/* Generic hash table
**
** Copyright 2001, Travis Geiselbrecht. All rights reserved.
** Distributed under the terms of the NewOS License.
*/

#include "hash.h"

#include <stdlib.h>

#include "fssh_errors.h"
#include "fssh_kernel_export.h"


#undef TRACE
#define TRACE_HASH 0
#if TRACE_HASH
#       define TRACE(x) fssh_dprintf x
#else
#       define TRACE(x) ;
#endif

#undef ASSERT
#define ASSERT(x)


namespace FSShell {


// TODO: the hashtable is not expanded when necessary (no load factor, nothing)
//              resizing should be optional, though, in case the hash is used at times
//              that forbid resizing.

struct hash_table {
        struct          hash_element **table;
        int                     next_ptr_offset;
        uint32_t        table_size;
        int                     num_elements;
        int                     flags;
        int                     (*compare_func)(void *e, const void *key);
        uint32_t        (*hash_func)(void *e, const void *key, uint32_t range);
};

// XXX gross hack
#define NEXT_ADDR(t, e) ((void *)(((unsigned long)(e)) + (t)->next_ptr_offset))
#define NEXT(t, e) ((void *)(*(unsigned long *)NEXT_ADDR(t, e)))
#define PUT_IN_NEXT(t, e, val) (*(unsigned long *)NEXT_ADDR(t, e) = (long)(val))


static inline void *
next_element(hash_table *table, void *element)
{
        // ToDo: should we use this instead of the NEXT() macro?
        return (void *)(*(unsigned long *)NEXT_ADDR(table, element));
}


struct hash_table *
hash_init(uint32_t table_size, int next_ptr_offset,
        int compare_func(void *e, const void *key),
        uint32_t hash_func(void *e, const void *key, uint32_t range))
{
        struct hash_table *t;
        unsigned int i;

        if (compare_func == NULL || hash_func == NULL) {
                fssh_dprintf("hash_init() called with NULL function pointer\n");
                return NULL;
        }

        t = (struct hash_table *)malloc(sizeof(struct hash_table));
        if (t == NULL)
                return NULL;

        t->table = (struct hash_element **)malloc(sizeof(void *) * table_size);
        if (t->table == NULL) {
                free(t);
                return NULL;
        }

        for (i = 0; i < table_size; i++)
                t->table[i] = NULL;

        t->table_size = table_size;
        t->next_ptr_offset = next_ptr_offset;
        t->flags = 0;
        t->num_elements = 0;
        t->compare_func = compare_func;
        t->hash_func = hash_func;

        TRACE(("hash_init: created table %p, next_ptr_offset %d, compare_func %p, hash_func %p\n",
                t, next_ptr_offset, compare_func, hash_func));

        return t;
}


int
hash_uninit(struct hash_table *table)
{
        ASSERT(table->num_elements == 0);

        free(table->table);
        free(table);

        return 0;
}


fssh_status_t
hash_insert(struct hash_table *table, void *element)
{
        uint32_t hash;

        ASSERT(table != NULL && element != NULL);
        TRACE(("hash_insert: table 0x%x, element 0x%x\n", table, element));

        hash = table->hash_func(element, NULL, table->table_size);
        PUT_IN_NEXT(table, element, table->table[hash]);
        table->table[hash] = (struct hash_element *)element;
        table->num_elements++;

        // ToDo: resize hash table if it's grown too much!

        return FSSH_B_OK;
}


fssh_status_t
hash_remove(struct hash_table *table, void *_element)
{
        uint32_t hash = table->hash_func(_element, NULL, table->table_size);
        void *element, *lastElement = NULL;

        for (element = table->table[hash]; element != NULL;
                        lastElement = element, element = NEXT(table, element)) {
                if (element == _element) {
                        if (lastElement != NULL) {
                                // connect the previous entry with the next one
                                PUT_IN_NEXT(table, lastElement, NEXT(table, element));
                        } else
                                table->table[hash] = (struct hash_element *)NEXT(table, element);
                        table->num_elements--;

                        return FSSH_B_OK;
                }
        }

        return FSSH_B_ERROR;
}


void
hash_remove_current(struct hash_table *table, struct hash_iterator *iterator)
{
        uint32_t index = iterator->bucket;
        void *element;

        if (iterator->current == NULL)
                fssh_panic("hash_remove_current() called too early.");

        for (element = table->table[index]; index < table->table_size; index++) {
                void *lastElement = NULL;

                while (element != NULL) {
                        if (element == iterator->current) {
                                iterator->current = lastElement;

                                if (lastElement != NULL) {
                                        // connect the previous entry with the next one
                                        PUT_IN_NEXT(table, lastElement, NEXT(table, element));
                                } else {
                                        table->table[index] = (struct hash_element *)NEXT(table,
                                                element);
                                }

                                table->num_elements--;
                                return;
                        }

                        element = NEXT(table, element);
                }
        }
}


void *
hash_remove_first(struct hash_table *table, uint32_t *_cookie)
{
        uint32_t index;

        for (index = _cookie ? *_cookie : 0; index < table->table_size; index++) {
                void *element = table->table[index];
                if (element != NULL) {
                        // remove the first element we find
                        table->table[index] = (struct hash_element *)NEXT(table, element);
                        table->num_elements--;
                        if (_cookie)
                                *_cookie = index;
                        return element;
                }
        }

        return NULL;
}


void *
hash_find(struct hash_table *table, void *searchedElement)
{
        uint32_t hash = table->hash_func(searchedElement, NULL, table->table_size);
        void *element;

        for (element = table->table[hash]; element != NULL; element = NEXT(table, element)) {
                if (element == searchedElement)
                        return element;
        }

        return NULL;
}


void *
hash_lookup(struct hash_table *table, const void *key)
{
        uint32_t hash = table->hash_func(NULL, key, table->table_size);
        void *element;

        for (element = table->table[hash]; element != NULL; element = NEXT(table, element)) {
                if (table->compare_func(element, key) == 0)
                        return element;
        }

        return NULL;
}


struct hash_iterator *
hash_open(struct hash_table *table, struct hash_iterator *iterator)
{
        if (iterator == NULL) {
                iterator = (struct hash_iterator *)malloc(sizeof(struct hash_iterator));
                if (iterator == NULL)
                        return NULL;
        }

        hash_rewind(table, iterator);

        return iterator;
}


void
hash_close(struct hash_table *table, struct hash_iterator *iterator, bool freeIterator)
{
        if (freeIterator)
                free(iterator);
}


void
hash_rewind(struct hash_table *table, struct hash_iterator *iterator)
{
        iterator->current = NULL;
        iterator->bucket = -1;
}


void *
hash_next(struct hash_table *table, struct hash_iterator *iterator)
{
        uint32_t index;

restart:
        if (iterator->current == NULL) {
                // get next bucket
                for (index = (uint32_t)(iterator->bucket + 1); index < table->table_size; index++) {
                        if (table->table[index]) {
                                iterator->bucket = index;
                                iterator->current = table->table[index];
                                break;
                        }
                }
        } else {
                iterator->current = NEXT(table, iterator->current);
                if (!iterator->current)
                        goto restart;
        }

        return iterator->current;
}


uint32_t
hash_hash_string(const char *string)
{
        uint32_t hash = 0;
        char c;

        // we assume hash to be at least 32 bits
        while ((c = *string++) != 0) {
                hash ^= hash >> 28;
                hash <<= 4;
                hash ^= c;
        }

        return hash;
}

}       // namespace FSShell