Add some client callbacks

callbacks.go

@@ -0,0 +1,12 @@
+package torrent
+
+import (
+	pp "github.com/anacrolix/torrent/peer_protocol"
+)
+
+// These are called synchronously, and do not pass ownership. The Client and other locks may still
+// be held. nil functions are not called.
+type Callbacks struct {
+	CompletedHandshake func(_ *PeerConn, infoHash InfoHash)
+	ReadMessage        func(*PeerConn, *pp.Message)
+}

client.go

@@ -860,6 +860,9 @@ func (cl *Client) connBtHandshake(c *PeerConn, ih *metainfo.Hash) (ret metainfo.
 	c.PeerExtensionBytes = res.PeerExtensionBits
 	c.PeerID = res.PeerID
 	c.completedHandshake = time.Now()
+	if cb := cl.config.Callbacks.CompletedHandshake; cb != nil {
+		cb(c, res.Hash)
+	}
 	return
 }
 

config.go

@@ -133,6 +133,8 @@ type ClientConfig struct {
 
 	DisableWebtorrent bool
 	DisableWebseeds   bool
+
+	Callbacks Callbacks
 }
 
 func (cfg *ClientConfig) SetListenAddr(addr string) *ClientConfig {

peerconn.go

@@ -1059,6 +1059,9 @@ func (c *PeerConn) mainReadLoop() (err error) {
 			defer cl.lock()
 			err = decoder.Decode(&msg)
 		}()
+		if cb := cl.config.Callbacks.ReadMessage; cb != nil && err == nil {
+			cb(c, &msg)
+		}
 		if t.closed.IsSet() || c.closed.IsSet() {
 			return nil
 		}