libbinder_ndk: Add C++ wrapper code.
This library wraps libbinder_ndk with types similar to those found in
libbinder. This makes implementations more familiar and reduces the
amount of auto-generated code that has to be repeated in AIDL.
In order to simplify the distribution of the this code, it is
header-only in the NDK headers. This allows NDK users to use AIDL
against the NDK with no additional dependencies.
Bug: 112664205
Test: atest android.binder.cts
Change-Id: I6e6ef646226d474d538639f740e340c4e37fa7f7
diff --git a/libs/binder/ndk/include_ndk/android/binder_auto_utils.h b/libs/binder/ndk/include_ndk/android/binder_auto_utils.h
new file mode 100644
index 0000000..11b1e8e
--- /dev/null
+++ b/libs/binder/ndk/include_ndk/android/binder_auto_utils.h
@@ -0,0 +1,234 @@
+/*
+ * Copyright (C) 2018 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.
+ */
+
+/**
+ * @addtogroup NdkBinder
+ * @{
+ */
+
+/**
+ * @file binder_auto_utils.h
+ * @brief These objects provide a more C++-like thin interface to the .
+ */
+
+#pragma once
+
+#include <android/binder_ibinder.h>
+#include <android/binder_parcel.h>
+#include <android/binder_status.h>
+
+#ifdef __cplusplus
+
+#include <cstddef>
+
+namespace android {
+
+/**
+ * Represents one strong pointer to an AIBinder object.
+ */
+class AutoAIBinder {
+public:
+ /**
+ * Takes ownership of one strong refcount of binder.
+ */
+ explicit AutoAIBinder(AIBinder* binder = nullptr) : mBinder(binder) {}
+
+ /**
+ * Convenience operator for implicitly constructing an AutoAIBinder from nullptr. This is not
+ * explicit because it is not taking ownership of anything.
+ */
+ AutoAIBinder(std::nullptr_t) : AutoAIBinder() {}
+
+ /**
+ * This will delete the underlying object if it exists. See operator=.
+ */
+ AutoAIBinder(const AutoAIBinder& other) { *this = other; }
+
+ /**
+ * This deletes the underlying object if it exists. See set.
+ */
+ ~AutoAIBinder() { set(nullptr); }
+
+ /**
+ * This takes ownership of a binder from another AIBinder object but it does not affect the
+ * ownership of that other object.
+ */
+ AutoAIBinder& operator=(const AutoAIBinder& other) {
+ AIBinder_incStrong(other.mBinder);
+ set(other.mBinder);
+ return *this;
+ }
+
+ /**
+ * Takes ownership of one strong refcount of binder
+ */
+ void set(AIBinder* binder) {
+ if (mBinder != nullptr) AIBinder_decStrong(mBinder);
+ mBinder = binder;
+ }
+
+ /**
+ * This returns the underlying binder object for transactions. If it is used to create another
+ * AutoAIBinder object, it should first be incremented.
+ */
+ AIBinder* get() const { return mBinder; }
+
+ /**
+ * This allows the value in this class to be set from beneath it. If you call this method and
+ * then change the value of T*, you must take ownership of the value you are replacing and add
+ * ownership to the object that is put in here.
+ *
+ * Recommended use is like this:
+ * AutoAIBinder a; // will be nullptr
+ * SomeInitFunction(a.getR()); // value is initialized with refcount
+ *
+ * Other usecases are discouraged.
+ *
+ */
+ AIBinder** getR() { return &mBinder; }
+
+private:
+ AIBinder* mBinder = nullptr;
+};
+
+/**
+ * This baseclass owns a single object, used to make various classes RAII.
+ */
+template <typename T, void (*Destroy)(T*)>
+class AutoA {
+public:
+ /**
+ * Takes ownership of t.
+ */
+ explicit AutoA(T* t = nullptr) : mT(t) {}
+
+ /**
+ * This deletes the underlying object if it exists. See set.
+ */
+ ~AutoA() { set(nullptr); }
+
+ /**
+ * Takes ownership of t.
+ */
+ void set(T* t) {
+ Destroy(mT);
+ mT = t;
+ }
+
+ /**
+ * This returns the underlying object to be modified but does not affect ownership.
+ */
+ T* get() { return mT; }
+
+ /**
+ * This returns the const underlying object but does not affect ownership.
+ */
+ const T* get() const { return mT; }
+
+ /**
+ * This allows the value in this class to be set from beneath it. If you call this method and
+ * then change the value of T*, you must take ownership of the value you are replacing and add
+ * ownership to the object that is put in here.
+ *
+ * Recommended use is like this:
+ * AutoA<T> a; // will be nullptr
+ * SomeInitFunction(a.getR()); // value is initialized with refcount
+ *
+ * Other usecases are discouraged.
+ *
+ */
+ T** getR() { return &mT; }
+
+ // copy-constructing, or move/copy assignment is disallowed
+ AutoA(const AutoA&) = delete;
+ AutoA& operator=(const AutoA&) = delete;
+ AutoA& operator=(AutoA&&) = delete;
+
+ // move-constructing is okay
+ AutoA(AutoA&&) = default;
+
+private:
+ T* mT;
+};
+
+/**
+ * Convenience wrapper. See AParcel.
+ */
+class AutoAParcel : public AutoA<AParcel, AParcel_delete> {
+public:
+ /**
+ * Takes ownership of a.
+ */
+ explicit AutoAParcel(AParcel* a = nullptr) : AutoA(a) {}
+ ~AutoAParcel() {}
+ AutoAParcel(AutoAParcel&&) = default;
+};
+
+/**
+ * Convenience wrapper. See AStatus.
+ */
+class AutoAStatus : public AutoA<AStatus, AStatus_delete> {
+public:
+ /**
+ * Takes ownership of a.
+ */
+ explicit AutoAStatus(AStatus* a = nullptr) : AutoA(a) {}
+ ~AutoAStatus() {}
+ AutoAStatus(AutoAStatus&&) = default;
+
+ /**
+ * See AStatus_isOk.
+ */
+ bool isOk() { return get() != nullptr && AStatus_isOk(get()); }
+};
+
+/**
+ * Convenience wrapper. See AIBinder_DeathRecipient.
+ */
+class AutoAIBinder_DeathRecipient
+ : public AutoA<AIBinder_DeathRecipient, AIBinder_DeathRecipient_delete> {
+public:
+ /**
+ * Takes ownership of a.
+ */
+ explicit AutoAIBinder_DeathRecipient(AIBinder_DeathRecipient* a = nullptr) : AutoA(a) {}
+ ~AutoAIBinder_DeathRecipient() {}
+ AutoAIBinder_DeathRecipient(AutoAIBinder_DeathRecipient&&) = default;
+};
+
+/**
+ * Convenience wrapper. See AIBinder_Weak.
+ */
+class AutoAIBinder_Weak : public AutoA<AIBinder_Weak, AIBinder_Weak_delete> {
+public:
+ /**
+ * Takes ownership of a.
+ */
+ explicit AutoAIBinder_Weak(AIBinder_Weak* a = nullptr) : AutoA(a) {}
+ ~AutoAIBinder_Weak() {}
+ AutoAIBinder_Weak(AutoAIBinder_Weak&&) = default;
+
+ /**
+ * See AIBinder_Weak_promote.
+ */
+ AutoAIBinder promote() { return AutoAIBinder(AIBinder_Weak_promote(get())); }
+};
+
+} // namespace android
+
+#endif // __cplusplus
+
+/** @} */