add support for ssl socket wrappers

Jamfile

@@ -78,6 +78,12 @@ lib simulator
 	# make sure asio uses std::chrono
 	<define>BOOST_ASIO_HAS_STD_CHRONO
 
+	# io_executor only implements the legacy (Networking TS v1) executor
+	# concept: this falls any_io_executor back to boost::asio::executor,
+	# which it can wrap, so boost::asio::ssl::stream's bookkeeping timers
+	# work for consumers that include simulator/ssl.hpp.
+	<define>BOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT
+
 	# disable auto-link
 	<define>BOOST_ALL_NO_LIB
 
@@ -96,6 +102,7 @@ lib simulator
 	<define>BOOST_ASIO_DISABLE_BOOST_DATE_TIME
 	<define>BOOST_ASIO_HAS_MOVE
 	<define>BOOST_ASIO_ENABLE_CANCELIO
+	<define>BOOST_ASIO_USE_TS_EXECUTOR_AS_DEFAULT
 	<threading>multi
 	<include>include
 	<link>shared:<define>SIMULATOR_LINKING_SHARED

include/simulator/ssl.hpp

@@ -0,0 +1,44 @@
+/*
+
+Copyright (c) 2026, Arvid Norberg
+All rights reserved.
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+*/
+
+#ifndef SIMULATOR_SSL_HPP_INCLUDED
+#define SIMULATOR_SSL_HPP_INCLUDED
+
+#include "simulator/simulator.hpp"
+
+#include "simulator/push_warnings.hpp"
+#include <boost/asio/ssl.hpp>
+#include "simulator/pop_warnings.hpp"
+
+namespace sim {
+namespace asio {
+
+namespace ssl
+{
+	using boost::asio::ssl::context;
+	using boost::asio::ssl::stream_base;
+	using boost::asio::ssl::verify_context;
+
+	template <typename Stream>
+	using stream = boost::asio::ssl::stream<Stream>;
+} // ssl
+
+} // asio
+} // sim
+
+#endif

src/tcp_socket.cpp

@@ -537,6 +537,15 @@ namespace ip {
 		std::vector<boost::asio::mutable_buffer> const& bufs
 		, boost::system::error_code& ec)
 	{
+		// a zero-sized read always completes immediately with 0 bytes;
+		// boost.asio's SSL implementation relies on this to post a
+		// completion handler without transferring any data.
+		if (boost::asio::buffer_size(bufs) == 0)
+		{
+			ec.clear();
+			return 0;
+		}
+
 		assert(!bufs.empty());
 		if (!m_open)
 		{
@@ -635,8 +644,18 @@ namespace ip {
 	void tcp::socket::async_read_some_impl(std::vector<boost::asio::mutable_buffer> const& bufs
 		, aux::function<void(boost::system::error_code const&, std::size_t)> handler)
 	{
+		// a zero-sized read always completes immediately with 0 bytes
+		// transferred, regardless of connection or queue state. boost.asio's
+		// SSL implementation relies on this to bounce a completion handler
+		// through the executor without actually transferring any data.
+		if (boost::asio::buffer_size(bufs) == 0)
+		{
+			post(m_io_service, aux::make_malloc(std::bind(std::move(handler)
+				, boost::system::error_code(), std::size_t(0))));
+			return;
+		}
+
 		assert(!bufs.empty());
-		assert(bufs[0].size());
 
 		boost::system::error_code ec;
 		std::size_t bytes_transferred = read_some_impl(bufs, ec);