move hash_topic function to public utils

Cargo.toml

@@ -32,6 +32,7 @@ colmeia-hyperswarm-mdns = { git = "https://github.com/bltavares/colmeia.git", re
 libutp-rs = { git = "https://github.com/Frando/libutp-rs.git", branch = "feat/clone2", optional = true }
 async-trait = "0.1.53"
 async-compat = "0.2.1"
+blake2-rfc = "0.2.18"
 
 [dev-dependencies]
 env_logger = "0.8.3"

examples/hyperchat.rs

@@ -3,14 +3,14 @@ use async_std::io::{self, ReadExt, WriteExt};
 use async_std::stream::StreamExt;
 use async_std::sync::Mutex;
 use async_std::task::{self, JoinHandle};
-use blake2_rfc::blake2b::Blake2b;
 use clap::Parser;
 use futures::future::{select, Either};
-use std::convert::TryInto;
 use std::net::SocketAddr;
 use std::sync::Arc;
 
-use hyperswarm::{BootstrapNode, Config, DhtConfig, Hyperswarm, HyperswarmStream, TopicConfig};
+use hyperswarm::{
+    hash_topic, BootstrapNode, Config, DhtConfig, Hyperswarm, HyperswarmStream, TopicConfig,
+};
 
 const DISCOVERY_NS_BUF: &[u8] = b"hyperchat:v0";
 
@@ -80,7 +80,7 @@ async fn main() -> anyhow::Result<()> {
             let handle = swarm.handle();
             let config = TopicConfig::announce_and_lookup();
             for topic in join_opts.topics {
-                let hash = hash_topic(topic.as_bytes());
+                let hash = hash_topic(DISCOVERY_NS_BUF, topic.as_bytes());
                 handle.configure(hash, config.clone());
                 eprintln!("join topic \"{}\": {}", topic, hex::encode(hash));
             }
@@ -277,12 +277,6 @@ async fn connection_loop(
     }
 }
 
-pub fn hash_topic(key: &[u8]) -> [u8; 32] {
-    let mut hasher = Blake2b::with_key(32, key);
-    hasher.update(DISCOVERY_NS_BUF);
-    hasher.finalize().as_bytes().try_into().unwrap()
-}
-
 pub fn random_name() -> String {
     let bytes = rand::random::<[u8; 4]>();
     hex::encode(&bytes)

src/lib.rs

@@ -28,6 +28,7 @@ pub use discovery::dht::DhtConfig;
 pub use discovery::mdns::MdnsConfig;
 
 pub use hyperswarm_dht::{IdBytes, DEFAULT_BOOTSTRAP};
+pub use util::hash_topic;
 
 use transport::combined::CombinedStream;
 pub use transport::Connection;

src/util.rs

@@ -1,3 +1,5 @@
+use blake2_rfc::blake2b::Blake2b;
+use std::convert::TryInto;
 use std::io;
 use std::net::{SocketAddr, ToSocketAddrs};
 
@@ -7,3 +9,9 @@ pub fn to_socket_addr<A: ToSocketAddrs>(addr: A) -> io::Result<SocketAddr> {
         "Invalid socket address",
     ))
 }
+
+pub fn hash_topic(namespace: &[u8], topic: &[u8]) -> [u8; 32] {
+    let mut hasher = Blake2b::with_key(32, topic);
+    hasher.update(namespace);
+    hasher.finalize().as_bytes().try_into().unwrap()
+}