diff --git a/source/oar.cpp b/source/oar.cpp
new file mode 100644
index 0000000..dacae13
--- /dev/null
+++ b/source/oar.cpp
@@ -0,0 +1,44 @@
+export module oar;
+
+import core;
+import core.files;
+
+export namespace oar {
+	constexpr core::usize signature_length{4};
+
+	constexpr core::u8 signature_magic[signature_length]{'o', 'a', 'r', 0};
+
+	struct entry {
+		core::u8 signature_magic[signature_length];
+
+		core::path path;
+
+		core::u64 data_offset;
+
+		core::u64 data_length;
+
+		core::u8 padding[244];
+	};
+
+	struct archive : public core::fs {
+		using core::fs::access_result;
+
+		archive() {
+
+		}
+
+		access_result read_file(core::path const & file_path,
+			core::callable<void(core::readable const &)> const & then) override {
+
+			return access_result::access_denied;
+		}
+
+		virtual access_result write_file(core::path const & file_path,
+			core::callable<void(core::writable const &)> const & then) override {
+
+			return access_result::access_denied;
+		}
+	};
+}
+
+static_assert(sizeof(oar::entry) == 512);