Optimization - don't use futures, use simple pointers.

The local count atomic is used to tell if there are any unanswered
ex-futures yet.

include/incredis/batch.hpp

@@ -23,10 +23,6 @@
 #include <vector>
 #include <memory>
 
-namespace std {
-	template <class R> class future;
-} //namespace std
-
 namespace redis {
 	class Command;
 	class AsyncConnection;
@@ -40,6 +36,7 @@ namespace redis {
 		~Batch ( void ) noexcept;
 
 		const std::vector<Reply>& replies ( void );
+		std::vector<Reply>& replies_nonconst ( void );
 		bool replies_requested ( void ) const;
 		void throw_if_failed ( void );
 
@@ -57,7 +54,7 @@ namespace redis {
 		explicit Batch ( AsyncConnection* parConn, ThreadContext& parThreadContext );
 		void run_pvt ( int parArgc, const char** parArgv, std::size_t* parLengths );
 
-		std::vector<std::future<Reply>> m_futures;
+		std::vector<std::unique_ptr<Reply>> m_futures;
 		std::vector<Reply> m_replies;
 		std::unique_ptr<LocalData> m_local_data;
 		AsyncConnection* m_async_conn;

include/incredis/command.hpp

@@ -65,7 +65,7 @@ namespace redis {
 		auto batch = make_batch();
 		batch.run(parCommand, std::forward<Args>(parArgs)...);
 		batch.throw_if_failed();
-		return batch.replies().front();
+		return std::move(batch.replies_nonconst().front());
 	}
 
 	template <typename T>

include/incredis/reply.hpp

@@ -77,8 +77,14 @@ namespace redis {
 		Reply ( ErrorString&& parVal ) : base_class(std::move(parVal)) {}
 		Reply ( StatusString&& parVal ) : base_class(std::move(parVal)) {}
 		Reply ( std::nullptr_t parVal ) : base_class(parVal) {}
+
+		Reply ( Reply&& ) = default;
+		Reply ( const Reply& ) = default;
 		~Reply ( void ) noexcept = default;
 
+		Reply& operator= ( Reply&& ) = default;
+		Reply& operator= ( const Reply& ) = default;
+
 		bool is_integer ( void ) const;
 		bool is_string ( void ) const;
 		bool is_array ( void ) const;

src/batch.cpp

@@ -21,7 +21,6 @@
 #include <hiredis/hiredis.h>
 #include <hiredis/async.h>
 #include <cassert>
-#include <future>
 #include <ciso646>
 #include <boost/iterator/transform_iterator.hpp>
 #include <mutex>
@@ -39,16 +38,20 @@ namespace redis {
 		const std::size_t g_max_redis_unanswered_commands = 1000;
 
 		struct HiredisCallbackData {
-			HiredisCallbackData ( std::atomic_size_t& parPendingFutures, std::condition_variable& parSendCmdCond ) :
-				promise(),
+			HiredisCallbackData ( std::atomic_size_t& parPendingFutures, std::atomic_size_t& parLocalPendingFutures, std::condition_variable& parSendCmdCond, std::condition_variable& parLocalCmdsCond ) :
 				pending_futures(parPendingFutures),
-				send_command_condition(parSendCmdCond)
+				local_pending_futures(parLocalPendingFutures),
+				reply_ptr(nullptr),
+				send_command_condition(parSendCmdCond),
+				local_commands_condition(parLocalCmdsCond)
 			{
 			}
 
-			std::promise<Reply> promise;
+			Reply* reply_ptr;
 			std::atomic_size_t& pending_futures;
+			std::atomic_size_t& local_pending_futures;
 			std::condition_variable& send_command_condition;
+			std::condition_variable& local_commands_condition;
 		};
 
 		Reply make_redis_reply_type (redisReply* parReply) {
@@ -80,19 +83,28 @@ namespace redis {
 		void hiredis_run_callback (redisAsyncContext*, void* parReply, void* parPrivData) {
 			assert(parPrivData);
 			auto* data = static_cast<HiredisCallbackData*>(parPrivData);
-			const auto old_count = data->pending_futures.fetch_add(-1);
-			assert(old_count > 0);
-			if (old_count == g_max_redis_unanswered_commands)
-				data->send_command_condition.notify_one();
+			{
+				const auto old_count = data->pending_futures.fetch_add(-1);
+				assert(old_count > 0);
+				if (old_count == g_max_redis_unanswered_commands)
+					data->send_command_condition.notify_one();
+			}
 
 			if (parReply) {
 				auto reply = make_redis_reply_type(static_cast<redisReply*>(parReply));
-				data->promise.set_value(std::move(reply));
+				assert(data->reply_ptr);
+				*data->reply_ptr = std::move(reply);
 			}
 			else {
 				assert(false); //Should this case also be managed?
 			}
 
+			{
+				const auto old_value = data->local_pending_futures.fetch_add(-1);
+				assert(old_value > 0);
+				if (1 == old_value)
+					data->local_commands_condition.notify_one();
+			}
 			delete data;
 		}
 
@@ -115,13 +127,19 @@ namespace redis {
 	struct Batch::LocalData {
 		explicit LocalData ( ThreadContext& parThreadContext ) :
 			free_cmd_slot(),
+			no_more_pending_futures(),
 			futures_mutex(),
+			pending_futures_mutex(),
+			local_pending_futures(0),
 			thread_context(parThreadContext)
 		{
 		}
 
 		std::condition_variable free_cmd_slot;
+		std::condition_variable no_more_pending_futures;
 		std::mutex futures_mutex;
+		std::mutex pending_futures_mutex;
+		std::atomic_size_t local_pending_futures;
 		ThreadContext& thread_context;
 	};
 
@@ -149,8 +167,9 @@ namespace redis {
 		assert(parLengths); //This /could/ be null, but I don't see why it should
 		assert(m_local_data);
 
+		m_local_data->local_pending_futures.fetch_add(1);
 		const auto pending_futures = m_local_data->thread_context.pending_futures.fetch_add(1);
-		auto* data = new HiredisCallbackData(m_local_data->thread_context.pending_futures, m_local_data->free_cmd_slot);
+		auto* data = new HiredisCallbackData(m_local_data->thread_context.pending_futures, m_local_data->local_pending_futures, m_local_data->free_cmd_slot, m_local_data->no_more_pending_futures);
 
 #if defined(VERBOSE_HIREDIS_COMM)
 		std::cout << "run_pvt(), " << pending_futures << " items pending... ";
@@ -166,7 +185,9 @@ namespace redis {
 		std::cout << " emplace_back(future)... ";
 #endif
 
-		m_futures.emplace_back(data->promise.get_future());
+		std::unique_ptr<Reply> new_reply(new Reply);
+		data->reply_ptr = new_reply.get();
+		m_futures.emplace_back(std::move(new_reply));
 		{
 			std::lock_guard<std::mutex> lock(m_async_conn->event_mutex());
 			const int command_added = redisAsyncCommandArgv(m_async_conn->connection(), &hiredis_run_callback, data, parArgc, parArgv, parLengths);
@@ -185,10 +206,19 @@ namespace redis {
 	}
 
 	const std::vector<Reply>& Batch::replies() {
+		return replies_nonconst();
+	}
+
+	std::vector<Reply>& Batch::replies_nonconst() {
 		if (not replies_requested()) {
+			if (m_local_data->local_pending_futures > 0) {
+				std::unique_lock<std::mutex> u_lock(m_local_data->pending_futures_mutex);
+				m_local_data->no_more_pending_futures.wait(u_lock, [this]() { return m_local_data->local_pending_futures == 0; });
+			}
+
 			m_replies.reserve(m_futures.size());
-			for (auto& fut : m_futures) {
-				m_replies.emplace_back(fut.get());
+			for (auto& itm : m_futures) {
+				m_replies.emplace_back(std::move(*itm));
 			}
 
 			auto empty_vec = std::move(m_futures);
@@ -217,7 +247,7 @@ namespace redis {
 		}
 
 		assert(m_local_data);
-		assert(0 == m_local_data->thread_context.pending_futures);
+		assert(0 == m_local_data->local_pending_futures);
 		m_futures.clear();
 		m_replies.clear();
 	}

src/incredis.cpp

@@ -40,7 +40,7 @@ namespace redis {
 				return boost::none;
 			}
 			else {
-				auto replies = get_array(parReply);
+				auto replies(get_array(parReply));
 				IncRedis::opt_string_list::value_type retval;
 				retval.reserve(replies.size());
 				for (const auto& rep : replies) {