https://github.com/barrust/counting_bloom
https://github.com/barrust/counting_bloom
Last synced: 9 months ago
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- Host: GitHub
- URL: https://github.com/barrust/counting_bloom
- Owner: barrust
- License: mit
- Created: 2015-09-30T04:57:25.000Z (over 10 years ago)
- Default Branch: master
- Last Pushed: 2022-01-10T19:45:22.000Z (almost 4 years ago)
- Last Synced: 2025-04-01T00:29:49.797Z (9 months ago)
- Language: C
- Size: 49.8 KB
- Stars: 1
- Watchers: 2
- Forks: 1
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
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README
# Counting Bloom
[](https://opensource.org/licenses/MIT)
[](https://github.com/barrust/counting_bloom/releases)
[](https://github.com/barrust/counting_bloom/actions)
[](https://codecov.io/gh/barrust/counting_bloom)
Counting Bloom Filter implementation written in **C**
A counting bloom filter is similar to a standard bloom filter except that instead
of using bits, one increments each index in the array. This allows for the removal
of items from the filter. The data stored in a Bloom Filter is not retrievable. Once
data is 'inserted', data can be checked to see if it likely has been seen or if
it definitely has not. Bloom Filters guarantee a 0% False Negative rate with a
pre-selected false positive rate.
To use the library, copy the `src/counting_bloom.h` and `src/counting_bloom.c`
files into your project and include it where needed.
For a **python version**, please check out [pyprobables](https://github.com/barrust/pyprobables)
which has a binary compatible output.
## License:
MIT 2015
## Usage:
``` c
#include
#include "counting_bloom.h"
CountingBloom cb;
counting_bloom_init(&cb, 10, 0.01);
counting_bloom_add_string(&cb, "google");
counting_bloom_add_string(&cb, "facebook");
counting_bloom_add_string(&cb, "twitter");
counting_bloom_add_string(&cb, "google");
if (counting_bloom_check_string(&cb, "google") == COUNTING_BLOOM_SUCCESS) {
printf("'google' is in the counting bloom a maximum of %d times!\n", counting_bloom_get_max_insertions(&cb, "google"));
}
counting_bloom_remove_string(&cb, "google");
counting_bloom_stats(&cb);
counting_bloom_destroy(&cb);
```
## Required Compile Flags:
-lm
## Backward Compatible Hash Function
To use the older counting bloom filters (v1.0.3 or lower) that utilized the default hashing
algorithm, then change use the following code as the hash function:
``` c
/* NOTE: The caller will free the results */
static uint64_t* original_default_hash(unsigned int num_hashes, const char* str) {
uint64_t *results = (uint64_t*)calloc(num_hashes, sizeof(uint64_t));
char key[17] = {0}; // largest value is 7FFF,FFFF,FFFF,FFFF
results[0] = __fnv_1a(str);
for (unsigned int i = 1; i < num_hashes; ++i) {
sprintf(key, "%" PRIx64 "", results[i-1]);
results[i] = old_fnv_1a(key);
}
return results;
}
static uint64_t old_fnv_1a(const char* key) {
// FNV-1a hash (http://www.isthe.com/chongo/tech/comp/fnv/)
int i, len = strlen(key);
uint64_t h = 14695981039346656073ULL; // FNV_OFFSET 64 bit
for (i = 0; i < len; ++i){
h = h ^ (unsigned char) key[i];
h = h * 1099511628211ULL; // FNV_PRIME 64 bit
}
return h;
}
```
If using only older Counting Bloom Filters, then you can update the // FNV_OFFSET 64 bit
to use `14695981039346656073ULL`