SQLite wrapper user-defined serialization and deserialization hooks

user-hooks.cc

#include "SQLiteWrapper.h"
#include <google/protobuf/message.h>

// This alias template is used below to define a serialization hook and
// a deserialization hook for `google::protobuf::Message`s.
template <typename T>
using is_a_protobuf_message
    = std::enable_if_t<std::is_base_of_v<google::protobuf::Message, T>>;

// Serialize a `google::protobuf::Message` into a `sqlite::blob` by invoking the
// `SerializeAsString` instance method.  Internally, `sqlite::blob` corresponds
// to SQLite's BLOB data type.
template <typename T>
constexpr auto sqlite::user_serialize_fn<T, is_a_protobuf_message<T>> =
  [] (const google::protobuf::Message &message) -> sqlite::blob {
    return sqlite::blob{message.SerializeAsString()};
  };

// Deserialize a `sqlite::blob` into a `google::protobuf::Message` by parsing
// the underlying bytes of the `sqlite::blob`.
template <typename T>
constexpr auto sqlite::user_deserialize_fn<T, is_a_protobuf_message<T>> =
  [] (sqlite::blob_view serialized_message) -> T {
    T message;
    message.ParseFromArray(&serialized_message[0],
                           serialized_message.length());
    return message;
  };

static const char db_name[] = "my_database.db";
using db = sqlite::Database<db_name>;

void example(const std::string &name,
             const google::protobuf::Message &new_message) {
  static const char insert_query[]
    = R"(insert into my_table (my_name, my_column) values (?1, ?2))";
  // We can now bind `google::protobuf::Message`s natively.  The wrapper will use the
  // serialization and deserialization hooks to convert the messages to and from a native
  // SQLite data type.
  db::query<insert_query>(name, new_message);
}