Include size of response body in media type header

CONFIGURATION.md

@@ -62,6 +62,11 @@ certbot certonly --config-dir /home/www/certs \
 Provide the path to the certificate file at `certs/live/$DOMAIN/fullchain.pem`
 and the private key file at `certs/live/$DOMAIN/privkey.pem` to twins.
 
+### DisableSize
+
+The size of the response body is included in the media type header by default.
+Set this option to `true` to disable this feature. 
+
 ### Path
 
 #### Resources

config.go

@@ -57,6 +57,8 @@ type serverConfig struct {
 
 	Hosts map[string]*hostConfig
 
+	DisableSize bool
+
 	hostname  string
 	port      int
 	fcgiPools map[string]gofast.ConnFactory

server_file.go

@@ -141,7 +141,12 @@ func serveFile(c net.Conn, request *url.URL, filePath string, listDir bool) {
 	buf := make([]byte, 261)
 	n, _ := file.Read(buf)
 
-	// Write header
+	// Write response header
+	size := int64(-1)
+	info, err := file.Stat()
+	if err == nil {
+		size = info.Size()
+	}
 	var mimeType string
 	if strings.HasSuffix(filePath, ".html") && strings.HasSuffix(filePath, ".htm") {
 		mimeType = "text/html; charset=utf-8"
@@ -156,7 +161,13 @@ func serveFile(c net.Conn, request *url.URL, filePath string, listDir bool) {
 	if mimeType == "" {
 		mimeType = "text/gemini; charset=utf-8"
 	}
-	writeHeader(c, statusSuccess, mimeType)
+	var meta string
+	if !config.DisableSize && size >= 0 {
+		meta = fmt.Sprintf("%s; size=%d", mimeType, size)
+	} else {
+		meta = mimeType
+	}
+	writeHeader(c, statusSuccess, meta)
 
 	// Write body
 	c.Write(buf[:n])