libutils: add sp::cast method
Previously, sp::sp(T*) internally had a static cast, and people
frequently wrote code like this:
sp<A> a = ...;
sp<B> b(a.get()); // implicit static cast
Luckily, none of the other sp constructors have this implicit cast. So,
for explicit code, rather than making those use static_cast internally,
adding an sp::cast function.
Bug: 184190315
Test: use in libbinder
Change-Id: Id205c88d03e16cf85ccb8f493ce88b4bbc65a688
diff --git a/libutils/include/utils/StrongPointer.h b/libutils/include/utils/StrongPointer.h
index 1f07052..dd53b9e 100644
--- a/libutils/include/utils/StrongPointer.h
+++ b/libutils/include/utils/StrongPointer.h
@@ -72,6 +72,12 @@
template<typename U> sp(const sp<U>& other); // NOLINT(implicit)
template<typename U> sp(sp<U>&& other); // NOLINT(implicit)
+ // Cast a strong pointer directly from one type to another. Constructors
+ // allow changing types, but only if they are pointer-compatible. This does
+ // a static_cast internally.
+ template <typename U>
+ static inline sp<T> cast(const sp<U>& other);
+
~sp();
// Assignment
@@ -279,6 +285,12 @@
other.m_ptr = nullptr;
}
+template <typename T>
+template <typename U>
+sp<T> sp<T>::cast(const sp<U>& other) {
+ return sp<T>::fromExisting(static_cast<T*>(other.get()));
+}
+
template<typename T>
sp<T>::~sp() {
if (m_ptr)