Common: Add convenience function for hashing a struct

src/common/hash.h

@@ -20,4 +20,17 @@ static inline u64 ComputeHash64(const void* data, size_t len) {
     return CityHash64(static_cast<const char*>(data), len);
 }
 
+/**
+ * Computes a 64-bit hash of a struct. In addition to being POD (trivially copyable and having
+ * standard layout), it is also critical that either the struct includes no padding, or that any
+ * padding is initialized to a known value by memsetting the struct to 0 before filling it in.
+ */
+template <typename T>
+static inline u64 ComputeStructHash64(const T& data) {
+    static_assert(
+        std::is_trivially_copyable<T>::value && std::is_standard_layout<T>::value,
+        "Type passed to ComputeStructHash64 must be trivially copyable and standard layout");
+    return ComputeHash64(&data, sizeof(data));
+}
+
 } // namespace Common