Add make_secure_unique helper

Co-authored-by: Pieter Wuille <bitcoin-dev@wuille.net>

src/support/allocators/secure.h

@@ -57,4 +57,28 @@ struct secure_allocator {
 // TODO: Consider finding a way to make incoming RPC request.params[i] mlock()ed as well
 typedef std::basic_string<char, std::char_traits<char>, secure_allocator<char> > SecureString;
 
+template<typename T>
+struct SecureUniqueDeleter {
+    void operator()(T* t) noexcept {
+        secure_allocator<T>().deallocate(t, 1);
+    }
+};
+
+template<typename T>
+using secure_unique_ptr = std::unique_ptr<T, SecureUniqueDeleter<T>>;
+
+template<typename T, typename... Args>
+secure_unique_ptr<T> make_secure_unique(Args&&... as)
+{
+    T* p = secure_allocator<T>().allocate(1);
+
+    // initialize in place, and return as secure_unique_ptr
+    try {
+        return secure_unique_ptr<T>(new (p) T(std::forward(as)...));
+    } catch (...) {
+        secure_allocator<T>().deallocate(p, 1);
+        throw;
+    }
+}
+
 #endif // BITCOIN_SUPPORT_ALLOCATORS_SECURE_H