Add format support

src/format/mod.rs

@@ -0,0 +1,18 @@
+mod fixed;
+
+use crate::types::*;
+
+pub fn fmt_message(mes: &mut Vec<Message>, opt: FormatOptions) {
+    match opt {
+        FormatOptions::Fixed {
+            length,
+            keep_original,
+        } => {
+            let formatter = fixed::FixedFormatter::new(length, keep_original);
+            for message in mes.iter_mut() {
+                message.message = formatter.format(&message.message);
+            }
+        }
+        FormatOptions::None => {}
+    }
+}