-#include <stdio.h>
-#include <stdlib.h>
-#include <inttypes.h>
-#include <string.h>
-#include <assert.h>
+/*
+ * Copyright (C) 2008 Andre Noll <maan@systemlinux.org>
+ *
+ * Licensed under the GPL v2. For licencing details see COPYING.
+ */
+
+/** \file bloom.c Simple bloom filter implementation. */
#include "adu.h"
#include "string.h"
void *adu_calloc(size_t size)
{
void *ret = malloc(size);
+
+ if (!ret)
+ exit(EXIT_FAILURE);
memset(ret, 0, size);
return ret;
}
* http://www.azillionmonkeys.com/qed/hash.html
*/
+/** \cond */
#if (defined(__GNUC__) && defined(__i386__))
#define get16bits(d) (*((const uint16_t *) (d)))
#else
#define get16bits(d) ((((uint32_t)(((const uint8_t *)(d))[1])) << 8)\
+(uint32_t)(((const uint8_t *)(d))[0]) )
#endif
-
+/** \endcond */
static uint32_t super_fast_hash(const uint8_t *data, uint32_t len, uint32_t hash)
{
return ret;
}
-int bloom_test_and_insert(const uint8_t *data, size_t len, struct bloom *b)
+/**
+ * Insert data to the given bloom filter.
+ *
+ * This function computes \a k hashes from the given data where \a k is the
+ * number of hash functions of the filter \a b. Each hash value corresponds to
+ * a position in the bit array of the filter and each of these bits are being
+ * tested and set. If not all \a k bits were already set, the given data was
+ * not yet contained in the filter and the function returns non-zero.
+ *
+ * Otherwise either (a) the same data has already been inserted previously or
+ * (b) a hash collision occurred or (c) the \a k bits are set due to previous
+ * insertion of other data (i.e. a false positive occurred). It is impossible
+ * to distinguish these cases.
+ *
+ * \param data The data to insert.
+ * \param len Number of bytes of \a data.
+ * \param b The filter to insert to.
+ *
+ * \return Zero if the entry was already contained in the filter (or in case of
+ * false positives), non-zero otherwise.
+ */
+int bloom_insert(const uint8_t *data, size_t len, struct bloom *b)
{
int i, ret = 0;
uint32_t h = 0xb11924e1; /* some arbitrary value */
}
/**
- * Initialize a bloom filter.
+ * Allocate and initialize a new bloom filter.
*
* \param order Use a filter containing 2^order bits.
* \param num_hash_functions Set that many bits in the filter per entry.
+ *
+ * \return This function either returns a freshly allocated and initialized
+ * bloom filter or does not return at all (if the underlying malloc() failed).
*/
-int bloom_init(unsigned order, unsigned num_hash_functions,
- struct bloom **result)
+struct bloom *bloom_new(unsigned order, unsigned num_hash_functions)
{
struct bloom *b = adu_calloc(sizeof(*b));
b->order = order;
b->num_hash_functions = num_hash_functions;
b->filter = adu_calloc(filter_bits(b) / 8);
- *result = b;
- return 1;
+ return b;
}
#ifdef TEST_BLOOM
-int bloom_test_and_insert_string(const char *str, struct bloom *b)
+int bloom_insert_string(const char *str, struct bloom *b)
{
uint32_t len = strlen(str);
- return bloom_test_and_insert((const uint8_t *)str, len, b);
+ return bloom_insert((const uint8_t *)str, len, b);
}
void add_stdin(struct bloom *b)
continue;
if (buf[len - 1] == '\n')
buf[len - 1] = '\0';
- if (bloom_test_and_insert_string(buf, b))
+ if (bloom_insert_string(buf, b))
false_positives++;
}
INFO_LOG("filter contains %llu entries\n", b->num_entries);
printf("k: # of hash functions to use\n");
exit(1);
}
- bloom_init(atoi(argv[1]), atoi(argv[2]), &b);
+ b = bloom_new(atoi(argv[1]), atoi(argv[2]));
add_stdin(b);
INFO_LOG("%u%% of bits are set\n", (unsigned)
(b->num_set_bits * 100ULL / filter_bits(b)));