--- a/src/types.rs	Sat Jun 11 12:24:09 2016 +0200
+++ b/src/types.rs	Sat Jun 11 12:24:19 2016 +0200
@@ -1,9 +1,12 @@
+use std::default::Default;
+use std::collections::LinkedList;
 
 pub enum ValueType {
     TypeDeletion = 0,
     TypeValue = 1,
 }
 
+/// Represents a snapshot or the sequence number of a single entry.
 pub type SequenceNumber = u64;
 
 #[allow(dead_code)]
@@ -16,8 +19,68 @@
     IOError(String),
 }
 
+/// An extension of the standard `Iterator` trait that supports some methods necessary for LevelDB.
+/// This works because the iterators used are stateful and keep the last returned element.
 pub trait LdbIterator<'a>: Iterator {
     fn seek(&mut self, key: &Vec<u8>);
     fn valid(&self) -> bool;
     fn current(&'a self) -> Self::Item;
 }
+
+/// Supplied to DB read operations.
+pub struct ReadOptions {
+    pub verify_checksums: bool,
+    pub fill_cache: bool,
+    pub snapshot: Option<SequenceNumber>,
+}
+
+impl Default for ReadOptions {
+    fn default() -> Self {
+        ReadOptions {
+            verify_checksums: false,
+            fill_cache: true,
+            snapshot: None,
+        }
+    }
+}
+
+/// A list of all snapshots is kept in the DB.
+pub struct SnapshotList {
+    snapshots: LinkedList<SequenceNumber>,
+}
+
+impl SnapshotList {
+    pub fn new() -> SnapshotList {
+        SnapshotList { snapshots: LinkedList::new() }
+    }
+
+    pub fn new_snapshot(&mut self, seq: SequenceNumber) {
+        self.snapshots.push_back(seq);
+    }
+
+    pub fn oldest(&self) -> SequenceNumber {
+        assert!(!self.snapshots.is_empty());
+        self.snapshots.front().map(|s| *s).unwrap()
+    }
+
+    pub fn newest(&self) -> SequenceNumber {
+        assert!(!self.snapshots.is_empty());
+        self.snapshots.back().map(|s| *s).unwrap()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_snapshot_list() {
+        let mut l = SnapshotList::new();
+
+        l.new_snapshot(1);
+        l.new_snapshot(2);
+
+        assert_eq!(l.oldest(), 1);
+        assert_eq!(l.newest(), 2);
+    }
+}