support lib for libcutils<->NDK AIDL handle

The native_handle API is notoriously tricky to work with, and this is
expected to be very common. So, adding a small helper library.

Fixes: 175432703
Test: atest libaidlcommonsupport_test
Change-Id: I4a00d2b14fefe6c979ee656e353e117661a1a483

common/TEST_MAPPING

@@ -0,0 +1,7 @@
+{
+  "presubmit": [
+    {
+      "name": "libaidlcommonsupport_test"
+    }
+  ]
+}

common/support/Android.bp

@@ -0,0 +1,27 @@
+cc_library_static {
+    name: "libaidlcommonsupport",
+    vendor_available: true,
+    host_supported: true,
+    defaults: ["libbinder_ndk_host_user"],
+    srcs: ["NativeHandle.cpp"],
+    export_include_dirs: ["include"],
+    shared_libs: [
+        "android.hardware.common-unstable-ndk_platform",
+        "libcutils",
+    ],
+}
+
+cc_test {
+    name: "libaidlcommonsupport_test",
+    host_supported: true,
+    defaults: ["libbinder_ndk_host_user"],
+    srcs: ["test.cpp"],
+    static_libs: [
+        "libaidlcommonsupport",
+    ],
+    shared_libs: [
+        "android.hardware.common-unstable-ndk_platform",
+        "libcutils",
+    ],
+    test_suites: ["general-tests"],
+}

common/support/NativeHandle.cpp

@@ -0,0 +1,66 @@
+/*
+ * Copyright (C) 2020 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 <aidlcommonsupport/NativeHandle.h>
+
+#include <fcntl.h>
+
+namespace android {
+
+using aidl::android::hardware::common::NativeHandle;
+
+static native_handle_t* fromAidl(const NativeHandle& handle, bool doDup) {
+    native_handle_t* to = native_handle_create(handle.fds.size(), handle.ints.size());
+    if (!to) return nullptr;
+
+    for (size_t i = 0; i < handle.fds.size(); i++) {
+        int fd = handle.fds[i].get();
+        to->data[i] = doDup ? fcntl(fd, F_DUPFD_CLOEXEC, 0) : fd;
+    }
+    memcpy(to->data + handle.fds.size(), handle.ints.data(), handle.ints.size() * sizeof(int));
+    return to;
+}
+
+native_handle_t* makeFromAidl(const NativeHandle& handle) {
+    return fromAidl(handle, false /* doDup */);
+}
+native_handle_t* dupFromAidl(const NativeHandle& handle) {
+    return fromAidl(handle, true /* doDup */);
+}
+
+static NativeHandle toAidl(const native_handle_t* handle, bool doDup) {
+    NativeHandle to;
+
+    to.fds = std::vector<ndk::ScopedFileDescriptor>(handle->numFds);
+    for (size_t i = 0; i < handle->numFds; i++) {
+        int fd = handle->data[i];
+        to.fds.at(i).set(doDup ? fcntl(fd, F_DUPFD_CLOEXEC, 0) : fd);
+    }
+
+    to.ints = std::vector<int32_t>(handle->data + handle->numFds,
+                                   handle->data + handle->numFds + handle->numInts);
+    return to;
+}
+
+NativeHandle makeToAidl(const native_handle_t* handle) {
+    return toAidl(handle, false /* doDup */);
+}
+
+NativeHandle dupToAidl(const native_handle_t* handle) {
+    return toAidl(handle, true /* doDup */);
+}
+
+}  // namespace android

common/support/include/aidlcommonsupport/NativeHandle.h

@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+
+#pragma once
+
+#include <aidl/android/hardware/common/NativeHandle.h>
+#include <cutils/native_handle.h>
+
+namespace android {
+
+/**
+ * Creates a libcutils native handle from an AIDL native handle, but it does not
+ * dup internally, so it will contain the same FDs as the handle itself. The
+ * result should be deleted with native_handle_delete.
+ */
+native_handle_t* makeFromAidl(const aidl::android::hardware::common::NativeHandle& handle);
+
+/**
+ * Creates a libcutils native handle from an AIDL native handle with a dup
+ * internally. It's expected the handle is cleaned up with native_handle_close
+ * and native_handle_delete.
+ */
+native_handle_t* dupFromAidl(const aidl::android::hardware::common::NativeHandle& handle);
+
+/**
+ * Creates an AIDL native handle from a libcutils native handle, but does not
+ * dup internally, so the result will contain the same FDs as the handle itself.
+ *
+ * Warning: this passes ownership of the FDs to the ScopedFileDescriptor
+ * objects.
+ */
+aidl::android::hardware::common::NativeHandle makeToAidl(const native_handle_t* handle);
+
+/**
+ * Creates an AIDL native handle from a libcutils native handle with a dup
+ * internally.
+ */
+aidl::android::hardware::common::NativeHandle dupToAidl(const native_handle_t* handle);
+
+}  // namespace android

common/support/test.cpp

@@ -0,0 +1,138 @@
+/*
+ * Copyright (C) 2020 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 <aidlcommonsupport/NativeHandle.h>
+#include <gtest/gtest.h>
+
+namespace android {
+
+using aidl::android::hardware::common::NativeHandle;
+using ndk::ScopedFileDescriptor;
+
+static void checkEq(const NativeHandle& aidl, native_handle_t* libcutils, bool exceptFds) {
+    ASSERT_NE(libcutils, nullptr);
+    ASSERT_EQ(libcutils->numFds, aidl.fds.size());
+
+    for (size_t i = 0; i < libcutils->numFds; i++) {
+        int afd = aidl.fds.at(i).get();
+        int lfd = libcutils->data[i];
+
+        EXPECT_GE(afd, 0) << "Invalid fd at index " << i;
+        EXPECT_GE(lfd, 0) << "Invalid fd at index " << i;
+
+        if (exceptFds) {
+            EXPECT_NE(afd, lfd) << "Index matched at " << i << " but should be dup'd fd";
+        } else {
+            EXPECT_EQ(afd, lfd) << "Index mismatched at " << i << " but should be same fd";
+        }
+    }
+
+    ASSERT_EQ(libcutils->numInts, aidl.ints.size());
+
+    for (size_t i = 0; i < libcutils->numInts; i++) {
+        int afd = aidl.ints.at(i);
+        int lfd = libcutils->data[libcutils->numFds + i];
+
+        EXPECT_EQ(afd, lfd) << "Index mismatch at " << i;
+    }
+}
+
+static NativeHandle makeTestAidlHandle() {
+    NativeHandle handle = {
+            .fds = std::vector<ScopedFileDescriptor>(2),
+            .ints = {1, 2, 3, 4},
+    };
+    handle.fds[0].set(dup(0));
+    handle.fds[1].set(dup(0));
+    return handle;
+}
+
+TEST(ConvertNativeHandle, MakeFromAidlEmpty) {
+    NativeHandle handle;
+    native_handle_t* to = makeFromAidl(handle);
+    checkEq(handle, to, false /*exceptFds*/);
+    // no native_handle_close b/c fds are owned by NativeHandle
+    EXPECT_EQ(0, native_handle_delete(to));
+}
+
+TEST(ConvertNativeHandle, MakeFromAidl) {
+    NativeHandle handle = makeTestAidlHandle();
+    native_handle_t* to = makeFromAidl(handle);
+    checkEq(handle, to, false /*exceptFds*/);
+    // no native_handle_close b/c fds are owned by NativeHandle
+    EXPECT_EQ(0, native_handle_delete(to));
+}
+
+TEST(ConvertNativeHandle, DupFromAidlEmpty) {
+    NativeHandle handle;
+    native_handle_t* to = dupFromAidl(handle);
+    checkEq(handle, to, true /*exceptFds*/);
+    EXPECT_EQ(0, native_handle_close(to));
+    EXPECT_EQ(0, native_handle_delete(to));
+}
+
+TEST(ConvertNativeHandle, DupFromAidl) {
+    NativeHandle handle = makeTestAidlHandle();
+    native_handle_t* to = dupFromAidl(handle);
+    checkEq(handle, to, true /*exceptFds*/);
+    EXPECT_EQ(0, native_handle_close(to));
+    EXPECT_EQ(0, native_handle_delete(to));
+}
+
+static native_handle_t* makeTestLibcutilsHandle() {
+    native_handle_t* handle = native_handle_create(2, 4);
+    handle->data[0] = dup(0);
+    handle->data[1] = dup(0);
+    handle->data[2] = 1;
+    handle->data[3] = 2;
+    handle->data[4] = 3;
+    handle->data[5] = 4;
+    return handle;
+}
+
+TEST(ConvertNativeHandle, MakeToAidlEmpty) {
+    native_handle_t* handle = native_handle_create(0, 0);
+    NativeHandle to = makeToAidl(handle);
+    checkEq(to, handle, false /*exceptFds*/);
+    // no native_handle_close b/c fds are owned by NativeHandle now
+    EXPECT_EQ(0, native_handle_delete(handle));
+}
+
+TEST(ConvertNativeHandle, MakeToAidl) {
+    native_handle_t* handle = makeTestLibcutilsHandle();
+    NativeHandle to = makeToAidl(handle);
+    checkEq(to, handle, false /*exceptFds*/);
+    // no native_handle_close b/c fds are owned by NativeHandle now
+    EXPECT_EQ(0, native_handle_delete(handle));
+}
+
+TEST(ConvertNativeHandle, DupToAidlEmpty) {
+    native_handle_t* handle = native_handle_create(0, 0);
+    NativeHandle to = dupToAidl(handle);
+    checkEq(to, handle, true /*exceptFds*/);
+    EXPECT_EQ(0, native_handle_close(handle));
+    EXPECT_EQ(0, native_handle_delete(handle));
+}
+
+TEST(ConvertNativeHandle, DupToAidl) {
+    native_handle_t* handle = makeTestLibcutilsHandle();
+    NativeHandle to = dupToAidl(handle);
+    checkEq(to, handle, true /*exceptFds*/);
+    EXPECT_EQ(0, native_handle_close(handle));
+    EXPECT_EQ(0, native_handle_delete(handle));
+}
+
+}  // namespace android