cOMS/Stdlib/HashTable.h

/**
 * Karaka
 *
 * @package   Stdlib
 * @copyright Dennis Eichhorn
 * @license   OMS License 1.0
 * @version   1.0.0
 * @link      https://jingga.app
 */
#ifndef STDLIB_HASH_TABLE_H
#define STDLIB_HASH_TABLE_H

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "../Hash/MeowHash.h"

namespace Stdlib
{
    namespace HashTable
    {
        typedef struct {
            const char *key;
            void *value;
        } entry;

        struct ht {
            bool is_fixed = false;
            entry *entries;
            size_t max;
            size_t size;
        };

        typedef struct {
            const char *key;
            void *value;

            ht *table;
            size_t index;
        } it;

        inline
        unsigned long long hash_key(const char *key)
        {
            return (unsigned long long) MeowU64From(
                Hash::Meow::MeowHash(Hash::Meow::MeowDefaultSeed,
                strlen(key),
                (void *) key),
                0
            );
        }

        ht *create_table(int max = 0, bool is_fixed = false)
        {
            ht *table = (ht *) malloc(sizeof(ht));
            if (table == NULL) {
                return NULL;
            }

            table->size = 0;
            table->max  = max == 0 ? 16 : max;
            table->is_fixed = is_fixed;

            table->entries = (entry *) calloc(table->max, sizeof(entry));
            if (table->entries == NULL) {
                free(table);
                return NULL;
            }

            return table;
        }

        void *get_entry(ht *table, const char *key)
        {
            unsigned long long hash = hash_key(key);
            size_t index = (size_t) (hash & (unsigned long long)(table->max - 1));

            while (table->entries[index].key != NULL) {
                if (strcmp(key, table->entries[index].key) == 0) {
                    return table->entries[index].value;
                }

                ++index;
                if (index >= table->max) {
                    index = 0;
                }
            }

            return NULL;
        }

        const char *_set_entry(entry *entries, size_t max, const char *key, void *value, size_t *size)
        {
            unsigned long long hash = hash_key(key);
            size_t index            = (size_t) (hash & (unsigned long long)(max - 1));

            while (entries[index].key != NULL) {
                if (strcmp(key, entries[index].key) == 0) {
                    entries[index].value = value;

                    return entries[index].key;
                }

                ++index;
                if (index >= max) {
                    index = 0;
                }
            }

            if (size != NULL) {
                #ifdef _WIN32
                    key = _strdup(key);
                #else
                    key = strdup(key);
                #endif

                if (key == NULL) {
                    return NULL;
                }

                ++(*size);
            }

            entries[index].key = (char *) key;
            entries[index].value = value;

            return key;
        }

        bool expand_table(ht *table)
        {
            size_t new_max = table->max * 2;
            if (new_max < table->max) {
                return false;
            }

            entry *new_entries = (entry *) calloc(new_max, sizeof(entry));
            if (new_entries == NULL) {
                return false;
            }

            for (size_t i = 0; i < table->max; ++i) {
                entry tmp = table->entries[i];
                if (tmp.key != NULL) {
                    _set_entry(new_entries, new_max, tmp.key, tmp.value, NULL);
                }
            }

            free(table->entries);
            table->entries = new_entries;
            table->max     = new_max;

            return true;
        }

        const char *set_entry(ht *table, const char *key, void *value)
        {
            if (value == NULL) {
                return NULL;
            }

            if (table->is_fixed && table->size == table->max) {
                return NULL;
            }

            if (!table->is_fixed && table->size >= table->max / 2) {
                if (!expand_table(table)) {
                    return NULL;
                }
            }

            return _set_entry(table->entries, table->max, key, value, &table->size);
        }

        it table_iterator(ht *table)
        {
            it it;
            it.table = table;
            it.index = 0;

            return it;
        }

        bool next(it *it)
        {
            ht *table = it->table;
            while (it->index < table->max) {
                size_t i = it->index;
                ++(it->index);

                if (table->entries[i].key != NULL) {
                    entry tmp = table->entries[i];
                    it->key   = tmp.key;
                    it->value = tmp.value;

                    return true;
                }
            }

            return false;
        }

        void free_table(ht *table)
        {
            if (!table || !table->entries) {
                return;
            }

            for (size_t i = 0; i < table->max; ++i) {
                if (table->entries[i].key) {
                    free((void *) table->entries[i].key);
                }
            }

            free(table->entries);
        }
    }
}

#endif