feat: more efficient regexp use in parser

pkg/message/parser/handler.go

@@ -22,7 +22,7 @@ import "regexp"
 type HandlerFunc func(*Part) error
 
 type handler struct {
-	typeRegExp, dispRegExp string
+	typeRegExp, dispRegExp *regexp.Regexp
 	fn                     HandlerFunc
 }
 
@@ -31,7 +31,7 @@ func (h *handler) matchPart(p *Part) bool {
 }
 
 func (h *handler) matchType(p *Part) bool {
-	if h.typeRegExp == "" {
+	if h.typeRegExp == nil {
 		return false
 	}
 
@@ -40,11 +40,11 @@ func (h *handler) matchType(p *Part) bool {
 		t = ""
 	}
 
-	return regexp.MustCompile(h.typeRegExp).MatchString(t)
+	return h.typeRegExp.MatchString(t)
 }
 
 func (h *handler) matchDisp(p *Part) bool {
-	if h.dispRegExp == "" {
+	if h.dispRegExp == nil {
 		return false
 	}
 
@@ -53,5 +53,5 @@ func (h *handler) matchDisp(p *Part) bool {
 		disp = ""
 	}
 
-	return regexp.MustCompile(h.dispRegExp).MatchString(disp)
+	return h.dispRegExp.MatchString(disp)
 }

pkg/message/parser/visitor.go

@@ -37,13 +37,13 @@ type Visit func(*Part) (interface{}, error)
 type VisitorRule func(*Part, Visit) (interface{}, error)
 
 type visitorRule struct {
-	re string
+	re *regexp.Regexp
 	fn VisitorRule
 }
 
 func (v *Visitor) RegisterRule(contentTypeRegex string, fn VisitorRule) *Visitor {
 	v.rules = append(v.rules, &visitorRule{
-		re: contentTypeRegex,
+		re: regexp.MustCompile(contentTypeRegex),
 		fn: fn,
 	})
 
@@ -69,7 +69,7 @@ func (v *Visitor) visit(p *Part) (interface{}, error) {
 
 func (v *Visitor) getRuleForContentType(contentType string) *visitorRule {
 	for _, rule := range v.rules {
-		if regexp.MustCompile(rule.re).MatchString(contentType) {
+		if rule.re.MatchString(contentType) {
 			return rule
 		}
 	}

pkg/message/parser/walker.go

@@ -17,6 +17,8 @@
 
 package parser
 
+import "regexp"
+
 type Walker struct {
 	root *Part
 
@@ -56,7 +58,7 @@ func (w *Walker) RegisterDefaultHandler(fn HandlerFunc) *Walker {
 
 func (w *Walker) RegisterContentTypeHandler(typeRegExp string, fn HandlerFunc) *Walker {
 	w.handlers = append(w.handlers, &handler{
-		typeRegExp: typeRegExp,
+		typeRegExp: regexp.MustCompile(typeRegExp),
 		fn:         fn,
 	})
 
@@ -65,7 +67,7 @@ func (w *Walker) RegisterContentTypeHandler(typeRegExp string, fn HandlerFunc) *
 
 func (w *Walker) RegisterContentDispositionHandler(dispRegExp string, fn HandlerFunc) *Walker {
 	w.handlers = append(w.handlers, &handler{
-		dispRegExp: dispRegExp,
+		dispRegExp: regexp.MustCompile(dispRegExp),
 		fn:         fn,
 	})
 
@@ -73,9 +75,9 @@ func (w *Walker) RegisterContentDispositionHandler(dispRegExp string, fn Handler
 }
 
 func (w *Walker) getHandlerFunc(p *Part) HandlerFunc {
-	for _, hdl := range w.handlers {
-		if hdl.matchPart(p) {
-			return hdl.fn
+	for _, handler := range w.handlers {
+		if handler.matchPart(p) {
+			return handler.fn
 		}
 	}