fix(perf): switch to string based operations.

* Remove regexp usage, and swith to `strings.ReplaceAll`.

Signed-off-by: Thibault Normand <me@zenithar.org>

Author: Zenithar

cjson/canonicaljson.go

@@ -6,15 +6,10 @@ import (
 	"errors"
 	"fmt"
 	"reflect"
-	"regexp"
 	"sort"
 	"strings"
 )
 
-var (
-	stringEscapeRE = regexp.MustCompile(`([\"\\])`)
-)
-
 /*
 encodeCanonicalString is a helper function to canonicalize the passed string
 according to the OLPC canonical JSON specification for strings (see
@@ -23,7 +18,12 @@ escaping backslashes ("\") and double quotes (") and wrapping the resulting
 string in double quotes (").
 */
 func encodeCanonicalString(s string) string {
-	return fmt.Sprintf("\"%s\"", stringEscapeRE.ReplaceAllString(s, "\\$1"))
+	// Escape backslashes
+	s = strings.ReplaceAll(s, "\\", "\\\\")
+	// Escape double quotes
+	s = strings.ReplaceAll(s, "\"", "\\\"")
+	// Wrap with double quotes
+	return fmt.Sprintf("\"%s\"", s)
 }
 
 /*