caddyfile: Switch to strings.Builder for better performance

caddyconfig/caddyfile/formatter.go

@@ -17,6 +17,7 @@ package caddyfile
 import (
 	"bytes"
 	"io"
+	"strings"
 	"unicode"
 )
 
@@ -57,8 +58,8 @@ func Format(input []byte) []byte {
 
 		heredoc              heredocState // whether we're in a heredoc
 		heredocEscaped       bool         // whether heredoc is escaped
-		heredocMarker        []rune
-		heredocClosingMarker []rune
+		heredocMarker        strings.Builder
+		heredocClosingMarker strings.Builder
 
 		nesting int // indentation level
 	)
@@ -99,10 +100,10 @@ func Format(input []byte) []byte {
 
 		if heredoc == heredocOpening {
 			if ch == '\n' {
-				if len(heredocMarker) > 0 && heredocMarkerRegexp.MatchString(string(heredocMarker)) {
+				if heredocMarker.Len() > 0 && heredocMarkerRegexp.MatchString(heredocMarker.String()) {
 					heredoc = heredocOpened
 				} else {
-					heredocMarker = nil
+					heredocMarker.Reset()
 					heredoc = heredocClosed
 					nextLine()
 					continue
@@ -112,25 +113,23 @@ func Format(input []byte) []byte {
 			}
 			if unicode.IsSpace(ch) {
 				// a space means it's just a regular token and not a heredoc
-				heredocMarker = nil
+				heredocMarker.Reset()
 				heredoc = heredocClosed
 			} else {
-				heredocMarker = append(heredocMarker, ch)
+				heredocMarker.WriteRune(ch)
 				write(ch)
 				continue
 			}
 		}
 		// if we're in a heredoc, all characters are read&write as-is
 		if heredoc == heredocOpened {
 			write(ch)
-			heredocClosingMarker = append(heredocClosingMarker, ch)
-			if len(heredocClosingMarker) > len(heredocMarker) {
-				heredocClosingMarker = heredocClosingMarker[1:]
-			}
+			heredocClosingMarker.WriteRune(ch)
 			// check if we're done
-			if string(heredocClosingMarker) == string(heredocMarker) {
-				heredocMarker = nil
-				heredocClosingMarker = nil
+			if heredocClosingMarker.Len() >= heredocMarker.Len() &&
+				heredocClosingMarker.String()[heredocClosingMarker.Len()-heredocMarker.Len():] == heredocMarker.String() {
+				heredocMarker.Reset()
+				heredocClosingMarker.Reset()
 				heredoc = heredocClosed
 			}
 			continue