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| 1 | +//! Bucket data structure |
| 2 | +//! |
| 3 | +//! A collection data structure that discriminates its unique items and place them into "buckets". |
| 4 | +//! |
| 5 | +//! The item must implement the [`Bucketable`] trait that defines how to create the discriminant |
| 6 | +//! from the item type. The data structure will internally contain any item into "buckets" or vectors |
| 7 | +//! of sized capacity `N` that regroup all the stored items with this specific discriminant. |
| 8 | +//! |
| 9 | +//! A practical example of this data structure is for storing `N` amount of IP discriminated by their subnets. |
| 10 | +//! You can store in each "buckets" corresponding to a `/16` subnet up to `N` IPs of that subnet. |
| 11 | +//! |
| 12 | +//! # Example |
| 13 | +//! |
| 14 | +//! ``` |
| 15 | +//! use cuprate_p2p_bucket::Bucket; |
| 16 | +//! use std::net::Ipv4Addr; |
| 17 | +//! |
| 18 | +//! // Create a new bucket that can store at most 2 IPs in a particular `/16` subnet. |
| 19 | +//! let mut bucket = Bucket::<2,Ipv4Addr>::new(); |
| 20 | +//! |
| 21 | +//! // Fulfill the `96.96.0.0/16` bucket. |
| 22 | +//! bucket.push("96.96.0.1".parse().unwrap()); |
| 23 | +//! bucket.push("96.96.0.2".parse().unwrap()); |
| 24 | +//! assert_eq!(2, bucket.len()); |
| 25 | +//! assert_eq!(2, bucket.len_bucket(&[96_u8,96_u8]).unwrap()); |
| 26 | +//! |
| 27 | +//! // Push a new IP from another subnet |
| 28 | +//! bucket.push("127.0.0.1".parse().unwrap()); |
| 29 | +//! assert_eq!(3, bucket.len()); |
| 30 | +//! assert_eq!(2, bucket.len_bucket(&[96_u8,96_u8]).unwrap()); |
| 31 | +//! assert_eq!(1, bucket.len_bucket(&[127_u8,0_u8]).unwrap()); |
| 32 | +//! |
| 33 | +//! // Attempting to push a new IP within `96.96.0.0/16` bucket will return the IP back |
| 34 | +//! // as this subnet is already full. |
| 35 | +//! let pushed = bucket.push("96.96.0.3".parse().unwrap()); |
| 36 | +//! assert!(pushed.is_some()); |
| 37 | +//! assert_eq!(2, bucket.len_bucket(&[96_u8,96_u8]).unwrap()); |
| 38 | +//! |
| 39 | +//! ``` |
| 40 | +
|
| 41 | +use arrayvec::{ArrayVec, CapacityError}; |
| 42 | +use rand::random; |
| 43 | + |
| 44 | +use std::{collections::BTreeMap, net::Ipv4Addr}; |
| 45 | + |
| 46 | +/// A discriminant that can be computed from the type. |
| 47 | +pub trait Bucketable: Sized + Eq + Clone { |
| 48 | + /// The type of the discriminant being used in the Binary tree. |
| 49 | + type Discriminant: Ord + AsRef<[u8]>; |
| 50 | + |
| 51 | + /// Method that can compute the discriminant from the item. |
| 52 | + fn discriminant(&self) -> Self::Discriminant; |
| 53 | +} |
| 54 | + |
| 55 | +/// A collection data structure discriminating its unique items |
| 56 | +/// with a specified method. Limiting the amount of items stored |
| 57 | +/// with that discriminant to the const `N`. |
| 58 | +pub struct Bucket<const N: usize, I: Bucketable> { |
| 59 | + /// The storage of the bucket |
| 60 | + storage: BTreeMap<I::Discriminant, ArrayVec<I, N>>, |
| 61 | +} |
| 62 | + |
| 63 | +impl<const N: usize, I: Bucketable> Bucket<N, I> { |
| 64 | + /// Create a new Bucket |
| 65 | + pub const fn new() -> Self { |
| 66 | + Self { |
| 67 | + storage: BTreeMap::new(), |
| 68 | + } |
| 69 | + } |
| 70 | + |
| 71 | + /// Push a new element into the Bucket |
| 72 | + /// |
| 73 | + /// Will internally create a new vector for each new discriminant being |
| 74 | + /// generated from an item. |
| 75 | + /// |
| 76 | + /// This function WILL NOT push the element if it already exists. |
| 77 | + /// |
| 78 | + /// Return `None` if the item has been pushed or ignored. `Some(I)` if |
| 79 | + /// the vector is full. |
| 80 | + /// |
| 81 | + /// # Example |
| 82 | + /// |
| 83 | + /// ``` |
| 84 | + /// use cuprate_p2p_bucket::Bucket; |
| 85 | + /// use std::net::Ipv4Addr; |
| 86 | + /// |
| 87 | + /// let mut bucket = Bucket::<8,Ipv4Addr>::new(); |
| 88 | + /// |
| 89 | + /// // Push a first IP address. |
| 90 | + /// bucket.push("127.0.0.1".parse().unwrap()); |
| 91 | + /// assert_eq!(1, bucket.len()); |
| 92 | + /// |
| 93 | + /// // Push the same IP address a second time. |
| 94 | + /// bucket.push("127.0.0.1".parse().unwrap()); |
| 95 | + /// assert_eq!(1, bucket.len()); |
| 96 | + /// ``` |
| 97 | + pub fn push(&mut self, item: I) -> Option<I> { |
| 98 | + let discriminant = item.discriminant(); |
| 99 | + |
| 100 | + if let Some(vec) = self.storage.get_mut(&discriminant) { |
| 101 | + // Push the item if it doesn't exist. |
| 102 | + if !vec.contains(&item) { |
| 103 | + return vec.try_push(item).err().map(CapacityError::element); |
| 104 | + } |
| 105 | + } else { |
| 106 | + // Initialize the vector if not found. |
| 107 | + let mut vec = ArrayVec::<I, N>::new(); |
| 108 | + vec.push(item); |
| 109 | + self.storage.insert(discriminant, vec); |
| 110 | + } |
| 111 | + |
| 112 | + None |
| 113 | + } |
| 114 | + |
| 115 | + /// Will attempt to remove an item from the bucket. |
| 116 | + pub fn remove(&mut self, item: &I) -> Option<I> { |
| 117 | + self.storage.get_mut(&item.discriminant()).and_then(|vec| { |
| 118 | + vec.iter() |
| 119 | + .enumerate() |
| 120 | + .find_map(|(i, v)| (item == v).then_some(i)) |
| 121 | + .map(|index| vec.swap_remove(index)) |
| 122 | + }) |
| 123 | + } |
| 124 | + |
| 125 | + /// Return the number of item stored within the storage |
| 126 | + pub fn len(&self) -> usize { |
| 127 | + self.storage.values().map(ArrayVec::len).sum() |
| 128 | + } |
| 129 | + |
| 130 | + /// Return the number of item stored with a specific discriminant. |
| 131 | + /// |
| 132 | + /// This method returns None if the bucket with this discriminant |
| 133 | + /// doesn't exist. |
| 134 | + pub fn len_bucket(&self, discriminant: &I::Discriminant) -> Option<usize> { |
| 135 | + self.storage.get(discriminant).map(ArrayVec::len) |
| 136 | + } |
| 137 | + |
| 138 | + /// Return `true` if the storage contains no items |
| 139 | + pub fn is_empty(&self) -> bool { |
| 140 | + self.len() == 0 |
| 141 | + } |
| 142 | + |
| 143 | + /// Return a reference to an item chosen at random. |
| 144 | + /// |
| 145 | + /// Repeated use of this function will provide a normal distribution of |
| 146 | + /// items based on their discriminants. |
| 147 | + pub fn get_random(&mut self) -> Option<&I> { |
| 148 | + // Get the total amount of discriminants to explore. |
| 149 | + let len = self.storage.len(); |
| 150 | + |
| 151 | + // Get a random bucket. |
| 152 | + let (_, vec) = self.storage.iter().nth(random::<usize>() / len).unwrap(); |
| 153 | + |
| 154 | + // Return a reference chose at random. |
| 155 | + vec.get(random::<usize>() / vec.len()) |
| 156 | + } |
| 157 | +} |
| 158 | + |
| 159 | +impl<const N: usize, I: Bucketable> Default for Bucket<N, I> { |
| 160 | + fn default() -> Self { |
| 161 | + Self::new() |
| 162 | + } |
| 163 | +} |
| 164 | + |
| 165 | +impl Bucketable for Ipv4Addr { |
| 166 | + /// We are discriminating by `/16` subnets. |
| 167 | + type Discriminant = [u8; 2]; |
| 168 | + |
| 169 | + fn discriminant(&self) -> Self::Discriminant { |
| 170 | + [self.octets()[0], self.octets()[1]] |
| 171 | + } |
| 172 | +} |
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