Adding rust wrapper lib for libfakeServiceManager

rust lib which setup libfakeservicemanager and sets it as default
is being added here. It uses c++ backend underneath.

Test: m libfakeservicemanager_rs
Test: atest fakeservicemanager_test
Bug: 296909761
Change-Id: Ia1e7ebe5174f05fb4f8673a2feaad9b1171eb60c
diff --git a/libs/fakeservicemanager/Android.bp b/libs/fakeservicemanager/Android.bp
index 96dcce1..3823393 100644
--- a/libs/fakeservicemanager/Android.bp
+++ b/libs/fakeservicemanager/Android.bp
@@ -17,6 +17,7 @@
     shared_libs: [
         "libbinder",
         "libutils",
+        "liblog",
     ],
     target: {
         darwin: {
@@ -40,3 +41,41 @@
     static_libs: ["libgmock"],
     local_include_dirs: ["include"],
 }
+
+rust_bindgen {
+    name: "libfakeservicemanager_bindgen",
+    crate_name: "fakeservicemanager_bindgen",
+    host_supported: true,
+    wrapper_src: "rust/wrappers/FakeServiceManagerWrapper.hpp",
+    source_stem: "bindings",
+    visibility: [":__subpackages__"],
+    bindgen_flags: [
+        "--allowlist-function",
+        "setupFakeServiceManager",
+        "--allowlist-function",
+        "clearFakeServiceManager",
+    ],
+    shared_libs: [
+        "libc++",
+        "libbinder",
+        "libfakeservicemanager",
+    ],
+}
+
+rust_library {
+    name: "libfakeservicemanager_rs",
+    crate_name: "fakeservicemanager_rs",
+    host_supported: true,
+    srcs: [
+        "rust/src/lib.rs",
+    ],
+    shared_libs: [
+        "libc++",
+        "libfakeservicemanager",
+    ],
+    rustlibs: [
+        "libfakeservicemanager_bindgen",
+    ],
+    lints: "none",
+    clippy_lints: "none",
+}
diff --git a/libs/fakeservicemanager/FakeServiceManager.cpp b/libs/fakeservicemanager/FakeServiceManager.cpp
index 80661c1..241c866 100644
--- a/libs/fakeservicemanager/FakeServiceManager.cpp
+++ b/libs/fakeservicemanager/FakeServiceManager.cpp
@@ -16,6 +16,10 @@
 
 #include "fakeservicemanager/FakeServiceManager.h"
 
+using android::sp;
+using android::FakeServiceManager;
+using android::setDefaultServiceManager;
+
 namespace android {
 
 FakeServiceManager::FakeServiceManager() {}
@@ -123,3 +127,24 @@
     mNameToService.clear();
 }
 }  // namespace android
+
+[[clang::no_destroy]] static sp<FakeServiceManager> gFakeServiceManager;
+[[clang::no_destroy]] static std::once_flag gSmOnce;
+
+extern "C" {
+
+// Setup FakeServiceManager to mock dependencies in test using this API for rust backend
+void setupFakeServiceManager() {
+    /* Create a FakeServiceManager instance and add required services */
+    std::call_once(gSmOnce, [&]() {
+        gFakeServiceManager = new FakeServiceManager();
+        android::setDefaultServiceManager(gFakeServiceManager);
+    });
+}
+
+// Clear existing services from Fake SM for rust backend
+void clearFakeServiceManager() {
+    LOG_ALWAYS_FATAL_IF(gFakeServiceManager == nullptr, "Fake Service Manager is not available. Forgot to call setupFakeServiceManager?");
+    gFakeServiceManager->clear();
+}
+} //extern "C"
\ No newline at end of file
diff --git a/libs/fakeservicemanager/rust/src/lib.rs b/libs/fakeservicemanager/rust/src/lib.rs
new file mode 100644
index 0000000..5b7e756
--- /dev/null
+++ b/libs/fakeservicemanager/rust/src/lib.rs
@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2023 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.
+ */
+
+use fakeservicemanager_bindgen::{clearFakeServiceManager, setupFakeServiceManager};
+// Setup FakeServiceManager for testing and fuzzing purposes
+pub fn setup_fake_service_manager() {
+    unsafe {
+        // Safety: This API creates a new FakeSm object which will be always valid and sets up
+        // defaultServiceManager
+        setupFakeServiceManager();
+    }
+}
+
+// Setup FakeServiceManager for testing and fuzzing purposes
+pub fn clear_fake_service_manager() {
+    unsafe {
+        // Safety: This API clears all registered services with Fake SM. This should be only used
+        // setupFakeServiceManager is already called.
+        clearFakeServiceManager();
+    }
+}
diff --git a/libs/fakeservicemanager/rust/wrappers/FakeServiceManagerWrapper.hpp b/libs/fakeservicemanager/rust/wrappers/FakeServiceManagerWrapper.hpp
new file mode 100644
index 0000000..1f5923a
--- /dev/null
+++ b/libs/fakeservicemanager/rust/wrappers/FakeServiceManagerWrapper.hpp
@@ -0,0 +1,25 @@
+/*
+ * Copyright (C) 2023 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 "fakeservicemanager/FakeServiceManager.h"
+
+extern "C" {
+    // Setup FakeServiceManager to mock dependencies in test using this API
+    void setupFakeServiceManager();
+
+    // Clear existing services from Fake SM.
+    void clearFakeServiceManager();
+} // extern "C"
diff --git a/libs/fakeservicemanager/test_sm.cpp b/libs/fakeservicemanager/test_sm.cpp
index 6fc21c6..cb6784c0 100644
--- a/libs/fakeservicemanager/test_sm.cpp
+++ b/libs/fakeservicemanager/test_sm.cpp
@@ -22,6 +22,7 @@
 #include <binder/IServiceManager.h>
 
 #include "fakeservicemanager/FakeServiceManager.h"
+#include "rust/wrappers/FakeServiceManagerWrapper.hpp"
 
 using android::sp;
 using android::BBinder;
@@ -31,6 +32,7 @@
 using android::FakeServiceManager;
 using android::String16;
 using android::IServiceManager;
+using android::defaultServiceManager;
 using testing::ElementsAre;
 
 static sp<IBinder> getBinder() {
@@ -83,7 +85,7 @@
     EXPECT_EQ(sm->getService(String16("foo")), service);
 }
 
-TEST(GetService, NonExistant) {
+TEST(GetService, NonExistent) {
     auto sm = new FakeServiceManager();
 
     EXPECT_EQ(sm->getService(String16("foo")), nullptr);
@@ -108,7 +110,7 @@
         String16("sd")));
 }
 
-TEST(WaitForService, NonExistant) {
+TEST(WaitForService, NonExistent) {
     auto sm = new FakeServiceManager();
 
     EXPECT_EQ(sm->waitForService(String16("foo")), nullptr);
@@ -124,7 +126,7 @@
     EXPECT_EQ(sm->waitForService(String16("foo")), service);
 }
 
-TEST(IsDeclared, NonExistant) {
+TEST(IsDeclared, NonExistent) {
     auto sm = new FakeServiceManager();
 
     EXPECT_FALSE(sm->isDeclared(String16("foo")));
@@ -139,3 +141,31 @@
 
     EXPECT_TRUE(sm->isDeclared(String16("foo")));
 }
+
+TEST(SetupFakeServiceManager, NonExistent) {
+    setupFakeServiceManager();
+
+    EXPECT_EQ(defaultServiceManager()->getService(String16("foo")), nullptr);
+}
+
+TEST(SetupFakeServiceManager, GetExistingService) {
+    setupFakeServiceManager();
+    sp<IBinder> service = getBinder();
+
+    EXPECT_EQ(defaultServiceManager()->addService(String16("foo"), service, false /*allowIsolated*/,
+    IServiceManager::DUMP_FLAG_PRIORITY_DEFAULT), OK);
+
+    EXPECT_EQ(defaultServiceManager()->getService(String16("foo")), service);
+    clearFakeServiceManager();
+}
+
+TEST(ClearFakeServiceManager, GetServiceAfterClear) {
+    setupFakeServiceManager();
+
+    sp<IBinder> service = getBinder();
+    EXPECT_EQ(defaultServiceManager()->addService(String16("foo"), service, false /*allowIsolated*/,
+    IServiceManager::DUMP_FLAG_PRIORITY_DEFAULT), OK);
+
+    clearFakeServiceManager();
+    EXPECT_EQ(defaultServiceManager()->getService(String16("foo")), nullptr);
+}
\ No newline at end of file