Change entry header. Expand api

storage_engine/src/index.rs

@@ -0,0 +1,68 @@
+use std::marker::PhantomData;
+use tokio::io::{AsyncReadExt, AsyncWriteExt, AsyncSeekExt, SeekFrom};
+use tokio::fs::{File, OpenOptions, DirBuilder};
+use std::path::Path;
+
+use std::collections::{BTreeMap};
+
+use bincode;
+use bincode::{Decode, Encode};
+use crate::binary_coding::{encode, decode, encode_sequence, decode_sequence};
+use tokio::fs;
+
+use crate::error::{Error, DecodeErrorKind};
+
+use std::mem::size_of;
+
+type Result<T> = std::result::Result<T, Error>;
+
+// Implements a persistant self-balancing Binary Search Tree. Nope.
+// We need fixed-size nodes. But we want to index Strings which are variable length.
+
+pub struct Index<K, V> {
+    file: File,
+    // None means index is asleep on disk.
+    in_memory: Option<BTreeMap<K, V>>,
+    header: IndexHeader,
+    key_type: PhantomData<K>,
+    value_type: PhantomData<V>,
+}
+
+pub struct IndexHeader {
+}
+
+impl <I, V>Index<I, V> {
+    pub async fn new(file_name: &str) -> Result<Index<I, V>> {
+        todo!()
+    }
+
+    pub async fn connect(file_name: &str) -> Result<Index<I, V>> {
+        todo!()
+    }
+
+    // Saves the in-memory index to disk and deallocates.
+    pub async fn sleep() -> Result<Index<I, V>> {
+        todo!()
+    }
+
+    // Loads the index into memory
+    pub async fn wake() -> Result<Index<I, V>> {
+        todo!()
+    }
+
+    pub async fn insert() -> Result<()>
+        where I: Encode, V: Encode
+    {
+        todo!()
+    }
+
+    pub async fn lookup(&mut self, k: I) -> Result<Option<V>> 
+        where I: Encode + Decode,
+    {
+        todo!()
+    }
+
+    pub async fn delete(&mut self, k: I) -> Result<Option<V>> {
+        todo!()
+    }
+}