From de04e73e820061b17da26e309629198191099552 Mon Sep 17 00:00:00 2001
From: Dane Everitt <dane@daneeveritt.com>
Date: Sun, 23 Jan 2022 18:31:53 -0500
Subject: [PATCH] Reduce the size of the buffered reader to improve CPU
 performance

---
 system/utils.go      |  9 ++++++++-
 system/utils_test.go | 20 +++++++++++++++++++-
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/system/utils.go b/system/utils.go
index b6a2894..5dcf687 100644
--- a/system/utils.go
+++ b/system/utils.go
@@ -46,7 +46,14 @@ func MustInt(v string) int {
 // over the websocket. If a line exceeds that size, it is truncated and only that
 // amount is sent over.
 func ScanReader(r io.Reader, callback func(line []byte)) error {
-	br := bufio.NewReader(r)
+	// Based on benchmarking this seems to be the best size for the reader buffer
+	// to maintain fast enough workflows without hammering the CPU for allocations.
+	//
+	// Additionally, most games are outputting a high-frequency of smaller lines,
+	// rather than a bunch of massive lines. This allocation amount is the total
+	// number of bytes being output for each call to ReadLine() before it moves on
+	// to the next data pull.
+	br := bufio.NewReaderSize(r, 256)
 	// Avoid constantly re-allocating memory when we're flooding lines through this
 	// function by using the same buffer for the duration of the call and just truncating
 	// the value back to 0 every loop.
diff --git a/system/utils_test.go b/system/utils_test.go
index b05019f..1e4f9aa 100644
--- a/system/utils_test.go
+++ b/system/utils_test.go
@@ -1,13 +1,15 @@
 package system
 
 import (
+	"math/rand"
 	"strings"
 	"testing"
+	"time"
 
 	. "github.com/franela/goblin"
 )
 
-func TestScanReader(t *testing.T) {
+func Test_Utils(t *testing.T) {
 	g := Goblin(t)
 
 	g.Describe("ScanReader", func() {
@@ -39,3 +41,19 @@ func TestScanReader(t *testing.T) {
 		})
 	})
 }
+
+func Benchmark_ScanReader(b *testing.B) {
+	r := rand.New(rand.NewSource(time.Now().UnixNano()))
+	var str string
+	for i := 0; i < 10; i++ {
+		str += strings.Repeat("hello \rworld", r.Intn(2000)) + "\n"
+	}
+	reader := strings.NewReader(str)
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		_ = ScanReader(reader, func(line []byte) {
+			// no op
+		})
+	}
+}