AssetManager2: Various fixes

- Use FileMaps to open Assets (prevents closing of ApkAssets underlying
zip)
- Implement OpenDir and List methods
- Fix issue where DynamicRefTable wasn't properly constructed

Test: make libandroidfw_tests
Change-Id: Ib21a84e1114d028120744aa3bc1c6eb9d9399fa8
diff --git a/libs/androidfw/Util.cpp b/libs/androidfw/Util.cpp
index 202bc8e..575cd18 100644
--- a/libs/androidfw/Util.cpp
+++ b/libs/androidfw/Util.cpp
@@ -41,5 +41,31 @@
   }
 }
 
+std::u16string Utf8ToUtf16(const StringPiece& utf8) {
+  ssize_t utf16_length =
+      utf8_to_utf16_length(reinterpret_cast<const uint8_t*>(utf8.data()), utf8.length());
+  if (utf16_length <= 0) {
+    return {};
+  }
+
+  std::u16string utf16;
+  utf16.resize(utf16_length);
+  utf8_to_utf16(reinterpret_cast<const uint8_t*>(utf8.data()), utf8.length(), &*utf16.begin(),
+                utf16_length + 1);
+  return utf16;
+}
+
+std::string Utf16ToUtf8(const StringPiece16& utf16) {
+  ssize_t utf8_length = utf16_to_utf8_length(utf16.data(), utf16.length());
+  if (utf8_length <= 0) {
+    return {};
+  }
+
+  std::string utf8;
+  utf8.resize(utf8_length);
+  utf16_to_utf8(utf16.data(), utf16.length(), &*utf8.begin(), utf8_length + 1);
+  return utf8;
+}
+
 } // namespace util
 } // namespace android