Adding {read,write}Embedded{From,To} methods for hidl_handle

This change implements helper functions for serializing/deserializing
hidl_handle types to/from parcels, similar to the other HIDL types
(hidl_string, hild_string).

Bug: 35098567
Test: Ran the hidl_test suite
Change-Id: I5f6720c42d69a7f760a91442fbdeec202cb2ffcd
diff --git a/transport/HidlBinderSupport.cpp b/transport/HidlBinderSupport.cpp
index a221b46..cd05c3d 100644
--- a/transport/HidlBinderSupport.cpp
+++ b/transport/HidlBinderSupport.cpp
@@ -47,6 +47,30 @@
     return mRecipient;
 }
 
+const size_t hidl_handle::kOffsetOfNativeHandle = offsetof(hidl_handle, mHandle);
+static_assert(hidl_handle::kOffsetOfNativeHandle == 0, "wrong offset");
+
+status_t readEmbeddedFromParcel(const hidl_handle& /* handle */,
+        const Parcel &parcel, size_t parentHandle, size_t parentOffset) {
+    const native_handle_t *handle;
+    status_t _hidl_err = parcel.readNullableEmbeddedNativeHandle(
+            parentHandle,
+            parentOffset + hidl_handle::kOffsetOfNativeHandle,
+            &handle);
+
+    return _hidl_err;
+}
+
+status_t writeEmbeddedToParcel(const hidl_handle &handle,
+        Parcel *parcel, size_t parentHandle, size_t parentOffset) {
+    status_t _hidl_err = parcel->writeEmbeddedNativeHandle(
+            handle.getNativeHandle(),
+            parentHandle,
+            parentOffset + hidl_handle::kOffsetOfNativeHandle);
+
+    return _hidl_err;
+}
+
 const size_t hidl_memory::kOffsetOfHandle = offsetof(hidl_memory, mHandle);
 const size_t hidl_memory::kOffsetOfName = offsetof(hidl_memory, mName);
 static_assert(hidl_memory::kOffsetOfHandle == 0, "wrong offset");
@@ -54,6 +78,7 @@
 
 status_t readEmbeddedFromParcel(const hidl_memory& memory,
         const Parcel &parcel, size_t parentHandle, size_t parentOffset) {
+    // TODO(b/111883309): Invoke readEmbeddedFromParcel(hidl_handle, ...).
     const native_handle_t *handle;
     ::android::status_t _hidl_err = parcel.readNullableEmbeddedNativeHandle(
             parentHandle,
@@ -73,6 +98,7 @@
 
 status_t writeEmbeddedToParcel(const hidl_memory &memory,
         Parcel *parcel, size_t parentHandle, size_t parentOffset) {
+    // TODO(b/111883309): Invoke writeEmbeddedToParcel(hidl_handle, ...).
     status_t _hidl_err = parcel->writeEmbeddedNativeHandle(
             memory.handle(),
             parentHandle,