Expose offset of private member hidl_string::mBuffer.

Bug: 30575790
Change-Id: Id8ca6cc8a82cc0133732d10aa4fdc107694f7e00

Author: theandi666

HidlSupport.cpp

@@ -113,6 +113,9 @@ status_t hidl_string::writeEmbeddedToParcel(
             parentOffset + offsetof(hidl_string, mBuffer));
 }
 
+// static
+const size_t hidl_string::kOffsetOfBuffer = offsetof(hidl_string, mBuffer);
+
 }  // namespace hardware
 }  // namespace android
 

include/hidl/HidlSupport.h

@@ -47,6 +47,9 @@ struct hidl_string {
     status_t writeEmbeddedToParcel(
             Parcel *parcel, size_t parentHandle, size_t parentOffset) const;
 
+    // offsetof(hidl_string, mBuffer) exposed since mBuffer is private.
+    static const size_t kOffsetOfBuffer;
+
 private:
     char *mBuffer;
     size_t mSize;  // NOT including the terminating '\0'.