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195 lines
4.8 KiB
C
195 lines
4.8 KiB
C
/*
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* Copyright (c) 2010, Swedish Institute of Computer Science
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the Institute nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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/**
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* \file
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* A memory-resident hash map used as a DB index.
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* \author
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* Nicolas Tsiftes <nvt@sics.se>
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*/
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#include <string.h>
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#include "lib/memb.h"
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#include "db-options.h"
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#include "index.h"
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#define DEBUG DEBUG_NONE
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#include "net/ip/uip-debug.h"
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static db_result_t create(index_t *);
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static db_result_t destroy(index_t *);
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static db_result_t load(index_t *);
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static db_result_t release(index_t *);
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static db_result_t insert(index_t *, attribute_value_t *, tuple_id_t);
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static db_result_t delete(index_t *, attribute_value_t *);
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static tuple_id_t get_next(index_iterator_t *);
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index_api_t index_memhash = {
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INDEX_MEMHASH,
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INDEX_API_INTERNAL,
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create,
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destroy,
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load,
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release,
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insert,
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delete,
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get_next
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};
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struct hash_item {
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tuple_id_t tuple_id;
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attribute_value_t value;
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};
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typedef struct hash_item hash_item_t;
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typedef hash_item_t hash_map_t[DB_MEMHASH_TABLE_SIZE];
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MEMB(hash_map_memb, hash_map_t, DB_MEMHASH_INDEX_LIMIT);
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static unsigned
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calculate_hash(attribute_value_t *value)
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{
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unsigned char *cp, *end;
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unsigned hash_value;
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cp = (unsigned char *)value;
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end = cp + sizeof(*value);
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hash_value = 0;
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while(cp < end) {
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hash_value = hash_value * 33 + *cp++;
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}
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return hash_value % DB_MEMHASH_TABLE_SIZE;
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}
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static db_result_t
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create(index_t *index)
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{
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int i;
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hash_map_t *hash_map;
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PRINTF("Creating a memory-resident hash map index\n");
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hash_map = memb_alloc(&hash_map_memb);
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if(hash_map == NULL) {
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return DB_ALLOCATION_ERROR;
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}
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for(i = 0; i < DB_MEMHASH_TABLE_SIZE; i++) {
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hash_map[i]->tuple_id = INVALID_TUPLE;
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}
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index->opaque_data = hash_map;
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return DB_OK;
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}
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static db_result_t
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destroy(index_t *index)
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{
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memb_free(&hash_map_memb, index->opaque_data);
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return DB_OK;
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}
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static db_result_t
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load(index_t *index)
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{
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return create(index);
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}
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static db_result_t
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release(index_t *index)
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{
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return destroy(index);
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}
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static db_result_t
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insert(index_t *index, attribute_value_t *value, tuple_id_t tuple_id)
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{
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hash_map_t *hash_map;
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uint16_t hash_value;
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hash_map = index->opaque_data;
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hash_value = calculate_hash(value);
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hash_map[hash_value]->tuple_id = tuple_id;
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hash_map[hash_value]->value = *value;
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PRINTF("DB: Inserted value %ld into the hash table\n", VALUE_LONG(value));
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return DB_OK;
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}
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static db_result_t
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delete(index_t *index, attribute_value_t *value)
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{
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hash_map_t *hash_map;
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uint16_t hash_value;
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hash_map = index->opaque_data;
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hash_value = calculate_hash(value);
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if(memcmp(&hash_map[hash_value]->value, value, sizeof(*value)) != 0) {
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return DB_INDEX_ERROR;
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}
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hash_map[hash_value]->tuple_id = INVALID_TUPLE;
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return DB_OK;
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}
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static tuple_id_t
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get_next(index_iterator_t *iterator)
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{
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hash_map_t *hash_map;
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uint16_t hash_value;
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if(iterator->next_item_no == 1) {
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/* The memhash supports only unique values at the moment. */
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return INVALID_TUPLE;
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}
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hash_map = iterator->index->opaque_data;
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hash_value = calculate_hash(&iterator->min_value);
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if(memcmp(&hash_map[hash_value]->value, &iterator->min_value, sizeof(iterator->min_value)) != 0) {
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return INVALID_TUPLE;
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}
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iterator->next_item_no++;
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PRINTF("DB: Found value %ld in the hash table\n",
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VALUE_LONG(&iterator->min_value));
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return hash_map[hash_value]->tuple_id;
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}
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