core/: Add PeerId::try_from_multiaddr (#2551)

Cargo.toml

@@ -78,7 +78,7 @@ instant = "0.1.11" # Explicit dependency to be used in `wasm-bindgen` feature
 lazy_static = "1.2"
 
 libp2p-autonat = { version = "0.3.0", path = "protocols/autonat", optional = true }
-libp2p-core = { version = "0.32.0", path = "core",  default-features = false }
+libp2p-core = { version = "0.32.1", path = "core",  default-features = false }
 libp2p-dcutr = { version = "0.2.0", path = "protocols/dcutr",  optional = true }
 libp2p-floodsub = { version = "0.35.0", path = "protocols/floodsub", optional = true }
 libp2p-identify = { version = "0.35.0", path = "protocols/identify", optional = true }

core/CHANGELOG.md

@@ -1,3 +1,7 @@
+# 0.32.1 [unreleased]
+
+- Add `PeerId::try_from_multiaddr` to extract a `PeerId` from a `Multiaddr` that ends in `/p2p/<peer-id>`.
+
 # 0.32.0 [2022-02-22]
 
 - Remove `Network`. `libp2p-core` is from now on an auxiliary crate only. Users

core/Cargo.toml

@@ -3,7 +3,7 @@ name = "libp2p-core"
 edition = "2021"
 rust-version = "1.56.1"
 description = "Core traits and structs of libp2p"
-version = "0.32.0"
+version = "0.32.1"
 authors = ["Parity Technologies <admin@parity.io>"]
 license = "MIT"
 repository = "https://github.com/libp2p/rust-libp2p"

core/src/peer_id.rs

@@ -19,6 +19,7 @@
 // DEALINGS IN THE SOFTWARE.
 
 use crate::PublicKey;
+use multiaddr::{Multiaddr, Protocol};
 use multihash::{Code, Error, Multihash, MultihashDigest};
 use rand::Rng;
 use std::{convert::TryFrom, fmt, str::FromStr};
@@ -88,6 +89,17 @@ impl PeerId {
         }
     }
 
+    /// Tries to extract a [`PeerId`] from the given [`Multiaddr`].
+    ///
+    /// In case the given [`Multiaddr`] ends with `/p2p/<peer-id>`, this function
+    /// will return the encapsulated [`PeerId`], otherwise it will return `None`.
+    pub fn try_from_multiaddr(address: &Multiaddr) -> Option<PeerId> {
+        address.iter().last().map_or(None, |p| match p {
+            Protocol::P2p(hash) => PeerId::from_multihash(hash).ok(),
+            _ => None,
+        })
+    }
+
     /// Generates a random peer ID from a cryptographically secure PRNG.
     ///
     /// This is useful for randomly walking on a DHT, or for testing purposes.
@@ -271,4 +283,30 @@ mod tests {
             assert_eq!(peer_id, PeerId::from_bytes(&peer_id.to_bytes()).unwrap());
         }
     }
+
+    #[test]
+    fn extract_peer_id_from_multi_address() {
+        let address =
+            format!("/memory/1234/p2p/12D3KooWGQmdpzHXCqLno4mMxWXKNFQHASBeF99gTm2JR8Vu5Bdc")
+                .parse()
+                .unwrap();
+
+        let peer_id = PeerId::try_from_multiaddr(&address).unwrap();
+
+        assert_eq!(
+            peer_id,
+            "12D3KooWGQmdpzHXCqLno4mMxWXKNFQHASBeF99gTm2JR8Vu5Bdc"
+                .parse()
+                .unwrap()
+        );
+    }
+
+    #[test]
+    fn no_panic_on_extract_peer_id_from_multi_address_if_not_present() {
+        let address = format!("/memory/1234").parse().unwrap();
+
+        let maybe_empty = PeerId::try_from_multiaddr(&address);
+
+        assert!(maybe_empty.is_none());
+    }
 }