rust-libp2p/protocols/floodsub/src/topic.rs

// Copyright 2018 Parity Technologies (UK) Ltd.
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use bs58;
use protobuf::Message;
use rpc_proto;

/// Represents the hash of a topic.
///
/// Instead of a using the topic as a whole, the API of floodsub uses a hash of the topic. You only
/// have to build the hash once, then use it everywhere.
#[derive(Debug, Clone, PartialEq, Eq, Hash)]
pub struct TopicHash {
    hash: String,
}

impl TopicHash {
    /// Builds a new `TopicHash` from the given hash.
    #[inline]
    pub fn from_raw(hash: String) -> TopicHash {
        TopicHash { hash: hash }
    }

    #[inline]
    pub fn into_string(self) -> String {
        self.hash
    }
}

/// Built topic.
#[derive(Debug, Clone)]
pub struct Topic {
    descriptor: rpc_proto::TopicDescriptor,
    hash: TopicHash,
}

impl Topic {
    /// Returns the hash of the topic.
    #[inline]
    pub fn hash(&self) -> &TopicHash {
        &self.hash
    }
}

/// Builder for a `TopicHash`.
#[derive(Debug, Clone)]
pub struct TopicBuilder {
    builder: rpc_proto::TopicDescriptor,
}

impl TopicBuilder {
    pub fn new<S>(name: S) -> TopicBuilder
    where
        S: Into<String>,
    {
        let mut builder = rpc_proto::TopicDescriptor::new();
        builder.set_name(name.into());

        TopicBuilder { builder: builder }
    }

    /// Turns the builder into an actual `Topic`.
    pub fn build(self) -> Topic {
        let bytes = self.builder
            .write_to_bytes()
            .expect("protobuf message is always valid");
        let hash = TopicHash {
            hash: bs58::encode(&bytes).into_string(),
        };
        Topic {
            descriptor: self.builder,
            hash: hash,
        }
    }
}