)

{

    int klen;

    ogs_hash_this(hi, NULL, &klen, NULL);

    return klen;

}

void *ogs_hash_this_val(ogs_hash_index_t *hi)

{

    void *val;

    ogs_hash_this(hi, NULL, NULL, &val);

    return val;

}

static void expand_array(ogs_hash_t *ht)

{

    ogs_hash_index_t *hi;

    ogs_hash_entry_t **new_array;

    unsigned int new_max;

    new_max = ht->max * 2 + 1;

    new_array = alloc_array(ht, new_max);

    for (hi = ogs_hash_first(ht); hi; hi = ogs_hash_next(hi)) {

        unsigned int i = hi->this->hash & new_max;

        hi->this->next = new_array[i];

        new_array[i] = hi->this;

    }

    ogs_free(ht->array);

    ht->array = new_array;

    ht->max = new_max;

}

static unsigned int hashfunc_default(

        const char *char_key, int *klen, unsigned int hash)

{

    const unsigned char *key = (const unsigned char *)char_key;

    const unsigned char *p;

    int i;

    /*

     * This is the popular `times 33' hash algorithm which is used by

     * perl and also appears in Berkeley DB. This is one of the best

     * known hash functions for strings because it is both computed

     * very fast and distributes very well.

     *

     * The originator may be Dan Bernstein but the code in Berkeley DB

     * cites Chris Torek as the source. The best citation I have found

     * is "Chris Torek, Hash function for text in C, Usenet message

     * <27038@mimsy.umd.edu> in comp.lang.c , October, 1990." in Rich

     * Salz's USENIX 1992 paper about INN which can be found at

     * <http://citeseer.nj.nec.com/salz92internetnews.html>.

     *

     * The magic of number 33, i.e. why it works better than many other

     * constants, prime or not, has never been adequately explained by

     * anyone. So I try an explanation: if one experimentally tests all

     * multipliers between 1 and 256 (as I did while writing a low-level

     * data structure library some time ago) one detects that even

     * numbers are not useable at all. The remaining 128 odd numbers

     * (except for the number 1) work more or less all equally well.

     * They all distribute in an acceptable way and this way fill a hash

     * table with an average percent of approx. 86%.

     *

     * If one compares the chi^2 values of the variants (see

     * Bob Jenkins ``Hashing Frequently Asked Questions'' at

     * http://burtleburtle.net/bob/hash/hashfaq.html for a description

     * of chi^2), the number 33 not even has the best value. But the

     * number 33 and a few other equally good numbers like 17, 31, 63,

     * 127 and 129 have nevertheless a great advantage to the remaining

     * numbers in the large set of possible multipliers: their multiply

     * operation can be replaced by a faster operation based on just one

     * shift plus either a single addition or subtraction operation. And

     * because a hash function has to both distribute good _and_ has to

     * be very fast to compute, those few numbers should be preferred.

     *

     *                  -- Ralf S. Engelschall <rse@engelschall.com>

     */

    if (*klen == OGS_HASH_KEY_STRING) {

        for (p = key; *p; p++) {

            hash = hash * 33 + *p;

        }

        *klen = p - key;

    }

    else {

        for (p = key, i = *klen; i; i--, p++) {

            hash = hash * 33 + *p;

        }

    }

    return hash;

}

unsigned int ogs_hashfunc_default(const char *char_key, int *klen)

{

    return hashfunc_default(char_key, klen, 0);

}

static ogs_hash_entry_t **find_entry(ogs_hash_t *ht,

        const void *key, int klen, const void *val, const char *file_line)

{

    ogs_hash_entry_t **hep, *he;

    unsigned int hash;

    if (ht->hash_func)

        hash = ht->hash_func(key, &klen);

    else

        hash = hashfunc_default(key, &klen, ht->seed);

    /* scan linked list */

    for (hep = &ht->array[hash & ht->max], he = *hep;

         he; hep = &he->next, he = *hep) {

        if (he->hash == hash

            && he->klen == klen

            && memcmp(he->key, key, klen) == 0)

            break;

    }

    if (he || !val)

        return hep;

    /* add a new entry for non-NULL values */

    if ((he = ht->free) != NULL)

        ht->free = he->next;

    else {

        he = ogs_malloc(sizeof(*he));

        ogs_assert(he);

    }

    he->next = NULL;

    he->hash = hash;

    he->key  = key;

    he->klen = klen;

    he->val  = val;

    *hep = he;

    ht->count++;

    return hep;

}

void *ogs_hash_get_debug(ogs_hash_t *ht,

        const void *key, int klen, const char *file_line)

{

    ogs_hash_entry_t *he;

    ogs_assert(ht);

    ogs_assert(key);

    ogs_assert(klen);

    he = *find_entry(ht, key, klen, NULL, file_line);

    if (he)

        return (void *)he->val;

    else

        return NULL;

}

void ogs_hash_set_debug(ogs_hash_t *ht,

        const void *key, int klen, const void *val, const char *file_line)

{

    ogs_hash_entry_t **hep;

    ogs_assert(ht);

    ogs_assert(key);

    ogs_assert(klen);

    hep = find_entry(ht, key, klen, val, file_line);

    if (*hep) {

        if (!val) {

            /* delete entry */

            ogs_hash_entry_t *old = *hep;

            *hep = (*hep)->next;

            old->next = ht->free;

            ht->free = old;

            --ht->count;

        } else {

            /* replace entry */

            (*hep)->val = val;

            /* check that the collision rate isn't too high */

            if (ht->count > ht->max) {

                expand_array(ht);

            }

        }

    }

    /* else key not present and val==NULL */

}

void *ogs_hash_get_or_set_debug(ogs_hash_t *ht,

        const void *key, int klen, const void *val, const char *file_line)

{

    ogs_hash_entry_t **hep;

    ogs_assert(ht);

    ogs_assert(key);

    ogs_assert(klen);

    hep = find_entry(ht, key, klen, val, file_line);

    if (*hep) {

        val = (*hep)->val;

        /* check that the collision rate isn't too high */

        if (ht->count > ht->max) {

            expand_array(ht);

        }

        return (void *)val;

    }

    /* else key not present and val==NULL */

    return NULL;

}

unsigned int ogs_hash_count(ogs_hash_t *ht)

{

    ogs_assert(ht);

    return ht->count;

}

void ogs_hash_clear(ogs_hash_t *ht)

{

    ogs_hash_index_t *hi;

    ogs_assert(ht);

    for (hi = ogs_hash_first(ht); hi; hi = ogs_hash_next(hi))

        ogs_hash_set(ht, hi->this->key, hi->this->klen, NULL);

}

/* This is basically the following...

 * for every element in hash table {

 *    comp elemeny.key, element.value

 * }

 *

 * Like with table_do, the comp callback is called for each and every

 * element of the hash table.

 */

int ogs_hash_do(ogs_hash_do_callback_fn_t *comp,

                             void *rec, const ogs_hash_t *ht)

{

    ogs_hash_index_t  hix;

    ogs_hash_index_t *hi;

    int rv, dorv  = 1;

    hix.ht    = (ogs_hash_t *)ht;

    hix.index = 0;

    hix.this  = NULL;

    hix.next  = NULL;

    if ((hi = ogs_hash_next(&hix))) {

        /* Scan the entire table */

        do {

            rv = (*comp)(rec, hi->this->key, hi->this->klen, hi->this->val);

        } while (rv && (hi = ogs_hash_next(hi)));

        if (rv == 0) {

            dorv = 0;

        }

    }

    return dorv;

}