libp2p-kad 0.48.0

// Copyright 2019 Parity Technologies (UK) Ltd.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

mod memory;

use std::borrow::Cow;

pub use memory::{MemoryStore, MemoryStoreConfig};
use thiserror::Error;

use super::*;
use crate::K_VALUE;

/// The result of an operation on a `RecordStore`.
pub type Result<T> = std::result::Result<T, Error>;

/// The possible errors of a `RecordStore` operation.
#[derive(Error, Debug, Clone)]
pub enum Error {
    /// The store is at capacity w.r.t. the total number of stored records.
    #[error("the store cannot contain any more records")]
    MaxRecords,

    /// The store is at capacity w.r.t. the total number of stored provider records.
    #[error("the store cannot contain any more provider records")]
    MaxProvidedKeys,

    /// The store cannot store this value because it is too large.
    #[error("the value is too large to be stored")]
    ValueTooLarge,
}

/// Trait for types implementing a record store.
///
/// There are two types of records managed by a `RecordStore`:
///
///   1. Regular (value-)records. These records store an arbitrary value associated with a key which
///      is distributed to the closest nodes to the key in the Kademlia DHT as per the standard
///      Kademlia "push-model". These records are subject to re-replication and re-publication as
///      per the standard Kademlia protocol.
///
///   2. Provider records. These records associate the ID of a peer with a key who can supposedly
///      provide the associated value. These records are mere "pointers" to the data which may be
///      followed by contacting these providers to obtain the value. These records are specific to
///      the libp2p Kademlia specification and realise a "pull-model" for distributed content. Just
///      like a regular record, a provider record is distributed to the closest nodes to the key.
pub trait RecordStore {
    type RecordsIter<'a>: Iterator<Item = Cow<'a, Record>>
    where
        Self: 'a;
    type ProvidedIter<'a>: Iterator<Item = Cow<'a, ProviderRecord>>
    where
        Self: 'a;

    /// Gets a record from the store, given its key.
    fn get(&self, k: &Key) -> Option<Cow<'_, Record>>;

    /// Puts a record into the store.
    fn put(&mut self, r: Record) -> Result<()>;

    /// Removes the record with the given key from the store.
    fn remove(&mut self, k: &Key);

    /// Gets an iterator over all (value-) records currently stored.
    fn records(&self) -> Self::RecordsIter<'_>;

    /// Adds a provider record to the store.
    ///
    /// A record store only needs to store a number of provider records
    /// for a key corresponding to the replication factor and should
    /// store those records whose providers are closest to the key.
    fn add_provider(&mut self, record: ProviderRecord) -> Result<()>;

    /// Gets a copy of the stored provider records for the given key.
    fn providers(&self, key: &Key) -> Vec<ProviderRecord>;

    /// Gets an iterator over all stored provider records for which the
    /// node owning the store is itself the provider.
    fn provided(&self) -> Self::ProvidedIter<'_>;

    /// Removes a provider record from the store.
    fn remove_provider(&mut self, k: &Key, p: &PeerId);
}