libbinder_ndk: way to convert AParcel to libbinder

Bye-bye relative includes. Hello fresh C <-> C++ APIs.

Side note here - look at all the code for orthogonality.

Bug: 162794619
Test: binder_parcel_fuzzer, libbinder_ndk_unit_test
Change-Id: Ia44213343eca53f08fb2d9ff96f8def084b8f600
diff --git a/libs/binder/ndk/libbinder.cpp b/libs/binder/ndk/libbinder.cpp
new file mode 100644
index 0000000..f94d81d
--- /dev/null
+++ b/libs/binder/ndk/libbinder.cpp
@@ -0,0 +1,43 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * 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 <android/binder_libbinder.h>
+
+#include "ibinder_internal.h"
+#include "parcel_internal.h"
+
+using ::android::IBinder;
+using ::android::Parcel;
+using ::android::sp;
+
+sp<IBinder> AIBinder_toPlatformBinder(AIBinder* binder) {
+    if (binder == nullptr) return nullptr;
+    return binder->getBinder();
+}
+
+AIBinder* AIBinder_fromPlatformBinder(const sp<IBinder>& binder) {
+    sp<AIBinder> ndkBinder = ABpBinder::lookupOrCreateFromBinder(binder);
+    AIBinder_incStrong(ndkBinder.get());
+    return ndkBinder.get();
+}
+
+Parcel* AParcel_viewPlatformParcel(AParcel* parcel) {
+    return parcel->get();
+}
+
+const Parcel* AParcel_viewPlatformParcel(const AParcel* parcel) {
+    return parcel->get();
+}