From 73b6c27a6b89fcbaf1895542222d5b50b66c6b7a Mon Sep 17 00:00:00 2001
From: Yifan Hong <elsk@google.com>
Date: Tue, 31 Oct 2017 17:32:15 -0700
Subject: [PATCH] Allow equality checking and hash for HIDL interface proxies.

IFoo.Proxy.equals() -> HidlSupport.equals() ->
IHwInterface.asBinder().equals() -> HwRemoteBinder.equals().
IFoo.Stub.equals() -> default Object.equals()

Notice that IHwInterface.asBinder() returns mRemote(of type
HwRemoteBinder) for proxies and itself (of type HwBinder) for stubs.
If IFoo.Stub.asBinder() had not return "this", its equals()
should also be overridden.

Bug: 68727931
Test: hidl_test_java

Change-Id: I916983d7bc739747145e2ebb6830226310fd4980
---
 core/java/android/os/HidlSupport.java    | 23 +++++++++++
 core/java/android/os/HwRemoteBinder.java |  5 +++
 core/jni/android_os_HwRemoteBinder.cpp   | 49 +++++++++++++++++++++++-
 3 files changed, 76 insertions(+), 1 deletion(-)

diff --git a/core/java/android/os/HidlSupport.java b/core/java/android/os/HidlSupport.java
index 7dec4d724f15c..3544ea1e03e34 100644
--- a/core/java/android/os/HidlSupport.java
+++ b/core/java/android/os/HidlSupport.java
@@ -156,4 +156,27 @@ public class HidlSupport {
         // Should not reach here.
         throw new UnsupportedOperationException();
     }
+
+    /**
+     * Test that two interfaces are equal. This is the Java equivalent to C++
+     * interfacesEqual function.
+     * This essentially calls .equals on the internal binder objects (via Binder()).
+     * - If both interfaces are proxies, asBinder() returns a {@link HwRemoteBinder}
+     *   object, and they are compared in {@link HwRemoteBinder#equals}.
+     * - If both interfaces are stubs, asBinder() returns the object itself. By default,
+     *   auto-generated IFoo.Stub does not override equals(), but an implementation can
+     *   optionally override it, and {@code interfacesEqual} will use it here.
+     */
+    public static boolean interfacesEqual(IHwInterface lft, Object rgt) {
+        if (lft == rgt) {
+            return true;
+        }
+        if (lft == null || rgt == null) {
+            return false;
+        }
+        if (!(rgt instanceof IHwInterface)) {
+            return false;
+        }
+        return Objects.equals(lft.asBinder(), ((IHwInterface) rgt).asBinder());
+    }
 }
diff --git a/core/java/android/os/HwRemoteBinder.java b/core/java/android/os/HwRemoteBinder.java
index 2f89ce6270bed..a07e42c720c5b 100644
--- a/core/java/android/os/HwRemoteBinder.java
+++ b/core/java/android/os/HwRemoteBinder.java
@@ -63,4 +63,9 @@ public class HwRemoteBinder implements IHwBinder {
     }
 
     private long mNativeContext;
+
+    @Override
+    public final native boolean equals(Object other);
+    @Override
+    public final native int hashCode();
 }
diff --git a/core/jni/android_os_HwRemoteBinder.cpp b/core/jni/android_os_HwRemoteBinder.cpp
index cf59a56a13dc0..ca5e1e45dcdc9 100644
--- a/core/jni/android_os_HwRemoteBinder.cpp
+++ b/core/jni/android_os_HwRemoteBinder.cpp
@@ -22,9 +22,13 @@
 
 #include "android_os_HwParcel.h"
 
-#include <nativehelper/JNIHelp.h>
+#include <android/hidl/base/1.0/IBase.h>
+#include <android/hidl/base/1.0/BpHwBase.h>
+#include <android/hidl/base/1.0/BnHwBase.h>
 #include <android_runtime/AndroidRuntime.h>
 #include <hidl/Status.h>
+#include <hidl/HidlTransportSupport.h>
+#include <nativehelper/JNIHelp.h>
 #include <nativehelper/ScopedUtfChars.h>
 #include <nativehelper/ScopedLocalRef.h>
 
@@ -413,6 +417,44 @@ static jboolean JHwRemoteBinder_unlinkToDeath(JNIEnv* env, jobject thiz,
     return res;
 }
 
+static sp<hidl::base::V1_0::IBase> toIBase(JNIEnv* env, jclass hwRemoteBinderClazz, jobject jbinder)
+{
+    if (jbinder == nullptr) {
+        return nullptr;
+    }
+    if (!env->IsInstanceOf(jbinder, hwRemoteBinderClazz)) {
+        return nullptr;
+    }
+    sp<JHwRemoteBinder> context = JHwRemoteBinder::GetNativeContext(env, jbinder);
+    sp<hardware::IBinder> cbinder = context->getBinder();
+    return hardware::fromBinder<hidl::base::V1_0::IBase, hidl::base::V1_0::BpHwBase,
+                                hidl::base::V1_0::BnHwBase>(cbinder);
+}
+
+// equals iff other is also a non-null android.os.HwRemoteBinder object
+// and getBinder() returns the same object.
+// In particular, if other is an android.os.HwBinder object (for stubs) then
+// it returns false.
+static jboolean JHwRemoteBinder_equals(JNIEnv* env, jobject thiz, jobject other)
+{
+    if (env->IsSameObject(thiz, other)) {
+        return true;
+    }
+    if (other == NULL) {
+        return false;
+    }
+
+    ScopedLocalRef<jclass> clazz(env, FindClassOrDie(env, CLASS_PATH));
+
+    return hardware::interfacesEqual(toIBase(env, clazz.get(), thiz), toIBase(env, clazz.get(), other));
+}
+
+static jint JHwRemoteBinder_hashCode(JNIEnv* env, jobject thiz) {
+    jlong longHash = reinterpret_cast<jlong>(
+            JHwRemoteBinder::GetNativeContext(env, thiz)->getBinder().get());
+    return static_cast<jint>(longHash ^ (longHash >> 32)); // See Long.hashCode()
+}
+
 static JNINativeMethod gMethods[] = {
     { "native_init", "()J", (void *)JHwRemoteBinder_native_init },
 
@@ -430,6 +472,11 @@ static JNINativeMethod gMethods[] = {
     {"unlinkToDeath",
         "(Landroid/os/IHwBinder$DeathRecipient;)Z",
         (void*)JHwRemoteBinder_unlinkToDeath},
+
+    {"equals", "(Ljava/lang/Object;)Z",
+        (void*)JHwRemoteBinder_equals},
+
+    {"hashCode", "()I", (void*)JHwRemoteBinder_hashCode},
 };
 
 namespace android {