libbinder_ndk: remove NullableStrongBinder

Nullable types do not exist in Java. For most Java types, the type is
split into a nullable and non-nullable variant. This is because C++
types are more usually non-nullable, but everything in Java is
non-nullable. This does mean that some Java interfaces may have to have
'@Nullable' added to them in order to function as expected w/ the NDK.
It also means that some transactions will be allowed in Java which are
not allowed in C++. However, in Java, if a null is ignored, it will
just result in a NullPointerException and be delivered to the other
side. C++ does not have this same capacity (in Android), and so
instead, we distinguish nullability in the type system.

The basic layout is:
NDK layer - all objects are nullable if they are nullable in Java
NDK C++ wrapper - functions are provided for nullable and non-nullable
    variants
AIDL - @Nullable selects nullable wrapper if desired, but the default
    is to return an error to the remote process (like Java would throw
    NullPointerException).

Bug: 111445392
Test: android.binder.cts
Change-Id: I615420f735a45ef7869b9ee7e86ce21b844d84a2

4 files changed, 25 insertions, 29 deletions

diff --git a/libs/binder/ndk/include_ndk/android/binder_parcel.h b/libs/binder/ndk/include_ndk/android/binder_parcel.h
index 4ee1b67653..c6178984bc 100644
--- a/libs/binder/ndk/include_ndk/android/binder_parcel.h
+++ b/libs/binder/ndk/include_ndk/android/binder_parcel.h
@@ -297,12 +297,11 @@ typedef int8_t* (*AParcel_byteArrayAllocator)(void* arrayData, size_t length);
 binder_status_t AParcel_writeStrongBinder(AParcel* parcel, AIBinder* binder) __INTRODUCED_IN(29);
 
 /**
- * Reads an AIBinder from the next location in a non-null parcel. This will fail if the binder is
- * non-null. One strong ref-count of ownership is passed to the caller of this function.
+ * Reads an AIBinder from the next location in a non-null parcel. One strong ref-count of ownership
+ * is passed to the caller of this function.
  *
  * \param parcel the parcel to read from.
- * \param binder the out parameter for what is read from the parcel. This will not be null on
- * success.
+ * \param binder the out parameter for what is read from the parcel. This may be null.
  *
  * \return STATUS_OK on successful write.
  */
@@ -310,19 +309,6 @@ binder_status_t AParcel_readStrongBinder(const AParcel* parcel, AIBinder** binde
         __INTRODUCED_IN(29);
 
 /**
- * Reads an AIBinder from the next location in a non-null parcel. This may read a null. One strong
- * ref-count of ownership is passed to the caller of this function.
- *
- * \param parcel the parcel to read from.
- * \param binder the out parameter for what is read from the parcel. This may be null even on
- * success.
- *
- * \return STATUS_OK on successful write.
- */
-binder_status_t AParcel_readNullableStrongBinder(const AParcel* parcel, AIBinder** binder)
-        __INTRODUCED_IN(29);
-
-/**
  * Writes a file descriptor to the next location in a non-null parcel. This does not take ownership
  * of fd.
  *
diff --git a/libs/binder/ndk/include_ndk/android/binder_parcel_utils.h b/libs/binder/ndk/include_ndk/android/binder_parcel_utils.h
index 59c06ae610..657577ecbd 100644
--- a/libs/binder/ndk/include_ndk/android/binder_parcel_utils.h
+++ b/libs/binder/ndk/include_ndk/android/binder_parcel_utils.h
@@ -85,6 +85,28 @@ static inline void AParcel_stdVectorSetter(void* vectorData, size_t index, T val
 }
 
 /**
+ * Convenience method to write a strong binder but return an error if it is null.
+ */
+static inline binder_status_t AParcel_writeRequiredStrongBinder(AParcel* parcel, AIBinder* binder) {
+    if (binder == nullptr) {
+        return STATUS_UNEXPECTED_NULL;
+    }
+    return AParcel_writeStrongBinder(parcel, binder);
+}
+
+/**
+ * Convenience method to read a strong binder but return an error if it is null.
+ */
+static inline binder_status_t AParcel_readRequiredStrongBinder(const AParcel* parcel,
+                                                               AIBinder** binder) {
+    binder_status_t ret = AParcel_readStrongBinder(parcel, binder);
+    if (ret == STATUS_OK && *binder == nullptr) {
+        return STATUS_UNEXPECTED_NULL;
+    }
+    return ret;
+}
+
+/**
  * Allocates a std::string to length and returns the underlying buffer. For use with
  * AParcel_readString. See use below in AParcel_readString(const AParcel*, std::string*).
  */
diff --git a/libs/binder/ndk/libbinder_ndk.map.txt b/libs/binder/ndk/libbinder_ndk.map.txt
index 7a75942406..41df90bd64 100644
--- a/libs/binder/ndk/libbinder_ndk.map.txt
+++ b/libs/binder/ndk/libbinder_ndk.map.txt
@@ -39,7 +39,6 @@ LIBBINDER_NDK { # introduced=29
     AParcel_readInt32Array;
     AParcel_readInt64;
     AParcel_readInt64Array;
-    AParcel_readNullableStrongBinder;
     AParcel_readParcelFileDescriptor;
     AParcel_readStatusHeader;
     AParcel_readString;
diff --git a/libs/binder/ndk/parcel.cpp b/libs/binder/ndk/parcel.cpp
index 8e5b4776e3..53e50100a3 100644
--- a/libs/binder/ndk/parcel.cpp
+++ b/libs/binder/ndk/parcel.cpp
@@ -194,17 +194,6 @@ binder_status_t AParcel_writeStrongBinder(AParcel* parcel, AIBinder* binder) {
 }
 binder_status_t AParcel_readStrongBinder(const AParcel* parcel, AIBinder** binder) {
     sp<IBinder> readBinder = nullptr;
-    status_t status = parcel->get()->readStrongBinder(&readBinder);
-    if (status != STATUS_OK) {
-        return PruneStatusT(status);
-    }
-    sp<AIBinder> ret = ABpBinder::lookupOrCreateFromBinder(readBinder);
-    AIBinder_incStrong(ret.get());
-    *binder = ret.get();
-    return PruneStatusT(status);
-}
-binder_status_t AParcel_readNullableStrongBinder(const AParcel* parcel, AIBinder** binder) {
-    sp<IBinder> readBinder = nullptr;
     status_t status = parcel->get()->readNullableStrongBinder(&readBinder);
     if (status != STATUS_OK) {
         return PruneStatusT(status);