add dynamic library interface to enable testing

Add interface defining the methods for dynamic linking to enable
testing.

Change-Id: If4d090d3cedc019b426435a1f651191803bfc1a9
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/fs.cpp b/fs.cpp
new file mode 100644
index 0000000..0c20d83
--- /dev/null
+++ b/fs.cpp
@@ -0,0 +1,46 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "fs.hpp"
+
+#include <experimental/filesystem>
+#include <string>
+#include <vector>
+
+namespace blobs
+{
+namespace fs = std::experimental::filesystem;
+
+std::vector<std::string> getLibraryList(const std::string& path,
+                                        PathMatcher check)
+{
+    std::vector<std::string> output;
+
+    for (const auto& p : fs::recursive_directory_iterator(path))
+    {
+        auto ps = p.path().string();
+
+        if (check(ps))
+        {
+            output.push_back(ps);
+        }
+    }
+
+    /* Algorithm ends up being two-pass, but expectation is a list under 10. */
+    return output;
+}
+
+} // namespace blobs