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Implements P2P Bucket data structure
This commit implements a "Bucket" data structure that is a collection of data that discriminates its items into "buckets" (vector of size N) following a defined function. - Implements Bucket data structure and Bucketable trait - Implements Bucketable for Ipv4Addr - Added the crate to the workspace dependencies - Added arrayvec as a dependency
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| [package] | ||
| name = "cuprate-p2p-bucket" | ||
| version = "0.1.0" | ||
| edition = "2021" | ||
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| [dependencies] | ||
| arrayvec = { workspace = true } | ||
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| [lints] | ||
| workspace = true |
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| //! Bucket data structure | ||
| //! | ||
| //! A collection data structure that discriminates its unique items and place them into "buckets" | ||
| //! | ||
| //! The item must implement the [`Bucketable`] trait that defines how to create the discriminant | ||
| //! from the item type. The data structure will internally contain any item into "buckets" or vectors | ||
| //! of sized capacity N that regroup all the stored items with this specific discriminant. | ||
| //! | ||
| //! A practical example of this data structure is for storing N amount of IP discriminated by their subnets. | ||
| //! You can store in each "buckets" corresponding to a /16 subnet up to N IPs of that subnet. | ||
| //! | ||
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| use arrayvec::ArrayVec; | ||
| use std::{collections::BTreeMap, net::Ipv4Addr}; | ||
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| /// A discriminant can be compute from the type | ||
| pub trait Bucketable: Sized + Eq + Clone { | ||
| /// The type of the discriminant being used in the Binary tree. | ||
| type Discriminant: Ord + AsRef<[u8]>; | ||
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| /// Method that can compute the discriminant from the item. | ||
| fn discriminant(&self) -> Self::Discriminant; | ||
| } | ||
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| /// A collection data structure discriminating its unique items | ||
| /// with a specified method. Enable a fair distribution of the | ||
| /// items based on their discriminants when popped. | ||
| pub struct Bucket<const N: usize, I: Bucketable> { | ||
| /// The storage of the bucket | ||
| storage: BTreeMap<I::Discriminant, ArrayVec<I, N>>, | ||
| /// Internal round-robin state | ||
| round_robin: usize, | ||
| } | ||
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| impl<const N: usize, I: Bucketable> Bucket<N, I> { | ||
| /// Create a new Bucket | ||
| pub const fn new() -> Self { | ||
| Self { | ||
| storage: BTreeMap::new(), | ||
| round_robin: 0, | ||
| } | ||
| } | ||
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| /// Push a new element into the Bucket | ||
| /// | ||
| /// Will internally create a new vector for each new discriminant being | ||
| /// generated from an item. | ||
| /// | ||
| /// This function WILL NOT push the element if it already exists. | ||
| /// | ||
| pub fn push(&mut self, item: I) { | ||
| let discriminant = item.discriminant(); | ||
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| if let Some(vec) = self.storage.get_mut(&discriminant) { | ||
| // Check if the element already exists | ||
| let already_exist = vec.iter().any(|v| &item == v); | ||
| if !already_exist { | ||
| // Push the new element | ||
| vec.push(item); | ||
| } | ||
| } else { | ||
| // Initialize the vector if not found | ||
| let mut vec = ArrayVec::<I, N>::new(); | ||
| vec.push(item); | ||
| self.storage.insert(discriminant, vec); | ||
| } | ||
| } | ||
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| /// Will attempt to remove an item from the bucket | ||
| pub fn remove(&mut self, item: &I) -> Option<I> { | ||
| self.storage.get_mut(&item.discriminant()).and_then(|vec| { | ||
| let find = vec | ||
| .iter() | ||
| .enumerate() | ||
| .filter(|(_, v)| &item == v) | ||
| .map(|(i, _)| i) | ||
| .last(); | ||
| find.map(|index| vec.swap_remove(index)) | ||
| }) | ||
| } | ||
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| /// Will remove a new element from any bucket following a round-robin | ||
| /// pattern. | ||
| /// | ||
| /// Repeated use of this function will provide a fair distribution of | ||
| /// item based on their discriminants | ||
| pub fn pop(&mut self) -> Option<I> { | ||
| // Get the total amount of discriminants to explore | ||
| let len = self.storage.len(); | ||
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| // Loop over every bucket for an element. | ||
| for _ in 0..len { | ||
| let (_, vec) = self.storage.iter_mut().nth(self.round_robin / len).unwrap(); | ||
| self.round_robin = self.round_robin.wrapping_add(1); | ||
| if let Some(item) = vec.pop() { | ||
| return Some(item); | ||
| } | ||
| } | ||
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| None | ||
| } | ||
| } | ||
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| impl<const N: usize, I: Bucketable> Default for Bucket<N, I> { | ||
| fn default() -> Self { | ||
| Self::new() | ||
| } | ||
| } | ||
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| impl Bucketable for Ipv4Addr { | ||
| // We are discriminating by /16 subnets | ||
| type Discriminant = [u8; 2]; | ||
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| fn discriminant(&self) -> Self::Discriminant { | ||
| [self.octets()[0], self.octets()[1]] | ||
| } | ||
| } |