new file mode 100644
--- /dev/null
+++ b/src/util/mod.rs
@@ -0,0 +1,50 @@
+//! Module containing a bunch of helper modules.
+
+pub mod bitstream;
+pub mod lzss;
+
+#[cfg(test)]
+use std::io;
+
+#[cfg(test)]
+pub struct SeekableSlice<'a> {
+    slice: &'a [u8],
+    cursor: usize,
+}
+
+#[cfg(test)]
+impl SeekableSlice<'_> {
+    pub fn new(slice: &[u8]) -> SeekableSlice {
+        SeekableSlice {
+            slice,
+            cursor: 0,
+        }
+    }
+}
+
+#[cfg(test)]
+impl io::Read for SeekableSlice<'_> {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        let length = (&self.slice[self.cursor..]).read(buf)?;
+        self.cursor += length;
+        Ok(length)
+    }
+}
+
+#[cfg(test)]
+impl io::Seek for SeekableSlice<'_> {
+    fn seek(&mut self, seek_from: io::SeekFrom) -> io::Result<u64> {
+        match seek_from {
+            io::SeekFrom::Start(offset) => {
+                self.cursor = offset as usize;
+            }
+            io::SeekFrom::End(offset) => {
+                self.cursor = (self.slice.len() as i64 + offset) as usize;
+            }
+            io::SeekFrom::Current(offset) => {
+                self.cursor = (self.cursor as i64 + offset) as usize;
+            }
+        }
+        Ok(self.cursor as u64)
+    }
+}