454 lines
13 KiB
Rust
454 lines
13 KiB
Rust
//! Multilevel blockchain bloom filter.
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//!
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//! ```
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//! extern crate ethcore_util as util;
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//! use std::str::FromStr;
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//! use util::chainfilter::*;
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//! use util::sha3::*;
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//! use util::hash::*;
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//!
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//! fn main() {
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//! let (index_size, bloom_levels) = (16, 3);
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//! let mut cache = MemoryCache::new();
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//!
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//! let address = Address::from_str("ef2d6d194084c2de36e0dabfce45d046b37d1106").unwrap();
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//!
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//! // borrow cache for reading inside the scope
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//! let modified_blooms = {
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//! let filter = ChainFilter::new(&cache, index_size, bloom_levels);
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//! let block_number = 39;
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//! let mut bloom = H2048::new();
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//! bloom.shift_bloomed(&address.sha3());
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//! filter.add_bloom(&bloom, block_number)
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//! };
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//!
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//! // number of updated blooms is equal number of levels
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//! assert_eq!(modified_blooms.len(), bloom_levels as usize);
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//!
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//! // lets inserts modified blooms into the cache
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//! cache.insert_blooms(modified_blooms);
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//!
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//! // borrow cache for another reading operations
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//! {
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//! let filter = ChainFilter::new(&cache, index_size, bloom_levels);
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//! let blocks = filter.blocks_with_address(&address, 10, 40);
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//! assert_eq!(blocks.len(), 1);
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//! assert_eq!(blocks[0], 39);
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//! }
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//! }
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//! ```
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//!
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use std::collections::{HashMap};
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use hash::*;
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use sha3::*;
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/// Represents bloom index in cache
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///
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/// On cache level 0, every block bloom is represented by different index.
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/// On higher cache levels, multiple block blooms are represented by one
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/// index. Their `BloomIndex` can be created from block number and given level.
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#[derive(Eq, PartialEq, Hash, Clone, Debug)]
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pub struct BloomIndex {
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/// Bloom level
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pub level: u8,
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/// Filter Index
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pub index: usize,
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}
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impl BloomIndex {
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/// Default constructor for `BloomIndex`
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pub fn new(level: u8, index: usize) -> BloomIndex {
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BloomIndex {
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level: level,
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index: index,
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}
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}
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}
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/// Types implementing this trait should provide read access for bloom filters database.
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pub trait FilterDataSource {
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/// returns reference to log at given position if it exists
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fn bloom_at_index(&self, index: &BloomIndex) -> Option<&H2048>;
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}
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/// In memory cache for blooms.
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///
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/// Stores all blooms in HashMap, which indexes them by `BloomIndex`.
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pub struct MemoryCache {
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blooms: HashMap<BloomIndex, H2048>,
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}
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impl MemoryCache {
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/// Default constructor for MemoryCache
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pub fn new() -> MemoryCache {
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MemoryCache { blooms: HashMap::new() }
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}
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/// inserts all blooms into cache
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///
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/// if bloom at given index already exists, overwrites it
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pub fn insert_blooms(&mut self, blooms: HashMap<BloomIndex, H2048>) {
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self.blooms.extend(blooms);
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}
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}
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impl FilterDataSource for MemoryCache {
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fn bloom_at_index(&self, index: &BloomIndex) -> Option<&H2048> {
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self.blooms.get(index)
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}
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}
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/// Should be used for search operations on blockchain.
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pub struct ChainFilter<'a, D>
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where D: FilterDataSource + 'a
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{
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data_source: &'a D,
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index_size: usize,
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level_sizes: Vec<usize>,
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}
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impl<'a, D> ChainFilter<'a, D> where D: FilterDataSource
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{
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/// Creates new filter instance.
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///
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/// Borrows `FilterDataSource` for reading.
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pub fn new(data_source: &'a D, index_size: usize, levels: u8) -> Self {
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if levels == 0 {
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panic!("ChainFilter requires at least 1 level");
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}
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let mut filter = ChainFilter {
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data_source: data_source,
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index_size: index_size,
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// 0 level has always a size of 1
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level_sizes: vec![1]
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};
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// cache level sizes, so we do not have to calculate them all the time
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// eg. if levels == 3, index_size = 16
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// level_sizes = [1, 16, 256]
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let additional: Vec<usize> = (1..).into_iter()
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.scan(1, |acc, _| {
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*acc = *acc * index_size;
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Some(*acc)
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})
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.take(levels as usize - 1)
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.collect();
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filter.level_sizes.extend(additional);
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filter
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}
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/// unsafely get level size
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fn level_size(&self, level: u8) -> usize {
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self.level_sizes[level as usize]
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}
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/// converts block number and level to `BloomIndex`
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fn bloom_index(&self, block_number: usize, level: u8) -> BloomIndex {
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BloomIndex {
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level: level,
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index: block_number / self.level_size(level),
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}
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}
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/// return bloom which are dependencies for given index
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///
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/// bloom indexes are ordered from lowest to highest
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fn lower_level_bloom_indexes(&self, index: &BloomIndex) -> Vec<BloomIndex> {
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// this is the lowest level
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if index.level == 0 {
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return vec![];
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}
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let new_level = index.level - 1;
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let offset = self.index_size * index.index;
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(0..self.index_size).map(|i| BloomIndex::new(new_level, offset + i)).collect()
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}
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/// return number of levels
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fn levels(&self) -> u8 {
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self.level_sizes.len() as u8
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}
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/// returns max filter level
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fn max_level(&self) -> u8 {
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self.level_sizes.len() as u8 - 1
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}
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/// internal function which does bloom search recursively
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fn blocks(&self, bloom: &H2048, from_block: usize, to_block: usize, level: u8, offset: usize) -> Option<Vec<usize>> {
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let index = self.bloom_index(offset, level);
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match self.data_source.bloom_at_index(&index) {
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None => return None,
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Some(level_bloom) => match level {
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// if we are on the lowest level
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// take the value, exclude to_block
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0 if offset < to_block => return Some(vec![offset]),
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// return None if it is is equal to to_block
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0 => return None,
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// return None if current level doesnt contain given bloom
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_ if !level_bloom.contains(bloom) => return None,
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// continue processing && go down
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_ => ()
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}
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};
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let level_size = self.level_size(level - 1);
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let from_index = self.bloom_index(from_block, level - 1);
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let to_index = self.bloom_index(to_block, level - 1);
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let res: Vec<usize> = self.lower_level_bloom_indexes(&index).into_iter()
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// chose only blooms in range
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.filter(|li| li.index >= from_index.index && li.index <= to_index.index)
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// map them to offsets
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.map(|li| li.index * level_size)
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// get all blocks that may contain our bloom
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.map(|off| self.blocks(bloom, from_block, to_block, level - 1, off))
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// filter existing ones
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.filter_map(|x| x)
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// flatten nested structures
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.flat_map(|v| v)
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.collect();
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Some(res)
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}
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/// Adds new bloom to all filter levels
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pub fn add_bloom(&self, bloom: &H2048, block_number: usize) -> HashMap<BloomIndex, H2048> {
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let mut result: HashMap<BloomIndex, H2048> = HashMap::new();
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for level in 0..self.levels() {
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let bloom_index = self.bloom_index(block_number, level);
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let new_bloom = match self.data_source.bloom_at_index(&bloom_index) {
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Some(old_bloom) => old_bloom | bloom,
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None => bloom.clone(),
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};
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result.insert(bloom_index, new_bloom);
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}
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result
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}
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/// Adds new blooms starting from block number.
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pub fn add_blooms(&self, blooms: &[H2048], block_number: usize) -> HashMap<BloomIndex, H2048> {
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let mut result: HashMap<BloomIndex, H2048> = HashMap::new();
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for level in 0..self.levels() {
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for i in 0..blooms.len() {
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let bloom_index = self.bloom_index(block_number + i, level);
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let is_new_bloom = match result.get_mut(&bloom_index) {
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// it was already modified
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Some(to_shift) => {
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*to_shift = &blooms[i] | to_shift;
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false
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}
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None => true,
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};
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// it hasn't been modified yet
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if is_new_bloom {
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let new_bloom = match self.data_source.bloom_at_index(&bloom_index) {
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Some(old_bloom) => old_bloom | &blooms[i],
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None => blooms[i].clone(),
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};
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result.insert(bloom_index, new_bloom);
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}
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}
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}
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result
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}
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/// Resets bloom at level 0 and forces rebuild on higher levels.
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pub fn reset_bloom(&self, bloom: &H2048, block_number: usize) -> HashMap<BloomIndex, H2048> {
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let mut result: HashMap<BloomIndex, H2048> = HashMap::new();
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let mut reset_index = self.bloom_index(block_number, 0);
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result.insert(reset_index.clone(), bloom.clone());
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for level in 1..self.levels() {
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let index = self.bloom_index(block_number, level);
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// get all bloom indexes that were used to construct this bloom
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let lower_indexes = self.lower_level_bloom_indexes(&index);
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let new_bloom = lower_indexes.into_iter()
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// skip reseted one
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.filter(|li| li != &reset_index)
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// get blooms for these indexes
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.map(|li| self.data_source.bloom_at_index(&li))
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// filter existing ones
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.filter_map(|b| b)
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// BitOr all of them
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.fold(H2048::new(), |acc, bloom| &acc | bloom);
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reset_index = index.clone();
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result.insert(index, &new_bloom | bloom);
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}
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result
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}
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/// Sets lowest level bloom to 0 and forces rebuild on higher levels.
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pub fn clear_bloom(&self, block_number: usize) -> HashMap<BloomIndex, H2048> {
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self.reset_bloom(&H2048::new(), block_number)
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}
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/// Returns numbers of blocks that may contain Address.
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pub fn blocks_with_address(&self, address: &Address, from_block: usize, to_block: usize) -> Vec<usize> {
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let mut bloom = H2048::new();
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bloom.shift_bloomed(&address.sha3());
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self.blocks_with_bloom(&bloom, from_block, to_block)
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}
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/// Returns numbers of blocks that may contain Topic.
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pub fn blocks_with_topic(&self, topic: &H256, from_block: usize, to_block: usize) -> Vec<usize> {
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let mut bloom = H2048::new();
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bloom.shift_bloomed(&topic.sha3());
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self.blocks_with_bloom(&bloom, from_block, to_block)
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}
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/// Returns numbers of blocks that may log bloom.
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pub fn blocks_with_bloom(&self, bloom: &H2048, from_block: usize, to_block: usize) -> Vec<usize> {
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let mut result = vec![];
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// lets start from highest level
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let max_level = self.max_level();
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let level_size = self.level_size(max_level);
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let from_index = self.bloom_index(from_block, max_level);
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let to_index = self.bloom_index(to_block, max_level);
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for index in from_index.index..to_index.index + 1 {
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// offset will be used to calculate where we are right now
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let offset = level_size * index;
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// go doooown!
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if let Some(blocks) = self.blocks(bloom, from_block, to_block, max_level, offset) {
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result.extend(blocks);
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}
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}
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result
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}
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}
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#[cfg(test)]
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mod tests {
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use hash::*;
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use chainfilter::*;
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use sha3::*;
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use std::str::FromStr;
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#[test]
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fn test_level_size() {
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let cache = MemoryCache::new();
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let filter = ChainFilter::new(&cache, 16, 3);
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assert_eq!(filter.level_size(0), 1);
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assert_eq!(filter.level_size(1), 16);
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assert_eq!(filter.level_size(2), 256);
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}
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#[test]
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fn test_bloom_index() {
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let cache = MemoryCache::new();
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let filter = ChainFilter::new(&cache, 16, 3);
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let bi0 = filter.bloom_index(0, 0);
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assert_eq!(bi0.level, 0);
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assert_eq!(bi0.index, 0);
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let bi1 = filter.bloom_index(1, 0);
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assert_eq!(bi1.level, 0);
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assert_eq!(bi1.index, 1);
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let bi2 = filter.bloom_index(2, 0);
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assert_eq!(bi2.level, 0);
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assert_eq!(bi2.index, 2);
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let bi3 = filter.bloom_index(3, 1);
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assert_eq!(bi3.level, 1);
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assert_eq!(bi3.index, 0);
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let bi4 = filter.bloom_index(15, 1);
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assert_eq!(bi4.level, 1);
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assert_eq!(bi4.index, 0);
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let bi5 = filter.bloom_index(16, 1);
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assert_eq!(bi5.level, 1);
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assert_eq!(bi5.index, 1);
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let bi6 = filter.bloom_index(255, 2);
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assert_eq!(bi6.level, 2);
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assert_eq!(bi6.index, 0);
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let bi7 = filter.bloom_index(256, 2);
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assert_eq!(bi7.level, 2);
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assert_eq!(bi7.index, 1);
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}
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#[test]
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fn test_lower_level_bloom_indexes() {
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let cache = MemoryCache::new();
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let filter = ChainFilter::new(&cache, 16, 3);
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let bi = filter.bloom_index(256, 2);
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assert_eq!(bi.level, 2);
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assert_eq!(bi.index, 1);
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let mut ebis = vec![];
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for i in 16..32 {
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ebis.push(BloomIndex::new(1, i));
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}
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let bis = filter.lower_level_bloom_indexes(&bi);
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assert_eq!(ebis, bis);
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}
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#[test]
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fn test_topic_basic_search() {
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let index_size = 16;
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let bloom_levels = 3;
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let mut cache = MemoryCache::new();
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let topic = H256::from_str("8d936b1bd3fc635710969ccfba471fb17d598d9d1971b538dd712e1e4b4f4dba").unwrap();
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let modified_blooms = {
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let filter = ChainFilter::new(&cache, index_size, bloom_levels);
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let block_number = 23;
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let mut bloom = H2048::new();
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bloom.shift_bloomed(&topic.sha3());
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filter.add_bloom(&bloom, block_number)
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};
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// number of modified blooms should always be equal number of levels
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assert_eq!(modified_blooms.len(), bloom_levels as usize);
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cache.insert_blooms(modified_blooms);
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{
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let filter = ChainFilter::new(&cache, index_size, bloom_levels);
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let blocks = filter.blocks_with_topic(&topic, 0, 100);
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assert_eq!(blocks.len(), 1);
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assert_eq!(blocks[0], 23);
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}
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{
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let filter = ChainFilter::new(&cache, index_size, bloom_levels);
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let blocks = filter.blocks_with_topic(&topic, 0, 23);
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assert_eq!(blocks.len(), 0);
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}
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{
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let filter = ChainFilter::new(&cache, index_size, bloom_levels);
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let blocks = filter.blocks_with_topic(&topic, 23, 24);
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assert_eq!(blocks.len(), 1);
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assert_eq!(blocks[0], 23);
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}
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{
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let filter = ChainFilter::new(&cache, index_size, bloom_levels);
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let blocks = filter.blocks_with_topic(&topic, 24, 100);
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assert_eq!(blocks.len(), 0);
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}
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}
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}
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