[performance] http response encoding / writing improvements (#2374)

internal/api/wellknown/hostmeta/hostmetaget.go

@@ -18,8 +18,6 @@
 package hostmeta
 
 import (
-	"bytes"
-	"encoding/xml"
 	"net/http"
 
 	"github.com/gin-gonic/gin"
@@ -52,21 +50,12 @@ func (m *Module) HostMetaGETHandler(c *gin.Context) {
 
 	hostMeta := m.processor.Fedi().HostMetaGet()
 
-	// this setup with a separate buffer we encode into is used because
-	// xml.Marshal does not emit xml.Header by itself
-	var buf bytes.Buffer
-
-	// Preallocate buffer of reasonable length.
-	buf.Grow(len(xml.Header) + 64)
-
-	// No need to check for error on write to buffer.
-	_, _ = buf.WriteString(xml.Header)
-
-	// Encode host-meta as XML to in-memory buffer.
-	if err := xml.NewEncoder(&buf).Encode(hostMeta); err != nil {
-		apiutil.ErrorHandler(c, gtserror.NewErrorInternalError(err), m.processor.InstanceGetV1)
-		return
-	}
-
-	c.Data(http.StatusOK, HostMetaContentType, buf.Bytes())
+	// Encode XML HTTP response.
+	apiutil.EncodeXMLResponse(
+		c.Writer,
+		c.Request,
+		http.StatusOK,
+		HostMetaContentType,
+		hostMeta,
+	)
 }