DirectIO is working! Also a bit more cleanup.

src/main.rs

@@ -11,6 +11,8 @@ use anyhow;
 const FB_SECTOR_SIZE: usize = 2048;
 const FB_NULL_VALUE: u8 = 0;
 
+const MAX_BUFFER_SIZE: usize = FB_SECTOR_SIZE * 16;
+
 fn main() -> anyhow::Result<()> {
     let mut recover_tool = Recover::new()?;
     recover_tool.run()?;