contiki/apps/antelope/index-inline.c

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/*
* Copyright (c) 2010, Swedish Institute of Computer Science
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the Institute nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
/**
* \file
* A binary search index for attributes that are constrained to be
* monotonically increasing, which is a rather common pattern for
* time series or keys. Since this index has no storage overhead,
* it does not wear out the flash memory nor does it occupy any
* space. Furthermore, unlike B+-trees, it has a O(1) memory
* footprint in relation to the number of data items.
* \author
* Nicolas Tsiftes <nvt@sics.se>
*/
#include <stdlib.h>
#include <string.h>
#include "index.h"
#include "relation.h"
#include "result.h"
#include "storage.h"
#define DEBUG DEBUG_NONE
#include "net/ip/uip-debug.h"
struct search_handle {
index_t *index;
tuple_id_t start_row;
tuple_id_t end_row;
};
struct search_handle handle;
static db_result_t null_op(index_t *);
static db_result_t insert(index_t *, attribute_value_t *, tuple_id_t);
static db_result_t delete(index_t *, attribute_value_t *);
static tuple_id_t get_next(index_iterator_t *);
/*
* The create, destroy, load, release, insert, and delete operations
* of the index API always succeed because the index does not store
* items separately from the row file. The four former operations share
* the same signature, and are thus implemented by the null_op function
* to save space.
*/
index_api_t index_inline = {
INDEX_INLINE,
INDEX_API_EXTERNAL | INDEX_API_COMPLETE | INDEX_API_RANGE_QUERIES,
null_op,
null_op,
null_op,
null_op,
insert,
delete,
get_next
};
static attribute_value_t *
get_value(tuple_id_t *index, relation_t *rel, attribute_t *attr)
{
unsigned char row[rel->row_length];
static attribute_value_t value;
if(DB_ERROR(storage_get_row(rel, index, row))) {
return NULL;
}
if(DB_ERROR(relation_get_value(rel, attr, row, &value))) {
PRINTF("DB: Unable to retrieve a value from tuple %ld\n", (long)(*index));
return NULL;
}
return &value;
}
static tuple_id_t
binary_search(index_iterator_t *index_iterator,
attribute_value_t *target_value,
int exact_match)
{
relation_t *rel;
attribute_t *attr;
attribute_value_t *cmp_value;
tuple_id_t min;
tuple_id_t max;
tuple_id_t center;
rel = index_iterator->index->rel;
attr = index_iterator->index->attr;
max = relation_cardinality(rel);
if(max == INVALID_TUPLE) {
return INVALID_TUPLE;
}
max--;
min = 0;
do {
center = min + ((max - min) / 2);
cmp_value = get_value(&center, rel, attr);
if(cmp_value == NULL) {
PRINTF("DB: Failed to get the center value, index = %ld\n",
(long)center);
return INVALID_TUPLE;
}
if(db_value_to_long(target_value) > db_value_to_long(cmp_value)) {
min = center + 1;
} else {
max = center - 1;
}
} while(min <= max &&
db_value_to_long(target_value) != db_value_to_long(cmp_value));
if(exact_match &&
db_value_to_long(target_value) != db_value_to_long(cmp_value)) {
PRINTF("DB: Could not find value %ld in the inline index\n",
db_value_to_long(target_value));
return INVALID_TUPLE;
}
return center;
}
static tuple_id_t
range_search(index_iterator_t *index_iterator,
tuple_id_t *start, tuple_id_t *end)
{
attribute_value_t *low_target;
attribute_value_t *high_target;
int exact_match;
low_target = &index_iterator->min_value;
high_target = &index_iterator->max_value;
PRINTF("DB: Search index for value range (%ld, %ld)\n",
db_value_to_long(low_target), db_value_to_long(high_target));
exact_match = db_value_to_long(low_target) == db_value_to_long(high_target);
/* Optimize later so that the other search uses the result
from the first one. */
*start = binary_search(index_iterator, low_target, exact_match);
if(*start == INVALID_TUPLE) {
return DB_INDEX_ERROR;
}
*end = binary_search(index_iterator, high_target, exact_match);
if(*end == INVALID_TUPLE) {
return DB_INDEX_ERROR;
}
return DB_OK;
}
static db_result_t
null_op(index_t *index)
{
return DB_OK;
}
static db_result_t
insert(index_t *index, attribute_value_t *value, tuple_id_t tuple_id)
{
return DB_OK;
}
static db_result_t
delete(index_t *index, attribute_value_t *value)
{
return DB_OK;
}
static tuple_id_t
get_next(index_iterator_t *iterator)
{
static tuple_id_t cached_start;
static tuple_id_t cached_end;
if(iterator->next_item_no == 0) {
/*
* We conduct the actual index search when the caller attempts to
* access the first item in the iteration. The first and last tuple
* id:s of the result get cached for subsequent iterations.
*/
if(DB_ERROR(range_search(iterator, &cached_start, &cached_end))) {
cached_start = 0;
cached_end = 0;
return INVALID_TUPLE;
}
PRINTF("DB: Cached the tuple range (%ld,%ld)\n",
(long)cached_start, (long)cached_end);
++iterator->next_item_no;
return cached_start;
} else if(cached_start + iterator->next_item_no <= cached_end) {
return cached_start + iterator->next_item_no++;
}
return INVALID_TUPLE;
}