feat: work on version backend system

src/version/types.rs

@@ -0,0 +1,47 @@
+use std::io::{Read, Seek, SeekFrom};
+
+use tokio::io::{self, AsyncRead};
+
+#[derive(Debug)]
+pub struct VersionFile {
+  pub relative_filename: String,
+  pub permission: u32,
+}
+
+pub trait Skippable {
+  fn skip(&mut self, amount: u64);
+}
+impl<T> Skippable for T
+where
+  T: Seek,
+{
+  fn skip(&mut self, amount: u64) {
+    self.seek(SeekFrom::Start(amount)).unwrap();
+  }
+}
+
+pub trait MinimumFileObject: Read + Send + Skippable {}
+impl<T: Read + Send + Seek> MinimumFileObject for T {}
+
+// Intentionally not a generic, because of types in read_file
+pub struct ReadToAsyncRead {
+  pub inner: Box<(dyn Read + Send)>,
+}
+
+impl AsyncRead for ReadToAsyncRead {
+  fn poll_read(
+    mut self: std::pin::Pin<&mut Self>,
+    _cx: &mut std::task::Context<'_>,
+    buf: &mut tokio::io::ReadBuf<'_>,
+  ) -> std::task::Poll<io::Result<()>> {
+    let mut read_buf = [0u8; 8192];
+    let amount = self.inner.read(&mut read_buf).unwrap();
+    buf.put_slice(&read_buf[0..amount]);
+    std::task::Poll::Ready(Ok(()))
+  }
+}
+
+pub trait VersionBackend {
+  fn list_files(&mut self) -> Vec<VersionFile>;
+  fn reader(&mut self, file: &VersionFile) -> Option<Box<(dyn MinimumFileObject)>>;
+}