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

1 files changed, 66 insertions, 0 deletions

diff --git a/common/support/NativeHandle.cpp b/common/support/NativeHandle.cpp
new file mode 100644
index 0000000000..321d7a8cba
--- /dev/null
+++ b/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