From ffd00e1affd87457154661812a3721cd12b0a791 Mon Sep 17 00:00:00 2001
From: Shivaram Lingamneni <slingamn@cs.stanford.edu>
Date: Fri, 17 Jul 2020 04:53:30 -0400
Subject: [PATCH] minor optimization to Client.Friends

---
 irc/client.go | 27 +++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/irc/client.go b/irc/client.go
index 59dbc036..dcdf905a 100644
--- a/irc/client.go
+++ b/irc/client.go
@@ -1054,29 +1054,32 @@ func (client *Client) ModeString() (str string) {
 }
 
 // Friends refers to clients that share a channel with this client.
-func (client *Client) Friends(capabs ...caps.Capability) (result map[*Session]bool) {
-	result = make(map[*Session]bool)
+func (client *Client) Friends(capabs ...caps.Capability) (result map[*Session]empty) {
+	result = make(map[*Session]empty)
 
 	// look at the client's own sessions
-	for _, session := range client.Sessions() {
-		if session.capabilities.HasAll(capabs...) {
-			result[session] = true
-		}
-	}
+	addFriendsToSet(result, client, capabs...)
 
 	for _, channel := range client.Channels() {
 		for _, member := range channel.Members() {
-			for _, session := range member.Sessions() {
-				if session.capabilities.HasAll(capabs...) {
-					result[session] = true
-				}
-			}
+			addFriendsToSet(result, member, capabs...)
 		}
 	}
 
 	return
 }
 
+// helper for Friends
+func addFriendsToSet(set map[*Session]empty, client *Client, capabs ...caps.Capability) {
+	client.stateMutex.RLock()
+	defer client.stateMutex.RUnlock()
+	for _, session := range client.sessions {
+		if session.capabilities.HasAll(capabs...) {
+			set[session] = empty{}
+		}
+	}
+}
+
 func (client *Client) SetOper(oper *Oper) {
 	client.stateMutex.Lock()
 	defer client.stateMutex.Unlock()