From 8b460bc60f91860f9a78e571b55cc7df557e40e7 Mon Sep 17 00:00:00 2001
From: Kobe Housen <kobehousen@google.com>
Date: Fri, 10 Nov 2023 15:55:58 +0000
Subject: [PATCH] Use make size hint when copying channels in Nick()

70% faster when using a high number of channels

Old performance

```
$ go test ./state -bench=.
goos: linux
goarch: amd64
pkg: github.com/fluffle/goirc/state
cpu: AMD Ryzen Threadripper PRO 3945WX 12-Cores
BenchmarkNickSingleChan-24      15465226                76.35 ns/op
BenchmarkNickManyChan-24            5738            195721 ns/op
PASS
ok      github.com/fluffle/goirc/state  2.433s
```

new performance

```
$ go test ./state -bench=.
goos: linux
goarch: amd64
pkg: github.com/fluffle/goirc/state
cpu: AMD Ryzen Threadripper PRO 3945WX 12-Cores
BenchmarkNickSingleChan-24      15022640                79.13 ns/op
BenchmarkNickManyChan-24           10000            115104 ns/op
PASS
ok      github.com/fluffle/goirc/state  2.456s
```
---
 state/nick.go      |  4 +++-
 state/nick_test.go | 32 +++++++++++++++++++++++++++++++-
 2 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/state/nick.go b/state/nick.go
index b29d98a..24a03bd 100644
--- a/state/nick.go
+++ b/state/nick.go
@@ -71,7 +71,7 @@ func (nk *nick) Nick() *Nick {
 		Host:     nk.host,
 		Name:     nk.name,
 		Modes:    nk.modes.Copy(),
-		Channels: make(map[string]*ChanPrivs),
+		Channels: make(map[string]*ChanPrivs, len(nk.chans)),
 	}
 	for c, cp := range nk.chans {
 		n.Channels[c.name] = cp.Copy()
@@ -157,6 +157,7 @@ func (nm *NickMode) Equals(other *NickMode) bool {
 }
 
 // Returns a string representing the nick. Looks like:
+//
 //	Nick: <nick name> e.g. CowMaster
 //	Hostmask: <ident@host> e.g. moo@cows.org
 //	Real Name: <real name> e.g. Steve "CowMaster" Bush
@@ -181,6 +182,7 @@ func (nk *nick) String() string {
 }
 
 // Returns a string representing the nick modes. Looks like:
+//
 //	+iwx
 func (nm *NickMode) String() string {
 	if nm == nil {
diff --git a/state/nick_test.go b/state/nick_test.go
index 1344400..717c8a0 100644
--- a/state/nick_test.go
+++ b/state/nick_test.go
@@ -1,6 +1,9 @@
 package state
 
-import "testing"
+import (
+	"fmt"
+	"testing"
+)
 
 func compareNick(t *testing.T, nk *nick) {
 	n := nk.Nick()
@@ -86,3 +89,30 @@ func TestNickParseModes(t *testing.T) {
 		t.Errorf("Modes not flipped correctly by ParseModes.")
 	}
 }
+
+func BenchmarkNickSingleChan(b *testing.B) {
+	nk := newNick("test1")
+	ch := newChannel("#test1")
+	cp := new(ChanPrivs)
+	nk.addChannel(ch, cp)
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		nk.Nick()
+	}
+}
+
+func BenchmarkNickManyChan(b *testing.B) {
+	const numChans = 1000
+	nk := newNick("test1")
+	for i := 0; i < numChans; i++ {
+		ch := newChannel(fmt.Sprintf("#test%d", i))
+		cp := new(ChanPrivs)
+		nk.addChannel(ch, cp)
+	}
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		nk.Nick()
+	}
+}