From ca81dcf08d9a3bf49b3d540e3b3b792bfc3b3016 Mon Sep 17 00:00:00 2001
From: Roland Reichwein <mail@reichwein.it>
Date: Sun, 5 Feb 2023 10:09:33 +0100
Subject: Remove websocket mutex in favour of boost strands

---
 whiteboard.cpp | 41 +++++++++++++++++++++++++----------------
 whiteboard.h   |  1 -
 2 files changed, 25 insertions(+), 17 deletions(-)

diff --git a/whiteboard.cpp b/whiteboard.cpp
index ea56cc3..922bd37 100644
--- a/whiteboard.cpp
+++ b/whiteboard.cpp
@@ -95,11 +95,10 @@ class session: public std::enable_shared_from_this<session>
 public:
  using connection = std::shared_ptr<boost::beast::websocket::stream<boost::asio::ip::tcp::socket>>;
  
- session(ConnectionRegistry& registry, Storage& storage, std::mutex& storage_mutex, std::mutex& websocket_mutex, boost::asio::ip::tcp::socket socket):
+ session(ConnectionRegistry& registry, Storage& storage, std::mutex& storage_mutex, boost::asio::ip::tcp::socket socket):
   m_registry(registry),
   m_storage(storage),
   m_storage_mutex(storage_mutex),
-  m_websocket_mutex(websocket_mutex),
   m_ws(std::make_shared<connection::element_type>(std::move(socket))),
   m_connection_guard(m_registry, m_ws)
  {
@@ -115,7 +114,8 @@ public:
            std::string("Reichwein.IT Whiteboard"));
       }));
 
-  boost::beast::http::async_read(m_ws->next_layer(), m_buffer, m_parser, boost::beast::bind_front_handler(&session::on_read_handshake, shared_from_this()));
+  boost::beast::http::async_read(m_ws->next_layer(), m_buffer, m_parser,
+                                 boost::asio::bind_executor(m_ws->next_layer().get_executor(), boost::beast::bind_front_handler(&session::on_read_handshake, shared_from_this())));
  }
 
  void on_read_handshake(boost::beast::error_code ec, std::size_t bytes_transferred)
@@ -173,8 +173,9 @@ public:
   }
   if (data.size() > 0) {
    boost::beast::ostream(m_buffer) << data;
-   std::lock_guard<std::mutex> lock(m_websocket_mutex);
-   m_ws->async_write(m_buffer.data(), boost::beast::bind_front_handler(&session::on_write, shared_from_this()));
+   m_ws->async_write(m_buffer.data(),
+                     boost::asio::bind_executor(m_ws->next_layer().get_executor(),
+                                                boost::beast::bind_front_handler(&session::on_write, shared_from_this())));
   } else {
    do_read();
   }
@@ -196,22 +197,31 @@ public:
   do_read_handshake();
  }
 
+ void on_write_notify(std::shared_ptr<std::string> data, std::shared_ptr<boost::asio::const_buffer> buffer, boost::beast::error_code ec, std::size_t bytes_transferred)
+ {
+  boost::ignore_unused(bytes_transferred);
+
+  if (ec) {
+   std::cerr << "Error on session write notify: " << ec.message() << std::endl;
+  }
+ }
+
  void notify_other_connections_diff(const std::string& id, const Diff& diff)
  {
   std::for_each(m_registry.begin(id), m_registry.end(id), [&](const connection& ci)
                 {
                  if (m_ws != ci) {
-                  boost::beast::flat_buffer buffer;
                   pt::ptree ptree {make_ptree({
                     {"type", "getdiff"},
                     {"revision", std::to_string(m_storage.getRevision(id))},
                     {"pos", std::to_string(m_storage.getCursorPos(id)) }
                     })};
                   ptree.put_child("serverinfo.diff", diff.get_structure().get_child("diff"));
-                  boost::beast::ostream(buffer) << Reichwein::XML::plain_xml(ptree);
-                  std::lock_guard<std::mutex> lock(m_websocket_mutex);
+                  auto data{std::make_shared<std::string>(Reichwein::XML::plain_xml(ptree))};
+                  auto buffer{std::make_shared<boost::asio::const_buffer>(data->data(), data->size())};
                   try {
-                   ci->write(buffer.data());
+                   ci->async_write(*buffer, boost::asio::bind_executor(ci->next_layer().get_executor(),
+                                                                       boost::beast::bind_front_handler(&session::on_write_notify, shared_from_this(), data, buffer)));
                   } catch (const std::exception& ex) {
                    std::cerr << "Warning: Notify getdiff write for " << ci << " not possible, id " << id << std::endl;
                    m_registry.dump();
@@ -225,14 +235,14 @@ public:
   std::for_each(m_registry.begin(id), m_registry.end(id), [&](const connection& ci)
                 {
                  if (m_ws != ci) {
-                  boost::beast::flat_buffer buffer;
-                  boost::beast::ostream(buffer) << make_xml({
+                  auto data{std::make_shared<std::string>(make_xml({
                     {"type", "getpos"},
                     {"pos", std::to_string(m_storage.getCursorPos(id)) }
-                    });
-                  std::lock_guard<std::mutex> lock(m_websocket_mutex);
+                    }))};
+                  auto buffer{std::make_shared<boost::asio::const_buffer>(data->data(), data->size())};
                   try {
-                   ci->write(buffer.data());
+                   ci->async_write(*buffer, boost::asio::bind_executor(ci->next_layer().get_executor(),
+                                                                       boost::beast::bind_front_handler(&session::on_write_notify, shared_from_this(), data, buffer)));
                   } catch (const std::exception& ex) {
                    std::cerr << "Warning: Notify getpos write for " << ci << " not possible, id " << id << std::endl;
                    m_registry.dump();
@@ -348,7 +358,6 @@ private:
  ConnectionRegistry& m_registry;
  Storage& m_storage;
  std::mutex& m_storage_mutex;
- std::mutex& m_websocket_mutex;
  connection m_ws;
  ConnectionRegistry::RegistryGuard m_connection_guard;
 
@@ -370,7 +379,7 @@ void Whiteboard::on_accept(boost::system::error_code ec, boost::asio::ip::tcp::s
  if (ec) {
   std::cerr << "Error on accept: " << ec.message() << std::endl;
  } else {
-  std::make_shared<session>(m_registry, *m_storage, m_storage_mutex, m_websocket_mutex, std::move(socket))->run();
+  std::make_shared<session>(m_registry, *m_storage, m_storage_mutex, std::move(socket))->run();
  }
 
  do_accept();
diff --git a/whiteboard.h b/whiteboard.h
index 15d764a..7648bd4 100644
--- a/whiteboard.h
+++ b/whiteboard.h
@@ -22,7 +22,6 @@ private:
  std::unique_ptr<Config> m_config;
  std::unique_ptr<Storage> m_storage;
  std::mutex m_storage_mutex;
- std::mutex m_websocket_mutex;
 
  ConnectionRegistry m_registry;
  
-- 
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