trait.rs

use std::io::{Read, Write, Seek};

trait DataSink: Read + Write + Seek {}

trait Encoder<R: Read, W: Write> {
    fn read_record(&self, input: R) -> Result<Entry, ()>;
    fn write_record(&self, output: W, entry: &Entry) -> Result<(), ()>;
}

struct WAL<T: DataSink> {
  sink: T,
  encoder: Box<dyn Encoder>, // ???? encoder should have reference to data sink
}