Struct ofilter::SyncBloom

pub struct SyncBloom<T> { /* private fields */ }

Thread-safe Bloom filter.

Same as the standard Bloom filter, but safe to use in concurrent environments.

Examples

use std::thread;
use ofilter::SyncBloom;

let filter: SyncBloom<usize> = SyncBloom::new(1_000);

let f = filter.clone();
let handle1 = thread::spawn(move || {
    for i in 0..1_000 {
        f.set(&i);
    }
});

let f = filter.clone();
let handle2 = thread::spawn(move || {
    for i in 0..1_000 {
        f.check(&i);
    }
});

handle1.join().unwrap();
handle2.join().unwrap();

Implementations

impl<T> SyncBloom<T>

pub fn new(capacity: usize) -> Self

Create a new thread-safe Bloom filter, with given capacity.

All other parameters are set to defaults, or aligned to match capacity.

Examples

use ofilter::SyncBloom;

let filter: SyncBloom<usize> = SyncBloom::new(100);
assert_eq!(100, filter.capacity());

pub fn new_with_params(params: Params) -> Self

Create a new thread-safe Bloom filter, with specific parameters.

Examples

use ofilter::{SyncBloom, Params};

let filter: SyncBloom<usize> = SyncBloom::new_with_params(Params::with_nb_items_and_fp_rate(100, 0.1));
assert_eq!(100, filter.capacity());

pub fn params(&self) -> Params

Get filter params.

This can be useful because when creating the filter, the .adjust() func is called, and may decide to fine-tune some parameters. With this, one can know exactly what is used by the filter.

Examples

use ofilter::SyncBloom;

let filter: SyncBloom<usize> = SyncBloom::new(100);
println!("{}", filter.params());

pub fn capacity(&self) -> usize

Get filter capacity.

Returns the value of params.nb_items, that is the number of items the filter is designed for.

use ofilter::{SyncBloom, Params};

let filter: SyncBloom<usize> = SyncBloom::new_with_params(Params::with_bit_len(1_000_000));
assert_eq!(52681, filter.capacity());

pub fn clear(&self)

Clear the filter.

Clears the bit vector, but keeps parameters.

use ofilter::SyncBloom;

// Does not need to be `mut`
let filter: SyncBloom<usize> = SyncBloom::new(1_000);
filter.set(&10);
assert!(filter.check(&10));
filter.clear();
assert!(!filter.check(&10));

pub fn is_empty(&self) -> bool

Returns true if filter is empty.

use ofilter::SyncBloom;

// Does not need to be `mut`
let filter: SyncBloom<usize> = SyncBloom::new(1_000);
assert!(filter.is_empty());
filter.set(&10);
assert!(!filter.is_empty());

pub fn fp_rate(&self) -> f64

Returns the current false positive rate.

In theory the false positive rate fp_rate is known at filter creation. But that, is the theoretical fp_rate that the filter reaches when it is “wasted” because it has too many entries. Until then, it performs better than that, statistically.

This function returns the actual false positive rate. When this value is greater than the fp_rate from the parameters, one should not continue to add items to the filter.

use ofilter::SyncBloom;

// Does not need to be `mut`
let filter: SyncBloom<usize> = SyncBloom::new(1_000);
assert_eq!(0.0, filter.fp_rate());
filter.set(&10);
assert!(filter.fp_rate() > 0.0); // will be params.fp_rate when filter is full

pub fn level(&self) -> f64

Returns the ratio between real fp_rate, and theoretical fp_rate.

This is a helper to quickly compare the real fp_rate, given how filled the filter is, and the theoretical fp_rate.

When this value is greater than 1.0, one should not continue to add items to the filter.

use ofilter::SyncBloom;

// Does not need to be `mut`
let filter: SyncBloom<usize> = SyncBloom::new(1_000);
assert_eq!(0.0, filter.level());
filter.set(&10);
assert!(filter.level() > 0.0); // will be 1.0 when filter is full

pub fn is_ok(&self) -> bool

Returns true if there is still room in the filter.

This is a helper which returns true if the actual fp_rate is lower than the theoretical fp_rate.

When this is false, one should not continue to add items to the filter.

use ofilter::SyncBloom;

// Does not need to be `mut`
let filter: SyncBloom<usize> = SyncBloom::new(1_000);
assert_eq!(0.0, filter.level());
filter.set(&10);
assert!(filter.level() > 0.0); // will be 1.0 when filter is full

pub fn count_ones(&self) -> usize

Returns the number of ones in the bit vector.

By comparing this number with the size of the bit vector, one can estimate how “filled” the filter is.

use ofilter::SyncBloom;

// Does not need to be `mut`
let filter: SyncBloom<usize> = SyncBloom::new(1_000_000);
assert_eq!(0, filter.count_ones());
filter.set(&10);
assert_eq!(2, filter.count_ones());

pub fn export(&self) -> BitVec

Export the underlying bit vector.

use ofilter::SyncBloom;

// Does not need to be `mut`
let filter: SyncBloom<usize> = SyncBloom::new(1_000_000);
let bit_vec = filter.export();
println!("{:?}", &bit_vec);

pub fn import(&self, src: &BitVec)

Import the underlying bit vector.

use ofilter::SyncBloom;
use bitvec::prelude::BitVec;

// Does not need to be `mut`
let filter: SyncBloom<usize> = SyncBloom::new(1_000_000);
let mut bit_vec = BitVec::new();
bit_vec.resize(100, false);
bit_vec.set(42, true);
filter.import(&bit_vec); // safe to call even is sizes mismatch

impl<T> SyncBloom<T>

where T: Hash,

pub fn set(&self, item: &T)

Record an item in the set.

Once this has been called, any call to check() will return true, as there are no false negatives. However some other items may test positive as a consequence of recording this one.

use ofilter::SyncBloom;

// Does not need to be `mut`
let filter: SyncBloom<usize> = SyncBloom::new(1_000);
filter.set(&42);

pub fn check(&self, item: &T) -> bool

Guess whether an item is likely to be in the set.

If set() has been called before with value, then this returns true, as there are no false negatives. However it may respond true even if the item has never been recorded in the set.

use ofilter::SyncBloom;

// Does not need to be `mut`
let filter: SyncBloom<usize> = SyncBloom::new(1_000);
filter.set(&42);
assert!(filter.check(&42));

pub fn check_and_set(&self, item: &T) -> bool

Record an item in the set and returns its previous value.

Equivalent to calling get() then set() but performs hash lookup only once so it’s a bit more efficient.

use ofilter::SyncBloom;

// Does not need to be `mut`
let filter: SyncBloom<usize> = SyncBloom::new(1_000);
assert!(!filter.check_and_set(&42));
assert!(filter.check(&42));

Trait Implementations

impl<T: Clone> Clone for SyncBloom<T>

fn clone(&self) -> SyncBloom<T>

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<T: Debug> Debug for SyncBloom<T>

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<T> Display for SyncBloom<T>

where T: Hash,

Pretty-print the filter.

Examples

use ofilter::SyncBloom;

let filter: SyncBloom<usize> = SyncBloom::new(100);

assert_eq!("[sync] { fp_rate: 0.000000, params: { nb_hash: 2, bit_len: 1899, nb_items: 100, fp_rate: 0.009992, predict: false } }", format!("{}", filter));

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.