From 24cdbcfe449ac192605ae9de5d54e5efcb648750 Mon Sep 17 00:00:00 2001
From: mzz2017 <mzz@tuta.io>
Date: Sun, 14 Aug 2022 23:36:01 +0800
Subject: [PATCH] optimize: remove regexp and use bytes.IndexByte to improve
 the performance

---
 pkg/common/scan.go | 29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

diff --git a/pkg/common/scan.go b/pkg/common/scan.go
index 64f10eb..02e7223 100644
--- a/pkg/common/scan.go
+++ b/pkg/common/scan.go
@@ -1,23 +1,34 @@
 package common
 
 import (
-	"regexp"
+	"bytes"
 )
 
-var newlineReg = regexp.MustCompile(`\r?\n|\r\n?`)
-
 // ScanLines scan lines but keep the suffix \r and \n
 func ScanLines(data []byte, atEOF bool) (advance int, token []byte, err error) {
 	if atEOF && len(data) == 0 {
 		return 0, nil, nil
 	}
-	if loc := newlineReg.FindIndex(data); len(loc) > 0 {
-		delimiterLen := 1
-		i := loc[0]
-		if i+1 < len(data) && data[i] == '\r' && data[i+1] == '\n' {
-			delimiterLen = 2
+	if i, j := bytes.IndexByte(data, '\r'), bytes.IndexByte(data, '\n'); i >= 0 || j >= 0 {
+		// case 1: TOKEN\r\nTOKEN
+		if i >= 0 && j >= 0 {
+			if i+1 == j {
+				return i + 2, data[:i+2], nil
+			}
+			if i < j {
+				// case 2: TOKEN\rTOKEN\nTOKEN
+				return i + 1, data[:i+1], nil
+			} else {
+				// case 3: TOKEN\nTOKEN\rTOKEN
+				return j + 1, data[:j+1], nil
+			}
+		} else if i >= 0 {
+			// case 4: TOKEN\rTOKEN
+			return i + 1, data[:i+1], nil
+		} else {
+			// case 5: TOKEN\nTOKEN
+			return j + 1, data[:j+1], nil
 		}
-		return i + delimiterLen, data[:i+delimiterLen], nil
 	}
 	// If we're at EOF, we have a final, non-terminated line. Return it.
 	if atEOF {